A vocabulary and associated APIs for HTML and XHTML
This specification is also available as a single page HTML document.
Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C liability, trademark and document use rules apply.
This specification defines the 5th major revision of the core language of the World Wide Web: the Hypertext Markup Language (HTML). In this version, new features are introduced to help Web application authors, new elements are introduced based on research into prevailing authoring practices, and special attention has been given to defining clear conformance criteria for user agents in an effort to improve interoperability.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
If you wish to make comments regarding this document in a manner that is tracked by the W3C, please submit them via using our public bug database. If you cannot do this then you can also e-mail feedback to public-html-comments@w3.org (subscribe, archives), and arrangements will be made to transpose the comments to our public bug database. All feedback is welcome.
Work on extending this specification typically proceeds through extension specifications which should be consulted to see what new features are being reviewed.
The bulk of the text of this specification is also available in the WHATWG HTML Living Standard, under a license that permits reuse of the specification text.
The working groups maintains a list of all bug reports that the editors have not yet tried to address and a list of issues for which the chairs have not yet declared a decision. You are very welcome to file a new bug for any problem you may encounter. These bugs and issues apply to multiple HTML-related specifications, not just this one.
Implementors should be aware that this specification is not stable. Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should join the aforementioned mailing lists and take part in the discussions.
This is a work in progress! For the latest updates from the HTML WG, possibly including important bug fixes, please look at the editor's draft instead.
Publication as a Candidate Recommendation does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
The latest stable version of the editor's draft of this specification is always available on the W3C HTML git repository.
The W3C HTML Working Group is the W3C working group responsible for this specification's progress. This specification is the 04 February 2014 Candidate Recommendation. This specification is intended to become a W3C Recommendation.
Work on this specification is also done at the WHATWG. The W3C HTML working group actively pursues convergence of the HTML specification with the WHATWG living standard, within the bounds of the W3C HTML working group charter. There are various ways to follow this work at the WHATWG:
svn checkout http://svn.whatwg.org/webapps/
This document was published by the HTML Working Group as an updated revision to the Candidate Recommendation (http://www.w3.org/TR/2013/CR-html5-20130806/). This document is intended to become a W3C Recommendation. W3C publishes a Candidate Recommendation to indicate that the document is believed to be stable and to encourage implementation by the developer community. This Candidate Recommendation is expected to advance to Proposed Recommendation no earlier than 01 September 2014. All feedback is welcome.
For this specification to exit the CR stage, the conditions detailed in the CR Exit Criteria (Public Permissive version 3) document will have to be met.
The following features are at risk and may be removed due to lack of implementation.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
id
attributetitle
attributelang
and xml:lang
attributestranslate
attributexml:base
attribute (XML only)dir
attributeclass
attributestyle
attributedata-*
attributesp
elementhr
elementpre
elementblockquote
elementol
elementul
elementli
elementdl
elementdt
elementdd
elementfigure
elementfigcaption
elementdiv
elementmain
elementa
elementem
elementstrong
elementsmall
elements
elementcite
elementq
elementdfn
elementabbr
elementdata
elementtime
elementcode
elementvar
elementsamp
elementkbd
elementsub
and sup
elementsi
elementb
elementu
elementmark
elementruby
elementrb
elementrt
elementrtc
elementrp
elementbdi
elementbdo
elementspan
elementbr
elementwbr
elementimg
element
iframe
elementembed
elementobject
elementparam
elementvideo
elementaudio
elementsource
elementtrack
elementmap
elementarea
elementa
and area
elementsalternate
"author
"bookmark
"help
"icon
"license
"nofollow
"noreferrer
"prefetch
"search
"stylesheet
"tag
"table
element
caption
elementcolgroup
elementcol
elementtbody
elementthead
elementtfoot
elementtr
elementtd
elementth
elementtd
and th
elementsform
elementlabel
elementinput
element
type
attribute
type=hidden
)type=text
) state and Search state (type=search
)type=tel
)type=url
)type=email
)type=password
)type=datetime
)type=date
)type=month
)type=week
)type=time
)type=datetime-local
)type=number
)type=range
)type=color
)type=checkbox
)type=radio
)type=file
)type=submit
)type=image
)type=reset
)type=button
)input
element attributes
maxlength
and minlength
attributessize
attributereadonly
attributerequired
attributemultiple
attributepattern
attributemin
and max
attributesstep
attributelist
attributeplaceholder
attributeinput
element APIsbutton
elementselect
elementdatalist
elementoptgroup
elementoption
elementtextarea
elementkeygen
elementoutput
elementprogress
elementmeter
elementfieldset
elementlegend
elementname
attributedirname
attributemaxlength
attributeminlength
attributedisabled
attributeautofocus
attributeautocomplete
attributeWindow
object
Window
objectWindowProxy
objectmultipart/x-mixed-replace
resourceshidden
attributebutton
elementdetails
elementinput
element as a text entry widgetinput
element as domain-specific widgetsinput
element as a range controlinput
element as a color wellinput
element as a checkbox and radio button widgetsinput
element as a file upload controlinput
element as a buttonmarquee
elementmeter
elementprogress
elementselect
elementtextarea
elementkeygen
elementThis section is non-normative.
The World Wide Web's markup language has always been HTML. HTML was primarily designed as a language for semantically describing scientific documents, although its general design and adaptations over the years have enabled it to be used to describe a number of other types of documents.
The main area that has not been adequately addressed by HTML is a vague subject referred to as Web Applications. This specification attempts to rectify this, while at the same time updating the HTML specifications to address issues raised in the past few years.
This section is non-normative.
This specification is intended for authors of documents and scripts that use the features defined in this specification, implementors of tools that operate on pages that use the features defined in this specification, and individuals wishing to establish the correctness of documents or implementations with respect to the requirements of this specification.
This document is probably not suited to readers who do not already have at least a passing familiarity with Web technologies, as in places it sacrifices clarity for precision, and brevity for completeness. More approachable tutorials and authoring guides can provide a gentler introduction to the topic.
In particular, familiarity with the basics of DOM is necessary for a complete understanding of some of the more technical parts of this specification. An understanding of Web IDL, HTTP, XML, Unicode, character encodings, JavaScript, and CSS will also be helpful in places but is not essential.
This section is non-normative.
This specification is limited to providing a semantic-level markup language and associated semantic-level scripting APIs for authoring accessible pages on the Web ranging from static documents to dynamic applications.
The scope of this specification does not include providing mechanisms for media-specific customization of presentation (although default rendering rules for Web browsers are included at the end of this specification, and several mechanisms for hooking into CSS are provided as part of the language).
The scope of this specification is not to describe an entire operating system. In particular, hardware configuration software, image manipulation tools, and applications that users would be expected to use with high-end workstations on a daily basis are out of scope. In terms of applications, this specification is targeted specifically at applications that would be expected to be used by users on an occasional basis, or regularly but from disparate locations, with low CPU requirements. Examples of such applications include online purchasing systems, searching systems, games (especially multiplayer online games), public telephone books or address books, communications software (e-mail clients, instant messaging clients, discussion software), document editing software, etc.
This section is non-normative.
For its first five years (1990-1995), HTML went through a number of revisions and experienced a number of extensions, primarily hosted first at CERN, and then at the IETF.
With the creation of the W3C, HTML's development changed venue again. A first abortive attempt at extending HTML in 1995 known as HTML 3.0 then made way to a more pragmatic approach known as HTML 3.2, which was completed in 1997. HTML4 quickly followed later that same year.
The following year, the W3C membership decided to stop evolving HTML and instead begin work on an XML-based equivalent, called XHTML. This effort started with a reformulation of HTML4 in XML, known as XHTML 1.0, which added no new features except the new serialization, and which was completed in 2000. After XHTML 1.0, the W3C's focus turned to making it easier for other working groups to extend XHTML, under the banner of XHTML Modularization. In parallel with this, the W3C also worked on a new language that was not compatible with the earlier HTML and XHTML languages, calling it XHTML2.
Around the time that HTML's evolution was stopped in 1998, parts of the API for HTML developed by browser vendors were specified and published under the name DOM Level 1 (in 1998) and DOM Level 2 Core and DOM Level 2 HTML (starting in 2000 and culminating in 2003). These efforts then petered out, with some DOM Level 3 specifications published in 2004 but the working group being closed before all the Level 3 drafts were completed.
In 2003, the publication of XForms, a technology which was positioned as the next generation of Web forms, sparked a renewed interest in evolving HTML itself, rather than finding replacements for it. This interest was borne from the realization that XML's deployment as a Web technology was limited to entirely new technologies (like RSS and later Atom), rather than as a replacement for existing deployed technologies (like HTML).
A proof of concept to show that it was possible to extend HTML4's forms to provide many of the features that XForms 1.0 introduced, without requiring browsers to implement rendering engines that were incompatible with existing HTML Web pages, was the first result of this renewed interest. At this early stage, while the draft was already publicly available, and input was already being solicited from all sources, the specification was only under Opera Software's copyright.
The idea that HTML's evolution should be reopened was tested at a W3C workshop in 2004, where some of the principles that underlie the HTML5 work (described below), as well as the aforementioned early draft proposal covering just forms-related features, were presented to the W3C jointly by Mozilla and Opera. The proposal was rejected on the grounds that the proposal conflicted with the previously chosen direction for the Web's evolution; the W3C staff and membership voted to continue developing XML-based replacements instead.
Shortly thereafter, Apple, Mozilla, and Opera jointly announced their intent to continue working on the effort under the umbrella of a new venue called the WHATWG. A public mailing list was created, and the draft was moved to the WHATWG site. The copyright was subsequently amended to be jointly owned by all three vendors, and to allow reuse of the specification.
The WHATWG was based on several core principles, in particular that technologies need to be backwards compatible, that specifications and implementations need to match even if this means changing the specification rather than the implementations, and that specifications need to be detailed enough that implementations can achieve complete interoperability without reverse-engineering each other.
The latter requirement in particular required that the scope of the HTML5 specification include what had previously been specified in three separate documents: HTML4, XHTML1, and DOM2 HTML. It also meant including significantly more detail than had previously been considered the norm.
In 2006, the W3C indicated an interest to participate in the development of HTML5 after all, and in 2007 formed a working group chartered to work with the WHATWG on the development of the HTML5 specification. Apple, Mozilla, and Opera allowed the W3C to publish the specification under the W3C copyright, while keeping a version with the less restrictive license on the WHATWG site.
For a number of years, both groups then worked together under the same editor: Ian Hickson. In 2011, the groups came to the conclusion that they had different goals: the W3C wanted to draw a line in the sand for features for a HTML5 Recommendation, while the WHATWG wanted to continue working on a Living Standard for HTML, continuously maintaining the specification and adding new features. In mid 2012, a new editing team was introduced at the W3C to take care of creating a HTML5 Recommendation and prepare a Working Draft for the next HTML version.
Since then, the W3C HTML WG has been cherry picking patches from the WHATWG that resolved bugs registered on the W3C HTML specification or more accurately represented implemented reality in UAs. At time of publication of this document, patches from the WHATWG HTML specification have been merged until revision 8152 inclusive. The W3C HTML editors have also added patches that resulted from discussions and decisions made by the W3C HTML WG as well a bug fixes from bugs not shared by the WHATWG.
A separate document is published to document the differences between the HTML specified in this document and the language described in the HTML4 specification. [HTMLDIFF]
This section is non-normative.
It must be admitted that many aspects of HTML appear at first glance to be nonsensical and inconsistent.
HTML, its supporting DOM APIs, as well as many of its supporting technologies, have been developed over a period of several decades by a wide array of people with different priorities who, in many cases, did not know of each other's existence.
Features have thus arisen from many sources, and have not always been designed in especially consistent ways. Furthermore, because of the unique characteristics of the Web, implementation bugs have often become de-facto, and now de-jure, standards, as content is often unintentionally written in ways that rely on them before they can be fixed.
Despite all this, efforts have been made to adhere to certain design goals. These are described in the next few subsections.
This section is non-normative.
To avoid exposing Web authors to the complexities of multithreading, the HTML and DOM APIs are designed such that no script can ever detect the simultaneous execution of other scripts. Even with workers, the intent is that the behavior of implementations can be thought of as completely serializing the execution of all scripts in all browsing contexts.
The navigator.yieldForStorageUpdates()
method, in
this model, is equivalent to allowing other scripts to run while the calling script is
blocked.
This section is non-normative.
This specification interacts with and relies on a wide variety of other specifications. In certain circumstances, unfortunately, conflicting needs have led to this specification violating the requirements of these other specifications. Whenever this has occurred, the transgressions have each been noted as a "willful violation", and the reason for the violation has been noted.
This section is non-normative.
HTML has a wide number of extensibility mechanisms that can be used for adding semantics in a safe manner:
class
attribute to extend elements,
effectively creating their own elements, while using the most applicable existing "real" HTML
element, so that browsers and other tools that don't know of the extension can still support it
somewhat well. This is the tack used by microformats, for example.data-*=""
attributes. These are guaranteed to
never be touched by browsers, and allow scripts to include data on HTML elements that scripts can
then look for and process.<meta name="" content="">
mechanism to
include page-wide metadata by registering extensions to the
predefined set of metadata names.rel=""
mechanism to annotate
links with specific meanings by registering extensions to
the predefined set of link types. This is also used by microformats. Additionally,
absolute URLs that do not contain any non-ASCII characters, nor
characters in the range U+0041 (LATIN CAPITAL LETTER A) through
U+005A (LATIN CAPITAL LETTER Z) (inclusive), may be used as link
types.<script type="">
mechanism with a custom type, for further handling by inline or server-side scripts.embed
element. This is how Flash works.This section is non-normative.
This specification defines an abstract language for describing documents and applications, and some APIs for interacting with in-memory representations of resources that use this language.
The in-memory representation is known as "DOM HTML", or "the DOM" for short.
There are various concrete syntaxes that can be used to transmit resources that use this abstract language, two of which are defined in this specification.
The first such concrete syntax is the HTML syntax. This is the format suggested for most
authors. It is compatible with most legacy Web browsers. If a document is transmitted with the
text/html
MIME type, then it will be processed as an HTML document by
Web browsers. This specification defines version 5.0 of the HTML syntax, known as "HTML 5".
The second concrete syntax is the XHTML syntax, which is an application of XML. When a document
is transmitted with an XML MIME type, such as application/xhtml+xml
,
then it is treated as an XML document by Web browsers, to be parsed by an XML processor. Authors
are reminded that the processing for XML and HTML differs; in particular, even minor syntax errors
will prevent a document labeled as XML from being rendered fully, whereas they would be ignored in
the HTML syntax. This specification defines version 5.0 of the XHTML syntax, known as
"XHTML 5".
The DOM, the HTML syntax, and the XHTML syntax cannot all represent the same content. For
example, namespaces cannot be represented using the HTML syntax, but they are supported in the DOM
and in the XHTML syntax. Similarly, documents that use the noscript
feature can be
represented using the HTML syntax, but cannot be represented with the DOM or in the XHTML syntax.
Comments that contain the string "-->
" can only be represented in the
DOM, not in the HTML and XHTML syntaxes.
This section is non-normative.
This specification is divided into the following major sections:
There are also some appendices, listing obsolete features and IANA considerations, and several indices.
This specification should be read like all other specifications. First, it should be read cover-to-cover, multiple times. Then, it should be read backwards at least once. Then it should be read by picking random sections from the contents list and following all the cross-references.
As described in the conformance requirements section below, this specification describes conformance criteria for a variety of conformance classes. In particular, there are conformance requirements that apply to producers, for example authors and the documents they create, and there are conformance requirements that apply to consumers, for example Web browsers. They can be distinguished by what they are requiring: a requirement on a producer states what is allowed, while a requirement on a consumer states how software is to act.
For example, "the foo
attribute's value must be a valid
integer" is a requirement on producers, as it lays out the allowed values; in contrast,
the requirement "the foo
attribute's value must be parsed using the
rules for parsing integers" is a requirement on consumers, as it describes how to
process the content.
Requirements on producers have no bearing whatsoever on consumers.
Continuing the above example, a requirement stating that a particular attribute's value is constrained to being a valid integer emphatically does not imply anything about the requirements on consumers. It might be that the consumers are in fact required to treat the attribute as an opaque string, completely unaffected by whether the value conforms to the requirements or not. It might be (as in the previous example) that the consumers are required to parse the value using specific rules that define how invalid (non-numeric in this case) values are to be processed.
This is a definition, requirement, or explanation.
This is a note.
This is an example.
This is an open issue.
This is a warning.
interface Example { // this is an IDL definition };
method
( [ optionalArgument ] )This is a note to authors describing the usage of an interface.
/* this is a CSS fragment */
The defining instance of a term is marked up like this. Uses of that term are marked up like this or like this.
The defining instance of an element, attribute, or API is marked up like this
. References to that element, attribute, or API are marked
up like this
.
Other code fragments are marked up like this
.
Variables are marked up like this.
In an algorithm, steps in synchronous sections are marked with ⌛.
In some cases, requirements are given in the form of lists with conditions and corresponding requirements. In such cases, the requirements that apply to a condition are always the first set of requirements that follow the condition, even in the case of there being multiple sets of conditions for those requirements. Such cases are presented as follows:
This section is non-normative.
Some features of HTML trade user convenience for a measure of user privacy.
In general, due to the Internet's architecture, a user can be distinguished from another by the user's IP address. IP addresses do not perfectly match to a user; as a user moves from device to device, or from network to network, their IP address will change; similarly, NAT routing, proxy servers, and shared computers enable packets that appear to all come from a single IP address to actually map to multiple users. Technologies such as onion routing can be used to further anonymize requests so that requests from a single user at one node on the Internet appear to come from many disparate parts of the network.
However, the IP address used for a user's requests is not the only mechanism by which a user's requests could be related to each other. Cookies, for example, are designed specifically to enable this, and are the basis of most of the Web's session features that enable you to log into a site with which you have an account.
There are other mechanisms that are more subtle. Certain characteristics of a user's system can be used to distinguish groups of users from each other; by collecting enough such information, an individual user's browser's "digital fingerprint" can be computed, which can be as good, if not better, as an IP address in ascertaining which requests are from the same user.
Grouping requests in this manner, especially across multiple sites, can be used for both benign (and even arguably positive) purposes, as well as for malevolent purposes. An example of a reasonably benign purpose would be determining whether a particular person seems to prefer sites with dog illustrations as opposed to sites with cat illustrations (based on how often they visit the sites in question) and then automatically using the preferred illustrations on subsequent visits to participating sites. Malevolent purposes, however, could include governments combining information such as the person's home address (determined from the addresses they use when getting driving directions on one site) with their apparent political affiliations (determined by examining the forum sites that they participate in) to determine whether the person should be prevented from voting in an election.
Since the malevolent purposes can be remarkably evil, user agent implementors are encouraged to consider how to provide their users with tools to minimize leaking information that could be used to fingerprint a user.
Unfortunately, as the first paragraph in this section implies, sometimes there is great benefit to be derived from exposing the very information that can also be used for fingerprinting purposes, so it's not as easy as simply blocking all possible leaks. For instance, the ability to log into a site to post under a specific identity requires that the user's requests be identifiable as all being from the same user, more or less by definition. More subtly, though, information such as how wide text is, which is necessary for many effects that involve drawing text onto a canvas (e.g. any effect that involves drawing a border around the text) also leaks information that can be used to group a user's requests. (In this case, by potentially exposing, via a brute force search, which fonts a user has installed, information which can vary considerably from user to user.)
Features in this specification which can be used to
fingerprint the user are marked as this paragraph is.
Other features in the platform can be used for the same purpose, though, including, though not limited to:
Screen
object. [MQ] [CSSOMVIEW]This section is non-normative.
A basic HTML document looks like this:
<!DOCTYPE html> <html> <head> <title>Sample page</title> </head> <body> <h1>Sample page</h1> <p>This is a <a href="demo.html">simple</a> sample.</p> <!-- this is a comment --> </body> </html>
HTML documents consist of a tree of elements and text. Each element is denoted in the source by
a start tag, such as "<body>
", and
an end tag, such as "</body>
".
(Certain start tags and end tags can in certain cases be omitted and are implied by other tags.)
Tags have to be nested such that elements are all completely within each other, without overlapping:
<p>This is <em>very <strong>wrong</em>!</strong></p>
<p>This <em>is <strong>correct</strong>.</em></p>
This specification defines a set of elements that can be used in HTML, along with rules about the ways in which the elements can be nested.
Elements can have attributes, which control how the elements work. In the example below, there
is a hyperlink, formed using the a
element and its href
attribute:
<a href="demo.html">simple</a>
Attributes are placed inside the start tag, and consist
of a name and a value, separated by an "=
" character.
The attribute value can remain unquoted if it doesn't contain space characters or any of "
'
`
=
<
or
>
. Otherwise, it has to be quoted using either single or double quotes.
The value, along with the "=
" character, can be omitted altogether if the
value is the empty string.
<!-- empty attributes --> <input name=address disabled> <input name=address disabled=""> <!-- attributes with a value --> <input name=address maxlength=200> <input name=address maxlength='200'> <input name=address maxlength="200">
HTML user agents (e.g. Web browsers) then parse this markup, turning it into a DOM (Document Object Model) tree. A DOM tree is an in-memory representation of a document.
DOM trees contain several kinds of nodes, in particular a DocumentType
node,
Element
nodes, Text
nodes, Comment
nodes, and in some cases
ProcessingInstruction
nodes.
The markup snippet at the top of this section would be turned into the following DOM tree:
html
html
The root element of this tree is the html
element, which is the
element always found at the root of HTML documents. It contains two elements, head
and body
, as well as a Text
node between them.
There are many more Text
nodes in the DOM tree than one would initially expect,
because the source contains a number of spaces (represented here by "␣") and line breaks
("⏎") that all end up as Text
nodes in the DOM. However, for historical
reasons not all of the spaces and line breaks in the original markup appear in the DOM. In
particular, all the whitespace before head
start tag ends up being dropped silently,
and all the whitespace after the body
end tag ends up placed at the end of the
body
.
The head
element contains a title
element, which itself contains a
Text
node with the text "Sample page". Similarly, the body
element
contains an h1
element, a p
element, and a comment.
This DOM tree can be manipulated from scripts in the page. Scripts (typically in JavaScript)
are small programs that can be embedded using the script
element or using event
handler content attributes. For example, here is a form with a script that sets the value
of the form's output
element to say "Hello World":
<form name="main"> Result: <output name="result"></output> <script> document.forms.main.elements.result.value = 'Hello World'; </script> </form>
Each element in the DOM tree is represented by an object, and these objects have APIs so that
they can be manipulated. For instance, a link (e.g. the a
element in the tree above)
can have its "href
" attribute changed in several
ways:
var a = document.links[0]; // obtain the first link in the document a.href = 'sample.html'; // change the destination URL of the link a.protocol = 'https'; // change just the scheme part of the URL a.setAttribute('href', 'http://example.com/'); // change the content attribute directly
Since DOM trees are used as the way to represent HTML documents when they are processed and presented by implementations (especially interactive implementations like Web browsers), this specification is mostly phrased in terms of DOM trees, instead of the markup described above.
HTML documents represent a media-independent description of interactive content. HTML documents might be rendered to a screen, or through a speech synthesizer, or on a braille display. To influence exactly how such rendering takes place, authors can use a styling language such as CSS.
In the following example, the page has been made yellow-on-blue using CSS.
<!DOCTYPE html> <html> <head> <title>Sample styled page</title> <style> body { background: navy; color: yellow; } </style> </head> <body> <h1>Sample styled page</h1> <p>This page is just a demo.</p> </body> </html>
For more details on how to use HTML, authors are encouraged to consult tutorials and guides. Some of the examples included in this specification might also be of use, but the novice author is cautioned that this specification, by necessity, defines the language with a level of detail that might be difficult to understand at first.
This section is non-normative.
When HTML is used to create interactive sites, care needs to be taken to avoid introducing vulnerabilities through which attackers can compromise the integrity of the site itself or of the site's users.
A comprehensive study of this matter is beyond the scope of this document, and authors are strongly encouraged to study the matter in more detail. However, this section attempts to provide a quick introduction to some common pitfalls in HTML application development.
The security model of the Web is based on the concept of "origins", and correspondingly many of the potential attacks on the Web involve cross-origin actions. [ORIGIN]
When accepting untrusted input, e.g. user-generated content such as text comments, values in URL parameters, messages from third-party sites, etc, it is imperative that the data be validated before use, and properly escaped when displayed. Failing to do this can allow a hostile user to perform a variety of attacks, ranging from the potentially benign, such as providing bogus user information like a negative age, to the serious, such as running scripts every time a user looks at a page that includes the information, potentially propagating the attack in the process, to the catastrophic, such as deleting all data in the server.
When writing filters to validate user input, it is imperative that filters always be whitelist-based, allowing known-safe constructs and disallowing all other input. Blacklist-based filters that disallow known-bad inputs and allow everything else are not secure, as not everything that is bad is yet known (for example, because it might be invented in the future).
For example, suppose a page looked at its URL's query string to determine what to display, and the site then redirected the user to that page to display a message, as in:
<ul> <li><a href="message.cgi?say=Hello">Say Hello</a> <li><a href="message.cgi?say=Welcome">Say Welcome</a> <li><a href="message.cgi?say=Kittens">Say Kittens</a> </ul>
If the message was just displayed to the user without escaping, a hostile attacker could then craft a URL that contained a script element:
http://example.com/message.cgi?say=%3Cscript%3Ealert%28%27Oh%20no%21%27%29%3C/script%3E
If the attacker then convinced a victim user to visit this page, a script of the attacker's choosing would run on the page. Such a script could do any number of hostile actions, limited only by what the site offers: if the site is an e-commerce shop, for instance, such a script could cause the user to unknowingly make arbitrarily many unwanted purchases.
This is called a cross-site scripting attack.
There are many constructs that can be used to try to trick a site into executing code. Here are some that authors are encouraged to consider when writing whitelist filters:
img
, it is important to whitelist
any provided attributes as well. If one allowed all attributes then an attacker could, for
instance, use the onload
attribute to run arbitrary
script.javascript:
", but user agents can
implement (and indeed, have historically implemented) others.base
element to be inserted means any script
elements
in the page with relative links can be hijacked, and similarly that any form submissions can
get redirected to a hostile site.If a site allows a user to make form submissions with user-specific side-effects, for example posting messages on a forum under the user's name, making purchases, or applying for a passport, it is important to verify that the request was made by the user intentionally, rather than by another site tricking the user into making the request unknowingly.
This problem exists because HTML forms can be submitted to other origins.
Sites can prevent such attacks by populating forms with user-specific hidden tokens, or by
checking Origin
headers on all requests.
A page that provides users with an interface to perform actions that the user might not wish to perform needs to be designed so as to avoid the possibility that users can be tricked into activating the interface.
One way that a user could be so tricked is if a hostile site places the victim site in a
small iframe
and then convinces the user to click, for instance by having the user
play a reaction game. Once the user is playing the game, the hostile site can quickly position
the iframe under the mouse cursor just as the user is about to click, thus tricking the user
into clicking the victim site's interface.
To avoid this, sites that do not expect to be used in frames are encouraged to only enable
their interface if they detect that they are not in a frame (e.g. by comparing the window
object to the value of the top
attribute).
This section is non-normative.
Scripts in HTML have "run-to-completion" semantics, meaning that the browser will generally run the script uninterrupted before doing anything else, such as firing further events or continuing to parse the document.
On the other hand, parsing of HTML files happens asynchronously and incrementally, meaning that the parser can pause at any point to let scripts run. This is generally a good thing, but it does mean that authors need to be careful to avoid hooking event handlers after the events could have possibly fired.
There are two techniques for doing this reliably: use event handler content attributes, or create the element and add the event handlers in the same script. The latter is safe because, as mentioned earlier, scripts are run to completion before further events can fire.
One way this could manifest itself is with img
elements and the load
event. The event could fire as soon as the element has been
parsed, especially if the image has already been cached (which is common).
Here, the author uses the onload
handler on an
img
element to catch the load
event:
<img src="games.png" alt="Games" onload="gamesLogoHasLoaded(event)">
If the element is being added by script, then so long as the event handlers are added in the same script, the event will still not be missed:
<script> var img = new Image(); img.src = 'games.png'; img.alt = 'Games'; img.onload = gamesLogoHasLoaded; // img.addEventListener('load', gamesLogoHasLoaded, false); // would work also </script>
However, if the author first created the img
element and then in a separate
script added the event listeners, there's a chance that the load
event would be fired in between, leading it to be missed:
<!-- Do not use this style, it has a race condition! --> <img id="games" src="games.png" alt="Games"> <!-- the 'load' event might fire here while the parser is taking a break, in which case you will not see it! --> <script> var img = document.getElementById('games'); img.onload = gamesLogoHasLoaded; // might never fire! </script>
This section is non-normative.
Authors are encouraged to make use of conformance checkers (also known as validators) to catch common mistakes. The W3C provides a number of online validation services, including the Nu Markup Validation Service.
This section is non-normative.
Unlike previous versions of the HTML specification, this specification defines in some detail the required processing for invalid documents as well as valid documents.
However, even though the processing of invalid content is in most cases well-defined, conformance requirements for documents are still important: in practice, interoperability (the situation in which all implementations process particular content in a reliable and identical or equivalent way) is not the only goal of document conformance requirements. This section details some of the more common reasons for still distinguishing between a conforming document and one with errors.
This section is non-normative.
The majority of presentational features from previous versions of HTML are no longer allowed. Presentational markup in general has been found to have a number of problems:
While it is possible to use presentational markup in a way that provides users of assistive technologies (ATs) with an acceptable experience (e.g. using ARIA), doing so is significantly more difficult than doing so when using semantically-appropriate markup. Furthermore, even using such techniques doesn't help make pages accessible for non-AT non-graphical users, such as users of text-mode browsers.
Using media-independent markup, on the other hand, provides an easy way for documents to be authored in such a way that they work for more users (e.g. text browsers).
It is significantly easier to maintain a site written in such a way that the markup is
style-independent. For example, changing the color of a site that uses
<font color="">
throughout requires changes across the entire site, whereas
a similar change to a site based on CSS can be done by changing a single file.
Presentational markup tends to be much more redundant, and thus results in larger document sizes.
For those reasons, presentational markup has been removed from HTML in this version. This change should not come as a surprise; HTML4 deprecated presentational markup many years ago and provided a mode (HTML4 Transitional) to help authors move away from presentational markup; later, XHTML 1.1 went further and obsoleted those features altogether.
The only remaining presentational markup features in HTML are the style
attribute and the style
element. Use of the style
attribute is somewhat discouraged in production environments, but
it can be useful for rapid prototyping (where its rules can be directly moved into a separate
style sheet later) and for providing specific styles in unusual cases where a separate style sheet
would be inconvenient. Similarly, the style
element can be useful in syndication or
for page-specific styles, but in general an external style sheet is likely to be more convenient
when the styles apply to multiple pages.
It is also worth noting that some elements that were previously presentational have been
redefined in this specification to be media-independent: b
, i
,
hr
, s
, small
, and u
.
This section is non-normative.
The syntax of HTML is constrained to avoid a wide variety of problems.
Certain invalid syntax constructs, when parsed, result in DOM trees that are highly unintuitive.
To allow user agents to be used in controlled environments without having to implement the more bizarre and convoluted error handling rules, user agents are permitted to fail whenever encountering a parse error.
Some error-handling behavior, such as the behavior for the <table><hr>...
example mentioned above, are incompatible with streaming
user agents (user agents that process HTML files in one pass, without storing state). To avoid
interoperability problems with such user agents, any syntax resulting in such behavior is
considered invalid.
When a user agent based on XML is connected to an HTML parser, it is possible that certain invariants that XML enforces, such as comments never containing two consecutive hyphens, will be violated by an HTML file. Handling this can require that the parser coerce the HTML DOM into an XML-compatible infoset. Most syntax constructs that require such handling are considered invalid.
Certain syntax constructs can result in disproportionally poor performance. To discourage the use of such constructs, they are typically made non-conforming.
For example, the following markup results in poor performance, since all the unclosed
i
elements have to be reconstructed in each paragraph, resulting in progressively
more elements in each paragraph:
<p><i>He dreamt. <p><i>He dreamt that he ate breakfast. <p><i>Then lunch. <p><i>And finally dinner.
The resulting DOM for this fragment would be:
There are syntax constructs that, for historical reasons, are relatively fragile. To help reduce the number of users who accidentally run into such problems, they are made non-conforming.
For example, the parsing of certain named character references in attributes happens even with the closing semicolon being omitted. It is safe to include an ampersand followed by letters that do not form a named character reference, but if the letters are changed to a string that does form a named character reference, they will be interpreted as that character instead.
In this fragment, the attribute's value is "?bill&ted
":
<a href="?bill&ted">Bill and Ted</a>
In the following fragment, however, the attribute's value is actually "?art©
", not the intended "?art©
",
because even without the final semicolon, "©
" is handled the same
as "©
" and thus gets interpreted as "©
":
<a href="?art©">Art and Copy</a>
To avoid this problem, all named character references are required to end with a semicolon, and uses of named character references without a semicolon are flagged as errors.
Thus, the correct way to express the above cases is as follows:
<a href="?bill&ted">Bill and Ted</a> <!-- &ted is ok, since it's not a named character reference -->
<a href="?art&copy">Art and Copy</a> <!-- the & has to be escaped, since © is a named character reference -->
Certain syntax constructs are known to cause especially subtle or serious problems in legacy user agents, and are therefore marked as non-conforming to help authors avoid them.
For example, this is why the "`" (U+0060) character is not allowed in unquoted attributes. In certain legacy user agents, it is sometimes treated as a quote character.
Another example of this is the DOCTYPE, which is required to trigger no-quirks mode, because the behavior of legacy user agents in quirks mode is often largely undocumented.
Certain restrictions exist purely to avoid known security problems.
For example, the restriction on using UTF-7 exists purely to avoid authors falling prey to a known cross-site-scripting attack using UTF-7. [UTF7]
Markup where the author's intent is very unclear is often made non-conforming. Correcting these errors early makes later maintenance easier.
When a user makes a simple typo, it is helpful if the error can be caught early, as this can save the author a lot of debugging time. This specification therefore usually considers it an error to use element names, attribute names, and so forth, that do not match the names defined in this specification.
For example, if the author typed <capton>
instead of
<caption>
, this would be flagged as an error and the author could correct the
typo immediately.
In order to allow the language syntax to be extended in the future, certain otherwise harmless features are disallowed.
For example, "attributes" in end tags are ignored currently, but they are invalid, in case a future change to the language makes use of that syntax feature without conflicting with already-deployed (and valid!) content.
Some authors find it helpful to be in the practice of always quoting all attributes and always including all optional tags, preferring the consistency derived from such custom over the minor benefits of terseness afforded by making use of the flexibility of the HTML syntax. To aid such authors, conformance checkers can provide modes of operation wherein such conventions are enforced.
This section is non-normative.
Beyond the syntax of the language, this specification also places restrictions on how elements and attributes can be specified. These restrictions are present for similar reasons:
To avoid misuse of elements with defined meanings, content models are defined that restrict how elements can be nested when such nestings would be of dubious value.
For example, this specification disallows nesting a section
element inside a kbd
element, since it is highly unlikely for an author to indicate
that an entire section should be keyed in.
Similarly, to draw the author's attention to mistakes in the use of elements, clear contradictions in the semantics expressed are also considered conformance errors.
In the fragments below, for example, the semantics are nonsensical: a separator cannot simultaneously be a cell, nor can a radio button be a progress bar.
<hr role="cell">
<input type=radio role=progressbar>
Another example is the restrictions on the content models of the
ul
element, which only allows li
element children. Lists by definition
consist just of zero or more list items, so if a ul
element contains something
other than an li
element, it's not clear what was meant.
Certain elements have default styles or behaviors that make certain combinations likely to lead to confusion. Where these have equivalent alternatives without this problem, the confusing combinations are disallowed.
For example, div
elements are rendered as block boxes, and
span
elements as inline boxes. Putting a block box in an inline box is
unnecessarily confusing; since either nesting just div
elements, or nesting just
span
elements, or nesting span
elements inside div
elements all serve the same purpose as nesting a div
element in a span
element, but only the latter involves a block box in an inline box, the latter combination is
disallowed.
Another example would be the way interactive content cannot be
nested. For example, a button
element cannot contain a textarea
element. This is because the default behavior of such nesting interactive elements would be
highly confusing to users. Instead of nesting these elements, they can be placed side by
side.
Sometimes, something is disallowed because allowing it would likely cause author confusion.
For example, setting the disabled
attribute to the value "false
" is disallowed, because despite the
appearance of meaning that the element is enabled, it in fact means that the element is
disabled (what matters for implementations is the presence of the attribute, not its
value).
Some conformance errors simplify the language that authors need to learn.
For example, the area
element's shape
attribute, despite accepting both circ
and circle
values in practice as synonyms, disallows
the use of the circ
value, so as to simplify
tutorials and other learning aids. There would be no benefit to allowing both, but it would
cause extra confusion when teaching the language.
Certain elements are parsed in somewhat eccentric ways (typically for historical reasons), and their content model restrictions are intended to avoid exposing the author to these issues.
For example, a form
element isn't allowed inside phrasing content,
because when parsed as HTML, a form
element's start tag will imply a
p
element's end tag. Thus, the following markup results in two paragraphs, not one:
<p>Welcome. <form><label>Name:</label> <input></form>
It is parsed exactly like the following:
<p>Welcome. </p><form><label>Name:</label> <input></form>
Some errors are intended to help prevent script problems that would be hard to debug.
This is why, for instance, it is non-conforming to have two id
attributes with the same value. Duplicate IDs lead to the wrong
element being selected, with sometimes disastrous effects whose cause is hard to determine.
Some constructs are disallowed because historically they have been the cause of a lot of wasted authoring time, and by encouraging authors to avoid making them, authors can save time in future efforts.
For example, a script
element's src
attribute causes the element's contents to be ignored.
However, this isn't obvious, especially if the element's contents appear to be executable script
— which can lead to authors spending a lot of time trying to debug the inline script
without realizing that it is not executing. To reduce this problem, this specification makes it
non-conforming to have executable script in a script
element when the src
attribute is present. This means that authors who are
validating their documents are less likely to waste time with this kind of mistake.
Some authors like to write files that can be interpreted as both XML and HTML with similar results. Though this practice is discouraged in general due to the myriad of subtle complications involved (especially when involving scripting, styling, or any kind of automated serialization), this specification has a few restrictions intended to at least somewhat mitigate the difficulties. This makes it easier for authors to use this as a transitionary step when migrating between HTML and XHTML.
For example, there are somewhat complicated rules surrounding the lang
and xml:lang
attributes
intended to keep the two synchronized.
Another example would be the restrictions on the values of xmlns
attributes in the HTML serialization, which are intended to ensure that
elements in conforming documents end up in the same namespaces whether processed as HTML or
XML.
As with the restrictions on the syntax intended to allow for new syntax in future revisions of the language, some restrictions on the content models of elements and values of attributes are intended to allow for future expansion of the HTML vocabulary.
For example, limiting the values of the target
attribute that start with an "_" (U+005F) character to only specific predefined values allows new predefined values to be introduced
at a future time without conflicting with author-defined values.
Certain restrictions are intended to support the restrictions made by other specifications.
For example, requiring that attributes that take media queries use only valid media queries reinforces the importance of following the conformance rules of that specification.
This section is non-normative.
The following documents might be of interest to readers of this specification.
This Architectural Specification provides authors of specifications, software developers, and content developers with a common reference for interoperable text manipulation on the World Wide Web, building on the Universal Character Set, defined jointly by the Unicode Standard and ISO/IEC 10646. Topics addressed include use of the terms 'character', 'encoding' and 'string', a reference processing model, choice and identification of character encodings, character escaping, and string indexing.
Because Unicode contains such a large number of characters and incorporates the varied writing systems of the world, incorrect usage can expose programs or systems to possible security attacks. This is especially important as more and more products are internationalized. This document describes some of the security considerations that programmers, system analysts, standards developers, and users should take into account, and provides specific recommendations to reduce the risk of problems.
Web Content Accessibility Guidelines (WCAG) 2.0 covers a wide range of recommendations for making Web content more accessible. Following these guidelines will make content accessible to a wider range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning disabilities, cognitive limitations, limited movement, speech disabilities, photosensitivity and combinations of these. Following these guidelines will also often make your Web content more usable to users in general.
This specification provides guidelines for designing Web content authoring tools that are more accessible for people with disabilities. An authoring tool that conforms to these guidelines will promote accessibility by providing an accessible user interface to authors with disabilities as well as by enabling, supporting, and promoting the production of accessible Web content by all authors.
This document provides guidelines for designing user agents that lower barriers to Web accessibility for people with disabilities. User agents include browsers and other types of software that retrieve and render Web content. A user agent that conforms to these guidelines will promote accessibility through its own user interface and through other internal facilities, including its ability to communicate with other technologies (especially assistive technologies). Furthermore, all users, not just users with disabilities, should find conforming user agents to be more usable.
A document that uses polyglot markup is a document that is a stream of bytes that parses into identical document trees (with the exception of the xmlns attribute on the root element) when processed as HTML and when processed as XML. Polyglot markup that meets a well defined set of constraints is interpreted as compatible, regardless of whether they are processed as HTML or as XHTML, per the HTML5 specification. Polyglot markup uses a specific DOCTYPE, namespace declarations, and a specific case — normally lower case but occasionally camel case — for element and attribute names. Polyglot markup uses lower case for certain attribute values. Further constraints include those on empty elements, named entity references, and the use of scripts and style.
This is draft documentation mapping HTML elements and attributes to accessibility API Roles, States and Properties on a variety of platforms. It provides recommendations on deriving the accessible names and descriptions for HTML elements. It also provides accessible feature implementation examples.
This specification refers to both HTML and XML attributes and IDL attributes, often in the same context. When it is not clear which is being referred to, they are referred to as content attributes for HTML and XML attributes, and IDL attributes for those defined on IDL interfaces. Similarly, the term "properties" is used for both JavaScript object properties and CSS properties. When these are ambiguous they are qualified as object properties and CSS properties respectively.
Generally, when the specification states that a feature applies to the HTML syntax or the XHTML syntax, it also includes the other. When a feature specifically only applies to one of the two languages, it is called out by explicitly stating that it does not apply to the other format, as in "for HTML, ... (this does not apply to XHTML)".
This specification uses the term document to refer to any use of HTML,
ranging from short static documents to long essays or reports with rich multimedia, as well as to
fully-fledged interactive applications. The term is used to refer both to Document
objects and their descendant DOM trees, and to serialized byte streams using the HTML syntax or XHTML syntax, depending
on context.
In the context of the DOM structures, the terms HTML
document and XML document are used as defined in the DOM
specification, and refer specifically to two different modes that Document
objects
can find themselves in. [DOM] (Such uses are always hyperlinked to their
definition.)
In the context of byte streams, the term HTML document refers to resources labeled as
text/html
, and the term XML document refers to resources labeled with an XML
MIME type.
The term XHTML document is used to refer to both Document
s in the XML document mode that contains element nodes in the HTML
namespace, and byte streams labeled with an XML MIME type that contain
elements from the HTML namespace, depending on context.
For simplicity, terms such as shown, displayed, and visible might sometimes be used when referring to the way a document is rendered to the user. These terms are not meant to imply a visual medium; they must be considered to apply to other media in equivalent ways.
When an algorithm B says to return to another algorithm A, it implies that A called B. Upon returning to A, the implementation must continue from where it left off in calling B.
The term "transparent black" refers to the color with red, green, blue, and alpha channels all set to zero.
The specification uses the term supported when referring to whether a user agent has an implementation capable of decoding the semantics of an external resource. A format or type is said to be supported if the implementation can process an external resource of that format or type without critical aspects of the resource being ignored. Whether a specific resource is supported can depend on what features of the resource's format are in use.
For example, a PNG image would be considered to be in a supported format if its pixel data could be decoded and rendered, even if, unbeknownst to the implementation, the image also contained animation data.
An MPEG-4 video file would not be considered to be in a supported format if the compression format used was not supported, even if the implementation could determine the dimensions of the movie from the file's metadata.
What some specifications, in particular the HTTP specification, refer to as a representation is referred to in this specification as a resource. [HTTP]
The term MIME type is used to refer to what is sometimes called an Internet media type in protocol literature. The term media type in this specification is used to refer to the type of media intended for presentation, as used by the CSS specifications. [RFC2046] [MQ]
A string is a valid MIME type if it matches the media-type
rule defined in section 3.7 "Media Types" of RFC 2616. In particular, a valid MIME
type may include MIME type parameters. [HTTP]
A string is a valid MIME type with no parameters if it matches the media-type
rule defined in section 3.7 "Media Types" of RFC 2616, but does not
contain any ";" (U+003B) characters. In other words, if it consists only of a type and
subtype, with no MIME Type parameters. [HTTP]
The term HTML MIME type is used to refer to the MIME type
text/html
.
A resource's critical subresources are those that the resource needs to have available to be correctly processed. Which resources are considered critical or not is defined by the specification that defines the resource's format.
The term data:
URL refers to URLs that use the data:
scheme. [RFC2397]
To ease migration from HTML to XHTML, UAs conforming to this specification
will place elements in HTML in the http://www.w3.org/1999/xhtml
namespace, at least
for the purposes of the DOM and CSS. The term "HTML elements", when used in this
specification, refers to any element in that namespace, and thus refers to both HTML and XHTML
elements.
Except where otherwise stated, all elements defined or mentioned in this specification are in
the HTML namespace ("http://www.w3.org/1999/xhtml
"), and all attributes
defined or mentioned in this specification have no namespace.
The term element type is used to refer to the set of elements that have a given
local name and namespace. For example, button
elements are elements with the element
type button
, meaning they have the local name "button
" and
(implicitly as defined above) the HTML namespace.
Attribute names are said to be XML-compatible if they match the Name
production defined in
XML, they contain no ":" (U+003A) characters, and their first three characters are not an
ASCII case-insensitive match for the string "xml
". [XML]
The term XML MIME type is used to refer to the MIME
types text/xml
, application/xml
, and any
MIME type whose subtype ends with the four characters "+xml
".
[RFC3023]
The root element of a Document
object is that Document
's
first element child, if any. If it does not have one then the Document
has no root
element.
The term root element, when not referring to a Document
object's root
element, means the furthest ancestor element node of whatever node is being discussed, or the node
itself if it has no ancestors. When the node is a part of the document, then the node's root
element is indeed the document's root element; however, if the node is not currently part
of the document tree, the root element will be an orphaned node.
When an element's root element is the root element of a
Document
object, it is said to be in a Document
. An
element is said to have been inserted into a
document when its root element changes and is now the document's root
element. Analogously, an element is said to have been removed from a document when its root element changes from being the
document's root element to being another element.
A node's home subtree is the subtree rooted at that node's root
element. When a node is in a Document
, its home
subtree is that Document
's tree.
The Document
of a Node
(such as an element) is the
Document
that the Node
's ownerDocument
IDL attribute returns. When a
Node
is in a Document
then that Document
is
always the Node
's Document
, and the Node
's ownerDocument
IDL attribute thus always returns that
Document
.
The Document
of a content attribute is the Document
of the
attribute's element.
The term tree order means a pre-order, depth-first traversal of DOM nodes involved
(through the parentNode
/childNodes
relationship).
When it is stated that some element or attribute is ignored, or treated as some other value, or handled as if it was something else, this refers only to the processing of the node after it is in the DOM. A user agent must not mutate the DOM in such situations.
A content attribute is said to change value only if its new value is different than its previous value; setting an attribute to a value it already has does not change it.
The term empty, when used of an attribute value, Text
node, or
string, means that the length of the text is zero (i.e. not even containing spaces or control
characters).
The construction "a Foo
object", where Foo
is actually an interface,
is sometimes used instead of the more accurate "an object implementing the interface
Foo
".
An IDL attribute is said to be getting when its value is being retrieved (e.g. by author script), and is said to be setting when a new value is assigned to it.
If a DOM object is said to be live, then the attributes and methods on that object must operate on the actual underlying data, not a snapshot of the data.
In the contexts of events, the terms fire and dispatch are used as defined in the
DOM specification: firing an event means to create and dispatch it, and dispatching an event means to follow the steps that propagate
the event through the tree. The term trusted event is
used to refer to events whose isTrusted
attribute is
initialized to true. [DOM]
The term plugin refers to a user-agent defined set of content handlers used by the
user agent that can take part in the user agent's rendering of a Document
object, but
that neither act as child browsing contexts of the
Document
nor introduce any Node
objects to the Document
's
DOM.
Typically such content handlers are provided by third parties, though a user agent can also designate built-in content handlers as plugins.
A user agent must not consider the types text/plain
and
application/octet-stream
as having a registered plugin.
One example of a plugin would be a PDF viewer that is instantiated in a browsing context when the user navigates to a PDF file. This would count as a plugin regardless of whether the party that implemented the PDF viewer component was the same as that which implemented the user agent itself. However, a PDF viewer application that launches separate from the user agent (as opposed to using the same interface) is not a plugin by this definition.
This specification does not define a mechanism for interacting with plugins, as it is expected to be user-agent- and platform-specific. Some UAs might opt to support a plugin mechanism such as the Netscape Plugin API; others might use remote content converters or have built-in support for certain types. Indeed, this specification doesn't require user agents to support plugins at all. [NPAPI]
A plugin can be secured if it honors the semantics of
the sandbox
attribute.
For example, a secured plugin would prevent its contents from creating pop-up
windows when the plugin is instantiated inside a sandboxed iframe
.
Browsers should take extreme care when interacting with external content intended for plugins. When third-party software is run with the same privileges as the user agent itself, vulnerabilities in the third-party software become as dangerous as those in the user agent.
Since different users having differents sets of plugins provides a
fingerprinting vector that increases the chances of users being uniquely identified, user agents
are encouraged to support the exact same set of plugins for each
user.
A character encoding, or just encoding where that is not ambiguous, is a defined way to convert between byte streams and Unicode strings, as defined in the Encoding standard. An encoding has an encoding name and one or more encoding labels, referred to as the encoding's name and labels in the Encoding specification. [ENCODING]
An ASCII-compatible character encoding is a single-byte or variable-length encoding in which the bytes 0x09, 0x0A, 0x0C, 0x0D, 0x20 - 0x22, 0x26, 0x27, 0x2C - 0x3F, 0x41 - 0x5A, and 0x61 - 0x7A, ignoring bytes that are the second and later bytes of multibyte sequences, all correspond to single-byte sequences that map to the same Unicode characters as those bytes in Windows-1252. [ENCODING]
This includes such encodings as Shift_JIS, HZ-GB-2312, and variants of ISO-2022, even though it is possible in these encodings for bytes like 0x70 to be part of longer sequences that are unrelated to their interpretation as ASCII. It excludes UTF-16 variants, as well as obsolete legacy encodings such as UTF-7, GSM03.38, and EBCDIC variants.
The term a UTF-16 encoding refers to any variant of UTF-16: UTF-16LE or UTF-16BE, regardless of the presence or absence of a BOM. [ENCODING]
The term code unit is used as defined in the Web IDL specification: a 16 bit
unsigned integer, the smallest atomic component of a DOMString
. (This is a narrower
definition than the one used in Unicode, and is not the same as a code point.) [WEBIDL]
The term Unicode code point means a Unicode scalar value where possible, and an isolated surrogate code point when not. When a conformance requirement is defined in terms of characters or Unicode code points, a pair of code units consisting of a high surrogate followed by a low surrogate must be treated as the single code point represented by the surrogate pair, but isolated surrogates must each be treated as the single code point with the value of the surrogate. [UNICODE]
In this specification, the term character, when not qualified as Unicode character, is synonymous with the term Unicode code point.
The term Unicode character is used to mean a Unicode scalar value (i.e. any Unicode code point that is not a surrogate code point). [UNICODE]
The code-unit length of a string is the number of code units in that string.
This complexity results from the historical decision to define the DOM API in terms of 16 bit (UTF-16) code units, rather than in terms of Unicode characters.
All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. The key word "OPTIONALLY" in the normative parts of this document is to be interpreted with the same normative meaning as "MAY" and "OPTIONAL". For readability, these words do not appear in all uppercase letters in this specification. [RFC2119]
Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should", "may", etc) used in introducing the algorithm.
For example, were the spec to say:
To eat an orange, the user must: 1. Peel the orange. 2. Separate each slice of the orange. 3. Eat the orange slices.
...it would be equivalent to the following:
To eat an orange: 1. The user must peel the orange. 2. The user must separate each slice of the orange. 3. The user must eat the orange slices.
Here the key word is "must".
The former (imperative) style is generally preferred in this specification for stylistic reasons.
Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.)
This specification describes the conformance criteria for user agents (relevant to implementors) and documents (relevant to authors and authoring tool implementors).
Conforming documents are those that comply with all the conformance criteria for documents. For readability, some of these conformance requirements are phrased as conformance requirements on authors; such requirements are implicitly requirements on documents: by definition, all documents are assumed to have had an author. (In some cases, that author may itself be a user agent — such user agents are subject to additional rules, as explained below.)
For example, if a requirement states that "authors must not use the foobar
element", it would imply that documents are not allowed to contain elements
named foobar
.
There is no implied relationship between document conformance requirements and implementation conformance requirements. User agents are not free to handle non-conformant documents as they please; the processing model described in this specification applies to implementations regardless of the conformity of the input documents.
User agents fall into several (overlapping) categories with different conformance requirements.
Web browsers that support the XHTML syntax must process elements and attributes from the HTML namespace found in XML documents as described in this specification, so that users can interact with them, unless the semantics of those elements have been overridden by other specifications.
A conforming XHTML processor would, upon finding an XHTML script
element in an XML document, execute the script contained in that element. However, if the
element is found within a transformation expressed in XSLT (assuming the user agent also
supports XSLT), then the processor would instead treat the script
element as an
opaque element that forms part of the transform.
Web browsers that support the HTML syntax must process documents labeled with an HTML MIME type as described in this specification, so that users can interact with them.
User agents that support scripting must also be conforming implementations of the IDL fragments in this specification, as described in the Web IDL specification. [WEBIDL]
Unless explicitly stated, specifications that override the semantics of HTML
elements do not override the requirements on DOM objects representing those elements. For
example, the script
element in the example above would still implement the
HTMLScriptElement
interface.
User agents that process HTML and XHTML documents purely to render non-interactive versions of them must comply to the same conformance criteria as Web browsers, except that they are exempt from requirements regarding user interaction.
Typical examples of non-interactive presentation user agents are printers (static UAs) and overhead displays (dynamic UAs). It is expected that most static non-interactive presentation user agents will also opt to lack scripting support.
A non-interactive but dynamic presentation UA would still execute scripts, allowing forms to be dynamically submitted, and so forth. However, since the concept of "focus" is irrelevant when the user cannot interact with the document, the UA would not need to support any of the focus-related DOM APIs.
User agents, whether interactive or not, may be designated (possibly as a user option) as supporting the suggested default rendering defined by this specification.
This is not required. In particular, even user agents that do implement the suggested default rendering are encouraged to offer settings that override this default to improve the experience for the user, e.g. changing the color contrast, using different focus styles, or otherwise making the experience more accessible and usable to the user.
User agents that are designated as supporting the suggested default rendering must, while so designated, implement the rules in the rendering section that that section defines as the behavior that user agents are expected to implement.
Implementations that do not support scripting (or which have their scripting features disabled entirely) are exempt from supporting the events and DOM interfaces mentioned in this specification. For the parts of this specification that are defined in terms of an events model or in terms of the DOM, such user agents must still act as if events and the DOM were supported.
Scripting can form an integral part of an application. Web browsers that do not support scripting, or that have scripting disabled, might be unable to fully convey the author's intent.
Conformance checkers must verify that a document conforms to the applicable conformance
criteria described in this specification. Automated conformance checkers are exempt from
detecting errors that require interpretation of the author's intent (for example, while a
document is non-conforming if the content of a blockquote
element is not a quote,
conformance checkers running without the input of human judgement do not have to check that
blockquote
elements only contain quoted material).
Conformance checkers must check that the input document conforms when parsed without a browsing context (meaning that no scripts are run, and that the parser's scripting flag is disabled), and should also check that the input document conforms when parsed with a browsing context in which scripts execute, and that the scripts never cause non-conforming states to occur other than transiently during script execution itself. (This is only a "SHOULD" and not a "MUST" requirement because it has been proven to be impossible. [COMPUTABLE])
The term "HTML validator" can be used to refer to a conformance checker that itself conforms to the applicable requirements of this specification.
XML DTDs cannot express all the conformance requirements of this specification. Therefore, a validating XML processor and a DTD cannot constitute a conformance checker. Also, since neither of the two authoring formats defined in this specification are applications of SGML, a validating SGML system cannot constitute a conformance checker either.
To put it another way, there are three types of conformance criteria:
A conformance checker must check for the first two. A simple DTD-based validator only checks for the first class of errors and is therefore not a conforming conformance checker according to this specification.
Applications and tools that process HTML and XHTML documents for reasons other than to either render the documents or check them for conformance should act in accordance with the semantics of the documents that they process.
A tool that generates document outlines but increases the nesting level for each paragraph and does not increase the nesting level for each section would not be conforming.
Authoring tools and markup generators must generate conforming documents. Conformance criteria that apply to authors also apply to authoring tools, where appropriate.
Authoring tools are exempt from the strict requirements of using elements only for their specified purpose, but only to the extent that authoring tools are not yet able to determine author intent. However, authoring tools must not automatically misuse elements or encourage their users to do so.
For example, it is not conforming to use an address
element for
arbitrary contact information; that element can only be used for marking up contact information
for the author of the document or section. However, since an authoring tool is likely unable to
determine the difference, an authoring tool is exempt from that requirement. This does not mean,
though, that authoring tools can use address
elements for any block of italics text
(for instance); it just means that the authoring tool doesn't have to verify that when the user
uses a tool for inserting contact information for a section, that the user really is doing that
and not inserting something else instead.
In terms of conformance checking, an editor has to output documents that conform to the same extent that a conformance checker will verify.
When an authoring tool is used to edit a non-conforming document, it may preserve the conformance errors in sections of the document that were not edited during the editing session (i.e. an editing tool is allowed to round-trip erroneous content). However, an authoring tool must not claim that the output is conformant if errors have been so preserved.
Authoring tools are expected to come in two broad varieties: tools that work from structure or semantic data, and tools that work on a What-You-See-Is-What-You-Get media-specific editing basis (WYSIWYG).
The former is the preferred mechanism for tools that author HTML, since the structure in the source information can be used to make informed choices regarding which HTML elements and attributes are most appropriate.
However, WYSIWYG tools are legitimate. WYSIWYG tools should use elements they know are
appropriate, and should not use elements that they do not know to be appropriate. This might in
certain extreme cases mean limiting the use of flow elements to just a few elements, like
div
, b
, i
, and span
and making liberal use
of the style
attribute.
All authoring tools, whether WYSIWYG or not, should make a best effort attempt at enabling users to create well-structured, semantically rich, media-independent content.
User agents may impose implementation-specific limits on otherwise
unconstrained inputs, e.g. to prevent denial of service attacks, to guard against running out of
memory, or to work around platform-specific limitations.
For compatibility with existing content and prior specifications, this specification describes two authoring formats: one based on XML (referred to as the XHTML syntax), and one using a custom format inspired by SGML (referred to as the HTML syntax). Implementations must support at least one of these two formats, although supporting both is encouraged.
Some conformance requirements are phrased as requirements on elements, attributes, methods or objects. Such requirements fall into two categories: those describing content model restrictions, and those describing implementation behavior. Those in the former category are requirements on documents and authoring tools. Those in the second category are requirements on user agents. Similarly, some conformance requirements are phrased as requirements on authors; such requirements are to be interpreted as conformance requirements on the documents that authors produce. (In other words, this specification does not distinguish between conformance criteria on authors and conformance criteria on documents.)
This specification relies on several other underlying specifications.
The Unicode character set is used to represent textual data, and the Encoding standard defines requirements around character encodings. [UNICODE]
This specification introduces terminology based on the terms defined in those specifications, as described earlier.
The following terms are used as defined in the Encoding specification: [ENCODING]
The UTF-8 decoder is distinct from the UTF-8 decode algorithm. The latter first strips a Byte Order Mark (BOM), if any, and then invokes the former.
For readability, character encodings are sometimes referenced in this specification with a case that differs from the canonical case given in the encoding standard. (For example, "UTF-16LE" instead of "utf-16le".)
Implementations that support the XHTML syntax must support some version of XML, as well as its corresponding namespaces specification, because that syntax uses an XML serialization with namespaces. [XML] [XMLNS]
The following terms are defined in the URL standard: [URL]
URLUtils
interface
URLUtilsReadOnly
interface
href
attribute
protocol
attribute
URLUtils
URLUtils
URLUtils
URLUtils
object
URLUtils
object
URLUtils
object
The following terms are defined in the Cookie specification: [COOKIES]
The following terms are defined in the CORS specification: [CORS]
The IDL fragments in this specification must be interpreted as required for conforming IDL fragments, as described in the Web IDL specification. [WEBIDL]
The terms supported property indices, determine the value of an indexed property, support named properties, supported property names, determine the value of a named property, platform array objects, and read only (when applied to arrays) are used as defined in the Web IDL specification. The algorithm to convert a DOMString to a sequence of Unicode characters is similarly that defined in the Web IDL specification.
Where this specification says an interface or exception is exposed to JavaScript, it refers to the manner, described in the Web IDL specification, in which an ECMAScript global environment exposes interfaces and exceptions.
When this specification requires a user agent to create a Date
object
representing a particular time (which could be the special value Not-a-Number), the milliseconds
component of that time, if any, must be truncated to an integer, and the time value of the newly
created Date
object must represent the resulting truncated time.
For instance, given the time 23045 millionths of a second after 01:00 UTC on
January 1st 2000, i.e. the time 2000-01-01T00:00:00.023045Z, then the Date
object
created representing that time would represent the same time as that created representing the
time 2000-01-01T00:00:00.023Z, 45 millionths earlier. If the given time is NaN, then the result
is a Date
object that represents a time value NaN (indicating that the object does
not represent a specific instant of time).
Some parts of the language described by this specification only support JavaScript as the underlying scripting language. [ECMA262]
The term "JavaScript" is used to refer to ECMA262, rather than the official term
ECMAScript, since the term JavaScript is more widely known. Similarly, the MIME
type used to refer to JavaScript in this specification is text/javascript
, since that is the most commonly used type, despite it being an officially obsoleted type according to RFC 4329. [RFC4329]
The term JavaScript global environment refers to the global environment concept defined in the ECMAScript specification.
The ECMAScript SyntaxError
exception is also
defined in the ECMAScript specification. [ECMA262]
The Document Object Model (DOM) is a representation — a model — of a document and its content. The DOM is not just an API; the conformance criteria of HTML implementations are defined, in this specification, in terms of operations on the DOM. [DOM]
Implementations must support DOM and the events defined in DOM Events, because this specification is defined in terms of the DOM, and some of the features are defined as extensions to the DOM interfaces. [DOM] [DOMEVENTS]
In particular, the following features are defined in the DOM specification: [DOM]
Attr
interfaceComment
interfaceDOMImplementation
interfaceDocument
interfaceDocumentFragment
interfaceDocumentType
interfaceDOMException
interfaceChildNode
interfaceElement
interfaceNode
interfaceNodeList
interfaceProcessingInstruction
interfaceText
interfaceHTMLCollection
interfaceitem()
method
DOMTokenList
interfaceDOMSettableTokenList
interfacecreateDocument()
methodcreateHTMLDocument()
methodcreateElement()
methodcreateElementNS()
methodgetElementById()
methodinsertBefore()
methodownerDocument
attributechildNodes
attributelocalName
attributeparentNode
attributenamespaceURI
attributetagName
attributeid
attributetextContent
attributeEvent
interfaceEventTarget
interfaceEventInit
dictionary typetarget
attributeisTrusted
attributeEventTarget
Document
Node
, and the concept of cloning steps used by that algorithmMutationObserver
interfaceMutationObserver
scripting environment conceptMutationObserver
objects algorithmThe term throw in this specification is used as defined in the DOM specification.
The following DOMException
types are defined in the DOM specification: [DOM]
IndexSizeError
HierarchyRequestError
WrongDocumentError
InvalidCharacterError
NoModificationAllowedError
NotFoundError
NotSupportedError
InvalidStateError
SyntaxError
InvalidModificationError
NamespaceError
InvalidAccessError
SecurityError
NetworkError
AbortError
URLMismatchError
QuotaExceededError
TimeoutError
InvalidNodeTypeError
DataCloneError
For example, to throw a TimeoutError
exception, a user
agent would construct a DOMException
object whose type was the string "TimeoutError
" (and whose code was the number 23, for legacy reasons) and
actually throw that object as an exception.
The URL associated with a Document
, as
defined in the DOM specification, is referred to in this specification as the document's
address.
The following features are defined in the DOM Events specification: [DOMEVENTS]
MouseEvent
interfaceMouseEventInit
dictionary typeUIEvent
interface's detail
attributeclick
eventThis specification sometimes uses the term name to refer to the event's type
; as in, "an event named click
" or "if the event name is keypress
". The terms "name" and "type" for events
are synonymous.
The following features are defined in the DOM Parsing and Serialization specification: [DOMPARSING]
innerHTML
outerHTML
User agents are also encouraged to implement the
features described in the HTML Editing APIs and
UndoManager
and DOM Transaction
specifications.
[EDITING]
[UNDO]
The following parts of the Fullscreen specification are referenced from this specification,
in part to define the rendering of dialog
elements, and also to define how the
Fullscreen API interacts with the sandboxing features in HTML: [FULLSCREEN]
requestFullscreen()
The ArrayBuffer and ArrayBufferView interfaces and underlying concepts
from the Typed Array Specification are used for several features in this specification. The
Uint8ClampedArray interface type is specifically used in the definition of the
canvas
element's 2D API. [TYPEDARRAY]
This specification uses the following features defined in the File API specification: [FILEAPI]
Blob
File
FileList
Blob.close()
Blob.type
This specification references the XMLHttpRequest specification to describe how the two
specifications interact and to use its ProgressEvent
features. The following
features and terms are defined in the XMLHttpRequest specification: [XHR]
XMLHttpRequest
ProgressEvent
This specification references EventSource
which is specified
in the Server-Sent Events specification [EVENTSOURCE]
Implementations must support the Media Queries language. [MQ]
While support for CSS as a whole is not required of implementations of this specification (though it is encouraged, at least for Web browsers), some features are defined in terms of specific CSS requirements.
In particular, some features require that a string be parsed as a CSS <color> value. When parsing a CSS value, user agents are required by the CSS specifications to apply some error handling rules. These apply to this specification also. [CSSCOLOR] [CSS]
For example, user agents are required to close all open constructs upon
finding the end of a style sheet unexpectedly. Thus, when parsing the string "rgb(0,0,0
" (with a missing close-parenthesis) for a color value, the close
parenthesis is implied by this error handling rule, and a value is obtained (the color 'black').
However, the similar construct "rgb(0,0,
" (with both a missing parenthesis
and a missing "blue" value) cannot be parsed, as closing the open construct does not result in a
viable value.
The term CSS element reference identifier is used as defined in the CSS Image Values and Replaced Content specification to define the API that declares identifiers for use with the CSS 'element()' function. [CSSIMAGES]
Similarly, the term provides a paint source is used as defined in the CSS Image Values and Replaced Content specification to define the interaction of certain HTML elements with the CSS 'element()' function. [CSSIMAGES]
The term default object size is also defined in the CSS Image Values and Replaced Content specification. [CSSIMAGES]
Support for the CSS Object Model is required for implementations that support scripting. The following features and terms are defined in the CSSOM specifications: [CSSOM] [CSSOMVIEW]
Screen
LinkStyle
CSSStyleDeclaration
cssText
attribute of CSSStyleDeclaration
StyleSheet
sheet
disabled
The term CSS styling attribute is defined in the CSS Style Attributes specification. [CSSATTR]
The CanvasRenderingContext2D
object's use of fonts depends on the features
described in the CSS Fonts and Font Load Events specifications, including in particular
FontLoader
. [CSSFONTS] [CSSFONTLOAD]
The following interface is defined in the SVG specification: [SVG]
SVGMatrix
The following interface is defined in the WebGL specification: [WEBGL]
WebGLRenderingContext
Implementations may support WebVTT as a text track format for subtitles, captions, chapter titles, metadata, etc, for media resources. [WEBVTT]
The following terms, used in this specification, are defined in the WebVTT specification:
The following terms are defined in the WebSocket protocol specification: [WSP]
The terms strong native semantics is used as defined in the ARIA specification. The term default implicit ARIA semantics has the same meaning as the term implicit WAI-ARIA semantics as used in the ARIA specification. [ARIA]
The role
and aria-*
attributes are defined in the ARIA specification. [ARIA]
This specification does not require support of any particular network protocol, style sheet language, scripting language, or any of the DOM specifications beyond those required in the list above. However, the language described by this specification is biased towards CSS as the styling language, JavaScript as the scripting language, and HTTP as the network protocol, and several features assume that those languages and protocols are in use.
A user agent that implements the HTTP protocol must implement the Web Origin Concept specification and the HTTP State Management Mechanism specification (Cookies) as well. [HTTP] [ORIGIN] [COOKIES]
This specification might have certain additional requirements on character encodings, image formats, audio formats, and video formats in the respective sections.
Vendor-specific proprietary user agent extensions to this specification are strongly discouraged. Documents must not use such extensions, as doing so reduces interoperability and fragments the user base, allowing only users of specific user agents to access the content in question.
If such extensions are nonetheless needed, e.g. for experimental purposes, then vendors are strongly urged to use one of the following extension mechanisms:
For markup-level features that can be limited to the XML serialization and need not be supported in the HTML serialization, vendors should use the namespace mechanism to define custom namespaces in which the non-standard elements and attributes are supported.
For markup-level features that are intended for use with the HTML syntax,
extensions should be limited to new attributes of the form "x-vendor-feature
", where vendor is a
short string that identifies the vendor responsible for the extension, and feature is the name of the feature. New element names should not be created.
Using attributes for such extensions exclusively allows extensions from multiple vendors to
co-exist on the same element, which would not be possible with elements. Using the "x-vendor-feature
" form allows extensions
to be made without risk of conflicting with future additions to the specification.
For instance, a browser named "FerretBrowser" could use "ferret" as a vendor prefix, while a browser named "Mellblom Browser" could use "mb". If both of these browsers invented extensions that turned elements into scratch-and-sniff areas, an author experimenting with these features could write:
<p>This smells of lemons! <span x-ferret-smellovision x-ferret-smellcode="LEM01" x-mb-outputsmell x-mb-smell="lemon juice"></span></p>
Attribute names beginning with the two characters "x-
" are reserved for
user agent use and are guaranteed to never be formally added to the HTML language. For
flexibility, attributes names containing underscores (the U+005F LOW LINE character) are also
reserved for experimental purposes and are guaranteed to never be formally added to the HTML
language.
Pages that use such attributes are by definition non-conforming.
For DOM extensions, e.g. new methods and IDL attributes, the new members should be prefixed by vendor-specific strings to prevent clashes with future versions of this specification.
For events, experimental event types should be prefixed with vendor-specific strings.
For example, if a user agent called "Pleasold" were to add an event to indicate when
the user is going up in an elevator, it could use the prefix "pleasold
" and
thus name the event "pleasoldgoingup
", possibly with an event handler
attribute named "onpleasoldgoingup
".
All extensions must be defined so that the use of extensions neither contradicts nor causes the non-conformance of functionality defined in the specification.
For example, while strongly discouraged from doing so, an implementation "Foo Browser" could
add a new IDL attribute "fooTypeTime
" to a control's DOM interface that
returned the time it took the user to select the current value of a control (say). On the other
hand, defining a new control that appears in a form's elements
array would be in violation of the above requirement,
as it would violate the definition of elements
given in
this specification.
When adding new reflecting IDL attributes corresponding to content
attributes of the form "x-vendor-feature
", the IDL attribute should be named "vendorFeature
" (i.e. the "x
" is
dropped from the IDL attribute's name).
When vendor-neutral extensions to this specification are needed, either this specification can be updated accordingly, or an extension specification can be written that overrides the requirements in this specification. When someone applying this specification to their activities decides that they will recognize the requirements of such an extension specification, it becomes an applicable specification.
The conformance terminology for documents depends on the nature of the changes introduced by such applicable specifications, and on the content and intended interpretation of the document. Applicable specifications MAY define new document content (e.g. a foobar element), MAY prohibit certain otherwise conforming content (e.g. prohibit use of <table>s), or MAY change the semantics, DOM mappings, or other processing rules for content defined in this specification. Whether a document is or is not a conforming HTML5 document does not depend on the use of applicable specifications: if the syntax and semantics of a given conforming HTML5 document is unchanged by the use of applicable specification(s), then that document remains a conforming HTML5 document. If the semantics or processing of a given (otherwise conforming) document is changed by use of applicable specification(s), then it is not a conforming HTML5 document. For such cases, the applicable specifications SHOULD define conformance terminology.
As a suggested but not required convention, such specifications might define conformance terminology such as: "Conforming HTML5+XXX document", where XXX is a short name for the applicable specification. (Example: "Conforming HTML5+AutomotiveExtensions document").
a consequence of the rule given above is that certain syntactically correct HTML5 documents may not be conforming HTML5 documents in the presence of applicable specifications. (Example: the applicable specification defines <table> to be a piece of furniture — a document written to that specification and containing a <table> element is NOT a conforming HTML5 document, even if the element happens to be syntactically correct HTML5.)
User agents must treat elements and attributes that they do not understand as semantically neutral; leaving them in the DOM (for DOM processors), and styling them according to CSS (for CSS processors), but not inferring any meaning from them.
When support for a feature is disabled (e.g. as an emergency measure to mitigate a security problem, or to aid in development, or for performance reasons), user agents must act as if they had no support for the feature whatsoever, and as if the feature was not mentioned in this specification. For example, if a particular feature is accessed via an attribute in a Web IDL interface, the attribute itself would be omitted from the objects that implement that interface — leaving the attribute on the object but making it return null or throw an exception is insufficient.
Implementations of XPath 1.0 that operate on HTML
documents parsed or created in the manners described in this specification (e.g. as part of
the document.evaluate()
API) must act as if the following edit was applied
to the XPath 1.0 specification.
First, remove this paragraph:
A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. This is the same way expansion is done for element type names in start and end-tags except that the default namespace declared with
xmlns
is not used: if the QName does not have a prefix, then the namespace URI is null (this is the same way attribute names are expanded). It is an error if the QName has a prefix for which there is no namespace declaration in the expression context.
Then, insert in its place the following:
A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. If the QName has a prefix, then there must be a namespace declaration for this prefix in the expression context, and the corresponding namespace URI is the one that is associated with this prefix. It is an error if the QName has a prefix for which there is no namespace declaration in the expression context.
If the QName has no prefix and the principal node type of the axis is element, then the default element namespace is used. Otherwise if the QName has no prefix, the namespace URI is null. The default element namespace is a member of the context for the XPath expression. The value of the default element namespace when executing an XPath expression through the DOM3 XPath API is determined in the following way:
- If the context node is from an HTML DOM, the default element namespace is "http://www.w3.org/1999/xhtml".
- Otherwise, the default element namespace URI is null.
This is equivalent to adding the default element namespace feature of XPath 2.0 to XPath 1.0, and using the HTML namespace as the default element namespace for HTML documents. It is motivated by the desire to have implementations be compatible with legacy HTML content while still supporting the changes that this specification introduces to HTML regarding the namespace used for HTML elements, and by the desire to use XPath 1.0 rather than XPath 2.0.
This change is a willful violation of the XPath 1.0 specification, motivated by desire to have implementations be compatible with legacy content while still supporting the changes that this specification introduces to HTML regarding which namespace is used for HTML elements. [XPATH10]
XSLT 1.0 processors outputting to a DOM when the output method is "html" (either explicitly or via the defaulting rule in XSLT 1.0) are affected as follows:
If the transformation program outputs an element in no namespace, the processor must, prior to constructing the corresponding DOM element node, change the namespace of the element to the HTML namespace, ASCII-lowercase the element's local name, and ASCII-lowercase the names of any non-namespaced attributes on the element.
This requirement is a willful violation of the XSLT 1.0 specification, required because this specification changes the namespaces and case-sensitivity rules of HTML in a manner that would otherwise be incompatible with DOM-based XSLT transformations. (Processors that serialize the output are unaffected.) [XSLT10]
This specification does not specify precisely how XSLT processing interacts with the HTML
parser infrastructure (for example, whether an XSLT processor acts as if it puts any
elements into a stack of open elements). However, XSLT processors must stop
parsing if they successfully complete, and must set the current document
readiness first to "interactive
" and then to "complete
" if they are aborted.
This specification does not specify how XSLT interacts with the navigation algorithm, how it fits in with the event loop, nor how error pages are to be handled (e.g. whether XSLT errors are to replace an incremental XSLT output, or are rendered inline, etc).
There are also additional non-normative comments regarding the interaction of XSLT
and HTML in the script
element section, and of
XSLT, XPath, and HTML in the template
element
section.
Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point.
Comparing two strings in an ASCII case-insensitive manner means comparing them exactly, code point for code point, except that the characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are considered to also match.
Comparing two strings in a compatibility caseless manner means using the Unicode compatibility caseless match operation to compare the two strings, with no language-specific tailoirings. [UNICODE]
Except where otherwise stated, string comparisons must be performed in a case-sensitive manner.
Converting a string to ASCII uppercase means replacing all characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) with the corresponding characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z).
Converting a string to ASCII lowercase means replacing all characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) with the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z).
A string pattern is a prefix match for a string s when pattern is not longer than s and truncating s to pattern's length leaves the two strings as matches of each other.
There are various places in HTML that accept particular data types, such as dates or numbers. This section describes what the conformance criteria for content in those formats is, and how to parse them.
Implementors are strongly urged to carefully examine any third-party libraries they might consider using to implement the parsing of syntaxes described below. For example, date libraries are likely to implement error handling behavior that differs from what is required in this specification, since error-handling behavior is often not defined in specifications that describe date syntaxes similar to those used in this specification, and thus implementations tend to vary greatly in how they handle errors.
The space characters, for the purposes of this specification, are U+0020 SPACE, "tab" (U+0009), "LF" (U+000A), "FF" (U+000C), and "CR" (U+000D).
The White_Space characters are those that have the Unicode
property "White_Space" in the Unicode PropList.txt
data file. [UNICODE]
This should not be confused with the "White_Space" value (abbreviated "WS") of the
"Bidi_Class" property in the Unicode.txt
data file.
The control characters are those whose Unicode "General_Category" property has the
value "Cc" in the Unicode UnicodeData.txt
data file. [UNICODE]
The uppercase ASCII letters are the characters in the range uppercase ASCII letters.
The lowercase ASCII letters are the characters in the range lowercase ASCII letters.
The ASCII digits are the characters in the range ASCII digits.
The alphanumeric ASCII characters are those that are either uppercase ASCII letters, lowercase ASCII letters, or ASCII digits.
The ASCII hex digits are the characters in the ranges ASCII digits, U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F, and U+0061 LATIN SMALL LETTER A to U+0066 LATIN SMALL LETTER F.
The uppercase ASCII hex digits are the characters in the ranges ASCII digits and U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F only.
The lowercase ASCII hex digits are the characters in the ranges ASCII digits and U+0061 LATIN SMALL LETTER A to U+0066 LATIN SMALL LETTER F only.
Some of the micro-parsers described below follow the pattern of having an input variable that holds the string being parsed, and having a position variable pointing at the next character to parse in input.
For parsers based on this pattern, a step that requires the user agent to collect a sequence of characters means that the following algorithm must be run, with characters being the set of characters that can be collected:
Let input and position be the same variables as those of the same name in the algorithm that invoked these steps.
Let result be the empty string.
While position doesn't point past the end of input and the character at position is one of the characters, append that character to the end of result and advance position to the next character in input.
Return result.
The step skip whitespace means that the user agent must collect a sequence of characters that are space characters. The step skip White_Space characters means that the user agent must collect a sequence of characters that are White_Space characters. In both cases, the collected characters are not used. [UNICODE]
When a user agent is to strip line breaks from a string, the user agent must remove any "LF" (U+000A) and "CR" (U+000D) characters from that string.
When a user agent is to strip leading and trailing whitespace from a string, the user agent must remove all space characters that are at the start or end of the string.
When a user agent is to strip and collapse whitespace in a string, it must replace any sequence of one or more consecutive space characters in that string with a single U+0020 SPACE character, and then strip leading and trailing whitespace from that string.
When a user agent has to strictly split a string on a particular delimiter character delimiter, it must use the following algorithm:
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let tokens be an ordered list of tokens, initially empty.
While position is not past the end of input:
Collect a sequence of characters that are not the delimiter character.
Append the string collected in the previous step to tokens.
Advance position to the next character in input.
Return tokens.
For the special cases of splitting a string on spaces and on commas, this algorithm does not apply (those algorithms also perform whitespace trimming).
A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
The values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether.
Here is an example of a checkbox that is checked and disabled. The checked
and disabled
attributes are the boolean attributes.
<label><input type=checkbox checked name=cheese disabled> Cheese</label>
This could be equivalently written as this:
<label><input type=checkbox checked=checked name=cheese disabled=disabled> Cheese</label>
You can also mix styles; the following is still equivalent:
<label><input type='checkbox' checked name=cheese disabled=""> Cheese</label>
Some attributes are defined as taking one of a finite set of keywords. Such attributes are called enumerated attributes. The keywords are each defined to map to a particular state (several keywords might map to the same state, in which case some of the keywords are synonyms of each other; additionally, some of the keywords can be said to be non-conforming, and are only in the specification for historical reasons). In addition, two default states can be given. The first is the invalid value default, the second is the missing value default.
If an enumerated attribute is specified, the attribute's value must be an ASCII case-insensitive match for one of the given keywords that are not said to be non-conforming, with no leading or trailing whitespace.
When the attribute is specified, if its value is an ASCII case-insensitive match for one of the given keywords then that keyword's state is the state that the attribute represents. If the attribute value matches none of the given keywords, but the attribute has an invalid value default, then the attribute represents that state. Otherwise, if the attribute value matches none of the keywords but there is a missing value default state defined, then that is the state represented by the attribute. Otherwise, there is no default, and invalid values mean that there is no state represented.
When the attribute is not specified, if there is a missing value default state defined, then that is the state represented by the (missing) attribute. Otherwise, the absence of the attribute means that there is no state represented.
The empty string can be a valid keyword.
A string is a valid integer if it consists of one or more ASCII digits, optionally prefixed with a "-" (U+002D) character.
A valid integer without a "-" (U+002D) prefix represents the number that is represented in base ten by that string of digits. A valid integer with a "-" (U+002D) prefix represents the number represented in base ten by the string of digits that follows the U+002D HYPHEN-MINUS, subtracted from zero.
The rules for parsing integers are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will return either an integer or an error.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let sign have the value "positive".
If position is past the end of input, return an error.
If the character indicated by position (the first character) is a "-" (U+002D) character:
Otherwise, if the character indicated by position (the first character) is a "+" (U+002B) character:
+
"
is ignored, but it is not conforming.)If the character indicated by position is not an ASCII digit, then return an error.
Collect a sequence of characters that are ASCII digits, and interpret the resulting sequence as a base-ten integer. Let value be that integer.
If sign is "positive", return value, otherwise return the result of subtracting value from zero.
A string is a valid non-negative integer if it consists of one or more ASCII digits.
A valid non-negative integer represents the number that is represented in base ten by that string of digits.
The rules for parsing non-negative integers are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will return either zero, a positive integer, or an error.
Let input be the string being parsed.
Let value be the result of parsing input using the rules for parsing integers.
If value is an error, return an error.
If value is less than zero, return an error.
Return value.
A string is a valid floating-point number if it consists of:
A valid floating-point number represents the number obtained by multiplying the significand by ten raised to the power of the exponent, where the significand is the first number, interpreted as base ten (including the decimal point and the number after the decimal point, if any, and interpreting the significand as a negative number if the whole string starts with a "-" (U+002D) character and the number is not zero), and where the exponent is the number after the E, if any (interpreted as a negative number if there is a "-" (U+002D) character between the E and the number and the number is not zero, or else ignoring a "+" (U+002B) character between the E and the number if there is one). If there is no E, then the exponent is treated as zero.
The Infinity and Not-a-Number (NaN) values are not valid floating-point numbers.
The best representation of the number n as a floating-point number is the string obtained from applying the JavaScript operator ToString to n. The JavaScript operator ToString is not uniquely determined. When there are multiple possible strings that could be obtained from the JavaScript operator ToString for a particular value, the user agent must always return the same string for that value (though it may differ from the value used by other user agents).
The rules for parsing floating-point number values are as given in the following algorithm. This algorithm must be aborted at the first step that returns something. This algorithm will return either a number or an error.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let value have the value 1.
Let divisor have the value 1.
Let exponent have the value 1.
If position is past the end of input, return an error.
If the character indicated by position is a U+002D HYPHEN-MINUS character (-):
Otherwise, if the character indicated by position (the first character) is a "+" (U+002B) character:
+
"
is ignored, but it is not conforming.)If the character indicated by position is a "." (U+002E), and that is not the last character in input, and the character after the character indicated by position is an ASCII digit, then set value to zero and jump to the step labeled fraction.
If the character indicated by position is not an ASCII digit, then return an error.
Collect a sequence of characters that are ASCII digits, and interpret the resulting sequence as a base-ten integer. Multiply value by that integer.
Fraction: If the character indicated by position is a "." (U+002E), run these substeps:
Advance position to the next character.
If position is past the end of input, or if the character indicated by position is not an ASCII digit, "e" (U+0065), or "E" (U+0045), then jump to the step labeled conversion.
If the character indicated by position is a "e" (U+0065) character or a "E" (U+0045) character, skip the remainder of these substeps.
Fraction loop: Multiply divisor by ten.
Advance position to the next character.
If position is past the end of input, then jump to the step labeled conversion.
If the character indicated by position is an ASCII digit, jump back to the step labeled fraction loop in these substeps.
If the character indicated by position is a "e" (U+0065) character or a "E" (U+0045) character, run these substeps:
Advance position to the next character.
If position is past the end of input, then jump to the step labeled conversion.
If the character indicated by position is a "-" (U+002D) character:
If position is past the end of input, then jump to the step labeled conversion.
Otherwise, if the character indicated by position is a "+" (U+002B) character:
If position is past the end of input, then jump to the step labeled conversion.
If the character indicated by position is not an ASCII digit, then jump to the step labeled conversion.
Collect a sequence of characters that are ASCII digits, and interpret the resulting sequence as a base-ten integer. Multiply exponent by that integer.
Multiply value by ten raised to the exponentth power.
Conversion: Let S be the set of finite IEEE 754 double-precision floating-point values except −0, but with two special values added: 21024 and −21024.
Let rounded-value be the number in S that is closest to value, selecting the number with an even significand if there are two equally close values. (The two special values 21024 and −21024 are considered to have even significands for this purpose.)
If rounded-value is 21024 or −21024, return an error.
Return rounded-value.
The rules for parsing dimension values are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will return either a number greater than or equal to 1.0, or an error; if a number is returned, then it is further categorized as either a percentage or a length.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
If position is past the end of input, return an error.
If the character indicated by position is a U+002B PLUS SIGN character (+), advance position to the next character.
Collect a sequence of characters that are "0" (U+0030) characters, and discard them.
If position is past the end of input, return an error.
If the character indicated by position is not one of "1" (U+0031) to "9" (U+0039), then return an error.
Collect a sequence of characters that are ASCII digits, and interpret the resulting sequence as a base-ten integer. Let value be that number.
If position is past the end of input, return value as a length.
If the character indicated by position is a U+002E FULL STOP character (.):
Advance position to the next character.
If position is past the end of input, or if the character indicated by position is not an ASCII digit, then return value as a length.
Let divisor have the value 1.
Fraction loop: Multiply divisor by ten.
Advance position to the next character.
If position is past the end of input, then return value as a length.
If the character indicated by position is an ASCII digit, return to the step labeled fraction loop in these substeps.
If position is past the end of input, return value as a length.
If the character indicated by position is a "%" (U+0025) character, return value as a percentage.
Return value as a length.
A valid list of integers is a number of valid integers separated by U+002C COMMA characters, with no other characters (e.g. no space characters). In addition, there might be restrictions on the number of integers that can be given, or on the range of values allowed.
The rules for parsing a list of integers are as follows:
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let numbers be an initially empty list of integers. This list will be the result of this algorithm.
If there is a character in the string input at position position, and it is either a U+0020 SPACE, U+002C COMMA, or U+003B SEMICOLON character, then advance position to the next character in input, or to beyond the end of the string if there are no more characters.
If position points to beyond the end of input, return numbers and abort.
If the character in the string input at position position is a U+0020 SPACE, U+002C COMMA, or U+003B SEMICOLON character, then return to step 4.
Let negated be false.
Let value be 0.
Let started be false. This variable is set to true when the parser sees a number or a "-" (U+002D) character.
Let got number be false. This variable is set to true when the parser sees a number.
Let finished be false. This variable is set to true to switch parser into a mode where it ignores characters until the next separator.
Let bogus be false.
Parser: If the character in the string input at position position is:
Follow these substeps:
Follow these substeps:
Follow these substeps:
1,2,x,4
".Follow these substeps:
Follow these substeps:
Advance position to the next character in input, or to beyond the end of the string if there are no more characters.
If position points to a character (and not to beyond the end of input), jump to the big Parser step above.
If negated is true, then negate value.
If got number is true, then append value to the numbers list.
Return the numbers list and abort.
The rules for parsing a list of dimensions are as follows. These rules return a list of zero or more pairs consisting of a number and a unit, the unit being one of percentage, relative, and absolute.
Let raw input be the string being parsed.
If the last character in raw input is a "," (U+002C) character, then remove that character from raw input.
Split the string raw input on commas. Let raw tokens be the resulting list of tokens.
Let result be an empty list of number/unit pairs.
For each token in raw tokens, run the following substeps:
Let input be the token.
Let position be a pointer into input, initially pointing at the start of the string.
Let value be the number 0.
Let unit be absolute.
If position is past the end of input, set unit to relative and jump to the last substep.
If the character at position is an ASCII digit, collect a sequence of characters that are ASCII digits, interpret the resulting sequence as an integer in base ten, and increment value by that integer.
If the character at position is a "." (U+002E) character, run these substeps:
Collect a sequence of characters consisting of space characters and ASCII digits. Let s be the resulting sequence.
Remove all space characters in s.
If s is not the empty string, run these subsubsteps:
Let length be the number of characters in s (after the spaces were removed).
Let fraction be the result of interpreting s as a base-ten integer, and then dividing that number by 10length.
Increment value by fraction.
If the character at position is a "%" (U+0025) character, then set unit to percentage.
Otherwise, if the character at position is a U+002A ASTERISK character (*), then set unit to relative.
Add an entry to result consisting of the number given by value and the unit given by unit.
Return the list result.
In the algorithms below, the number of days in month month of year year is: 31 if month is 1, 3, 5, 7, 8, 10, or 12; 30 if month is 4, 6, 9, or 11; 29 if month is 2 and year is a number divisible by 400, or if year is a number divisible by 4 but not by 100; and 28 otherwise. This takes into account leap years in the Gregorian calendar. [GREGORIAN]
When ASCII digits are used in the date and time syntaxes defined in this section, they express numbers in base ten.
While the formats described here are intended to be subsets of the corresponding ISO8601 formats, this specification defines parsing rules in much more detail than ISO8601. Implementors are therefore encouraged to carefully examine any date parsing libraries before using them to implement the parsing rules described below; ISO8601 libraries might not parse dates and times in exactly the same manner. [ISO8601]
Where this specification refers to the proleptic Gregorian calendar, it means the modern Gregorian calendar, extrapolated backwards to year 1. A date in the proleptic Gregorian calendar, sometimes explicitly referred to as a proleptic-Gregorian date, is one that is described using that calendar even if that calendar was not in use at the time (or place) in question. [GREGORIAN]
The use of the Gregorian calendar as the wire format in this specification is an
arbitrary choice resulting from the cultural biases of those involved in the decision. See also
the section discussing date, time, and number formats in forms
(for authors), implemention notes regarding
localization of form controls, and the time
element.
A month consists of a specific proleptic-Gregorian date with no time-zone information and no date information beyond a year and a month. [GREGORIAN]
A string is a valid month string representing a year year and month month if it consists of the following components in the given order:
The rules to parse a month string are as follows. This will return either a year and month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a month component to obtain year and month. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Return year and month.
The rules to parse a month component, given an input string and a position, are as follows. This will return either a year and a month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the year.
If year is not a number greater than zero, then fail.
If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the month.
If month is not a number in the range 1 ≤ month ≤ 12, then fail.
Return year and month.
A date consists of a specific proleptic-Gregorian date with no time-zone information, consisting of a year, a month, and a day. [GREGORIAN]
A string is a valid date string representing a year year, month month, and day day if it consists of the following components in the given order:
The rules to parse a date string are as follows. This will return either a date, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a date component to obtain year, month, and day. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Let date be the date with year year, month month, and day day.
Return date.
The rules to parse a date component, given an input string and a position, are as follows. This will return either a year, a month, and a day, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Parse a month component to obtain year and month. If this returns nothing, then fail.
Let maxday be the number of days in month month of year year.
If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the day.
If day is not a number in the range 1 ≤ day ≤ maxday, then fail.
Return year, month, and day.
A yearless date consists of a Gregorian month and a day within that month, but with no associated year. [GREGORIAN]
A string is a valid yearless date string representing a month month and a day day if it consists of the following components in the given order:
In other words, if the month is "02
",
meaning February, then the day can be 29, as if the year was a leap year.
The rules to parse a yearless date string are as follows. This will return either a month and a day, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a yearless date component to obtain month and day. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Return month and day.
The rules to parse a yearless date component, given an input string and a position, are as follows. This will return either a month and a day, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Collect a sequence of characters that are "-" (U+002D) characters. If the collected sequence is not exactly zero or two characters long, then fail.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the month.
If month is not a number in the range 1 ≤ month ≤ 12, then fail.
Let maxday be the number of days in month month of any arbitrary leap year (e.g. 4 or 2000).
If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the day.
If day is not a number in the range 1 ≤ day ≤ maxday, then fail.
Return month and day.
A time consists of a specific time with no time-zone information, consisting of an hour, a minute, a second, and a fraction of a second.
A string is a valid time string representing an hour hour, a minute minute, and a second second if it consists of the following components in the given order:
The second component cannot be 60 or 61; leap seconds cannot be represented.
The rules to parse a time string are as follows. This will return either a time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Let time be the time with hour hour, minute minute, and second second.
Return time.
The rules to parse a time component, given an input string and a position, are as follows. This will return either an hour, a minute, and a second, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the hour.
If position is beyond the end of input or if the character at position is not a U+003A COLON character, then fail. Otherwise, move position forwards one character.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the minute.
Let second be a string with the value "0".
If position is not beyond the end of input and the character at position is a U+003A COLON, then run these substeps:
Advance position to the next character in input.
If position is beyond the end of input, or at the last character in input, or if the next two characters in input starting at position are not both ASCII digits, then fail.
Collect a sequence of characters that are either ASCII digits or U+002E FULL STOP characters. If the collected sequence is three characters long, or if it is longer than three characters long and the third character is not a U+002E FULL STOP character, or if it has more than one U+002E FULL STOP character, then fail. Otherwise, let the collected string be second instead of its previous value.
Interpret second as a base-ten number (possibly with a fractional part). Let second be that number instead of the string version.
If second is not a number in the range 0 ≤ second < 60, then fail.
Return hour, minute, and second.
A local date and time consists of a specific proleptic-Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, but expressed without a time zone. [GREGORIAN]
A string is a valid local date and time string representing a date and time if it consists of the following components in the given order:
A string is a valid normalized local date and time string representing a date and time if it consists of the following components in the given order:
The rules to parse a local date and time string are as follows. This will return either a date and time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a date component to obtain year, month, and day. If this returns nothing, then fail.
If position is beyond the end of input or if the character at position is neither a U+0054 LATIN CAPITAL LETTER T character (T) nor a U+0020 SPACE character, then fail. Otherwise, move position forwards one character.
Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Let date be the date with year year, month month, and day day.
Let time be the time with hour hour, minute minute, and second second.
Return date and time.
A time-zone offset consists of a signed number of hours and minutes.
A string is a valid time-zone offset string representing a time-zone offset if it consists of either:
A "Z" (U+005A) character, allowed only if the time zone is UTC
Or, the following components, in the given order:
This format allows for time-zone offsets from -23:59 to +23:59. In practice, however, right now the range of offsets of actual time zones is -12:00 to +14:00, and the minutes component of offsets of actual time zones is always either 00, 30, or 45. There is no guarantee that this will remain so forever, however; time zones are changed by countries at will and do not follow a standard.
See also the usage notes and examples in the global date and time section below for details on using time-zone offsets with historical times that predate the formation of formal time zones.
The rules to parse a time-zone offset string are as follows. This will return either a time-zone offset, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a time-zone offset component to obtain timezonehours and timezoneminutes. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Return the time-zone offset that is timezonehours hours and timezoneminutes minutes from UTC.
The rules to parse a time-zone offset component, given an input string and a position, are as follows. This will return either time-zone hours and time-zone minutes, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
If the character at position is a U+005A LATIN CAPITAL LETTER Z character (Z), then:
Let timezonehours be 0.
Let timezoneminutes be 0.
Advance position to the next character in input.
Otherwise, if the character at position is either a "+" (U+002B) or a "-" (U+002D), then:
If the character at position is a "+" (U+002B), let sign be "positive". Otherwise, it's a "-" (U+002D); let sign be "negative".
Advance position to the next character in input.
Collect a sequence of characters that are ASCII digits. Let s be the collected sequence.
If s is exactly two characters long, then run these substeps:
Interpret s as a base-ten integer. Let that number be the timezonehours.
If position is beyond the end of input or if the character at position is not a U+003A COLON character, then fail. Otherwise, move position forwards one character.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the timezoneminutes.
If s is exactly four characters long, then run these substeps:
Interpret the first two characters of s as a base-ten integer. Let that number be the timezonehours.
Interpret the last two characters of s as a base-ten integer. Let that number be the timezoneminutes.
Otherwise, fail.
Otherwise, fail.
Return timezonehours and timezoneminutes.
A global date and time consists of a specific proleptic-Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, expressed with a time-zone offset, consisting of a signed number of hours and minutes. [GREGORIAN]
A string is a valid global date and time string representing a date, time, and a time-zone offset if it consists of the following components in the given order:
Times in dates before the formation of UTC in the mid twentieth century must be expressed and interpreted in terms of UT1 (contemporary Earth solar time at the 0° longitude), not UTC (the approximation of UT1 that ticks in SI seconds). Time before the formation of time zones must be expressed and interpeted as UT1 times with explicit time zones that approximate the contemporary difference between the appropriate local time and the time observed at the location of Greenwich, London.
The following are some examples of dates written as valid global date and time strings.
0037-12-13 00:00Z
"1979-10-14T12:00:00.001-04:00
"8592-01-01T02:09+02:09
"Several things are notable about these dates:
T
" is replaced by a space, it must be a single space
character. The string "2001-12-21 12:00Z
" (with two spaces
between the components) would not be parsed successfully.The zone offset is not a complete time zone specification. When working with real date and time values, consider using a separate field for time zone, perhaps using IANA time zone IDs. [TIMEZONES]
A string is a valid normalized forced-UTC global date and time string representing a date, time, and a time-zone offset if it consists of the following components in the given order:
The rules to parse a global date and time string are as follows. This will return either a time in UTC, with associated time-zone offset information for round-tripping or display purposes, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Parse a date component to obtain year, month, and day. If this returns nothing, then fail.
If position is beyond the end of input or if the character at position is neither a U+0054 LATIN CAPITAL LETTER T character (T) nor a U+0020 SPACE character, then fail. Otherwise, move position forwards one character.
Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail.
If position is beyond the end of input, then fail.
Parse a time-zone offset component to obtain timezonehours and timezoneminutes. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
Let time be the moment in time at year year, month month, day day, hours hour, minute minute, second second, subtracting timezonehours hours and timezoneminutes minutes. That moment in time is a moment in the UTC time zone.
Let timezone be timezonehours hours and timezoneminutes minutes from UTC.
Return time and timezone.
A week consists of a week-year number and a week number representing a seven-day period starting on a Monday. Each week-year in this calendaring system has either 52 or 53 such seven-day periods, as defined below. The seven-day period starting on the Gregorian date Monday December 29th 1969 (1969-12-29) is defined as week number 1 in week-year 1970. Consecutive weeks are numbered sequentially. The week before the number 1 week in a week-year is the last week in the previous week-year, and vice versa. [GREGORIAN]
A week-year with a number year has 53 weeks if it corresponds to either a year year in the proleptic Gregorian calendar that has a Thursday as its first day (January 1st), or a year year in the proleptic Gregorian calendar that has a Wednesday as its first day (January 1st) and where year is a number divisible by 400, or a number divisible by 4 but not by 100. All other week-years have 52 weeks.
The week number of the last day of a week-year with 53 weeks is 53; the week number of the last day of a week-year with 52 weeks is 52.
The week-year number of a particular day can be different than the number of the year that contains that day in the proleptic Gregorian calendar. The first week in a week-year y is the week that contains the first Thursday of the Gregorian year y.
For modern purposes, a week as defined here is equivalent to ISO weeks as defined in ISO 8601. [ISO8601]
A string is a valid week string representing a week-year year and week week if it consists of the following components in the given order:
The rules to parse a week string are as follows. This will return either a week-year number and week number, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the year.
If year is not a number greater than zero, then fail.
If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character.
If position is beyond the end of input or if the character at position is not a "W" (U+0057) character, then fail. Otherwise, move position forwards one character.
Collect a sequence of characters that are ASCII digits. If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the week.
Let maxweek be the week number of the last day of year year.
If week is not a number in the range 1 ≤ week ≤ maxweek, then fail.
If position is not beyond the end of input, then fail.
Return the week-year number year and the week number week.
A duration consists of a number of seconds.
Since months and seconds are not comparable (a month is not a precise number of seconds, but is instead a period whose exact length depends on the precise day from which it is measured) a duration as defined in this specification cannot include months (or years, which are equivalent to twelve months). Only durations that describe a specific number of seconds can be described.
A string is a valid duration string representing a duration t if it consists of either of the following:
A literal U+0050 LATIN CAPITAL LETTER P character followed by one or more of the following subcomponents, in the order given, where the number of days, hours, minutes, and seconds corresponds to the same number of seconds as in t:
One or more ASCII digits followed by a U+0044 LATIN CAPITAL LETTER D character, representing a number of days.
A U+0054 LATIN CAPITAL LETTER T character followed by one or more of the following subcomponents, in the order given:
One or more ASCII digits followed by a U+0048 LATIN CAPITAL LETTER H character, representing a number of hours.
One or more ASCII digits followed by a U+004D LATIN CAPITAL LETTER M character, representing a number of minutes.
The following components:
One or more ASCII digits, representing a number of seconds.
Optionally, a "." (U+002E) character followed by one, two, or three ASCII digits, representing a fraction of a second.
A U+0053 LATIN CAPITAL LETTER S character.
This, as with a number of other date- and time-related microsyntaxes defined in this specification, is based on one of the formats defined in ISO 8601. [ISO8601]
One or more duration time components, each with a different duration time component scale, in any order; the sum of the represented seconds being equal to the number of seconds in t.
A duration time component is a string consisting of the following components:
Zero or more space characters.
One or more ASCII digits, representing a number of time units, scaled by the duration time component scale specified (see below) to represent a number of seconds.
If the duration time component scale specified is 1 (i.e. the units are seconds), then, optionally, a "." (U+002E) character followed by one, two, or three ASCII digits, representing a fraction of a second.
Zero or more space characters.
One of the following characters, representing the duration time component scale of the time unit used in the numeric part of the duration time component:
Zero or more space characters.
This is not based on any of the formats in ISO 8601. It is intended to be a more human-readable alternative to the ISO 8601 duration format.
The rules to parse a duration string are as follows. This will return either a duration or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let months, seconds, and component count all be zero.
Let M-disambiguator be minutes.
This flag's other value is months. It is used to disambiguate the "M" unit in ISO8601 durations, which use the same unit for months and minutes. Months are not allowed, but are parsed for future compatibility and to avoid misinterpreting ISO8601 durations that would be valid in other contexts.
If position is past the end of input, then fail.
If the character in input pointed to by position is a U+0050 LATIN CAPITAL LETTER P character, then advance position to the next character, set M-disambiguator to months, and skip whitespace.
Run the following substeps in a loop, until a step requiring the loop to be broken or the entire algorithm to fail is reached:
Let units be undefined. It will be assigned one of the following values: years, months, weeks, days, hours, minutes, and seconds.
Let next character be undefined. It is used to process characters from the input.
If position is past the end of input, then break the loop.
If the character in input pointed to by position is a U+0054 LATIN CAPITAL LETTER T character, then advance position to the next character, set M-disambiguator to minutes, skip whitespace, and return to the top of the loop.
Set next character to the character in input pointed to by position.
If next character is a "." (U+002E) character, then let N equal zero. (Do not advance position. That is taken care of below.)
Otherwise, if next character is an ASCII digit, then collect a sequence of characters that are ASCII digits, interpret the resulting sequence as a base-ten integer, and let N be that number.
Otherwise next character is not part of a number; fail.
If position is past the end of input, then fail.
Set next character to the character in input pointed to by position, and this time advance position to the next character. (If next character was a U+002E FULL STOP character (.) before, it will still be that character this time.)
If next character is a "." (U+002E) character, then run these substeps:
Collect a sequence of characters that are ASCII digits. Let s be the resulting sequence.
If s is the empty string, then fail.
Let length be the number of characters in s.
Let fraction be the result of interpreting s as a base-ten integer, and then dividing that number by 10length.
Increment N by fraction.
If position is past the end of input, then fail.
Set next character to the character in input pointed to by position, and advance position to the next character.
If next character is neither a U+0053 LATIN CAPITAL LETTER S character nor a U+0073 LATIN SMALL LETTER S character, then fail.
Set units to seconds.
Otherwise, run these substeps:
If next character is a space character, then skip whitespace, set next character to the character in input pointed to by position, and advance position to the next character.
If next character is a U+0059 LATIN CAPITAL LETTER Y character, or a U+0079 LATIN SMALL LETTER Y character, set units to years and set M-disambiguator to months.
If next character is a U+004D LATIN CAPITAL LETTER M character or a U+006D LATIN SMALL LETTER M character, and M-disambiguator is months, then set units to months.
If next character is a U+0057 LATIN CAPITAL LETTER W character or a U+0077 LATIN SMALL LETTER W character, set units to weeks and set M-disambiguator to minutes.
If next character is a U+0044 LATIN CAPITAL LETTER D character or a U+0064 LATIN SMALL LETTER D character, set units to days and set M-disambiguator to minutes.
If next character is a U+0048 LATIN CAPITAL LETTER H character or a U+0068 LATIN SMALL LETTER H character, set units to hours and set M-disambiguator to minutes.
If next character is a U+004D LATIN CAPITAL LETTER M character or a U+006D LATIN SMALL LETTER M character, and M-disambiguator is minutes, then set units to minutes.
If next character is a U+0053 LATIN CAPITAL LETTER S character or a U+0073 LATIN SMALL LETTER S character, set units to seconds and set M-disambiguator to minutes.
Otherwise if next character is none of the above characters, then fail.
Increment component count.
Let multiplier be 1.
If units is years, multiply multiplier by 12 and set units to months.
If units is months, add the product of N and multiplier to months.
Otherwise, run these substeps:
If units is weeks, multiply multiplier by 7 and set units to days.
If units is days, multiply multiplier by 24 and set units to hours.
If units is hours, multiply multiplier by 60 and set units to minutes.
If units is minutes, multiply multiplier by 60 and set units to seconds.
Forcibly, units is now seconds. Add the product of N and multiplier to seconds.
If component count is zero, fail.
If months is not zero, fail.
Return the duration consisting of seconds seconds.
A string is a valid date string with optional time if it is also one of the following:
The rules to parse a date or time string are as follows. The algorithm will return either a date, a time, a global date and time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Set start position to the same position as position.
Set the date present and time present flags to true.
Parse a date component to obtain year, month, and day. If this fails, then set the date present flag to false.
If date present is true, and position is not beyond the end of input, and the character at position is either a "T" (U+0054) character or a U+0020 SPACE character, then advance position to the next character in input.
Otherwise, if date present is true, and either position is beyond the end of input or the character at position is neither a "T" (U+0054) character nor a U+0020 SPACE character, then set time present to false.
Otherwise, if date present is false, set position back to the same position as start position.
If the time present flag is true, then parse a time component to obtain hour, minute, and second. If this returns nothing, then fail.
If the date present and time present flags are both true, but position is beyond the end of input, then fail.
If the date present and time present flags are both true, parse a time-zone offset component to obtain timezonehours and timezoneminutes. If this returns nothing, then fail.
If position is not beyond the end of input, then fail.
If the date present flag is true and the time present flag is false, then let date be the date with year year, month month, and day day, and return date.
Otherwise, if the time present flag is true and the date present flag is false, then let time be the time with hour hour, minute minute, and second second, and return time.
Otherwise, let time be the moment in time at year year, month month, day day, hours hour, minute minute, second second, subtracting timezonehours hours and timezoneminutes minutes, that moment in time being a moment in the UTC time zone; let timezone be timezonehours hours and timezoneminutes minutes from UTC; and return time and timezone.
A simple color consists of three 8-bit numbers in the range 0..255, representing the red, green, and blue components of the color respectively, in the sRGB color space. [SRGB]
A string is a valid simple color if it is exactly seven characters long, and the first character is a "#" (U+0023) character, and the remaining six characters are all ASCII hex digits, with the first two digits representing the red component, the middle two digits representing the green component, and the last two digits representing the blue component, in hexadecimal.
A string is a valid lowercase simple color if it is a valid simple color and doesn't use any characters in the range U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F.
The rules for parsing simple color values are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will return either a simple color or an error.
Let input be the string being parsed.
If input is not exactly seven characters long, then return an error.
If the first character in input is not a U+0023 NUMBER SIGN character (#), then return an error.
If the last six characters of input are not all ASCII hex digits, then return an error.
Let result be a simple color.
Interpret the second and third characters as a hexadecimal number and let the result be the red component of result.
Interpret the fourth and fifth characters as a hexadecimal number and let the result be the green component of result.
Interpret the sixth and seventh characters as a hexadecimal number and let the result be the blue component of result.
Return result.
The rules for serializing simple color values given a simple color are as given in the following algorithm:
Let result be a string consisting of a single "#" (U+0023) character.
Convert the red, green, and blue components in turn to two-digit hexadecimal numbers using lowercase ASCII hex digits, zero-padding if necessary, and append these numbers to result, in the order red, green, blue.
Return result, which will be a valid lowercase simple color.
Some obsolete legacy attributes parse colors in a more complicated manner, using the rules for parsing a legacy color value, which are given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will return either a simple color or an error.
Let input be the string being parsed.
If input is the empty string, then return an error.
Strip leading and trailing whitespace from input.
If input is an ASCII case-insensitive match for the
string "transparent
", then return an error.
If input is an ASCII case-insensitive match for one of the keywords listed in the SVG color keywords section of the CSS3 Color specification, then return the simple color corresponding to that keyword. [CSSCOLOR]
CSS2 System Colors are not recognised.
If input is four characters long, and the first character in input is a "#" (U+0023) character, and the last three characters of input are all ASCII hex digits, then run these substeps:
Let result be a simple color.
Interpret the second character of input as a hexadecimal digit; let the red component of result be the resulting number multiplied by 17.
Interpret the third character of input as a hexadecimal digit; let the green component of result be the resulting number multiplied by 17.
Interpret the fourth character of input as a hexadecimal digit; let the blue component of result be the resulting number multiplied by 17.
Return result.
Replace any characters in input that have a Unicode code point greater
than U+FFFF (i.e. any characters that are not in the basic multilingual plane) with the
two-character string "00
".
If input is longer than 128 characters, truncate input, leaving only the first 128 characters.
If the first character in input is a "#" (U+0023) character, remove it.
Replace any character in input that is not an ASCII hex digit with the character "0" (U+0030).
While input's length is zero or not a multiple of three, append a "0" (U+0030) character to input.
Split input into three strings of equal length, to obtain three components. Let length be the length of those components (one third the length of input).
If length is greater than 8, then remove the leading length-8 characters in each component, and let length be 8.
While length is greater than two and the first character in each component is a "0" (U+0030) character, remove that character and reduce length by one.
If length is still greater than two, truncate each component, leaving only the first two characters in each.
Let result be a simple color.
Interpret the first component as a hexadecimal number; let the red component of result be the resulting number.
Interpret the second component as a hexadecimal number; let the green component of result be the resulting number.
Interpret the third component as a hexadecimal number; let the blue component of result be the resulting number.
Return result.
A set of space-separated tokens is a string containing zero or more words (known as tokens) separated by one or more space characters, where words consist of any string of one or more characters, none of which are space characters.
A string containing a set of space-separated tokens may have leading or trailing space characters.
An unordered set of unique space-separated tokens is a set of space-separated tokens where none of the tokens are duplicated.
An ordered set of unique space-separated tokens is a set of space-separated tokens where none of the tokens are duplicated but where the order of the tokens is meaningful.
Sets of space-separated tokens sometimes have a defined set of allowed values. When a set of allowed values is defined, the tokens must all be from that list of allowed values; other values are non-conforming. If no such set of allowed values is provided, then all values are conforming.
How tokens in a set of space-separated tokens are to be compared (e.g. case-sensitively or not) is defined on a per-set basis.
When a user agent has to split a string on spaces, it must use the following algorithm:
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let tokens be an ordered list of tokens, initially empty.
While position is not past the end of input:
Collect a sequence of characters that are not space characters.
Append the string collected in the previous step to tokens.
Return tokens.
A set of comma-separated tokens is a string containing zero or more tokens each separated from the next by a single "," (U+002C) character, where tokens consist of any string of zero or more characters, neither beginning nor ending with space characters, nor containing any "," (U+002C) characters, and optionally surrounded by space characters.
For instance, the string " a ,b,,d d
" consists of four tokens: "a", "b", the empty
string, and "d d". Leading and trailing whitespace around each token doesn't count as part of
the token, and the empty string can be a token.
Sets of comma-separated tokens sometimes have further restrictions on what consists a valid token. When such restrictions are defined, the tokens must all fit within those restrictions; other values are non-conforming. If no such restrictions are specified, then all values are conforming.
When a user agent has to split a string on commas, it must use the following algorithm:
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Let tokens be an ordered list of tokens, initially empty.
Token: If position is past the end of input, jump to the last step.
Collect a sequence of characters that are not "," (U+002C) characters. Let s be the resulting sequence (which might be the empty string).
Append s to tokens.
If position is not past the end of input, then the character at position is a "," (U+002C) character; advance position past that character.
Jump back to the step labeled token.
Return tokens.
A valid hash-name reference to an element of type type is a
string consisting of a "#" (U+0023) character followed by a string which exactly matches
the value of the name
attribute of an element with type type in the document.
The rules for parsing a hash-name reference to an element of type type are as follows:
If the string being parsed does not contain a U+0023 NUMBER SIGN character, or if the first such character in the string is the last character in the string, then return null and abort these steps.
Let s be the string from the character immediately after the first U+0023 NUMBER SIGN character in the string being parsed up to the end of that string.
Return the first element of type type that has an id
attribute whose value is a case-sensitive match for s or a name
attribute whose value is a compatibility
caseless match for s.
A string is a valid media query if it matches the media_query_list
production of the Media Queries specification. [MQ]
A string matches the environment of the user if it is the empty string, a string consisting of only space characters, or is a media query that matches the user's environment according to the definitions given in the Media Queries specification. [MQ]
A URL is a valid URL if it conforms to the authoring conformance requirements in the URL standard. [URL]
A string is a valid non-empty URL if it is a valid URL but it is not the empty string.
A string is a valid URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid URL.
A string is a valid non-empty URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid non-empty URL.
This specification defines the URL about:legacy-compat
as a reserved,
though unresolvable, about:
URL, for use in DOCTYPEs in HTML documents when needed for
compatibility with XML tools. [ABOUT]
This specification defines the URL about:srcdoc
as a reserved, though
unresolvable, about:
URL, that is used as the document's
address of iframe
srcdoc
documents. [ABOUT]
The fallback base URL of a Document
object is the absolute
URL obtained by running these substeps:
If the Document
is an iframe
srcdoc
document, then return the document base
URL of the Document
's browsing context's browsing context
container's Document
and abort these steps.
If the document's address is about:blank
, and the
Document
's browsing context has a creator browsing
context, then return the document base URL of the creator
Document
, and abort these steps.
Return the document's address.
The document base URL of a Document
object is the absolute
URL obtained by running these substeps:
If there is no base
element that has an href
attribute in the Document
, then the
document base URL is the Document
's fallback base URL;
abort these steps.
Otherwise, the document base URL is the frozen base URL of the
first base
element in the Document
that has an href
attribute, in tree order.
Resolving a URL is the process of taking a relative URL and obtaining the absolute URL that it implies.
To resolve a URL to an absolute URL relative to either another absolute URL or an element, the user agent must use the following steps. Resolving a URL can result in an error, in which case the URL is not resolvable.
Let url be the URL being resolved.
Let encoding be determined as follows:
Document
, and the URL character encoding is the
document's character encoding.If encoding is a UTF-16 encoding, then change the value of encoding to UTF-8.
If the algorithm was invoked with an absolute URL to use as the base URL, let base be that absolute URL.
Otherwise, let base be the element's base URL.
Apply the URL parser to url, with base as the base URL, with encoding as the encoding.
If this returns failure, then abort these steps with an error.
Let parsed URL be the result of the URL parser.
Let serialized URL be the result of apply the URL serializer to parsed URL.
Return serialized URL as the resulting absolute URL and parsed URL as the resulting parsed URL.
Given an element, the element's base URL is the base URI of the element, as
defined by the XML Base specification, with the base URI of the document entity being
defined as the document base URL of the Document
that owns the element.
[XMLBASE]
For the purposes of the XML Base specification, user agents must act as if all
Document
objects represented XML documents.
It is possible for xml:base
attributes to be
present even in HTML fragments, as such attributes can be added dynamically using script. (Such
scripts would not be conforming, however, as xml:base
attributes are not allowed in HTML documents.)
When an xml:base
attribute is set, changed, or removed, the
attribute's element, and all descendant elements, are affected by a base URL
change.
When a document's document base URL changes, all elements in that document are affected by a base URL change.
The following are base URL change steps, which run when an element is affected by a base URL change (as defined by the DOM specification):
If the absolute URL identified by the hyperlink is being shown to the user, or
if any data derived from that URL is affecting the display, then the href
attribute should be re-resolved relative to the element and the UI updated appropriately.
For example, the CSS :link
/:visited
pseudo-classes might have been affected.
q
, blockquote
, ins
, or
del
element with a cite
attributeIf the absolute URL identified by the cite
attribute is
being shown to the user, or if any data derived from that URL is affecting the display, then the
URL should be re-resolved relative to the
element and the UI updated appropriately.
The element is not directly affected.
For instance, changing the base URL doesn't affect the image displayed by
img
elements, although subsequent accesses of the src
IDL attribute from script will return a new absolute
URL that might no longer correspond to the image being shown.
User agents can implement a variety of transfer protocols, but this specification mostly defines behavior in terms of HTTP. [HTTP]
The HTTP GET method is equivalent to the default retrieval action of the protocol. For example, RETR in FTP. Such actions are idempotent and safe, in HTTP terms.
The HTTP response codes are equivalent to statuses in other protocols that have the same basic meanings. For example, a "file not found" error is equivalent to a 404 code, a server error is equivalent to a 5xx code, and so on.
The HTTP headers are equivalent to fields in other protocols that have the same basic meaning. For example, the HTTP authentication headers are equivalent to the authentication aspects of the FTP protocol.
A referrer source is either a Document
or a URL.
When a user agent is to fetch a resource or URL, optionally from an origin origin, optionally using a specific referrer source as an override referrer source, and optionally with any of a synchronous flag, a manual redirect flag, a force same-origin flag, and a block cookies flag, the following steps must be run. (When a URL is to be fetched, the URL identifies a resource to be obtained.)
If there is a specific override referrer source, and it is a URL, then let referrer be the override referrer source, and jump to the step labeled clean referrer.
Let document be the appropriate Document
as given by the
following list:
Document
.While document is an iframe
srcdoc
document, let document be
document's browsing context's browsing context
container's Document
instead.
If the origin of Document is not a scheme/host/port tuple, then set referrer to the empty string and jump to the step labeled clean referrer.
Let referrer be the document's address of document.
Clean referrer: Apply the URL parser to referrer and let parsed referrer be the resulting parsed URL.
Let referrer be the result of applying the URL serializer to parsed referrer, with the exclude fragment flag set.
If referrer is not the empty string, is not a data:
URL, and is not the URL
"about:blank
", then generate the address of the resource from which Request-URIs
are obtained as required by HTTP for the Referer
(sic)
header from referrer. [HTTP]
Otherwise, the Referer
(sic) header must be omitted,
regardless of its value.
If the algorithm was not invoked with the synchronous flag, perform the remaining steps asynchronously.
If the Document
with which any tasks queued by this algorithm would be associated doesn't have an
associated browsing context, then abort these steps.
This is the main step.
If the resource is to be obtained from an application cache, then use the data from that application cache, as if it had been obtained in the manner appropriate given its URL.
If the resource is identified by an absolute URL, and the resource is to be
obtained using an idempotent action (such as an HTTP GET or equivalent), and it is already being downloaded
for other reasons (e.g. another invocation of this algorithm), and this request would be
identical to the previous one (e.g. same Accept
and Origin
headers), and the user agent is configured such that it is to
reuse the data from the existing download instead of initiating a new one, then use the results
of the existing download instead of starting a new one.
Otherwise, if the resource is identified by an absolute URL with a scheme that
does not define a mechanism to obtain the resource (e.g. it is a mailto:
URL) or that the user agent does not support, then act as if the resource was an HTTP 204 No
Content response with no other metadata.
Otherwise, if the resource is identified by the URL
about:blank
, then the resource is immediately available and consists of
the empty string, with no metadata.
Otherwise, at a time convenient to the user and the user agent, download (or otherwise
obtain) the resource, applying the semantics of the relevant specifications (e.g. performing an
HTTP GET or POST operation, or reading the file from disk, or expanding data:
URLs, etc).
For the purposes of the Referer
(sic) header, use the
address of the resource from which Request-URIs are obtained generated in the earlier
step.
For the purposes of the Origin
header, if the fetching algorithm was explicitly initiated from an origin,
then the origin that initiated the HTTP request is origin.
Otherwise, this is a request from a "privacy-sensitive" context. [ORIGIN]
If the algorithm was not invoked with the block cookies flag, and there are cookies to be set, then the user agent must run the following substeps:
Wait until ownership of the storage mutex can be taken by this instance of the fetching algorithm.
Take ownership of the storage mutex.
Update the cookies. [COOKIES]
Release the storage mutex so that it is once again free.
If the fetched resource is an HTTP redirect or equivalent, then:
Abort these steps and return failure from this algorithm, as if the remote host could not be contacted.
Continue, using the fetched resource (the redirect) as the result of the algorithm. If the calling algorithm subsequently requires the user agent to transparently follow the redirect, then the user agent must resume this algorithm from the main step, but using the target of the redirect as the resource to fetch, rather than the original resource.
First, apply any relevant requirements for redirects (such as showing any appropriate
prompts). Then, redo main step, but using the target of the redirect as the resource to
fetch, rather than the original resource. For HTTP requests, the new request must include the
same headers as the original request, except for headers for which other requirements are
specified (such as the Host
header). [HTTP]
The HTTP specification requires that 301, 302, and 307 redirects, when applied to methods other than the safe methods, not be followed without user confirmation. That would be an appropriate prompt for the purposes of the requirement in the paragraph above. [HTTP]
If the algorithm was not invoked with the synchronous flag: When the resource is available, or if there is an error of some description, queue a task that uses the resource as appropriate. If the resource can be processed incrementally, as, for instance, with a progressively interlaced JPEG or an HTML file, additional tasks may be queued to process the data as it is downloaded. The task source for these tasks is the networking task source.
Otherwise, return the resource or error information to the calling algorithm.
If the user agent can determine the actual length of the resource being fetched for an instance of this algorithm, and if that length is finite, then
that length is the file's size. Otherwise, the subject of
the algorithm (that is, the resource being fetched) has no known size. (For example, the HTTP Content-Length
header might provide this information.)
The user agent must also keep track of the number of bytes downloaded for each instance of this algorithm. This number must exclude any out-of-band metadata, such as HTTP headers.
The application cache processing model introduces some changes to the networking model to handle the returning of cached resources.
The navigation processing model handles redirects itself, overriding the redirection handling that would be done by the fetching algorithm.
Whether the type sniffing rules apply to the fetched resource depends on the algorithm that invokes the rules — they are not always applicable.
Anything in this specification that refers to HTTP also applies to HTTP-over-TLS, as
represented by URLs representing the https
scheme.
[HTTPS]
User agents should report certificate errors to the user and must either refuse to download resources sent with erroneous certificates or must act as if such resources were in fact served with no encryption.
User agents should warn the user that there is a potential problem whenever the user visits a page that the user has previously visited, if the page uses less secure encryption on the second visit.
Not doing so can result in users not noticing man-in-the-middle attacks.
If a user connects to a server with a self-signed certificate, the user agent could allow the connection but just act as if there had been no encryption. If the user agent instead allowed the user to override the problem and then displayed the page as if it was fully and safely encrypted, the user could be easily tricked into accepting man-in-the-middle connections.
If a user connects to a server with full encryption, but the page then refers to an external resource that has an expired certificate, then the user agent will act as if the resource was unavailable, possibly also reporting the problem to the user. If the user agent instead allowed the resource to be used, then an attacker could just look for "secure" sites that used resources from a different host and only apply man-in-the-middle attacks to that host, for example taking over scripts in the page.
If a user bookmarks a site that uses a CA-signed certificate, and then later revisits that site directly but the site has started using a self-signed certificate, the user agent could warn the user that a man-in-the-middle attack is likely underway, instead of simply acting as if the page was not encrypted.
The Content-Type metadata of a resource must be obtained and interpreted in a manner consistent with the requirements of the MIME Sniffing specification. [MIMESNIFF]
The sniffed type of a resource must be found in a manner consistent with the requirements given in the MIME Sniffing specification for finding the sniffed media type of the relevant sequence of octets. [MIMESNIFF]
The rules for sniffing images specifically and the rules for distinguishing if a resource is text or binary are also defined in the MIME Sniffing specification. Both sets of rules return a MIME type as their result. [MIMESNIFF]
It is imperative that the rules in the MIME Sniffing specification be followed exactly. When a user agent uses different heuristics for content type detection than the server expects, security problems can occur. For more details, see the MIME Sniffing specification. [MIMESNIFF]
meta
elementsThe algorithm for extracting a character encoding from a meta
element,
given a string s, is as follows. It either returns a character encoding or
nothing.
Let position be a pointer into s, initially pointing at the start of the string.
Loop: Find the first seven characters in s after position that are an ASCII case-insensitive match for the word "charset
". If no such match is found, return nothing and abort these
steps.
Skip any space characters that immediately follow the
word "charset
" (there might not be any).
If the next character is not a "=" (U+003D), then move position to point just before that next character, and jump back to the step labeled loop.
Skip any space characters that immediately follow the equals sign (there might not be any).
Process the next character as follows:
This algorithm is distinct from those in the HTTP specification (for example, HTTP doesn't allow the use of single quotes and requires supporting a backslash-escape mechanism that is not supported by this algorithm). While the algorithm is used in contexts that, historically, were related to HTTP, the syntax as supported by implementations diverged some time ago. [HTTP]
A CORS settings attribute is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.
Keyword | State | Brief description |
---|---|---|
anonymous
| Anonymous | Cross-origin CORS requests for the element will have the omit credentials flag set. |
use-credentials
| Use Credentials | Cross-origin CORS requests for the element will not have the omit credentials flag set. |
The empty string is also a valid keyword, and maps to the Anonymous state. The attribute's invalid value
default is the Anonymous state. For the
purposes of reflection, the canonical case for the Anonymous state is the anonymous
keyword. The missing value
default, used when the attribute is omitted, is the No
CORS state.
When the user agent is required to perform a potentially CORS-enabled fetch of an absolute URL URL with a mode mode that is either "No CORS", "Anonymous", or "Use Credentials", optionally using a referrer source referrer source, with an origin origin, and with a default origin behaviour default which is either "taint" or "fail", it must run the first applicable set of steps from the following list. The default origin behaviour is only used if mode is "No CORS". This algorithm wraps the fetch algorithm above, and labels the obtained resource as either CORS-same-origin or CORS-cross-origin, or blocks the resource entirely.
data:
URLabout:blank
Run these substeps:
Fetch URL, using referrer source if one was specified, with the manual redirect flag set.
Loop: Wait for the fetch algorithm to know if the result is a redirect or not.
Follow the first appropriate steps from the following list:
Set URL to the target URL of the redirect and return to the top of the potentially CORS-enabled fetch algorithm (this time, one of the other branches below might be taken, based on the value of mode).
The origin of the target URL of the redirect is the same origin as origin.
Transparently follow the redirect and jump to the step labeled loop above.
The resource is available, it is not a redirect, and its origin is the same origin as origin.
The tasks from the fetch algorithm are queued normally, and for the purposes of the calling algorithm, the obtained resource is CORS-same-origin.
The URL does not have the same origin as origin.
Fetch URL, using referrer source if one was specified.
The tasks from the fetch algorithm are queued normally, but for the purposes of the calling algorithm, the obtained resource is CORS-cross-origin. The user agent may report a cross-origin resource access failure to the user (e.g. in a debugging console).
The URL does not have the same origin as origin, and default is fail.
Discard any data fetched as part of this algorithm, and prevent any tasks from such invocations of the fetch algorithm from being queued. For the purposes of the calling algorithm, the user agent must act as if there was a fatal network error and no resource was obtained. The user agent may report a cross-origin resource access failure to the user (e.g. in a debugging console).
The URL does not have the same origin as origin.
Run these steps:
Perform a cross-origin request with the request URL set to URL, with the CORS referrer source set to referrer source if one was specified, the source origin set to origin, and with the omit credentials flag set if mode is "Anonymous" and not set otherwise. [CORS]
Wait for the CORS cross-origin request status to have a value.
Jump to the appropriate step from the following list:
Discard all fetched data and prevent any tasks from the fetch algorithm from being queued. For the purposes of the calling algorithm, the user agent must act as if there was a fatal network error and no resource was obtained. If a CORS resource sharing check failed, the user agent may report a cross-origin resource access failure to the user (e.g. in a debugging console).
The tasks from the fetch algorithm are queued normally, and for the purposes of the calling algorithm, the obtained resource is CORS-same-origin.
Some IDL attributes are defined to reflect a particular content attribute. This means that on getting, the IDL attribute returns the current value of the content attribute, and on setting, the IDL attribute changes the value of the content attribute to the given value.
In general, on getting, if the content attribute is not present, the IDL attribute must act as if the content attribute's value is the empty string; and on setting, if the content attribute is not present, it must first be added.
If a reflecting IDL attribute is a DOMString
attribute whose content attribute is
defined to contain a URL, then on getting, the IDL attribute must resolve the value of the content attribute relative to the element
and return the resulting absolute URL if that was successful, or the empty string
otherwise; and on setting, must set the content attribute to the specified literal value. If the
content attribute is absent, the IDL attribute must return the default value, if the content
attribute has one, or else the empty string.
If a reflecting IDL attribute is a DOMString
attribute whose content attribute is
defined to contain one or more URLs, then on getting, the IDL attribute
must split the content attribute on spaces and
return the concatenation of resolving each token URL to an
absolute URL relative to the element, with a single U+0020 SPACE character between
each URL, ignoring any tokens that did not resolve successfully. If the content attribute is
absent, the IDL attribute must return the default value, if the content attribute has one, or else
the empty string. On setting, the IDL attribute must set the content attribute to the specified
literal value.
If a reflecting IDL attribute is a DOMString
attribute whose content attribute is
an enumerated attribute, and the IDL attribute is limited to only known
values, then, on getting, the IDL attribute must return the conforming value associated with
the state the attribute is in (in its canonical case), if any, or the empty string if the
attribute is in a state that has no associated keyword value or if the attribute is not in a defined state
(e.g. the attribute is missing and there is no missing value default); and on setting, the
content attribute must be set to the specified new value.
If a reflecting IDL attribute is a DOMString
attribute but doesn't fall into any
of the above categories, then the getting and setting must be done in a transparent,
case-preserving manner.
If a reflecting IDL attribute is a boolean
attribute, then on getting the
IDL attribute must return true if the content attribute is set, and false if it is absent. On
setting, the content attribute must be removed if the IDL attribute is set to false, and must be
set to the empty string if the IDL attribute is set to true. (This corresponds to the rules for
boolean content attributes.)
If a reflecting IDL attribute has a signed integer type (long
) then, on getting,
the content attribute must be parsed according to the rules for parsing signed integers, and if that is successful, and the value is in
the range of the IDL attribute's type, the resulting value must be returned. If, on the other
hand, it fails or returns an out of range value, or if the attribute is absent, then the default
value must be returned instead, or 0 if there is no default value. On setting, the given value
must be converted to the shortest possible string representing the number as a valid
integer and then that string must be used as the new content attribute value.
If a reflecting IDL attribute has a signed integer type (long
) that is
limited to only non-negative numbers then, on getting, the content attribute must be
parsed according to the rules for parsing non-negative integers, and if that is
successful, and the value is in the range of the IDL attribute's type, the resulting value must be
returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is
absent, the default value must be returned instead, or −1 if there is no default value. On
setting, if the value is negative, the user agent must throw an IndexSizeError
exception. Otherwise, the given value must be converted to the shortest possible string
representing the number as a valid non-negative integer and then that string must be
used as the new content attribute value.
If a reflecting IDL attribute has an unsigned integer type (unsigned
long
) then, on getting, the content attribute must be parsed according to the rules
for parsing non-negative integers, and if that is successful, and the value is in the range
0 to 2147483647 inclusive, the resulting value must be returned. If, on the other hand, it fails
or returns an out of range value, or if the attribute is absent, the default value must be
returned instead, or 0 if there is no default value. On setting, first, if the new value is in the
range 0 to 2147483647, then let n be the new value, otherwise let n be the default value, or 0 if there is no default value; then, n must be converted to the shortest possible string representing the number as a
valid non-negative integer and that string must be used as the new content attribute
value.
If a reflecting IDL attribute has an unsigned integer type (unsigned long
) that is
limited to only non-negative numbers greater than zero, then the behavior is similar to
the previous case, but zero is not allowed. On getting, the content attribute must first be parsed
according to the rules for parsing non-negative integers, and if that is successful,
and the value is in the range 1 to 2147483647 inclusive, the resulting value must be returned. If,
on the other hand, it fails or returns an out of range value, or if the attribute is absent, the
default value must be returned instead, or 1 if there is no default value. On setting, if the
value is zero, the user agent must throw an IndexSizeError
exception. Otherwise,
first, if the new value is in the range 1 to 2147483647, then let n be the new
value, otherwise let n be the default value, or 1 if there is no default
value; then, n must be converted to the shortest possible string representing
the number as a valid non-negative integer and that string must be used as the new
content attribute value.
If a reflecting IDL attribute has a floating-point number type (double
or
unrestricted double
), then, on getting, the content attribute must be parsed
according to the rules for parsing floating-point number values, and if that is
successful, the resulting value must be returned. If, on the other hand, it fails, or if the
attribute is absent, the default value must be returned instead, or 0.0 if there is no default
value. On setting, the given value must be converted to the best representation of the
number as a floating-point number and then that string must be used as the new content
attribute value.
If a reflecting IDL attribute has a floating-point number type (double
or
unrestricted double
) that is limited to numbers greater than zero, then
the behavior is similar to the previous case, but zero and negative values are not allowed. On
getting, the content attribute must be parsed according to the rules for parsing
floating-point number values, and if that is successful and the value is greater than 0.0,
the resulting value must be returned. If, on the other hand, it fails or returns an out of range
value, or if the attribute is absent, the default value must be returned instead, or 0.0 if there
is no default value. On setting, if the value is less than or equal to zero, then the value must
be ignored. Otherwise, the given value must be converted to the best representation of the
number as a floating-point number and then that string must be used as the new content
attribute value.
The values Infinity and Not-a-Number (NaN) values throw an exception on setting, as defined in the Web IDL specification. [WEBIDL]
If a reflecting IDL attribute has the type DOMTokenList
or
DOMSettableTokenList
, then on getting it must return a DOMTokenList
or
DOMSettableTokenList
object (as appropriate) whose associated element is the element
in question and whose associated attribute's local name is the name of the attribute in question.
The same DOMTokenList
or DOMSettableTokenList
object must be returned
every time for each attribute.
If a reflecting IDL attribute has the type HTMLElement
, or an interface that
descends from HTMLElement
, then, on getting, it must run the following algorithm
(stopping at the first point where a value is returned):
document.getElementById()
method would find when
called on the content attribute's document if it were passed as its argument the current value of
the corresponding content attribute.On setting, if the given element has an id
attribute, and has the
same home subtree as the element of the attribute being set, and the given element is
the first element in that home subtree whose ID is
the value of that id
attribute, then the content attribute must be
set to the value of that id
attribute. Otherwise, the content
attribute must be set to the empty string.
The HTMLAllCollection
,
HTMLFormControlsCollection
,
HTMLOptionsCollection
,
interfaces are collections derived from the
HTMLCollection
interface.
The HTMLAllCollection
interface is used for generic collections of
elements just like HTMLCollection
, with the exception that its namedItem()
method returns an
HTMLCollection
object when there are multiple matching elements, and that its item()
method can be used as a synonym for its namedItem()
method. It is intended only for the
legacy document.all
attribute.
interface HTMLAllCollection : HTMLCollection {
// inherits length and item(unsigned long index)
(HTMLCollection or Element)? item(DOMString name);
legacycaller getter (HTMLCollection or Element)? namedItem(DOMString name); // shadows inherited namedItem()
HTMLAllCollection tags(DOMString tagName);
};
length
Returns the number of elements in the collection.
item
(index)Returns the item with index index from the collection. The items are sorted in tree order.
item
(name)item
(name)namedItem
(name)namedItem
(name)Returns the item with ID or name name from the collection.
If there are multiple matching items, then an HTMLCollection
object containing all those elements is returned.
Only a
, applet
, area
, embed
,
form
, frame
, frameset
, iframe
,
img
, and object
elements can have a name for the purpose of this
method; their name is given by the value of their name
attribute.
tags
(tagName)Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name.
The object's supported property indices are as defined for
HTMLCollection
objects.
The supported property names consist of the non-empty values of all the id
attributes of all the elements represented by the
collection, and the non-empty values of all the name
attributes of all the
a
, applet
, area
, embed
, form
,
frame
, frameset
, iframe
, img
, and
object
elements represented by the collection, in tree
order, ignoring later duplicates, with the id
of an element
preceding its name
if it contributes both, they differ from each other, and neither
is the duplicate of an earlier entry.
The item(name)
and namedItem(name)
methods must act according to the following algorithm:
Let collection be an HTMLCollection
object rooted at the
same node as the HTMLAllCollection
object on which the method was invoked, whose
filter matches only elements that already match the filter of the HTMLAllCollection
object on which the method was invoked and that are either:
The tags(tagName)
method must return an HTMLAllCollection
rooted
at the same node as the HTMLAllCollection
object on which the method was invoked,
whose filter matches only HTML elements whose local name is the tagName argument and that already match the filter of the
HTMLAllCollection
object on which the method was invoked. In HTML
documents, the argument must first be converted to ASCII lowercase.
The HTMLFormControlsCollection
interface is used for collections of
listed elements in form
and
fieldset
elements.
interface HTMLFormControlsCollection : HTMLCollection {
// inherits length and item()
legacycaller getter (RadioNodeList or Element)? namedItem(DOMString name); // shadows inherited namedItem()
};
interface RadioNodeList : NodeList {
attribute DOMString value;
};
length
Returns the number of elements in the collection.
item
(index)Returns the item with index index from the collection. The items are sorted in tree order.
namedItem
(name)namedItem
(name)Returns the item with ID or name
name from the collection.
If there are multiple matching items, then a RadioNodeList
object containing all those elements is returned.
Returns the value of the first checked radio button represented by the object.
Can be set, to check the first radio button with the given value represented by the object.
The object's supported property indices are as defined for
HTMLCollection
objects.
The supported property names consist of the non-empty values of all the id
and name
attributes of all the
elements represented by the collection, in tree order, ignoring later
duplicates, with the id
of an element preceding its name
if it contributes both, they differ from each other, and neither is the
duplicate of an earlier entry.
The namedItem(name)
method must act according to the following algorithm:
id
attribute or a name
attribute equal to name, then return that node and stop the algorithm.id
attribute or a name
attribute equal
to name, then return null and stop the algorithm.RadioNodeList
object representing a live
view of the HTMLFormControlsCollection
object, further filtered so that the only
nodes in the RadioNodeList
object are those that have either an id
attribute or a name
attribute equal
to name. The nodes in the RadioNodeList
object must be sorted in
tree order.RadioNodeList
object.Members of the RadioNodeList
interface inherited from the NodeList
interface must behave as they would on a NodeList
object.
The value
IDL attribute on the
RadioNodeList
object, on getting, must return the value returned by running the
following steps:
Let element be the first element in tree order
represented by the RadioNodeList
object that is an input
element whose
type
attribute is in the Radio Button state and whose checkedness is true. Otherwise, let it be null.
If element is null, or if it is an element with no value
attribute, return the empty string.
Otherwise, return the value of element's value
attribute.
On setting, the value
IDL attribute must run the
following steps:
Let element be the first element in tree order
represented by the RadioNodeList
object that is an input
element whose
type
attribute is in the Radio Button state and whose value
content attribute is present and equal to the new value, if
any. Otherwise, let it be null.
If element is not null, then set its checkedness to true.
The HTMLOptionsCollection
interface is used for collections of
option
elements. It is always rooted on a select
element and has
attributes and methods that manipulate that element's descendants.
interface HTMLOptionsCollection : HTMLCollection { // inherits item() attribute unsigned long length; // shadows inherited length legacycaller HTMLOptionElement? (DOMString name); setter creator void (unsigned long index, HTMLOptionElement? option); void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null); void remove(long index); attribute long selectedIndex; };
length
[ = value ]Returns the number of elements in the collection.
When set to a smaller number, truncates the number of option
elements in the corresponding container.
When set to a greater number, adds new blank option
elements to that container.
item
(index)Returns the item with index index from the collection. The items are sorted in tree order.
namedItem
(name)namedItem
(name)Returns the item with ID or name
name from the collection.
If there are multiple matching items, then the first is returned.
add
(element [, before ] )Inserts element before the node given by before.
The before argument can be a number, in which case element is inserted before the item with that number, or an element from the collection, in which case element is inserted before that element.
If before is omitted, null, or a number out of range, then element will be added at the end of the list.
This method will throw a HierarchyRequestError
exception if element is an ancestor of the element into which it is to be inserted.
selectedIndex
[ = value ]Returns the index of the first selected item, if any, or −1 if there is no selected item.
Can be set, to change the selection.
The object's supported property indices are as defined for
HTMLCollection
objects.
On getting, the length
attribute must return the number of nodes represented by the collection.
On setting, the behavior depends on whether the new value is equal to, greater than, or less
than the number of nodes represented by the collection at that time. If the number is
the same, then setting the attribute must do nothing. If the new value is greater, then n new option
elements with no attributes and no child nodes must be
appended to the select
element on which the HTMLOptionsCollection
is
rooted, where n is the difference between the two numbers (new value minus old
value). Mutation events must be fired as if a DocumentFragment
containing the new
option
elements had been inserted. If the new value is lower, then the last n nodes in the collection must be removed from their parent nodes, where n is the difference between the two numbers (old value minus new value).
Setting length
never removes
or adds any optgroup
elements, and never adds new children to existing
optgroup
elements (though it can remove children from them).
The supported property names consist of the non-empty values of all the id
and name
attributes of all the
elements represented by the collection, in tree order, ignoring later
duplicates, with the id
of an element preceding its name
if it contributes both, they differ from each other, and neither is
the duplicate of an earlier entry.
The legacy caller of the
HTMLOptionsCollection
interface must act like the namedItem()
method on the ancestor
HTMLCollection
interface.
When the user agent is to set the value of a new indexed property or set the value of an existing indexed property for a given property index index to a new value value, it must run the following algorithm:
If value is null, invoke the steps for the remove
method with index as
the argument, and abort these steps.
Let length be the number of nodes represented by the collection.
Let n be index minus length.
If n is greater than zero, then append a DocumentFragment
consisting of n-1 new option
elements with no attributes and
no child nodes to the select
element on which the HTMLOptionsCollection
is rooted.
If n is greater than or equal to zero, append value to the select
element. Otherwise, replace the indexth element in the collection by value.
The add(element, before)
method must act according to the following algorithm:
If element is an ancestor of the select
element on which
the HTMLOptionsCollection
is rooted, then throw a HierarchyRequestError
exception and abort these steps.
If before is an element, but that element isn't a descendant of the
select
element on which the HTMLOptionsCollection
is rooted, then throw
a NotFoundError
exception and abort these steps.
If element and before are the same element, then return and abort these steps.
If before is a node, then let reference be that node. Otherwise, if before is an integer, and there is a beforeth node in the collection, let reference be that node. Otherwise, let reference be null.
If reference is not null, let parent be the parent
node of reference. Otherwise, let parent be the
select
element on which the HTMLOptionsCollection
is rooted.
Act as if the DOM insertBefore()
method was
invoked on the parent node, with element as the first
argument and reference as the second argument.
The remove(index)
method must act according to the following algorithm:
If the number of nodes represented by the collection is zero, abort these steps.
If index is not a number greater than or equal to 0 and less than the number of nodes represented by the collection, abort these steps.
Let element be the indexth element in the collection.
Remove element from its parent node.
The selectedIndex
IDL
attribute must act like the identically named attribute on the select
element on
which the HTMLOptionsCollection
is rooted
The DOMStringMap
interface represents a set of name-value pairs. It exposes these
using the scripting language's native mechanisms for property access.
When a DOMStringMap
object is instantiated, it is associated with three
algorithms, one for getting the list of name-value pairs, one for setting names to certain values,
and one for deleting names.
[OverrideBuiltins] interface DOMStringMap { getter DOMString (DOMString name); setter creator void (DOMString name, DOMString value); deleter void (DOMString name); };
The supported property names on a DOMStringMap
object at any instant
are the names of each pair returned from the algorithm for getting the list of name-value pairs at
that instant, in the order returned.
To determine the value of a named property name in a DOMStringMap
, the user agent must return the value component
of the name-value pair whose name component is name in the list returned by
the algorithm for getting the list of name-value pairs.
To set the value of a new or existing named property name to value
value, the algorithm for setting names to certain values must be run, passing
name as the name and the result of converting value to a
DOMString
as the value.
To delete an existing named property name, the algorithm for deleting names must be run, passing name as the name.
The DOMStringMap
interface definition here is only intended for
JavaScript environments. Other language bindings will need to define how DOMStringMap
is to be implemented for those languages.
The dataset
attribute on elements exposes the data-*
attributes on the element.
Given the following fragment and elements with similar constructions:
<img class="tower" id="tower5" data-x="12" data-y="5" data-ai="robotarget" data-hp="46" data-ability="flames" src="towers/rocket.png alt="Rocket Tower">
...one could imagine a function splashDamage()
that takes some arguments, the first
of which is the element to process:
function splashDamage(node, x, y, damage) { if (node.classList.contains('tower') && // checking the 'class' attribute node.dataset.x == x && // reading the 'data-x' attribute node.dataset.y == y) { // reading the 'data-y' attribute var hp = parseInt(node.dataset.hp); // reading the 'data-hp' attribute hp = hp - damage; if (hp < 0) { hp = 0; node.dataset.ai = 'dead'; // setting the 'data-ai' attribute delete node.dataset.ability; // removing the 'data-ability' attribute } node.dataset.hp = hp; // setting the 'data-hp' attribute } }
Some objects support being copied and closed in one operation. This is called transferring the object, and is used in particular to transfer ownership of unsharable or expensive resources across worker boundaries.
The following Transferable
types exist:
ArrayBuffer
[TYPEDARRAY]
MessagePort
(defined in this specification)
The following IDL block formalizes this:
[NoInterfaceObject] interface Transferable { }; ArrayBuffer implements Transferable; MessagePort implements Transferable;
To transfer a Transferable
object to a
new owner, the user agent must run the steps defined for the type of
object in question. The steps will return a new object of the same
type, and will permanently neuter the original
object. (This is an irreversible and non-idempotent operation; once
an object has been transferred, it cannot be transferred, or indeed
used, again.)
To transfer an
ArrayBuffer
object old to a new owner owner,
a user agent must create a new ArrayBuffer
object pointing at the same underlying
data as old, thus obtaining new, must neuter the old object, and must
finally return new. [TYPEDARRAY]
Rules for how to transfer a
MessagePort
object are given in the relevant sections of this specification.
When a user agent is required to obtain a structured clone of a value, optionally
with a transfer map, it must run the following algorithm, which either returns a separate
value, or throws an exception. If a transfer map is provided, it consists of an association
list of Transferable
objects to placeholder objects.
Let input be the value being cloned.
Let transfer map be the transfer map passed to the algorithm, if any, or the empty list otherwise.
Let memory be an association list of pairs of objects, initially empty. This is used to handle duplicate references. In each pair of objects, one is called the source object and the other the destination object.
For each mapping in transfer map, add a mapping from the
Transferable
object (the source object) to the placeholder object (the destination
object) to memory.
Let output be the value resulting from calling the internal structured cloning algorithm with input as the "input" argument, and memory as the "memory" argument.
Return output.
The internal structured cloning algorithm is always called with two arguments, input and memory, and its behavior is as follows:
If input is the source object of a pair of objects in memory, then return the destination object in that pair of objects and abort these steps.
If input is a primitive value, then return that value and abort these steps.
Let deep clone be none.
The input value is an object. Jump to the appropriate step below:
Boolean
objectLet output be a newly constructed Boolean object with the same value as input.
Number
objectLet output be a newly constructed Number object with the same value as input.
String
objectLet output be a newly constructed String object with the same value as input.
Date
objectLet output be a newly constructed Date
object with the
same value as input.
RegExp
objectLet output be a newly constructed RegExp
object with the
same pattern and flags as input.
The value of the lastIndex
property is not copied.
Blob
objectIf input has been disabled through the close()
method, throw a DataCloneError
exception
and abort the overall structured clone algorithm. Otherwise, let output be a newly constructed object of the same class as input, corresponding to the same underlying data.
FileList
objectLet output be a newly constructed FileList
object
containing a list of newly constructed File
objects corresponding to the same
underlying data as those in input, maintaining their relative
order.
ImageData
objectLet output be a newly constructed ImageData
object
whose width
, height
, and resolution
attributes have values equal to the
corresponding attributes on input, and whose data
attribute has the value obtained from invoking the
internal structured cloning algorithm recursively with the value of the data
attribute on input as the new "input" argument and memory as the new "memory" argument.
ArrayBuffer
objectIf input has been neutered, throw a DataCloneError
exception and abort the overall structured clone algorithm. Otherwise, let output be a newly constructed ArrayBuffer
object whose contents are
a copy of input's contents, with the same length.
ArrayBufferView
objectLet output be a newly constructed object of the same class as input, with each IDL attribute defined for that class being set to the value obtained from invoking the internal structured cloning algorithm recursively with the value of the attribute on input as the new "input" argument and memory as the new "memory" argument.
Only IDL attributes defined on the class (including the
ArrayBufferView
attributes) are cloned. Properties added by a script, for
example, are not cloned.
Array
objectLet output be a newly constructed empty Array
object whose
length
is equal to the length
of input, and set deep clone to own.
This means that the length of sparse arrays is preserved.
Object
objectLet output be a newly constructed empty Object
object, and set deep clone to own.
Map
objectLet output be a newly constructed empty Map
object, and set deep clone to map.
Set
objectLet output be a newly constructed empty Set
object, and set deep clone to set.
Let output be a clone of the object as defined by the other specification.
Error
, Function
)Throw a DataCloneError
exception and abort the overall structured
clone algorithm.
For the purposes of the algorithm above, an object is a particular type of object class if its [[Class]] internal property is equal to class.
For example, "input is an Object
object" if
input's [[Class]] internal property is equal to the string "Object
".
Add a mapping from input (the source object) to output (the destination object) to memory.
If deep clone is set to map, then run these substeps. These substeps use the terminology and typographic conventions used in the JavaScript specification's definition of Maps. [ECMA262]
Let source be the List that is the value of input's [[MapData]] internal slot, if any. If there is no such slot, then
instead throw a DataCloneError
exception and abort the overall structured
clone algorithm. [ECMA262]
Let target be the List that is the value of output's [[MapData]] internal slot.
For each Record {[[key]], [[value]]} entry that is an element of source, run the following substeps:
Let key have the value obtained from invoking the internal structured cloning algorithm recursively with entry.[[key]] as the new "input" argument and memory as the new "memory" argument.
Let value have the value obtained from invoking the internal structured cloning algorithm recursively with entry.[[value]] as the new "input" argument and memory as the new "memory" argument.
Let new entry be the Record {[[key]]: key, [[value]]: value}.
Append new entry as the last element of target.
Set deep clone to own.
If deep clone is set to set, then run these substeps. These substeps use the terminology and typographic conventions used in the JavaScript specification's definition of Sets. [ECMA262]
Let source be the List that is the value of input's [[SetData]] internal slot, if any. If there is no such slot, then
instead throw a DataCloneError
exception and abort the overall structured
clone algorithm. [ECMA262]
Let target be the List that is the value of output's [[SetData]] internal slot.
For each entry that is an element of source that is not empty, run the following substeps:
Let new entry have the value obtained from invoking the internal structured cloning algorithm recursively with entry as the new "input" argument and memory as the new "memory" argument.
Append new entry as the last element of target.
Set deep clone to own.
If deep clone is set to own, then, for each enumerable own property in input, run the following steps:
Let name be the name of the property.
Let source value be the result of calling the [[Get]] internal method of input with the argument name. If the [[Get]] internal method of a property involved executing script, and that script threw an uncaught exception, then abort the overall structured clone algorithm, with that exception being passed through to the caller.
Let cloned value be the result of invoking the internal structured cloning algorithm recursively with source value as the "input" argument and memory as the "memory" argument. If this results in an exception, then abort the overall structured clone algorithm, with that exception being passed through to the caller.
Add a new property to output having the name name, and having the value cloned value.
The order of the properties in the input and output objects must be the same, and any properties whose [[Get]] internal method involves running script must be processed in that same order.
This does not walk the prototype chain.
Property descriptors, setters, getters, and analogous features are not copied in this process. For example, the property in the input could be marked as read-only, but in the output it would just have the default state (typically read-write, though that could depend on the scripting environment).
Properties of Array objects are not treated any differently than those of other Objects. In particular, this means that non-index properties of arrays are copied as well.
Return output.
This algorithm preserves cycles and preserves the identity of duplicate objects in graphs.
The following callback function type is used in various APIs that interact with
File
objects:
callback FileCallback = void (File file);
There is an implied strong reference from any IDL attribute that returns a pre-existing object to that object.
The HTML namespace is: http://www.w3.org/1999/xhtml
The MathML namespace is: http://www.w3.org/1998/Math/MathML
The SVG namespace is: http://www.w3.org/2000/svg
The XLink namespace is: http://www.w3.org/1999/xlink
The XML namespace is: http://www.w3.org/XML/1998/namespace
The XMLNS namespace is: http://www.w3.org/2000/xmlns/
Data mining tools and other user agents that perform operations on content without running scripts, evaluating CSS or XPath expressions, or otherwise exposing the resulting DOM to arbitrary content, may "support namespaces" by just asserting that their DOM node analogues are in certain namespaces, without actually exposing the above strings.
In the HTML syntax, namespace prefixes and namespace declarations do not have the same effect as in XML. For instance, the colon has no special meaning in HTML element names.
Every XML and HTML document in an HTML UA is represented by a Document
object. [DOM]
The document's address is an absolute URL that is initially set when
the Document
is created but that can change during the lifetime of the
Document
, for example when the user navigates to a
fragment identifier on the page or when the pushState()
method is called with a new URL.
Interactive user agents typically expose the document's address in their user interface. This is the primary mechanism by which a user can tell if a site is attempting to impersonate another.
When a Document
is created by a script using
the createDocument()
or createHTMLDocument()
APIs, the
document's address is the same as the document's address of the responsible
document specified by the script's settings
object, and the Document
is both ready for post-load tasks and
completely loaded immediately.
The document's referrer is an absolute URL that can be set when the
Document
is created. If it is not explicitly set, then its value is the empty
string.
Each Document
object has a reload override flag that is originally
unset. The flag is set by the document.open()
and document.write()
methods in certain situations. When the flag is
set, the Document
also has a reload override buffer which is a Unicode
string that is used as the source of the document when it is reloaded.
When the user agent is to perform an overridden reload, given a source browsing context, it must act as follows:
Let source be the value of the browsing context's active document's reload override buffer.
Let address be the browsing context's active document's address.
Navigate the browsing context
to a resource whose source is source, with replacement enabled
and exceptions enabled.
The source browsing context is that given to the overridden reload algorithm.
When the navigate algorithm creates a Document
object for this purpose,
set that Document
's reload override flag and set its reload
override buffer to source.
When it comes time to set the document's address in the navigation algorithm, use address as the override URL.
Document
objectThe DOM specification defines a Document
interface, which
this specification extends significantly:
enum DocumentReadyState { "loading", "interactive", "complete" }; [OverrideBuiltins] partial /*sealed*/ interface Document { // resource metadata management [PutForwards=href, Unforgeable] readonly attribute Location? location; attribute DOMString domain; readonly attribute DOMString referrer; attribute DOMString cookie; readonly attribute DOMString lastModified; readonly attribute DocumentReadyState readyState; // DOM tree accessors getter object (DOMString name); attribute DOMString title; attribute DOMString dir; attribute HTMLElement? body; readonly attribute HTMLHeadElement? head; readonly attribute HTMLCollection images; readonly attribute HTMLCollection embeds; readonly attribute HTMLCollection plugins; readonly attribute HTMLCollection links; readonly attribute HTMLCollection forms; readonly attribute HTMLCollection scripts; NodeList getElementsByName(DOMString elementName); // dynamic markup insertion Document open(optional DOMString type = "text/html", optional DOMString replace = ""); WindowProxy open(DOMString url, DOMString name, DOMString features, optional boolean replace = false); void close(); void write(DOMString... text); void writeln(DOMString... text); // user interaction readonly attribute WindowProxy? defaultView; readonly attribute Element? activeElement; boolean hasFocus(); attribute DOMString designMode; boolean execCommand(DOMString commandId, optional boolean showUI = false, optional DOMString value = ""); boolean queryCommandEnabled(DOMString commandId); boolean queryCommandIndeterm(DOMString commandId); boolean queryCommandState(DOMString commandId); boolean queryCommandSupported(DOMString commandId); DOMString queryCommandValue(DOMString commandId); // special event handler IDL attributes that only apply to Document objects [LenientThis] attribute EventHandler onreadystatechange; }; Document implements GlobalEventHandlers;
referrer
Returns the address of the Document
from which the user navigated to this one, unless it was blocked or there was no such document,
in which case it returns the empty string.
The noreferrer
link type can be used to block the
referrer.
The referrer
attribute must return
the document's referrer.
In the case of HTTP, the referrer
IDL
attribute will match the Referer
(sic) header that was sent when
fetching the current page.
Typically user agents are configured to not report referrers in the case where the
referrer uses an encrypted protocol and the current page does not (e.g. when navigating from an
https:
page to an http:
page).
cookie
[ = value ]Returns the HTTP cookies that apply to the Document
. If there are no cookies or
cookies can't be applied to this resource, the empty string will be returned.
Can be set, to add a new cookie to the element's set of HTTP cookies.
If the contents are sandboxed into a
unique origin (e.g. in an iframe
with the sandbox
attribute), a SecurityError
exception
will be thrown on getting and setting.
The cookie
attribute represents the cookies
of the resource identified by the document's address.
A Document
object that falls into one of the following conditions is a
cookie-averse Document
object:
Document
that has no browsing context.Document
whose address does not
use a server-based naming authority.On getting, if the document is a cookie-averse Document
object, then the user agent must return the empty string. Otherwise, if the
Document
's origin is not a scheme/host/port tuple, the user agent must
throw a SecurityError
exception. Otherwise, the user agent must first obtain
the storage mutex and then return the cookie-string for the document's address
for a "non-HTTP" API, decoded using the UTF-8 decoder. [COOKIES]
On setting, if the document is a cookie-averse Document
object, then
the user agent must do nothing. Otherwise, if the Document
's origin is
not a scheme/host/port tuple, the user agent must throw a SecurityError
exception.
Otherwise, the user agent must obtain the storage mutex and then act as it would when
receiving a set-cookie-string for the
document's address via a "non-HTTP" API, consisting of the new value encoded as UTF-8. [COOKIES] [RFC3629]
Since the cookie
attribute is accessible
across frames, the path restrictions on cookies are only a tool to help manage which cookies are
sent to which parts of the site, and are not in any way a security feature.
lastModified
Returns the date of the last modification to the document, as reported by the server, in the
form "MM/DD/YYYY hh:mm:ss
", in the user's local time zone.
If the last modification date is not known, the current time is returned instead.
The lastModified
attribute, on
getting, must return the date and time of the Document
's source file's last
modification, in the user's local time zone, in the following format:
All the numeric components above, other than the year, must be given as two ASCII digits representing the number in base ten, zero-padded if necessary. The year must be given as the shortest possible string of four or more ASCII digits representing the number in base ten, zero-padded if necessary.
The Document
's source file's last modification date and time must be derived from
relevant features of the networking protocols used, e.g. from the value of the HTTP Last-Modified
header of the document, or from metadata in the
file system for local files. If the last modification date and time are not known, the attribute
must return the current date and time in the above format.
readyState
Returns "loading
" while the Document
is loading, "interactive
" once it is finished parsing but still loading sub-resources, and
"complete
" once it has loaded.
The readystatechange
event fires on the
Document
object when this value changes.
Each document has a current document readiness. When a Document
object
is created, it must have its current document readiness set to the string "loading
" if the document is associated with an HTML parser, an
XML parser, or an XSLT processor, and to the string "complete
"
otherwise. Various algorithms during page loading affect this value. When the value is set, the
user agent must fire a simple event named readystatechange
at the Document
object.
A Document
is said to have an active parser if it is associated with an
HTML parser or an XML parser that has not yet been stopped or aborted.
The readyState
IDL attribute must, on
getting, return the current document readiness.
The html
element of a document is the
document's root element, if there is one and it's an
html
element, or null otherwise.
head
Returns the head
element.
The head
element of a document is the
first head
element that is a child of the
html
element, if there is one, or null
otherwise.
The head
attribute, on getting, must return the head
element of the document (a head
element or
null).
title
[ = value ]Returns the document's title, as given by the
title
element.
Can be set, to update the document's title. If there is no
head
element,
the new value is ignored.
In SVG documents, the SVGDocument
interface's
title
attribute takes
precedence.
The title
element of a document is the
first title
element in the document (in tree order), if
there is one, or null otherwise.
The title
attribute must,
on getting, run the following algorithm:
If the root element is an svg
element in the "http://www.w3.org/2000/svg
"
namespace, and the user agent supports SVG, then return the value
that would have been returned by the IDL attribute of the same name
on the SVGDocument
interface. [SVG]
Otherwise, let value be a concatenation
of the data of all the child Text
nodes of the
title
element, in tree order, or
the empty string if the title
element is
null.
Strip and collapse whitespace in value.
Return value.
On setting, the following algorithm must be run. Mutation events must be fired as appropriate.
If the root element is an svg
element in the "http://www.w3.org/2000/svg
"
namespace, and the user agent supports SVG, then the setter must
act as if it was the setter for the IDL attribute of the same name
on the Document
interface defined by the SVG
specification. Stop the algorithm here. [SVG]
title
element is null and
the head
element is null, then the
attribute must do nothing. Stop the algorithm here.title
element is null, then a
new title
element must be created and appended to
the head
element. Let element be that element. Otherwise, let element be the title
element.Text
node whose data is the new value
being assigned must be appended to element.The title
IDL attribute
defined above must replace the attribute of the same name on the
Document
interface defined by the SVG specification
when the user agent supports both HTML and SVG. [SVG]
body
[ = value ]Returns the body element.
Can be set, to replace the body element.
If the new value is not a body
or frameset
element, this will throw a HierarchyRequestError
exception.
The body element of a document is the first child of the html
element that is either a body
element or a frameset
element. If
there is no such element, it is null.
The body
attribute, on getting, must return
the body element of the document (either a body
element, a
frameset
element, or null). On setting, the following algorithm must be run:
body
or frameset
element, then throw a
HierarchyRequestError
exception and abort these steps.replaceChild()
method had
been called with the new value and the incumbent body
element as its two arguments respectively, then abort these steps.HierarchyRequestError
exception
and abort these steps.images
Returns an HTMLCollection
of the img
elements in the Document
.
embeds
plugins
Return an HTMLCollection
of the embed
elements in the Document
.
links
Returns an HTMLCollection
of the a
and area
elements in the Document
that have href
attributes.
forms
Return an HTMLCollection
of the form
elements in the Document
.
scripts
Return an HTMLCollection
of the script
elements in the Document
.
The images
attribute must return an HTMLCollection
rooted at the
Document
node, whose filter matches only
img
elements.
The embeds
attribute must return an HTMLCollection
rooted at the
Document
node, whose filter matches only
embed
elements.
The plugins
attribute must return the same object as that returned by the embeds
attribute.
The links
attribute must return an HTMLCollection
rooted at the
Document
node, whose filter matches only a
elements with href
attributes and area
elements with href
attributes.
The forms
attribute must return an HTMLCollection
rooted at the
Document
node, whose filter matches only
form
elements.
The scripts
attribute must return an HTMLCollection
rooted at the
Document
node, whose filter matches only
script
elements.
getElementsByName
(name)Returns a NodeList
of elements in the
Document
that have a name
attribute with the value name.
The getElementsByName(name)
method takes a string name, and must return a live
NodeList
containing all the HTML elements
in that document that have a name
attribute
whose value is equal to the name argument (in a
case-sensitive manner), in tree order.
When the method is invoked on a Document
object again
with the same argument, the user agent may return the same as the
object returned by the earlier call. In other cases, a new
NodeList
object must be returned.
The Document
interface supports named properties. The supported property names at
any moment consist of the values of the name
content attributes of
all the
applet
,
exposed embed
,
form
,
iframe
,
img
, and
exposed object
elements in the Document
that have non-empty name
content
attributes, and the values of the id
content attributes of all the
applet
and
exposed object
elements in the Document
that have non-empty id
content
attributes, and the values of the id
content attributes of all the
img
elements in the Document
that have both non-empty name
content
attributes and non-empty id
content attributes. The supported property
names must be in tree order, ignoring later duplicates, with values from id
attributes coming before values from name
attributes when the same element
contributes both.
To determine the value of a named property name when the Document
object is indexed for property
retrieval, the user agent must return the value obtained using the following steps:
Let elements be the list of named elements with the name name in the Document
.
There will be at least one such element, by definition.
If elements has only one element, and that element is an
iframe
element, then return the WindowProxy
object of the nested
browsing context represented by that iframe
element, and abort these
steps.
Otherwise, if elements has only one element, return that element and abort these steps.
Otherwise return an HTMLCollection
rooted at the Document
node,
whose filter matches only named elements with
the name name.
Named elements with the name name, for the purposes of the above algorithm, are those that are either:
applet
, exposed embed
, form
,
iframe
, img
, or exposed object
elements that
have a name
content attribute whose value is name, orapplet
or exposed object
elements that have an id
content attribute whose value is name, orimg
elements that have an id
content attribute
whose value is name, and that have a non-empty name
content attribute present also.An embed
or object
element is said to be exposed if it has
no exposed object
ancestor, and, for object
elements, is
additionally either not showing its fallback content or has no object
or
embed
descendants.
The dir
attribute on the
Document
interface is defined along with the dir
content attribute.
partial interface XMLDocument { boolean load(DOMString url); };
The load(url)
method
must run the following steps:
Let document be the XMLDocument
object on which the
method was invoked.
Resolve the method's first argument, relative to the
API base URL specified by the
entry settings object. If this is not
successful, throw a SyntaxError
exception and abort these steps. Otherwise, let url be the resulting absolute URL.
If the origin of url is not the same as the
origin of document, throw a SecurityError
exception
and abort these steps.
Remove all child nodes of document, without firing any mutation events.
Set the current document readiness of document to "loading
".
Run the remainder of these steps asynchronously, and return true from the method.
Let result be a Document
object.
Let success be false.
Fetch url from the origin of document, using the API referrer source specified by the entry settings object, with the synchronous flag set and the force same-origin flag set.
If the fetch attempt was successful, and the resource's Content-Type metadata is an XML MIME type, then run these substeps:
Create a new XML parser associated with the result document.
Pass this parser the fetched document.
If there is an XML well-formedness or XML namespace well-formedness error, then remove all child nodes from result. Otherwise let success be true.
Queue a task to run the following steps.
Set the current document readiness of document to
"complete
".
Replace all the children of document by the children of result (even if it has no children), firing mutation events as if a
DocumentFragment
containing the new children had been inserted.
Fire a simple event named load
at document.
Elements, attributes, and attribute values in HTML are defined (by this specification) to have
certain meanings (semantics). For example, the ol
element represents an ordered list,
and the lang
attribute represents the language of the content.
These definitions allow HTML processors, such as Web browsers or search engines, to present and use documents and applications in a wide variety of contexts that the author might not have considered.
As a simple example, consider a Web page written by an author who only considered desktop computer Web browsers:
<!DOCTYPE HTML> <html> <head> <title>My Page</title> </head> <body> <h1>Welcome to my page</h1> <p>I like cars and lorries and have a big Jeep!</p> <h2>Where I live</h2> <p>I live in a small hut on a mountain!</p> </body> </html>
Because HTML conveys meaning, rather than presentation, the same page can also be used by a small browser on a mobile phone, without any change to the page. Instead of headings being in large letters as on the desktop, for example, the browser on the mobile phone might use the same size text for the whole the page, but with the headings in bold.
But it goes further than just differences in screen size: the same page could equally be used by a blind user using a browser based around speech synthesis, which instead of displaying the page on a screen, reads the page to the user, e.g. using headphones. Instead of large text for the headings, the speech browser might use a different volume or a slower voice.
That's not all, either. Since the browsers know which parts of the page are the headings, they can create a document outline that the user can use to quickly navigate around the document, using keys for "jump to next heading" or "jump to previous heading". Such features are especially common with speech browsers, where users would otherwise find quickly navigating a page quite difficult.
Even beyond browsers, software can make use of this information. Search engines can use the headings to more effectively index a page, or to provide quick links to subsections of the page from their results. Tools can use the headings to create a table of contents (that is in fact how this very specification's table of contents is generated).
This example has focused on headings, but the same principle applies to all of the semantics in HTML.
Authors must not use elements, attributes, or attribute values for purposes other than their appropriate intended semantic purpose, as doing so prevents software from correctly processing the page.
For example, the following document is non-conforming, despite being syntactically correct:
<!DOCTYPE HTML> <html lang="en-GB"> <head> <title> Demonstration </title> </head> <body> <table> <tr> <td> My favourite animal is the cat. </td> </tr> <tr> <td> —<a href="http://example.org/~ernest/"><cite>Ernest</cite></a>, in an essay from 1992 </td> </tr> </table> </body> </html>
...because the data placed in the cells is clearly not tabular data (and the cite
element mis-used). This would make software that relies on these semantics fail: for example, a
speech browser that allowed a blind user to navigate tables in the document would report the
quote above as a table, confusing the user; similarly, a tool that extracted titles of works from
pages would extract "Ernest" as the title of a work, even though it's actually a person's name,
not a title.
A corrected version of this document might be:
<!DOCTYPE HTML> <html lang="en-GB"> <head> <title> Demonstration </title> </head> <body> <blockquote> <p> My favourite animal is the cat. </p> </blockquote> <p> —<a href="http://example.org/~ernest/">Ernest</a>, in an essay from 1992 </p> </body> </html>
Authors must not use elements, attributes, or attribute values that are not permitted by this specification or other applicable specifications, as doing so makes it significantly harder for the language to be extended in the future.
In the next example, there is a non-conforming attribute value ("carpet") and a non-conforming attribute ("texture"), which is not permitted by this specification:
<label>Carpet: <input type="carpet" name="c" texture="deep pile"></label>
Here would be an alternative and correct way to mark this up:
<label>Carpet: <input type="text" class="carpet" name="c" data-texture="deep pile"></label>
Through scripting and using other mechanisms, the values of attributes, text, and indeed the entire structure of the document may change dynamically while a user agent is processing it. The semantics of a document at an instant in time are those represented by the state of the document at that instant in time, and the semantics of a document can therefore change over time. User agents must update their presentation of the document as this occurs.
HTML has a progress
element that describes a progress bar. If its
"value" attribute is dynamically updated by a script, the UA would update the rendering to show
the progress changing.
The nodes representing HTML elements in the DOM must implement, and expose to scripts, the interfaces listed for them in the relevant sections of this specification. This includes HTML elements in XML documents, even when those documents are in another context (e.g. inside an XSLT transform).
Elements in the DOM represent things; that is, they have intrinsic meaning, also known as semantics.
For example, an ol
element represents an ordered list.
The basic interface, from which all the HTML elements' interfaces inherit, and which must be used by elements that have no additional requirements, is
the HTMLElement
interface.
interface HTMLElement : Element {
// metadata attributes
attribute DOMString title;
attribute DOMString lang;
attribute boolean translate;
attribute DOMString dir;
readonly attribute DOMStringMap dataset;
// user interaction
attribute boolean hidden;
void click();
attribute long tabIndex;
void focus();
void blur();
attribute DOMString accessKey;
readonly attribute DOMString accessKeyLabel;
attribute boolean draggable;
[PutForwards=value] readonly attribute DOMSettableTokenList dropzone;
attribute DOMString contentEditable;
readonly attribute boolean isContentEditable;
attribute boolean spellcheck;
};
HTMLElement implements GlobalEventHandlers;
interface HTMLUnknownElement : HTMLElement { };
The HTMLElement
interface holds methods and attributes related to a number of
disparate features, and the members of this interface are therefore described in various different
sections of this specification.
The HTMLUnknownElement
interface must be used for HTML elements that
are not defined by this specification (or other applicable specifications).
Each element in this specification has a definition that includes the following information:
A list of categories to which the element belongs. These are used when defining the content models for each element.
A non-normative description of where the element can be used. This information is redundant with the content models of elements that allow this one as a child, and is provided only as a convenience.
For simplicity, only the most specific expectations are listed. For example, an element that is both flow content and phrasing content can be used anywhere that either flow content or phrasing content is expected, but since anywhere that flow content is expected, phrasing content is also expected (since all phrasing content is flow content), only "where phrasing content is expected" will be listed.
A normative description of what content must be included as children and descendants of the element.
A non-normative description of whether, in the text/html
syntax, the
start and end tags can
be omitted. This information is redundant with the normative requirements given in the optional tags section, and is provided in the element
definitions only as a convenience.
A normative list of attributes that may be specified on the element (except where otherwise disallowed), along with non-normative descriptions of those attributes. (The content to the left of the dash is normative, the content to the right of the dash is not.)
A normative definition of a DOM interface that such elements must implement.
This is then followed by a description of what the element represents, along with any additional normative conformance criteria that may apply to authors and implementations. Examples are sometimes also included.
Except where otherwise specified, attributes on HTML elements may have any string value, including the empty string. Except where explicitly stated, there is no restriction on what text can be specified in such attributes.
Each element defined in this specification has a content model: a description of the element's
expected contents. An HTML
element must have contents that match the requirements described in the element's content
model. The contents of an element are its children in the
DOM, except for template
elements, where the children are those in the template
contents (a separate DocumentFragment
assigned to the element when the element
is created).
The space characters are always allowed between elements.
User agents represent these characters between elements in the source markup as Text
nodes in the DOM. Empty
Text
nodes and Text
nodes consisting of just sequences of those
characters are considered inter-element whitespace.
Inter-element whitespace, comment nodes, and processing instruction nodes must be ignored when establishing whether an element's contents match the element's content model or not, and must be ignored when following algorithms that define document and element semantics.
Thus, an element A is said to be preceded or followed
by a second element B if A and B have
the same parent node and there are no other element nodes or Text
nodes (other than
inter-element whitespace) between them. Similarly, a node is the only child of
an element if that element contains no other nodes other than inter-element
whitespace, comment nodes, and processing instruction nodes.
Authors must not use HTML elements anywhere except where they are explicitly allowed, as defined for each element, or as explicitly required by other specifications. For XML compound documents, these contexts could be inside elements from other namespaces, if those elements are defined as providing the relevant contexts.
For example, the Atom specification defines a content
element. When its
type
attribute has the value xhtml
, the Atom
specification requires that it contain a single HTML div
element. Thus, a
div
element is allowed in that context, even though this is not explicitly
normatively stated by this specification. [ATOM]
In addition, HTML elements may be orphan nodes (i.e. without a parent node).
For example, creating a td
element and storing it in a global variable in a
script is conforming, even though td
elements are otherwise only supposed to be used
inside tr
elements.
var data = { name: "Banana", cell: document.createElement('td'), };
Each element in HTML falls into zero or more categories that group elements with similar characteristics together. The following broad categories are used in this specification:
Some elements also fall into other categories, which are defined in other parts of this specification.
These categories are related as follows:
Sectioning content, heading content, phrasing content, embedded content, and interactive content are all types of flow content. Metadata is sometimes flow content. Metadata and interactive content are sometimes phrasing content. Embedded content is also a type of phrasing content, and sometimes is interactive content.
Other categories are also used for specific purposes, e.g. form controls are specified using a number of categories to define common requirements. Some elements have unique requirements and do not fit into any particular category.
Metadata content is content that sets up the presentation or behavior of the rest of the content, or that sets up the relationship of the document with other documents, or that conveys other "out of band" information.
Elements from other namespaces whose semantics are primarily metadata-related (e.g. RDF) are also metadata content.
Thus, in the XML serialization, one can use RDF, like this:
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:r="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <head> <title>Hedral's Home Page</title> <r:RDF> <Person xmlns="http://www.w3.org/2000/10/swap/pim/contact#" r:about="http://hedral.example.com/#"> <fullName>Cat Hedral</fullName> <mailbox r:resource="mailto:hedral@damowmow.com"/> <personalTitle>Sir</personalTitle> </Person> </r:RDF> </head> <body> <h1>My home page</h1> <p>I like playing with string, I guess. Sister says squirrels are fun too so sometimes I follow her to play with them.</p> </body> </html>
This isn't possible in the HTML serialization, however.
Most elements that are used in the body of documents and applications are categorized as flow content.
a
abbr
address
area
(if it is a descendant of a map
element)article
aside
audio
b
bdi
bdo
blockquote
br
button
canvas
cite
code
data
datalist
del
details
dfn
dialog
div
dl
em
embed
fieldset
figure
footer
form
h1
h2
h3
h4
h5
h6
header
hr
i
iframe
img
input
ins
kbd
keygen
label
main
map
mark
math
meter
nav
noscript
object
ol
output
p
pre
progress
q
ruby
s
samp
script
section
select
small
span
strong
style
(if the scoped
attribute is present)sub
sup
svg
table
template
textarea
time
u
ul
var
video
wbr
Sectioning content is content that defines the scope of headings and footers.
Each sectioning content element potentially has a heading and an outline. See the section on headings and sections for further details.
There are also certain elements that are sectioning roots. These are distinct from sectioning content, but they can also have an outline.
Heading content defines the header of a section (whether explicitly marked up using sectioning content elements, or implied by the heading content itself).
Phrasing content is the text of the document, as well as elements that mark up that text at the intra-paragraph level. Runs of phrasing content form paragraphs.
a
abbr
area
(if it is a descendant of a map
element)audio
b
bdi
bdo
br
button
canvas
cite
code
data
datalist
del
dfn
em
embed
i
iframe
img
input
ins
kbd
keygen
label
map
mark
math
meter
noscript
object
output
progress
q
ruby
s
samp
script
select
small
span
strong
sub
sup
svg
template
textarea
time
u
var
video
wbr
Most elements that are categorized as phrasing content can only contain elements that are themselves categorized as phrasing content, not any flow content.
Text, in the context of content models, means either nothing,
or Text
nodes. Text is sometimes used as a content
model on its own, but is also phrasing content, and can be inter-element
whitespace (if the Text
nodes are empty or contain just space characters).
Text
nodes and attribute values must consist of Unicode characters, must not contain U+0000 characters, must not contain
permanently undefined Unicode characters (noncharacters), and must not contain control characters
other than space characters.
This specification includes extra constraints on the exact value of Text
nodes and
attribute values depending on their precise context.
Embedded content is content that imports another resource into the document, or content from another vocabulary that is inserted into the document.
Elements that are from namespaces other than the HTML namespace and that convey content but not metadata, are embedded content for the purposes of the content models defined in this specification. (For example, MathML, or SVG.)
Some embedded content elements can have fallback content: content that is to be used when the external resource cannot be used (e.g. because it is of an unsupported format). The element definitions state what the fallback is, if any.
Interactive content is content that is specifically intended for user interaction.
a
audio
(if the controls
attribute is present)button
details
embed
iframe
img
(if the usemap
attribute is present)input
(if the type
attribute is not in the Hidden state)keygen
label
object
(if the usemap
attribute is present)select
textarea
video
(if the controls
attribute is present)Certain elements in HTML have an activation behavior, which means that the user
can activate them. This triggers a sequence of events dependent on the activation mechanism, and
normally culminating in a click
event, as
described below.
The user agent should allow the user to manually trigger elements that have an activation behavior, for instance using keyboard or voice input, or through mouse clicks. When the user triggers an element with a defined activation behavior in a manner other than clicking it, the default action of the interaction event must be to run synthetic click activation steps on the element.
Each element has a click in progress flag, initially set to false.
When a user agent is to run synthetic click activation steps on an element, the user agent must run the following steps:
If the element's click in progress flag is set to true, then abort these steps.
Set the click in progress flag on the element to true.
Run pre-click activation steps on the element.
Fire a click
event at the element. If the
run synthetic click activation steps algorithm was invoked because the click()
method was invoked, then the isTrusted
attribute must be initialized to false.
If this click
event is not canceled, run post-click
activation steps on the element.
If the event is canceled, the user agent must run canceled activation steps on the element instead.
Set the click in progress flag on the element to false.
When a pointing device is clicked, the user agent must run these steps:
If the element's click in progress flag is set to true, then abort these steps.
Set the click in progress flag on the element to true.
Let e be the nearest activatable element of the element designated by the user (defined below), if any.
If there is an element e, run pre-click activation steps on it.
Dispatch the required click
event.
If there is an element e and the click
event is not canceled, run post-click activation steps on element e.
If there is an element e and the event is canceled, run canceled activation steps on element e.
Set the click in progress flag on the element to false.
The algorithms above don't run for arbitrary synthetic events dispatched by author
script. The click()
method can be used to make the run
synthetic click activation steps algorithm happen programmatically.
Click-focusing behavior (e.g. the focusing of a text field when user clicks in one) typically happens before the click, when the mouse button is first depressed, and is therefore not discussed here.
Given an element target, the nearest activatable element is the element returned by the following algorithm:
If target has a defined activation behavior, then return target and abort these steps.
If target has a parent element, then set target to that parent element and return to the first step.
Otherwise, there is no nearest activatable element.
When a user agent is to run pre-click activation steps on an element, it must run the pre-click activation steps defined for that element, if any.
When a user agent is to run canceled activation steps on an element, it must run the canceled activation steps defined for that element, if any.
When a user agent is to run post-click activation steps on an element, it must run
the activation behavior defined for that element, if any. Activation behaviors can
refer to the click
event that was fired by the steps above
leading up to this point.
As a general rule, elements whose content model allows any flow content or
phrasing content should have at least one node in its contents that is palpable
content and that does not have the hidden
attribute
specified.
This requirement is not a hard requirement, however, as there are many cases where an element can be empty legitimately, for example when it is used as a placeholder which will later be filled in by a script, or when the element is part of a template and would on most pages be filled in but on some pages is not relevant.
Conformance checkers are encouraged to provide a mechanism for authors to find elements that fail to fulfill this requirement, as an authoring aid.
The following elements are palpable content:
a
abbr
address
article
aside
audio
(if the controls
attribute is present)b
bdi
bdo
blockquote
button
canvas
cite
code
data
details
dfn
div
dl
(if the element's children include at least one name-value group)em
embed
fieldset
figure
footer
form
h1
h2
h3
h4
h5
h6
header
i
iframe
img
input
(if the type
attribute is not in the Hidden state)ins
kbd
keygen
label
main
map
mark
math
meter
nav
object
ol
(if the element's children include at least one li
element)output
p
pre
progress
q
ruby
s
samp
section
select
small
span
strong
sub
sup
svg
table
textarea
time
u
ul
(if the element's children include at least one li
element)var
video
Script-supporting elements are those that do not represent anything themselves (i.e. they are not rendered), but are used to support scripts, e.g. to provide functionality for the user.
The following elements are script-supporting elements:
Some elements are described as transparent; they have "transparent" in the description of their content model. The content model of a transparent element is derived from the content model of its parent element: the elements required in the part of the content model that is "transparent" are the same elements as required in the part of the content model of the parent of the transparent element in which the transparent element finds itself.
For instance, an ins
element inside a ruby
element cannot contain an
rt
element, because the part of the ruby
element's content model that
allows ins
elements is the part that allows phrasing content, and the
rt
element is not phrasing content.
In some cases, where transparent elements are nested in each other, the process has to be applied iteratively.
Consider the following markup fragment:
<p><object><param><ins><map><a href="/">Apples</a></map></ins></object></p>
To check whether "Apples" is allowed inside the a
element, the content models are
examined. The a
element's content model is transparent, as is the map
element's, as is the ins
element's, as is the part of the object
element's in which the ins
element is found. The object
element is
found in the p
element, whose content model is phrasing content. Thus,
"Apples" is allowed, as text is phrasing content.
When a transparent element has no parent, then the part of its content model that is "transparent" must instead be treated as accepting any flow content.
The term paragraph as defined in this section is used for more than
just the definition of the p
element. The paragraph concept defined here
is used to describe how to interpret documents. The p
element is merely one of
several ways of marking up a paragraph.
A paragraph is typically a run of phrasing content that forms a block of text with one or more sentences that discuss a particular topic, as in typography, but can also be used for more general thematic grouping. For instance, an address is also a paragraph, as is a part of a form, a byline, or a stanza in a poem.
In the following example, there are two paragraphs in a section. There is also a heading, which contains phrasing content that is not a paragraph. Note how the comments and inter-element whitespace do not form paragraphs.
<section> <h1>Example of paragraphs</h1> This is the <em>first</em> paragraph in this example. <p>This is the second.</p> <!-- This is not a paragraph. --> </section>
Paragraphs in flow content are defined relative to what the document looks like
without the a
, ins
, del
, and map
elements
complicating matters, since those elements, with their hybrid content models, can straddle
paragraph boundaries, as shown in the first two examples below.
Generally, having elements straddle paragraph boundaries is best avoided. Maintaining such markup can be difficult.
The following example takes the markup from the earlier example and puts ins
and
del
elements around some of the markup to show that the text was changed (though in
this case, the changes admittedly don't make much sense). Notice how this example has exactly the
same paragraphs as the previous one, despite the ins
and del
elements
— the ins
element straddles the heading and the first paragraph, and the
del
element straddles the boundary between the two paragraphs.
<section> <ins><h1>Example of paragraphs</h1> This is the <em>first</em> paragraph in</ins> this example<del>. <p>This is the second.</p></del> <!-- This is not a paragraph. --> </section>
Let view be a view of the DOM that replaces all a
,
ins
, del
, and map
elements in the document with their
contents. Then, in view, for each run of sibling phrasing content
nodes uninterrupted by other types of content, in an element that accepts content other than
phrasing content as well as phrasing content, let first be the first node of the run, and let last be the last
node of the run. For each such run that consists of at least one node that is neither
embedded content nor inter-element whitespace, a paragraph exists in the
original DOM from immediately before first to immediately after last. (Paragraphs can thus span across a
, ins
,
del
, and map
elements.)
Conformance checkers may warn authors of cases where they have paragraphs that overlap each
other (this can happen with object
, video
, audio
, and
canvas
elements, and indirectly through elements in other namespaces that allow HTML
to be further embedded therein, like svg
or math
).
A paragraph is also formed explicitly by p
elements.
The p
element can be used to wrap individual paragraphs when there
would otherwise not be any content other than phrasing content to separate the paragraphs from
each other.
In the following example, the link spans half of the first paragraph, all of the heading separating the two paragraphs, and half of the second paragraph. It straddles the paragraphs and the heading.
<header> Welcome! <a href="about.html"> This is home of... <h1>The Falcons!</h1> The Lockheed Martin multirole jet fighter aircraft! </a> This page discusses the F-16 Fighting Falcon's innermost secrets. </header>
Here is another way of marking this up, this time showing the paragraphs explicitly, and splitting the one link element into three:
<header> <p>Welcome! <a href="about.html">This is home of...</a></p> <h1><a href="about.html">The Falcons!</a></h1> <p><a href="about.html">The Lockheed Martin multirole jet fighter aircraft!</a> This page discusses the F-16 Fighting Falcon's innermost secrets.</p> </header>
It is possible for paragraphs to overlap when using certain elements that define fallback content. For example, in the following section:
<section> <h1>My Cats</h1> You can play with my cat simulator. <object data="cats.sim"> To see the cat simulator, use one of the following links: <ul> <li><a href="cats.sim">Download simulator file</a> <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a> </ul> Alternatively, upgrade to the Mellblom Browser. </object> I'm quite proud of it. </section>
There are five paragraphs:
object
element.The first paragraph is overlapped by the other four. A user agent that supports the "cats.sim" resource will only show the first one, but a user agent that shows the fallback will confusingly show the first sentence of the first paragraph as if it was in the same paragraph as the second one, and will show the last paragraph as if it was at the start of the second sentence of the first paragraph.
To avoid this confusion, explicit p
elements can be used. For example:
<section> <h1>My Cats</h1> <p>You can play with my cat simulator.</p> <object data="cats.sim"> <p>To see the cat simulator, use one of the following links:</p> <ul> <li><a href="cats.sim">Download simulator file</a> <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a> </ul> <p>Alternatively, upgrade to the Mellblom Browser.</p> </object> <p>I'm quite proud of it.</p> </section>
The following attributes are common to and may be specified on all HTML elements (even those not defined in this specification):
accesskey
class
contenteditable
dir
draggable
dropzone
hidden
id
lang
spellcheck
style
tabindex
title
translate
These attributes are only defined by this specification as attributes for HTML elements. When this specification refers to elements having these attributes, elements from namespaces that are not defined as having these attributes must not be considered as being elements with these attributes.
For example, in the following XML fragment, the "bogus
" element does not
have a dir
attribute as defined in this specification, despite
having an attribute with the literal name "dir
". Thus, the
directionality of the inner-most span
element is 'rtl', inherited from the div
element indirectly through
the "bogus
" element.
<div xmlns="http://www.w3.org/1999/xhtml" dir="rtl"> <bogus xmlns="http://example.net/ns" dir="ltr"> <span xmlns="http://www.w3.org/1999/xhtml"> </span> </bogus> </div>
To enable assistive technology products to expose a more fine-grained interface than is
otherwise possible with HTML elements and attributes, a set of annotations
for assistive technology products can be specified (the ARIA role
and aria-*
attributes). [ARIA]
The following event handler content attributes may be specified on any HTML element:
onabort
onblur
*oncancel
oncanplay
oncanplaythrough
onchange
onclick
onclose
oncuechange
ondblclick
ondrag
ondragend
ondragenter
ondragexit
ondragleave
ondragover
ondragstart
ondrop
ondurationchange
onemptied
onended
onerror
*onfocus
*oninput
oninvalid
onkeydown
onkeypress
onkeyup
onload
*onloadeddata
onloadedmetadata
onloadstart
onmousedown
onmouseenter
onmouseleave
onmousemove
onmouseout
onmouseover
onmouseup
onmousewheel
onpause
onplay
onplaying
onprogress
onratechange
onreset
onresize
*onscroll
*onseeked
onseeking
onselect
onshow
onstalled
onsubmit
onsuspend
ontimeupdate
ontoggle
onvolumechange
onwaiting
The attributes marked with an asterisk have a different meaning when specified on
body
elements as those elements expose event handlers of the
Window
object with the same names.
While these attributes apply to all elements, they are not useful on all elements.
For example, only media elements will ever receive a volumechange
event fired by the user agent.
Custom data attributes (e.g. data-foldername
or data-msgid
) can be specified on any HTML element, to store custom data specific to the page.
In HTML documents, elements in the HTML namespace may have an xmlns
attribute specified, if, and only if, it has the exact value
"http://www.w3.org/1999/xhtml
". This does not apply to XML
documents.
In HTML, the xmlns
attribute has absolutely no effect. It is
basically a talisman. It is allowed merely to make migration to and from XHTML mildly easier. When
parsed by an HTML parser, the attribute ends up in no namespace, not the
"http://www.w3.org/2000/xmlns/
" namespace like namespace declaration attributes in
XML do.
In XML, an xmlns
attribute is part of the namespace
declaration mechanism, and an element cannot actually have an xmlns
attribute in no namespace specified.
The XML specification also allows the use of the xml:space
attribute in the XML namespace on any element in an XML
document. This attribute has no effect on HTML elements, as the default
behavior in HTML is to preserve whitespace. [XML]
There is no way to serialize the xml:space
attribute on HTML elements in the text/html
syntax.
id
attributeThe id
attribute specifies its element's unique identifier (ID). [DOM]
The value must be unique amongst all the IDs in the element's home subtree and must contain at least one character. The value must not contain any space characters.
There are no other restrictions on what form an ID can take; in particular, IDs can consist of just digits, start with a digit, start with an underscore, consist of just punctuation, etc.
An element's unique identifier can be used for a variety of purposes, most notably as a way to link to specific parts of a document using fragment identifiers, as a way to target an element when scripting, and as a way to style a specific element from CSS.
Identifiers are opaque strings. Particular meanings should not be derived from the value of the
id
attribute.
title
attributeThe title
attribute represents advisory
information for the element, such as would be appropriate for a tooltip. On a link, this could be
the title or a description of the target resource; on an image, it could be the image credit or a
description of the image; on a paragraph, it could be a footnote or commentary on the text; on a
citation, it could be further information about the source; on interactive content,
it could be a label for, or instructions for, use of the element; and so forth. The value is
text.
Relying on the title
attribute is currently
discouraged as many user agents do not expose the attribute in an accessible manner as required by
this specification (e.g. requiring a pointing device such as a mouse to cause a tooltip to appear,
which excludes keyboard-only users and touch-only users, such as anyone with a modern phone or
tablet).
If this attribute is omitted from an element, then it implies that the title
attribute of the nearest ancestor HTML
element with a title
attribute set is also relevant to this
element. Setting the attribute overrides this, explicitly stating that the advisory information of
any ancestors is not relevant to this element. Setting the attribute to the empty string indicates
that the element has no advisory information.
If the title
attribute's value contains "LF" (U+000A)
characters, the content is split into multiple lines. Each "LF" (U+000A) character
represents a line break.
Caution is advised with respect to the use of newlines in title
attributes.
For instance, the following snippet actually defines an abbreviation's expansion with a line break in it:
<p>My logs show that there was some interest in <abbr title="Hypertext Transport Protocol">HTTP</abbr> today.</p>
Some elements, such as link
, abbr
, and input
, define
additional semantics for the title
attribute beyond the semantics
described above.
The advisory information of an element is the value that the following algorithm returns, with the algorithm being aborted once a value is returned. When the algorithm returns the empty string, then there is no advisory information.
If the element is a link
, style
, dfn
,
or abbr
element, then: if the element has a title
attribute, return the value of that attribute,
otherwise, return the empty string.
Otherwise, if the element has a title
attribute, then
return its value.
Otherwise, if the element has a parent element, then return the parent element's advisory information.
Otherwise, return the empty string.
User agents should inform the user when elements have advisory information, otherwise the information would not be discoverable.
The title
IDL attribute must reflect the
title
content attribute.
lang
and xml:lang
attributesThe lang
attribute (in no namespace) specifies the
primary language for the element's contents and for any of the element's attributes that contain
text. Its value must be a valid BCP 47 language tag, or the empty string. Setting the attribute to
the empty string indicates that the primary language is unknown. [BCP47]
The lang
attribute in the XML
namespace is defined in XML. [XML]
If these attributes are omitted from an element, then the language of this element is the same as the language of its parent element, if any.
The lang
attribute in no namespace may be used on any HTML element.
The lang
attribute in the XML
namespace may be used on HTML elements in XML documents,
as well as elements in other namespaces if the relevant specifications allow it (in particular,
MathML and SVG allow lang
attributes in the
XML namespace to be specified on their elements). If both the lang
attribute in no namespace and the lang
attribute in the XML namespace are specified on the same
element, they must have exactly the same value when compared in an ASCII
case-insensitive manner.
Authors must not use the lang
attribute in
the XML namespace on HTML elements in HTML
documents. To ease migration to and from XHTML, authors may specify an attribute in no
namespace with no prefix and with the literal localname "xml:lang
" on
HTML elements in HTML documents, but such attributes must only be
specified if a lang
attribute in no namespace is also specified,
and both attributes must have the same value when compared in an ASCII
case-insensitive manner.
The attribute in no namespace with no prefix and with the literal localname "xml:lang
" has no effect on language processing.
To determine the language of a node, user agents must look at the nearest ancestor
element (including the element itself if the node is an element) that has a lang
attribute in the XML
namespace set or is an HTML element and has a
lang
in no namespace attribute set. That attribute specifies the
language of the node (regardless of its value).
If both the lang
attribute in no namespace and the lang
attribute in the XML
namespace are set on an element, user agents must use the lang
attribute in the XML
namespace, and the lang
attribute in no namespace
must be ignored for the purposes of determining the element's
language.
If neither the node nor any of the node's ancestors, including the root element, have either attribute set, but there is a pragma-set default language set, then that is the language of the node. If there is no pragma-set default language set, then language information from a higher-level protocol (such as HTTP), if any, must be used as the final fallback language instead. In the absence of any such language information, and in cases where the higher-level protocol reports multiple languages, the language of the node is unknown, and the corresponding language tag is the empty string.
If the resulting value is not a recognized language tag, then it must be treated as an unknown language having the given language tag, distinct from all other languages. For the purposes of round-tripping or communicating with other services that expect language tags, user agents should pass unknown language tags through unmodified, and tagged as being BCP 47 language tags, so that subsequent services do not interpret the data as another type of language description. [BCP47]
Thus, for instance, an element with lang="xyzzy"
would be
matched by the selector :lang(xyzzy)
(e.g. in CSS), but it would not be
matched by :lang(abcde)
, even though both are equally invalid. Similarly, if
a Web browser and screen reader working in unison communicated about the language of the element,
the browser would tell the screen reader that the language was "xyzzy", even if it knew it was
invalid, just in case the screen reader actually supported a language with that tag after all.
Even if the screen reader supported both BCP 47 and another syntax for encoding language names,
and in that other syntax the string "xyzzy" was a way to denote the Belarusian language, it would
be incorrect for the screen reader to then start treating text as Belarusian, because
"xyzzy" is not how Belarusian is described in BCP 47 codes (BCP 47 uses the code "be" for
Belarusian).
If the resulting value is the empty string, then it must be interpreted as meaning that the language of the node is explicitly unknown.
User agents may use the element's language to determine proper processing or rendering (e.g. in the selection of appropriate fonts or pronunciations, for dictionary selection, or for the user interfaces of form controls such as date pickers).
The lang
IDL attribute must reflect the
lang
content attribute in no namespace.
translate
attributeThe translate
attribute is an enumerated
attribute that is used to specify whether an element's attribute values and the values of
its Text
node children are to be translated when the page is localized, or whether to
leave them unchanged.
The attribute's keywords are the empty string, yes
, and no
. The empty string and the yes
keyword map to the
yes state. The no
keyword maps to the no state. In addition,
there is a third state, the inherit state, which is the missing value default (and
the invalid value default).
Each element (even non-HTML elements) has a translation mode, which is in either the
translate-enabled state or the no-translate state. If an HTML element's translate
attribute is in the yes state, then the element's translation mode is in the
translate-enabled state; otherwise, if the element's translate
attribute is in the no state, then the element's
translation mode is in the no-translate state. Otherwise, either the
element's translate
attribute is in the inherit state,
or the element is not an HTML element and thus does not have a
translate
attribute; in either case, the element's
translation mode is in the same state as its parent element's, if any, or in the
translate-enabled state, if the element is a root element.
When an element is in the translate-enabled state, the element's translatable
attributes and the values of its Text
node children are to be translated when
the page is localized. Attributes of the element that are not listed as translatable
attributes should not be translated.
When an element is in the no-translate state, the element's attribute values (including
the values of translatable attributes) and the values of its Text
node
children are to be left as-is when the page is localized, e.g. because the element contains a person's
name or a the name of a computer program.
The following attributes are translatable attributes:
abbr
on th
elementsalt
on area
,
img
, and
input
elementscontent
on meta
elements, if the name
attribute specifies a metadata name whose value is known to be translatabledownload
on a
and
area
elementslabel
on optgroup
,
option
, and
track
elementslang
on HTML elements; must be "translated" to match the language used in the translationplaceholder
on input
and
textarea
elementssrcdoc
on iframe
elements; must be parsed and recursively processedstyle
on HTML elements; must be parsed and recursively processed (e.g. for the values of 'content' properties)title
on all HTML elementsvalue
on input
elements with a
type
attribute in the Button state
or the Reset Button stateThe translate
IDL attribute must, on getting,
return true if the element's translation mode is translate-enabled, and
false otherwise. On setting, it must set the content attribute's value to "yes
" if the new value is true, and set the content attribute's value to "no
" otherwise.
In this example, everything in the document is to be translated when the page is localized, except the sample keyboard input and sample program output:
<!DOCTYPE HTML> <html> <!-- default on the root element is translate=yes --> <head> <title>The Bee Game</title> <!-- implied translate=yes inherited from ancestors --> </head> <body> <p>The Bee Game is a text adventure game in English.</p> <p>When the game launches, the first thing you should do is type <kbd translate=no>eat honey</kbd>. The game will respond with:</p> <pre><samp translate=no>Yum yum! That was some good honey!</samp></pre> </body> </html>
xml:base
attribute (XML only)The xml:base
attribute is defined in XML Base. [XMLBASE]
The xml:base
attribute may be used on HTML
elements of XML documents. Authors must not use the xml:base
attribute on HTML elements in HTML
documents.
dir
attributeThe dir
attribute specifies the element's text directionality.
The attribute is an enumerated attribute with the following keywords and states:
ltr
keyword, which maps to the ltr stateIndicates that the contents of the element are explicitly directionally isolated left-to-right text.
rtl
keyword, which maps to the rtl stateIndicates that the contents of the element are explicitly directionally isolated right-to-left text.
auto
keyword, which maps to the auto stateIndicates that the contents of the element are explicitly directionally isolated text, but that the direction is to be determined programmatically using the contents of the element (as described below).
The heuristic used by this state is very crude (it just looks at the first character with a strong directionality, in a manner analogous to the Paragraph Level determination in the bidirectional algorithm). Authors are urged to only use this value as a last resort when the direction of the text is truly unknown and no better server-side heuristic can be applied. [BIDI]
For textarea
and pre
elements, the heuristic is
applied on a per-paragraph level.
The attribute has no invalid value default and no missing value default.
The directionality of an element (any element, not just an HTML element) is either 'ltr' or 'rtl', and is determined as per the first appropriate set of steps from the following list:
dir
attribute is in the ltr statedir
attribute is not in a defined state (i.e. it is not present or has an invalid value)input
element whose type
attribute is in the Telephone state, and the dir
attribute is not in a defined state (i.e. it is not present or has an invalid value)The directionality of the element is 'ltr'.
dir
attribute is in the rtl stateThe directionality of the element is 'rtl'.
input
element whose type
attribute is in the Text, Search,
Telephone, URL,
or E-mail state, and the dir
attribute is in the auto
statetextarea
element and the dir
attribute is in the auto stateIf the element's value contains a character of bidirectional character type AL or R, and there is no character of bidirectional character type L anywhere before it in the element's value, then the directionality of the element is 'rtl'. [BIDI]
Otherwise, if the element's value is not the empty string, or if the element is a root element, the directionality of the element is 'ltr'.
Otherwise, the directionality of the element is the same as the element's parent element's directionality.
dir
attribute is in the auto statebdi
element and the dir
attribute is not in a defined state (i.e. it is not present or has an invalid value)Find the first character in tree order that matches the following criteria:
The character is from a Text
node that is a descendant of the element whose
directionality is being determined.
The character is of bidirectional character type L, AL, or R. [BIDI]
The character is not in a Text
node that has an ancestor element that is a
descendant of the element whose directionality is
being determined and that is either:
If such a character is found and it is of bidirectional character type AL or R, the directionality of the element is 'rtl'.
If such a character is found and it is of bidirectional character type L, the directionality of the element is 'ltr'.
Otherwise, if the element is empty and is not a root element, the directionality of the element is the same as the element's parent element's directionality.
Otherwise, the directionality of the element is 'ltr'.
dir
attribute is
not in a defined state (i.e. it is not present or has an invalid value)The directionality of the element is the same as the element's parent element's directionality.
Since the dir
attribute is only defined for
HTML elements, it cannot be present on elements from other namespaces. Thus, elements
from other namespaces always just inherit their directionality from their parent element, or, if they don't have one,
default to 'ltr'.
This attribute has rendering requirements involving the bidirectional algorithm.
The directionality of an attribute of an HTML element, which is used when the text of that attribute is to be included in the rendering in some manner, is determined as per the first appropriate set of steps from the following list:
dir
attribute is in the auto
stateFind the first character (in logical order) of the attribute's value that is of bidirectional character type L, AL, or R. [BIDI]
If such a character is found and it is of bidirectional character type AL or R, the directionality of the attribute is 'rtl'.
Otherwise, the directionality of the attribute is 'ltr'.
The following attributes are directionality-capable attributes:
abbr
on th
elementsalt
on area
,
img
, and
input
elementscontent
on meta
elements, if the name
attribute specifies a metadata name whose value is primarily intended to be human-readable rather than machine-readablelabel
on optgroup
,
option
, and
track
elementsplaceholder
on input
and
textarea
elementstitle
on all HTML elementsdir
[ = value ]Returns the html
element's dir
attribute's value, if any.
Can be set, to either "ltr
", "rtl
", or "auto
" to replace the html
element's dir
attribute's value.
If there is no html
element, returns the empty string and ignores new values.
The dir
IDL attribute on an element must
reflect the dir
content attribute of that element,
limited to only known values.
The dir
IDL attribute on Document
objects must reflect the dir
content attribute of
the html
element, if any, limited to only known values. If
there is no such element, then the attribute must return the empty string and do nothing on
setting.
Authors are strongly encouraged to use the dir
attribute to indicate text direction rather than using CSS, since that way their documents will
continue to render correctly even in the absence of CSS (e.g. as interpreted by search
engines).
This markup fragment is of an IM conversation.
<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> How do you write "What's your name?" in Arabic?</p> <p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> ما اسمك؟</p> <p dir=auto class="u1"><b><bdi>Student</bdi>:</b> Thanks.</p> <p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> That's written "شكرًا".</p> <p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> Do you know how to write "Please"?</p> <p dir=auto class="u1"><b><bdi>Student</bdi>:</b> "من فضلك", right?</p>
Given a suitable style sheet and the default alignment styles for the p
element,
namely to align the text to the start edge of the paragraph, the resulting rendering could
be as follows:
As noted earlier, the auto
value is not a panacea. The
final paragraph in this example is misinterpreted as being right-to-left text, since it begins
with an Arabic character, which causes the "right?" to be to the left of the Arabic text.
class
attributeEvery HTML element may have a class
attribute specified.
The attribute, if specified, must have a value that is a set of space-separated tokens representing the various classes that the element belongs to.
The classes that an HTML element has assigned to it consists
of all the classes returned when the value of the class
attribute
is split on spaces. (Duplicates are ignored.)
Assigning classes to an element affects class matching in selectors in CSS, the
getElementsByClassName()
method in the
DOM, and other such features.
There are no additional restrictions on the tokens authors can use in the class
attribute, but authors are encouraged to use values that describe
the nature of the content, rather than values that describe the desired presentation of the
content.
The className
and classList
IDL attributes, defined in the DOM
specification, reflect the class
content attribute.
[DOM]
style
attributeAll HTML elements may have the style
content
attribute set. This is a CSS styling attribute as defined by the CSS Styling
Attribute Syntax specification. [CSSATTR]
In user agents that support CSS, the attribute's value must be parsed when the attribute is added or has its value changed, according to the rules given for CSS styling attributes. [CSSATTR]
Documents that use style
attributes on any of their elements
must still be comprehensible and usable if those attributes were removed.
In particular, using the style
attribute to hide
and show content, or to convey meaning that is otherwise not included in the document, is
non-conforming. (To hide and show content, use the hidden
attribute.)
style
Returns a CSSStyleDeclaration
object for the element's style
attribute.
The style
IDL attribute is defined in the CSS Object
Model (CSSOM) specification. [CSSOM]
In the following example, the words that refer to colors are marked up using the
span
element and the style
attribute to make those
words show up in the relevant colors in visual media.
<p>My sweat suit is <span style="color: green; background: transparent">green</span> and my eyes are <span style="color: blue; background: transparent">blue</span>.</p>
data-*
attributesA custom data attribute is an attribute in no namespace whose name starts with the
string "data-
", has at least one character after the
hyphen, is XML-compatible, and contains no uppercase ASCII letters.
All attribute names on HTML elements in HTML documents get ASCII-lowercased automatically, so the restriction on ASCII uppercase letters doesn't affect such documents.
Custom data attributes are intended to store custom data private to the page or application, for which there are no more appropriate attributes or elements.
These attributes are not intended for use by software that is independent of the site that uses the attributes.
For instance, a site about music could annotate list items representing tracks in an album with custom data attributes containing the length of each track. This information could then be used by the site itself to allow the user to sort the list by track length, or to filter the list for tracks of certain lengths.
<ol> <li data-length="2m11s">Beyond The Sea</li> ... </ol>
It would be inappropriate, however, for the user to use generic software not associated with that music site to search for tracks of a certain length by looking at this data.
This is because these attributes are intended for use by the site's own scripts, and are not a generic extension mechanism for publicly-usable metadata.
Every HTML element may have any number of custom data attributes specified, with any value.
dataset
Returns a DOMStringMap
object for the element's data-*
attributes.
Hyphenated names become camel-cased. For example, data-foo-bar=""
becomes element.dataset.fooBar
.
The dataset
IDL attribute provides convenient
accessors for all the data-*
attributes on an element. On
getting, the dataset
IDL attribute must return a
DOMStringMap
object, associated with the following algorithms, which expose these
attributes on their element:
data-
" and whose remaining characters (if any) do not include any
uppercase ASCII letters, in the order that those attributes are listed in the
element's attribute list, add a name-value pair to list whose
name is the attribute's name with the first five characters removed and whose value is the
attribute's value.SyntaxError
exception and abort these steps.data-
at the front of name.setAttribute()
would have thrown an exception when setting an attribute with
the name name, then this must throw the same exception.data-
at the front of name.This algorithm will only get invoked by the WebIDL specification for names that are given by the earlier algorithm for getting the list of name-value pairs. [WEBIDL]
The same object must be returned each time.
If a Web page wanted an element to represent a space ship, e.g. as part of a game, it would
have to use the class
attribute along with data-*
attributes:
<div class="spaceship" data-ship-id="92432" data-weapons="laser 2" data-shields="50%" data-x="30" data-y="10" data-z="90"> <button class="fire" onclick="spaceships[this.parentNode.dataset.shipId].fire()"> Fire </button> </div>
Notice how the hyphenated attribute name becomes camel-cased in the API.
Authors should carefully design such extensions so that when the attributes are ignored and any associated CSS dropped, the page is still usable.
User agents must not derive any implementation behavior from these attributes or values. Specifications intended for user agents must not define these attributes to have any meaningful values.
JavaScript libraries may use the custom data attributes, as they are considered to be part of the page on which they are used. Authors of libraries that are reused by many authors are encouraged to include their name in the attribute names, to reduce the risk of clashes. Where it makes sense, library authors are also encouraged to make the exact name used in the attribute names customizable, so that libraries whose authors unknowingly picked the same name can be used on the same page, and so that multiple versions of a particular library can be used on the same page even when those versions are not mutually compatible.
For example, a library called "DoQuery" could use attribute names like data-doquery-range
, and a library called "jJo" could use attributes names like
data-jjo-range
. The jJo library could also provide an API to set which
prefix to use (e.g. J.setDataPrefix('j2')
, making the attributes have names
like data-j2-range
).
Text content in HTML elements with Text
nodes in their
contents, and text in attributes of HTML
elements that allow free-form text, may contain characters in the ranges U+202A to U+202E
and U+2066 to U+2069 (the bidirectional-algorithm formatting characters). However, the use of
these characters is restricted so that any embedding or overrides generated by these characters do
not start and end with different parent elements, and so that all such embeddings and overrides
are explicitly terminated by a U+202C POP DIRECTIONAL FORMATTING character. This helps reduce
incidences of text being reused in a manner that has unforeseen effects on the bidirectional
algorithm. [BIDI]
The aforementioned restrictions are defined by specifying that certain parts of documents form bidirectional-algorithm formatting character ranges, and then imposing a requirement on such ranges.
The strings resulting from applying the following algorithm to an HTML element element are bidirectional-algorithm formatting character ranges:
Let output be an empty list of strings.
Let string be an empty string.
Let node be the first child node of element, if any, or null otherwise.
Loop: If node is null, jump to the step labeled end.
Process node according to the first matching step from the following list:
Text
nodeAppend the text data of node to string.
br
elementIf string is not the empty string, push string onto output, and let string be empty string.
Let node be node's next sibling, if any, or null otherwise.
Jump to the step labeled loop.
End: If string is not the empty string, push string onto output.
Return output as the bidirectional-algorithm formatting character ranges.
The value of a namespace-less attribute of an HTML element is a bidirectional-algorithm formatting character range.
Any strings that, as described above, are bidirectional-algorithm formatting character
ranges must match the string
production in the following ABNF, the
character set for which is Unicode. [ABNF]
string = *( plaintext ( embedding / override / isolation ) ) plaintext embedding = ( lre / rle ) string pdf override = ( lro / rlo ) string pdf isolation = ( lri / rli / fsi ) string pdi lre = %x202A ; U+202A LEFT-TO-RIGHT EMBEDDING rle = %x202B ; U+202B RIGHT-TO-LEFT EMBEDDING lro = %x202D ; U+202D LEFT-TO-RIGHT OVERRIDE rlo = %x202E ; U+202E RIGHT-TO-LEFT OVERRIDE pdf = %x202C ; U+202C POP DIRECTIONAL FORMATTING lri = %x2066 ; U+2066 LEFT-TO-RIGHT ISOLATE rli = %x2067 ; U+2067 RIGHT-TO-LEFT ISOLATE fsi = %x2068 ; U+2068 FIRST STRONG ISOLATE pdi = %x2069 ; U+2069 POP DIRECTIONAL ISOLATE plaintext = *( %x0000-2029 / %x202F-2065 / %x206A-10FFFF ) ; any string with no bidirectional-algorithm formatting characters
While the U+2069 POP DIRECTIONAL ISOLATE character implicitly also ends open embeddings and overrides, text that relies on this implicit scope closure is not conforming to this specification. All strings of embeddings, overrides, and isolations need to be explicitly terminated to conform to this section's requirements.
Authors are encouraged to use the dir
attribute, the
bdo
element, and the bdi
element, rather than maintaining the
bidirectional-algorithm formatting characters manually. The bidirectional-algorithm formatting
characters interact poorly with CSS.
User agents must implement the Unicode bidirectional algorithm to determine the proper ordering of characters when rendering documents and parts of documents. [BIDI]
The mapping of HTML to the Unicode bidirectional algorithm must be done in one of three ways. Either the user agent must implement CSS, including in particular the CSS 'unicode-bidi', 'direction', and 'content' properties, and must have, in its user agent style sheet, the rules using those properties given in this specification's rendering section, or, alternatively, the user agent must act as if it implemented just the aforementioned properties and had a user agent style sheet that included all the aforementioned rules, but without letting style sheets specified in documents override them, or, alternatively, the user agent must implement another styling language with equivalent semantics. [CSSWM] [CSSGC]
The following elements and attributes have requirements defined by the rendering section that, due to the requirements in this section, are requirements on all user agents (not just those that support the suggested default rendering):
Authors are encouraged to make use of the following documents for guidance on using ARIA in HTML beyond that which is provided in this section:
Authors may use the ARIA role
and aria-*
attributes on HTML elements, in accordance with the
requirements described in the ARIA specifications, except where these conflict with the
strong native semantics
described below. These exceptions are intended to prevent authors from making
assistive technology products report nonsensical states that do not represent the actual state of
the document. [ARIA]
User agents are required to implement ARIA semantics on all HTML elements, as defined in the ARIA specifications. The default implicit ARIA semantics defined below must be recognized by implementations for the purposes of ARIA processing. [ARIAIMPL]
The ARIA attributes defined in the ARIA specifications, and the strong native semantics and default implicit ARIA semantics defined below, do not have any effect on CSS pseudo-class matching, user interface modalities that don't use assistive technologies, or the default actions of user interaction events as described in this specification.
Every HTML element may have an ARIA role
attribute specified. This is an
ARIA Role attribute as defined by [ARIA] Section
5.4 Definition of Roles.
The attribute, if specified, must have a value that is a set of space-separated tokens representing the various WAI-ARIA roles that the element belongs to.
The WAI-ARIA role that an HTML element has assigned to it is the
first non-abstract role found in the list of values generated when the
role
attribute is split on
spaces.
Every HTML element may have ARIA state and property attributes specified. These attributes are defined by [ARIA] in Section 6.6, Definitions of States and Properties (all aria-* attributes).
A subset of the ARIA State and Property attributes are defined as "Global States and Properties" in Section 6.4. Global States and Properties of the [ARIA] Specification.
These attributes, if specified, must have a value that is the ARIA value type in the "Value" field of the definition for the state or property, mapped to the appropriate HTML value type according to [ARIA] Section 10.2 Mapping WAI-ARIA Value types to languages using the HTML 5 mapping.
ARIA State and Property attributes can be used on any element. They are not always meaningful, however, and in such cases user agents might not perform any processing aside from including them in the DOM. State and property attributes are processed according to the requirements of the sections Strong Native Semantics and Implicit ARIA semantics, as well as [ARIA] and [ARIAIMPL].
The following table defines the strong native semantics and corresponding default implicit ARIA semantics that apply to HTML elements. Each language feature (element or attribute) in a cell in the first column implies the ARIA semantics (any role, states, and properties) given in the cell in the second column of the same row. When multiple rows apply to an element, the role from the last row to define a role must be applied, and the states and properties from all the rows must be combined.
Documents must not use any role
values with elements
in the following table other than the corresponding role value (if any) as listed for that element in the second column,
or the role
value "presentation
", if the second column indicates that element's
semantics can be removed by using the "presentation
" role
value.
In the majority of cases setting an ARIA role
and/or aria-*
attribute that matches the default implicit ARIA semantics is
unnecessary and not recommended as these properties are already set by the browser.
Language feature | Strong native semantics and default implicit ARIA semantics |
---|---|
area element that creates a hyperlink
| link role
|
base element
| No role |
datalist element
| listbox role, with the aria-multiselectable property set to "false"
|
details element
| aria-expanded state set to "true" if the element's open attribute is present, and set to "false" otherwise
|
dialog element without an open attribute
| The aria-hidden state set to "true"
|
fieldset element
| group role
(semantics may be removed by using the presentation role)
|
footer element that is not a descendant of an article or section element.
| contentinfo role
(semantics may be removed by using the presentation role)
|
head element
| No role |
header element that is not a descendant of an article or section element.
| banner role
(semantics may be removed by using the presentation role)
|
hr element
| separator role
(semantics may be removed by using the presentation role)
|
html element
| No role |
img element whose alt attribute's value is empty
| presentation role
|
input element with a type attribute in the Checkbox state
| aria-checked state set to "mixed" if the element's indeterminate IDL attribute is true, or "true" if the element's checkedness is true, or "false" otherwise
|
input element with a type attribute in the Color state
| No role |
input element with a type attribute in the Date state
| No role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Date and Time state
| No role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Local Date and Time state
| No role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the E-mail state with no suggestions source element
| textbox role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the File Upload state
| No role |
input element with a type attribute in the Hidden state
| No role |
input element with a type attribute in the Month state
| No role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Number state
| spinbutton role, with the aria-readonly property set to "true" if the element has a readonly attribute, the aria-valuemax property set to the element's maximum, the aria-valuemin property set to the element's minimum, and, if the result of applying the rules for parsing floating-point number values to the element's value is a number, with the aria-valuenow property set to that number
|
input element with a type attribute in the Password state
| textbox role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Radio Button state
| aria-checked state set to "true" if the element's checkedness is true, or "false" otherwise
|
input element with a type attribute in the Range state
| slider role, with the aria-valuemax property set to the element's maximum, the aria-valuemin property set to the element's minimum, and the aria-valuenow property set to the result of applying the rules for parsing floating-point number values to the element's value, if that results in a number, or the default value otherwise
|
input element with a type attribute in the Reset Button state
| button role
|
input element with a type attribute in the Search state with no suggestions source element
| textbox role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Submit Button state
| button role
|
input element with a type attribute in the Telephone state with no suggestions source element
| textbox role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Text state with no suggestions source element
| textbox role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Text, Search, Telephone, URL, or E-mail states with a suggestions source element
| combobox role, with the aria-owns property set to the same value as the list attribute, and the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Time state
| No role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the URL state with no suggestions source element
| textbox role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
input element with a type attribute in the Week state
| No role, with the aria-readonly property set to "true" if the element has a readonly attribute
|
keygen element
| No role |
label element
| No role |
link element that creates a hyperlink
| link role
|
main element
| main role
(semantics may be removed by using the presentation role)
|
meta element
| No role |
meter element
| No role |
nav element
| navigation role (semantics may be removed by using the presentation role)
|
noscript element
| No role |
optgroup element
| No role |
option element that is in a list of options or that represents a suggestion in a datalist element
| option role, with the aria-selected state set to "true" if the element's selectedness is true, or "false" otherwise.
|
param element
| No role |
progress element
| progressbar role, with, if the progress bar is determinate, the aria-valuemax property set to the maximum value of the progress bar, the aria-valuemin property set to zero, and the aria-valuenow property set to the current value of the progress bar
|
script element
| No role |
select element with a multiple attribute
| listbox role, with the aria-multiselectable property set to "true"
|
select element with no multiple attribute
| listbox role, with the aria-multiselectable property set to "false"
|
source element
| No role |
style element
| No role |
summary element
| No role |
template element
| No role |
textarea element
| textbox role, with the aria-multiline property set to "true", and the aria-readonly property set to "true" if the element has a readonly attribute
|
title element
| No role |
Element that is disabled | The aria-disabled state set to "true"
|
Element that is inert | The aria-disabled state set to "true"
|
Element that is a candidate for constraint validation but that does not satisfy its constraints | The aria-invalid state set to "true"
|
Some HTML elements have native semantics that can be overridden. The following table lists these elements and their default implicit ARIA semantics, along with the restrictions that apply to those elements. Each language feature (element or attribute) in a cell in the first column implies, unless otherwise overridden, the ARIA semantic (role, state, or property) given in the cell in the second column of the same row, but this semantic may be overridden under the conditions listed in the cell in the third column of that row.
Language feature | Default implicit ARIA semantic | Restrictions |
---|---|---|
a element that creates a hyperlink
| link role
| If specified, role must be one of the following: link , button , checkbox , menuitem , menuitemcheckbox ,menuitemradio , tab , or treeitem
|
address element
| No role | If specified, role must be contentinfo
|
article element
| article role
| If specified, role must be one of the following: article , document , application , or main
|
aside element
| complementary role
| If specified, role must be one of the following: complementary ,
note , search or presentation
|
audio element
| No role | If specified, role must be application
|
body element
| document role
| If specified, role must be either document or application
|
button element
| button role
| If specified, role must be one of the following: button , link ,
menuitem , menuitemcheckbox ,
menuitemradio or radio
|
details element
| group role
| If specified, role must be a role that supports aria-expanded
|
dialog element
| dialog role
| If specified, role must be one of the following:
alert ,
alertdialog ,
application ,
contentinfo ,
dialog ,
document ,
log ,
main ,
marquee ,
region ,
search , or
status
|
embed element
| No role | If specified, role must be one of the following: application ,
document , or img
|
h1 element
| heading role, with the
aria-level property set to the element's outline depth
| If specified, role must be one of the following: heading , tab
or presentation
|
h2 element
| heading role, with the aria-level
property set to the element's outline depth
| If specified, role must be one of the following: heading , tab
or presentation
|
h3 element
| heading role, with the aria-level
property set to the element's outline depth
| If specified, role must be one of the following: heading , tab
or presentation
|
h4 element
| heading role, with the aria-level
property set to the element's outline depth
| If specified, role must be heading , tab or presentation
|
h5 element
| heading role, with the aria-level
property set to the element's outline depth
| If specified, role must be one of the following: heading , tab
or presentation
|
h6 element
| heading role, with the aria-level property set to the element's outline depth
| If specified, role must be one of the following: heading , tab
or presentation
|
iframe element
| No role | If specified, role must be one of the following: application , document , img , or presentation
|
img element whose alt attribute's value is absent
| img role
| No restrictions |
img element whose alt attribute's value is present and not empty
| img role
| No restrictions |
input element with a type attribute in the Button state
| button role
| If specified, role must be one of the following: button , link ,
menuitem , menuitemcheckbox ,
menuitemradio or radio
|
input element with a type attribute in the Checkbox state
| checkbox role
| If specified, role must be either checkbox or menuitemcheckbox
|
input element with a type attribute in the Image Button state
| button role
| If specified, role must be one of the following: button , link ,
menuitem , menuitemcheckbox ,
menuitemradio or radio
|
input element with a type attribute in the Radio Button state
| radio role
| If specified, role must be either radio or menuitemradio
|
input , select or textarea element with a required attribute
| The aria-required state set to "true"
| If specified, the aria-required state must be set to "true"
|
input , select or textarea element without a required attribute
| aria-required set to "false"
| If specified, the aria-required state set to "true" or "false"
|
li element whose parent is an ol or ul element
| listitem role
| If specified, role must be one of the following: listitem , menuitem , menuitemcheckbox , menuitemradio , option , tab , treeitem or presentation
|
menu element with a type attribute in the toolbar state
| toolbar role
| If specified, role must be one of the following: directory , list , listbox , menu , menubar , tablist , toolbar , or tree
or presentation
|
object element
| No role | If specified, role must be one of the following: application , document , img , or presentation
|
ol element
| list role
| If specified, role must be one of the following: directory , list , listbox , menu , menubar , tablist , toolbar , tree
or presentation
|
output element
| status role
| No restrictions |
section element
| region role Note:It is strongly recommended that user agents such as screen readers
only convey the presence of, and provide navigation for | If specified, role must be one of the following:
alert ,
alertdialog ,
application ,
contentinfo ,
dialog ,
document ,
log ,
main ,
marquee ,
region ,
search ,
status
or presentation
|
ul element
| list role
| If specified, role must be one of the following: directory , group , list , listbox , menu , menubar , tablist , toolbar , tree
or presentation
|
video element
| No role | If specified, role must be application
|
Element with a hidden attribute
| The aria-hidden state set to "true"
| If specified, the aria-hidden state set to "true" or "false"
|
Element without a hidden attribute
| The aria-hidden state set to "false"
| If specified, the aria-hidden state set to "true" or "false"
|
The entry "no role", when used as a strong native semantic, means that no role can be used and that the user agent has no default mapping to ARIA roles. (However, it could have its own mappings to the accessibility layer.) When used as a default implicit ARIA semantic, it means the user agent has no default mapping to ARIA roles. (However, it could have its own mappings to the accessibility layer.)
The WAI-ARIA specification neither requires or forbids user agents from enhancing native presentation and interaction behaviors on the basis of WAI- ARIA markup. Even mainstream user agents might choose to expose metadata or navigational features directly or via user-installed extensions; for example, exposing required form fields or landmark navigation. User agents are encouraged to maximize their usefulness to users, including users without disabilities.
Conformance checkers are encouraged to phrase errors such that authors are encouraged to use
more appropriate elements rather than remove accessibility annotations. For example, if an
a
element is marked as having the button
role, a conformance checker could say "Use a more appropriate element to represent a button, for
example a button
element or an input
element" rather than "The button
role cannot be used with a
elements".
These features can be used to make accessibility tools render content to their users in more useful ways. For example, ASCII art, which is really an image, appears to be text, and in the absence of appropriate annotations would end up being rendered by screen readers as a very painful reading of lots of punctuation. Using the features described in this section, one can instead make the ATs skip the ASCII art and just read the caption:
<figure role="img" aria-labelledby="fish-caption"> <pre> o .'`/ ' / ( O .-'` ` `'-._ .') _/ (o) '. .' / ) ))) >< < `\ |_\ _.' '. \ '-._ _ .-' '.) jgs `\__\ </pre> <figcaption id="fish-caption"> Joan G. Stark, "<cite>fish</cite>". October 1997. ASCII on electrons. 28×8. </figcaption> </figure>
html
elementhead
element followed by a body
element.manifest
— Application cache manifesthtml
element's start tag can be omitted
if the first thing inside the html
element is not a comment.html
element's end tag can be omitted if
the html
element is not immediately followed by a comment.interface HTMLHtmlElement : HTMLElement {};
The html
element represents the root of an HTML document.
Authors are encouraged to specify a lang
attribute on the root
html
element, giving the document's language. This aids speech synthesis tools to
determine what pronunciations to use, translation tools to determine what rules to use, and so
forth.
The manifest
attribute gives the address of
the document's application cache manifest, if there is one. If the attribute is present,
the attribute's value must be a valid non-empty URL potentially surrounded by
spaces.
The manifest
attribute only has an effect during the early stages of document load.
Changing the attribute dynamically thus has no effect (and thus, no DOM API is provided for this
attribute).
For the purposes of application cache
selection, later base
elements cannot affect the resolving of relative URLs in manifest
attributes, as the attributes are processed before those elements are seen.
The window.applicationCache
IDL
attribute provides scripted access to the offline application cache mechanism.
The html
element in the following example declares that the document's language
is English.
<!DOCTYPE html> <html lang="en"> <head> <title>Swapping Songs</title> </head> <body> <h1>Swapping Songs</h1> <p>Tonight I swapped some of the songs I wrote with some friends, who gave me some of the songs they wrote. I love sharing my music.</p> </body> </html>
head
elementhtml
element.iframe
srcdoc
document or if title information is available from a higher-level protocol: Zero or more elements of metadata content, of which no more than one is a title
element and no more than one is a base
element.title
element and no more than one is a base
element.head
element's start tag may be omitted if
the element is empty, or if the first thing inside the head
element is an element.head
element's end tag may be omitted if the
head
element is not immediately followed by a space character or a comment.interface HTMLHeadElement : HTMLElement {};
The head
element represents a collection of metadata for the
Document
.
The collection of metadata in a head
element can be large or small. Here is an
example of a very short one:
<!doctype html> <html> <head> <title>A document with a short head</title> </head> <body> ...
Here is an example of a longer one:
<!DOCTYPE HTML> <HTML> <HEAD> <META CHARSET="UTF-8"> <BASE HREF="http://www.example.com/"> <TITLE>An application with a long head</TITLE> <LINK REL="STYLESHEET" HREF="default.css"> <LINK REL="STYLESHEET ALTERNATE" HREF="big.css" TITLE="Big Text"> <SCRIPT SRC="support.js"></SCRIPT> <META NAME="APPLICATION-NAME" CONTENT="Long headed application"> </HEAD> <BODY> ...
The title
element is a required child in most situations, but when a
higher-level protocol provides title information, e.g. in the Subject line of an e-mail when HTML
is used as an e-mail authoring format, the title
element can be omitted.
title
elementhead
element containing no other title
elements.interface HTMLTitleElement : HTMLElement { attribute DOMString text; };
The title
element represents the document's title or name. Authors
should use titles that identify their documents even when they are used out of context, for
example in a user's history or bookmarks, or in search results. The document's title is often
different from its first heading, since the first heading does not have to stand alone when taken
out of context.
There must be no more than one title
element per document.
If it's reasonable for the Document
to have no title, then the
title
element is probably not required. See the head
element's content
model for a description of when the element is required.
text
[ = value ]Returns the contents of the element, ignoring child nodes that aren't Text
nodes.
Can be set, to replace the element's children with the given value.
The IDL attribute text
must return a
concatenation of the contents of all the Text
nodes that are children of the
title
element (ignoring any other nodes such as comments or elements), in tree order.
On setting, it must act the same way as the textContent
IDL attribute.
Here are some examples of appropriate titles, contrasted with the top-level headings that might be used on those same pages.
<title>Introduction to The Mating Rituals of Bees</title> ... <h1>Introduction</h1> <p>This companion guide to the highly successful <cite>Introduction to Medieval Bee-Keeping</cite> book is...
The next page might be a part of the same site. Note how the title describes the subject matter unambiguously, while the first heading assumes the reader knows what the context is and therefore won't wonder if the dances are Salsa or Waltz:
<title>Dances used during bee mating rituals</title> ... <h1>The Dances</h1>
The string to use as the document's title is given by the document.title
IDL attribute.
User agents should use the document's title when referring to the document in their user
interface. When the contents of a title
element are used in this way, the
directionality of that title
element should be used to set the directionality
of the document's title in the user interface.
base
elementhead
element containing no other base
elements.href
— Document base URLtarget
— Default browsing context for hyperlink navigation and form submissioninterface HTMLBaseElement : HTMLElement { attribute DOMString href; attribute DOMString target; };
The base
element allows authors to specify the document base URL for
the purposes of resolving relative URLs, and the name of the
default browsing context for the purposes of following hyperlinks. The
element does not represent any content beyond this
information.
There must be no more than one base
element per document.
A base
element must have either an href
attribute, a target
attribute, or both.
The href
content attribute, if specified, must
contain a valid URL potentially surrounded by spaces.
A base
element, if it has an href
attribute,
must come before any other elements in the tree that have attributes defined as taking URLs, except the html
element (its manifest
attribute isn't affected by base
elements).
The target
attribute, if specified, must
contain a valid browsing context name or keyword, which specifies which
browsing context is to be used as the default when hyperlinks and forms in the
Document
cause navigation.
A base
element, if it has a target
attribute, must come before any elements in the tree that represent hyperlinks.
If there are multiple base
elements with target
attributes, all but the first are ignored.
A base
element that is the first base
element with an href
content attribute in a particular Document
has a
frozen base URL. The frozen base URL must be set, synchronously, whenever any of the following situations occur:
base
element becomes the first base
element in tree
order with an href
content attribute in its
Document
.base
element is the first base
element in tree
order with an href
content attribute in its
Document
, and its href
content attribute is
changed.To set the frozen base URL, resolve
the value of the element's href
content attribute relative to
the Document
's fallback base URL; if this is successful, set the
frozen base URL to the resulting absolute URL, otherwise, set the
frozen base URL to the fallback base URL.
The href
IDL attribute, on getting, must return
the result of running the following algorithm:
If the base
element has no href
content
attribute, then return the document base URL and abort these steps.
Let fallback base url be the Document
's fallback
base URL.
Let url be the value of the href
attribute of the base
element.
Resolve url relative to fallback base url (thus, the base
href
attribute isn't affected by xml:base
attributes or base
elements).
If the previous step was successful, return the resulting absolute URL and abort these steps.
Otherwise, return the empty string.
The href
IDL attribute, on setting, must set the href
content attribute to the given new value.
The target
IDL attribute must
reflect the content attribute of the same name.
In this example, a base
element is used to set the document base
URL:
<!DOCTYPE html> <html> <head> <title>This is an example for the <base> element</title> <base href="http://www.example.com/news/index.html"> </head> <body> <p>Visit the <a href="archives.html">archives</a>.</p> </body> </html>
The link in the above example would be a link to "http://www.example.com/news/archives.html
".
link
elementnoscript
element that is a child of a head
element.href
— Address of the hyperlinkcrossorigin
— How the element handles crossorigin requestsrel
— Relationship between the document containing the hyperlink and the destination resourcemedia
— Applicable mediahreflang
— Language of the linked resourcetype
— Hint for the type of the referenced resourcesizes
— Sizes of the icons (for rel
="icon
")title
attribute has special semantics on this element: Title of the link; alternative style sheet set name.link
(default - do not set).aria-*
attributes applicable to the allowed roles.role
value interface HTMLLinkElement : HTMLElement {
attribute boolean disabled;
attribute DOMString href;
attribute DOMString crossOrigin;
attribute DOMString rel;
readonly attribute DOMTokenList relList;
attribute DOMString media;
attribute DOMString hreflang;
attribute DOMString type;
[PutForwards=value] readonly attribute DOMSettableTokenList sizes;
};
HTMLLinkElement implements LinkStyle;
The link
element allows authors to link their document to other resources.
The destination of the link(s) is given by the href
attribute, which must be present and must contain a
valid non-empty URL potentially surrounded by spaces. If the href
attribute is absent, then the element does not define a
link.
A link
element must have a rel
attribute.
If the rel
attribute is used, the element is
restricted to the head
element.
The types of link indicated (the relationships) are given by the value of the rel
attribute, which, if present, must have a value that
is a set of space-separated tokens. The allowed keywords and
their meanings are defined in a later section. If the rel
attribute is absent, has no keywords, or if none of the keywords
used are allowed according to the definitions in this specification, then the element does not
create any links.
Two categories of links can be created using the link
element: Links to external resources and hyperlinks. The link types section defines
whether a particular link type is an external resource or a hyperlink. One link
element can create multiple links (of which some might be external resource links and some might
be hyperlinks); exactly which and how many links are created depends on the keywords given in the
rel
attribute. User agents must process the links on a per-link
basis, not a per-element basis.
Each link created for a link
element is handled separately. For
instance, if there are two link
elements with rel="stylesheet"
,
they each count as a separate external resource, and each is affected by its own attributes
independently. Similarly, if a single link
element has a rel
attribute with the value next stylesheet
,
it creates both a hyperlink (for the next
keyword) and
an external resource link (for the stylesheet
keyword), and they are affected by other attributes (such as media
or title
)
differently.
For example, the following link
element creates two hyperlinks (to the same
page):
<link rel="author license" href="/about">
The two links created by this element are one whose semantic is that the target page has information about the current page's author, and one whose semantic is that the target page has information regarding the license under which the current page is provided.
The crossorigin
attribute is a CORS
settings attribute. It is intended for use with external resource links.
The exact behavior for links to external resources depends on the exact relationship, as defined for the relevant link type. Some of the attributes control whether or not the external resource is to be applied (as defined below).
For external resources that are represented in the DOM (for example, style sheets), the DOM representation must be made available (modulo cross-origin restrictions) even if the resource is not applied. To obtain the resource, the user agent must run the following steps:
If the href
attribute's value is the empty string,
then abort these steps.
Resolve the URL given by the href
attribute, relative to the element.
If the previous step fails, then abort these steps.
Do a potentially CORS-enabled fetch of the resulting absolute
URL, with the mode being the current state of the element's crossorigin
content attribute, the origin
being the origin of the link
element's Document
, and the
default origin behaviour set to taint.
The resource obtained in this fashion can be either CORS-same-origin or CORS-cross-origin.
User agents may opt to only try to obtain such resources when they are needed, instead of pro-actively fetching all the external resources that are not applied.
The semantics of the protocol used (e.g. HTTP) must be followed when fetching external resources. (For example, redirects will be followed and 404 responses will cause the external resource to not be applied.)
Once the attempts to obtain the resource and its critical subresources are
complete, the user agent must, if the loads were successful, queue a task to
fire a simple event named load
at the
link
element, or, if the resource or one of its critical subresources
failed to completely load for any reason (e.g. DNS error, HTTP 404 response, a connection being
prematurely closed, unsupported Content-Type), queue a task to fire a simple
event named error
at the link
element.
Non-network errors in processing the resource or its subresources (e.g. CSS parse errors, PNG
decoding errors) are not failures for the purposes of this paragraph.
The task source for these tasks is the DOM manipulation task source.
The element must delay the load event of the element's document until all the attempts to obtain the resource and its critical subresources are complete. (Resources that the user agent has not yet attempted to obtain, e.g. because it is waiting for the resource to be needed, do not delay the load event.)
Interactive user agents may provide users with a means to follow the hyperlinks created using the link
element, somewhere
within their user interface. The exact interface is not defined by this specification, but it
could include the following information (obtained from the element's attributes, again as defined
below), in some form or another (possibly simplified), for each hyperlink created with each
link
element in the document:
rel
attribute)title
attribute).href
attribute).hreflang
attribute).media
attribute).User agents could also include other information, such as the type of the resource (as given by
the type
attribute).
Hyperlinks created with the link
element and its rel
attribute apply to the whole page. This contrasts with the rel
attribute of a
and area
elements,
which indicates the type of a link whose context is given by the link's location within the
document.
The media
attribute says which media the
resource applies to. The value must be a valid media query.
If the link is a hyperlink then the media
attribute is purely advisory, and describes for which media the document in question was
designed.
However, if the link is an external resource link, then the media
attribute is prescriptive. The user agent must apply the
external resource when the media
attribute's value
matches the environment and the other relevant conditions apply, and must not apply
it otherwise.
The external resource might have further restrictions defined within that limit
its applicability. For example, a CSS style sheet might have some @media
blocks. This specification does not override such further restrictions or requirements.
The default, if the media
attribute is
omitted, is "all
", meaning that by default links apply to all media.
The hreflang
attribute on the
link
element has the same semantics as the hreflang
attribute on a
and
area
elements.
The type
attribute gives the MIME
type of the linked resource. It is purely advisory. The value must be a valid MIME
type.
For external resource links, the type
attribute is used as a hint to user agents so that they can
avoid fetching resources they do not support. If the attribute is present, then
the user agent must assume that the resource is of the given type (even if that is not a
valid MIME type, e.g. the empty string). If the attribute is omitted, but the
external resource link type has a default type defined, then the user agent must assume that the
resource is of that type. If the UA does not support the given MIME type for the
given link relationship, then the UA should not obtain
the resource; if the UA does support the given MIME type for the given link
relationship, then the UA should obtain the resource at
the appropriate time as specified for the external resource link's particular type.
If the attribute is omitted, and the external resource link type does not have a default type
defined, but the user agent would obtain the resource if
the type was known and supported, then the user agent should obtain the resource under the assumption that it will be
supported.
User agents must not consider the type
attribute
authoritative — upon fetching the resource, user agents must not use the type
attribute to determine its actual type. Only the actual type
(as defined in the next paragraph) is used to determine whether to apply the resource,
not the aforementioned assumed type.
If the external resource link type defines rules for processing the resource's Content-Type metadata, then those rules apply. Otherwise, if the resource is expected to be an image, user agents may apply the image sniffing rules, with the official type being the type determined from the resource's Content-Type metadata, and use the resulting sniffed type of the resource as if it was the actual type. Otherwise, if neither of these conditions apply or if the user agent opts not to apply the image sniffing rules, then the user agent must use the resource's Content-Type metadata to determine the type of the resource. If there is no type metadata, but the external resource link type has a default type defined, then the user agent must assume that the resource is of that type.
The stylesheet
link type defines rules for
processing the resource's Content-Type metadata.
Once the user agent has established the type of the resource, the user agent must apply the resource if it is of a supported type and the other relevant conditions apply, and must ignore the resource otherwise.
If a document contains style sheet links labeled as follows:
<link rel="stylesheet" href="A" type="text/plain"> <link rel="stylesheet" href="B" type="text/css"> <link rel="stylesheet" href="C">
...then a compliant UA that supported only CSS style sheets would fetch the B and C files, and
skip the A file (since text/plain
is not the MIME type for CSS style
sheets).
For files B and C, it would then check the actual types returned by the server. For those that
are sent as text/css
, it would apply the styles, but for those labeled as
text/plain
, or any other type, it would not.
If one of the two files was returned without a Content-Type metadata, or with a
syntactically incorrect type like Content-Type: "null"
, then the
default type for stylesheet
links would kick in. Since that
default type is text/css
, the style sheet would nonetheless be
applied.
The title
attribute gives the title of the
link. With one exception, it is purely advisory. The value is text. The exception is for style
sheet links, where the title
attribute defines
alternative style sheet sets.
The title
attribute on link
elements differs from the global title
attribute of most other
elements in that a link without a title does not inherit the title of the parent element: it
merely has no title.
The sizes
attribute is used with the icon
link type. The attribute must not be specified on link
elements that do not have a rel
attribute that specifies the
icon
keyword.
The activation behavior of link
elements that create hyperlinks is to run the following steps:
If the link
element's Document
is not fully active,
then abort these steps.
Follow the hyperlink created by the
link
element.
HTTP Link:
headers, if supported, must be assumed to come before
any links in the document, in the order that they were given in the HTTP message. These headers
are to be processed according to the rules given in the relevant specifications. [HTTP] [WEBLINK]
Registration of relation types in HTTP Link: headers is distinct from HTML link types, and thus their semantics can be different from same-named HTML types.
The IDL attributes href
, rel
, media
,
hreflang
, type
, and sizes
each must reflect the respective
content attributes of the same name.
The crossOrigin
IDL attribute must
reflect the crossorigin
content attribute,
limited to only known values.
The IDL attribute relList
must reflect the rel
content attribute.
The IDL attribute disabled
only applies to
style sheet links. When the link
element defines a style sheet link, then the disabled
attribute behaves as defined for the alternative style sheets DOM. For all other
link
elements it always return false and does nothing on setting.
The LinkStyle
interface is also implemented by this element; the styling
processing model defines how. [CSSOM]
Here, a set of link
elements provide some style sheets:
<!-- a persistent style sheet --> <link rel="stylesheet" href="default.css"> <!-- the preferred alternate style sheet --> <link rel="stylesheet" href="green.css" title="Green styles"> <!-- some alternate style sheets --> <link rel="alternate stylesheet" href="contrast.css" title="High contrast"> <link rel="alternate stylesheet" href="big.css" title="Big fonts"> <link rel="alternate stylesheet" href="wide.css" title="Wide screen">
The following example shows how you can specify versions of the page that use alternative formats, are aimed at other languages, and that are intended for other media:
<link rel=alternate href="/en/html" hreflang=en type=text/html title="English HTML"> <link rel=alternate href="/fr/html" hreflang=fr type=text/html title="French HTML"> <link rel=alternate href="/en/html/print" hreflang=en type=text/html media=print title="English HTML (for printing)"> <link rel=alternate href="/fr/html/print" hreflang=fr type=text/html media=print title="French HTML (for printing)"> <link rel=alternate href="/en/pdf" hreflang=en type=application/pdf title="English PDF"> <link rel=alternate href="/fr/pdf" hreflang=fr type=application/pdf title="French PDF">
meta
elementcharset
attribute is present, or if the element's http-equiv
attribute is in the encoding declaration state: in a head
element.http-equiv
attribute is present but not in the encoding declaration state: in a head
element.http-equiv
attribute is present but not in the encoding declaration state: in a noscript
element that is a child of a head
element.name
attribute is present: where metadata content is expected.name
— Metadata namehttp-equiv
— Pragma directivecontent
— Value of the elementcharset
— Character encoding declarationinterface HTMLMetaElement : HTMLElement { attribute DOMString name; attribute DOMString httpEquiv; attribute DOMString content; };
The meta
element represents various kinds of metadata that cannot be
expressed using the title
, base
, link
, style
,
and script
elements.
The meta
element can represent document-level metadata with the name
attribute, pragma directives with the http-equiv
attribute, and the file's character encoding
declaration when an HTML document is serialized to string form (e.g. for transmission over
the network or for disk storage) with the charset
attribute.
Exactly one of the name
, http-equiv
, and charset
,
attributes must be specified.
If either name
or http-equiv
is
specified, then the content
attribute must also be
specified. Otherwise, it must be omitted.
The charset
attribute specifies the character
encoding used by the document. This is a character encoding declaration. If the
attribute is present in an XML document, its value must be an
ASCII case-insensitive match for the string "UTF-8
" (and the
document is therefore forced to use UTF-8 as its encoding).
The charset
attribute on the
meta
element has no effect in XML documents, and is only allowed in order to
facilitate migration to and from XHTML.
There must not be more than one meta
element with a charset
attribute per document.
The content
attribute gives the value of the
document metadata or pragma directive when the element is used for those purposes. The allowed
values depend on the exact context, as described in subsequent sections of this specification.
If a meta
element has a name
attribute, it sets document metadata. Document metadata is expressed in terms of name-value pairs,
the name
attribute on the meta
element giving the
name, and the content
attribute on the same element giving
the value. The name specifies what aspect of metadata is being set; valid names and the meaning of
their values are described in the following sections. If a meta
element has no content
attribute, then the value part of the metadata name-value
pair is the empty string.
The name
and content
IDL attributes must reflect the
respective content attributes of the same name. The IDL attribute httpEquiv
must reflect the content
attribute http-equiv
.
This specification defines a few names for the name
attribute of the meta
element.
Names are case-insensitive, and must be compared in an ASCII case-insensitive manner.
application-name
The value must be a short free-form string giving the name of the Web application that the
page represents. If the page is not a Web application, the application-name
metadata name must not be used.
Translations of the Web application's name may be given, using the attribute to specify the language of each name.
There must not be more than one meta
element with a given language
and with its name
attribute set to the value application-name
per document.
User agents may use the application name in UI in preference to the page's
title
, since the title might include status messages and the like relevant to the
status of the page at a particular moment in time instead of just being the name of the
application.
To find the application name to use given an ordered list of languages (e.g. British English, American English, and English), user agents must run the following steps:
Let languages be the list of languages.
Let default language be the language of the
Document
's root element,
if any, and if that language is not unknown.
If there is a default language, and if it is not the same language as any of the languages is languages, append it to languages.
Let winning language be the first language in languages for which there is a meta
element in the
Document
that has its name
attribute set to
the value application-name
and whose
language is the language in question.
If none of the languages have such a meta
element, then abort these steps;
there's no given application name.
Return the value of the content
attribute of the
first meta
element in the Document
in tree order that
has its name
attribute set to the value application-name
and whose language is winning language.
author
The value must be a free-form string giving the name of one of the page's authors.
description
The value must be a free-form string that describes the page. The value must be
appropriate for use in a directory of pages, e.g. in a search engine. There must not be more than
one meta
element with its name
attribute set to
the value description
per document.
generator
The value must be a free-form string that identifies one of the software packages used to generate the document. This value must not be used on pages whose markup is not generated by software, e.g. pages whose markup was written by a user in a text editor.
Here is what a tool called "Frontweaver" could include in its output, in the page's
head
element, to identify itself as the tool used to generate the page:
<meta name=generator content="Frontweaver 8.2">
keywords
The value must be a set of comma-separated tokens, each of which is a keyword relevant to the page.
This page about typefaces on British motorways uses a meta
element to specify
some keywords that users might use to look for the page:
<!DOCTYPE HTML> <html> <head> <title>Typefaces on UK motorways</title> <meta name="keywords" content="british,type face,font,fonts,highway,highways"> </head> <body> ...
Many search engines do not consider such keywords, because this feature has historically been used unreliably and even misleadingly as a way to spam search engine results in a way that is not helpful for users.
To obtain the list of keywords that the author has specified as applicable to the page, the user agent must run the following steps:
Let keywords be an empty list.
For each meta
element with a name
attribute and a content
attribute and whose name
attribute's value is keywords
, run the following substeps:
Split the value of the element's content
attribute on commas.
Add the resulting tokens, if any, to keywords.
Remove any duplicates from keywords.
Return keywords. This is the list of keywords that the author has specified as applicable to the page.
User agents should not use this information when there is insufficient confidence in the reliability of the value.
For instance, it would be reasonable for a content management system to use the keyword information of pages within the system to populate the index of a site-specific search engine, but a large-scale content aggregator that used this information would likely find that certain users would try to game its ranking mechanism through the use of inappropriate keywords.
Extensions to the predefined set of metadata names may be registered in the WHATWG Wiki MetaExtensions page. [WHATWGWIKI]
Anyone is free to edit the WHATWG Wiki MetaExtensions page at any time to add a type. These new names must be specified with the following information:
The actual name being defined. The name should not be confusingly similar to any other defined name (e.g. differing only in case).
A short non-normative description of what the metadata name's meaning is, including the format the value is required to be in.
A list of other names that have exactly the same processing requirements. Authors should not use the names defined to be synonyms, they are only intended to allow user agents to support legacy content. Anyone may remove synonyms that are not used in practice; only names that need to be processed as synonyms for compatibility with legacy content are to be registered in this way.
One of the following:
If a metadata name is found to be redundant with existing values, it should be removed and listed as a synonym for the existing value.
If a metadata name is registered in the "proposed" state for a period of a month or more without being used or specified, then it may be removed from the registry.
If a metadata name is added with the "proposed" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. If a metadata name is added with the "proposed" status and found to be harmful, then it should be changed to "discontinued" status.
Anyone can change the status at any time, but should only do so in accordance with the definitions above.
Conformance checkers may use the information given on the WHATWG Wiki MetaExtensions page to establish if a value is allowed or not: values defined in this specification or marked as "proposed" or "ratified" must be accepted, whereas values marked as "discontinued" or not listed in either this specification or on the aforementioned page must be reported as invalid. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity).
When an author uses a new metadata name not defined by either this specification or the Wiki page, conformance checkers should offer to add the value to the Wiki, with the details described above, with the "proposed" status.
Metadata names whose values are to be URLs must not be proposed or
accepted. Links must be represented using the link
element, not the meta
element.
When the http-equiv
attribute is specified
on a meta
element, the element is a pragma directive.
The http-equiv
attribute is an enumerated
attribute. The following table lists the keywords defined for this attribute. The states
given in the first cell of the rows with keywords give the states to which those keywords map.
Some of the keywords are non-conforming, as noted in the last
column.
State | Keyword | Notes |
---|---|---|
Content Language | content-language
| Non-conforming |
Encoding declaration | content-type
| |
Default style | default-style
| |
Refresh | refresh
| |
Cookie setter | set-cookie
| Non-conforming |
When a meta
element is inserted
into the document, if its http-equiv
attribute is
present and represents one of the above states, then the user agent must run the algorithm
appropriate for that state, as described in the following list:
http-equiv="content-language"
)
This feature is non-conforming. Authors are encouraged to use the lang
attribute instead.
This pragma sets the pragma-set default language. Until such a pragma is successfully processed, there is no pragma-set default language.
If the meta
element has no content
attribute, then abort these steps.
If the element's content
attribute contains a
"," (U+002C) character then abort these steps.
Let input be the value of the element's content
attribute.
Let position point at the first character of input.
Collect a sequence of characters that are not space characters.
Let candidate be the string that resulted from the previous step.
If candidate is the empty string, abort these steps.
Set the pragma-set default language to candidate.
This pragma is almost, but not quite, entirely unlike the HTTP
Content-Language
header of the same name. [HTTP]
http-equiv="content-type"
)
The encoding declaration state is just
an alternative form of setting the charset
attribute: it is a
character encoding declaration. This state's user agent
requirements are all handled by the parsing section of the specification.
For meta
elements with an http-equiv
attribute in the Encoding declaration
state, the content
attribute must have a value
that is an ASCII case-insensitive match for a string that consists of: the literal
string "text/html;
", optionally followed by any number of space characters, followed by the literal string "charset=
", followed by one of the labels of
the character encoding of the character encoding
declaration.
A document must not contain both a meta
element with an http-equiv
attribute in the encoding declaration state and a
meta
element with the charset
attribute
present.
The encoding declaration state may be
used in HTML documents and in XML Documents. If the
encoding declaration state is used in
XML Documents, the name of the character
encoding must be an ASCII case-insensitive match for the string "UTF-8
" (and the document is therefore forced to use UTF-8 as its encoding).
The encoding declaration state has no effect in XML documents, and is only allowed in order to facilitate migration to and from XHTML.
http-equiv="default-style"
)
This pragma sets the name of the default alternative style sheet set.
If the meta
element has no content
attribute, or if that attribute's value is the empty string, then abort these steps.
Set the preferred style sheet set to the value of the element's content
attribute. [CSSOM]
http-equiv="refresh"
)
This pragma acts as timed redirect.
If another meta
element with an http-equiv
attribute in the Refresh state has already been successfully
processed (i.e. when it was inserted the user agent processed it and reached the last step of
this list of steps), then abort these steps.
If the meta
element has no content
attribute, or if that attribute's value is the empty string, then abort these steps.
Let input be the value of the element's content
attribute.
Let position point at the first character of input.
Collect a sequence of characters that are ASCII digits, and parse the resulting string using the rules for parsing non-negative integers. If the sequence of characters collected is the empty string, then no number will have been parsed; abort these steps. Otherwise, let time be the parsed number.
Collect a sequence of characters that are ASCII digits and "." (U+002E) characters. Ignore any collected characters.
Let url be the address of the current page.
If the character in input pointed to by position is a ";" (U+003B) character or a "," (U+002C) character, then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is a "U" (U+0055) character or a U+0075 LATIN SMALL LETTER U character (u), then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is a "R" (U+0052) character or a U+0072 LATIN SMALL LETTER R character (r), then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is s "L" (U+004C) character or a U+006C LATIN SMALL LETTER L character (l), then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is a "=" (U+003D), then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is either a "'" (U+0027) character or """ (U+0022) character, then let quote be that character, and advance position to the next character. Otherwise, let quote be the empty string.
Let url be equal to the substring of input from the character at position to the end of the string.
If quote is not the empty string, and there is a character in url equal to quote, then truncate url at that character, so that it and all subsequent characters are removed.
Strip any trailing space characters from the end of url.
Strip any "tab" (U+0009), "LF" (U+000A), and "CR" (U+000D) characters from url.
Resolve the url value to an
absolute URL, relative to the meta
element. If this fails, abort
these steps.
Perform one or more of the following steps:
After the refresh has come due (as defined below), if the user has not canceled the
redirect and if the meta
element's Document
's active
sandboxing flag set does not have the sandboxed automatic features browsing
context flag set, navigate the
Document
's browsing context to url, with
replacement enabled, and with the Document
's browsing
context as the source browsing context.
For the purposes of the previous paragraph, a refresh is said to have come due as soon as the later of the following two conditions occurs:
meta
element was inserted into the
Document
, adjusted to take into account user or user agent
preferences.Provide the user with an interface that, when selected, navigates a browsing context to
url, with the Document
's browsing context as
the source browsing context.
Do nothing.
In addition, the user agent may, as with anything, inform the user of any and all aspects of its operation, including the state of any timers, the destinations of any timed redirects, and so forth.
For meta
elements with an http-equiv
attribute in the Refresh state, the content
attribute must have a value consisting either of:
URL
", followed by a "=" (U+003D) character, followed by a valid
URL that does not start with a literal "'" (U+0027) or """ (U+0022) character.In the former case, the integer represents a number of seconds before the page is to be reloaded; in the latter case the integer represents a number of seconds before the page is to be replaced by the page at the given URL.
A news organization's front page could include the following markup in the page's
head
element, to ensure that the page automatically reloads from the server every
five minutes:
<meta http-equiv="Refresh" content="300">
A sequence of pages could be used as an automated slide show by making each page refresh to the next page in the sequence, using markup such as the following:
<meta http-equiv="Refresh" content="20; URL=page4.html">
http-equiv="set-cookie"
)
This pragma sets an HTTP cookie. [COOKIES]
It is non-conforming. Real HTTP headers should be used instead.
If the meta
element has no content
attribute, or if that attribute's value is the empty string, then abort these steps.
Act as if receiving a
set-cookie-string for the document's address via a "non-HTTP" API,
consisting of the value of the element's content
attribute encoded as UTF-8. [COOKIES] [RFC3629]
There must not be more than one meta
element with any particular state in the
document at a time.
Extensions to the predefined set of pragma directives may, under certain conditions, be registered in the WHATWG Wiki PragmaExtensions page. [WHATWGWIKI]
Such extensions must use a name that is identical to an HTTP header registered in the Permanent Message Header Field Registry, and must have behavior identical to that described for the HTTP header. [IANAPERMHEADERS]
Pragma directives corresponding to headers describing metadata, or not requiring specific user agent processing, must not be registered; instead, use metadata names. Pragma directives corresponding to headers that affect the HTTP processing model (e.g. caching) must not be registered, as they would result in HTTP-level behavior being different for user agents that implement HTML than for user agents that do not.
Anyone is free to edit the WHATWG Wiki PragmaExtensions page at any time to add a pragma directive satisfying these conditions. Such registrations must specify the following information:
The actual name being defined. The name must match a previously-registered HTTP name with the same requirements.
A short non-normative description of the purpose of the pragma directive.
Conformance checkers must use the information given on the WHATWG Wiki PragmaExtensions page to establish if a value is allowed or not: values defined in this specification or listed on the aforementioned page must be accepted, whereas values not listed in either this specification or on the aforementioned page must be rejected as invalid. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity).
A character encoding declaration is a mechanism by which the character encoding used to store or transmit a document is specified.
The following restrictions apply to character encoding declarations:
In addition, due to a number of restrictions on meta
elements, there can only be
one meta
-based character encoding declaration per document.
If an HTML document does not start with a BOM, and its
encoding is not explicitly given by Content-Type
metadata, and the document is not an iframe
srcdoc
document, then the character encoding used must be
an ASCII-compatible character encoding, and the encoding must be specified using a
meta
element with a charset
attribute or a
meta
element with an http-equiv
attribute
in the encoding declaration state.
A character encoding declaration is required (either in the Content-Type metadata or explicitly in the file) even if the encoding is US-ASCII, because a character encoding is needed to process non-ASCII characters entered by the user in forms, in URLs generated by scripts, and so forth.
If the document is an iframe
srcdoc
document, the document must not have a character encoding declaration. (In
this case, the source is already decoded, since it is part of the document that contained the
iframe
.)
If an HTML document contains a meta
element
with a charset
attribute or a meta
element
with an http-equiv
attribute in the encoding declaration state, then the character
encoding used must be an ASCII-compatible character encoding.
Authors should use UTF-8. Conformance checkers may advise authors against using legacy encodings. [RFC3629]
Authoring tools should default to using UTF-8 for newly-created documents. [RFC3629]
Encodings in which a series of bytes in the range 0x20 to 0x7E can encode characters other than
the corresponding characters in the range U+0020 to U+007E represent a potential security
vulnerability: a user agent that does not support the encoding (or does not support the label used
to declare the encoding, or does not use the same mechanism to detect the encoding of unlabeled
content as another user agent) might end up interpreting technically benign plain text content as
HTML tags and JavaScript. Authors should therefore not use these encodings. For example, this
applies to encodings in which the bytes corresponding to "<script>
" in
ASCII can encode a different string. Authors should not use such encodings, which are known to
include JIS_C6226-1983, JIS_X0212-1990,
HZ-GB-2312, JOHAB (Windows code page 1361), encodings based on
ISO-2022, and encodings
based on EBCDIC. Furthermore, authors must not use the CESU-8, UTF-7, BOCU-1 and SCSU encodings,
which also fall into this category; these encodings were never intended for use for Web content.
[RFC1345]
[RFC1842]
[RFC1468]
[RFC2237]
[RFC1554]
[CP50220]
[RFC1922]
[RFC1557]
[CESU8]
[UTF7]
[BOCU1]
[SCSU]
Authors should not use UTF-32, as the encoding detection algorithms described in this specification intentionally do not distinguish it from UTF-16. [UNICODE]
Using non-UTF-8 encodings can have unexpected results on form submission and URL encodings, which use the document's character encoding by default.
In XHTML, the XML declaration should be used for inline character encoding information, if necessary.
In HTML, to declare that the character encoding is UTF-8, the author could include the
following markup near the top of the document (in the head
element):
<meta charset="utf-8">
In XML, the XML declaration would be used instead, at the very top of the markup:
<?xml version="1.0" encoding="utf-8"?>
style
elementscoped
attribute is present: flow content.scoped
attribute is absent: where metadata content is expected.scoped
attribute is absent: in a noscript
element that is a child of a head
element.scoped
attribute is present: where flow content is expected, but before any other flow content other than inter-element whitespace and style
elements, and not as the child of an element whose content model is transparent.type
attribute, but must match requirements described in prose below.media
— Applicable mediatype
— Type of embedded resourcescoped
— Whether the styles apply to the entire document or just the parent subtreetitle
attribute has special semantics on this element: Alternative style sheet set name.interface HTMLStyleElement : HTMLElement { attribute boolean disabled; attribute DOMString media; attribute DOMString type; attribute boolean scoped; }; HTMLStyleElement implements LinkStyle;
The style
element allows authors to embed style information in their documents.
The style
element is one of several inputs to the styling processing
model. The element does not represent content for the
user.
The type
attribute gives the styling language.
If the attribute is present, its value must be a valid MIME type that designates a
styling language. The charset
parameter must not be specified. The default
value for the type
attribute, which is used if the attribute
is absent, is "text/css
". [RFC2318]
When examining types to
determine if they support the language, user agents must not ignore unknown MIME parameters
— types with unknown parameters must be assumed to be unsupported. The charset
parameter must be treated as an unknown parameter for the purpose of
comparing MIME types here.
The media
attribute says which media the
styles apply to. The value must be a valid media query. The user
agent must apply the styles when the media
attribute's value
matches the environment and the other relevant conditions apply, and must not apply
them otherwise.
The styles might be further limited in scope, e.g. in CSS with the use of @media
blocks. This specification does not override such further restrictions or
requirements.
The default, if the media
attribute is omitted, is "all
", meaning that by default styles apply to all
media.
The scoped
attribute is a boolean
attribute. If present, it indicates that the styles are intended just for the subtree
rooted at the style
element's parent element, as opposed to the whole
Document
.
If the scoped
attribute is present and the element has a
parent element, then the style
element must precede any flow content in
its parent element other than inter-element whitespace and other style
elements, and the parent element's content model must not have a transparent
component.
This implies that scoped style
elements cannot be children of, e.g.,
a
or ins
elements, even when those are used as flow content
containers.
A style
element without a scoped
attribute is restricted to appearing in the
head
of the document.
A style sheet declared by a style
element that has a scoped
attribute and has a parent node that is an element is
scoped, with the scoping element being the style
element's parent
element. [CSSSCOPED]
The following will eventually be moved to a CSS specification; it is specified here only on an interim basis until an editor can be found to own this.
Within scoped CSS resources, authors may use an @global
@-rule. The
syntax of this rule is defined as follows.
The following production is added to the grammar:
global : GLOBAL_SYM S* ruleset ;
The following rules are added to the Flex tokenizer:
B b|\\0{0,4}(42|62)(\r\n|[ \t\r\n\f])? @{G}{L}{O}{B}{A}{L} {return GLOBAL_SYM;}
Simple selectors in rule sets prefixed by the @global
@-rule in scoped
CSS resources must be processed in the same way as normal rule sets in non-scoped CSS
resources.
Simple selectors in scoped CSS resources that are not prefixed by an @global
@-rule must only match the style
element's parent element (if
any), and that element's descendants.
The title
attribute on
style
elements defines alternative style sheet sets. If the
style
element has no title
attribute, then it
has no title; the title
attribute of ancestors does not apply to
the style
element. [CSSOM]
The title
attribute on style
elements, like the title
attribute on link
elements, differs from the global title
attribute in that a
style
block without a title does not inherit the title of the parent element: it
merely has no title.
The textContent
of a style
element must match the style
production in the following ABNF, the character set for which is Unicode. [ABNF]
style = no-c-start *( c-start no-c-end c-end no-c-start ) no-c-start = < any string that doesn't contain a substring that matches c-start > c-start = "<!--" no-c-end = < any string that doesn't contain a substring that matches c-end > c-end = "-->"
All descendant elements must be processed, according to their semantics, before the
style
element itself is evaluated. For styling languages that consist of pure text
(as opposed to XML), user agents must evaluate style
elements by passing the
concatenation of the contents of all the Text
nodes that are children of the
style
element (not any other nodes such as comments or elements), in tree
order, to the style system. For XML-based styling languages, user agents must pass all the
child nodes of the style
element to the style system.
All URLs found by the styling language's processor must be resolved, relative to the element (or as defined by the styling language), when the processor is invoked.
Once the attempts to obtain the style sheet's critical subresources, if any, are
complete, or, if the style sheet has no critical subresources, once the style sheet
has been parsed and processed, the user agent must, if the loads were successful or there were
none, queue a task to fire a simple event named load
at the style
element, or, if one of the style sheet's
critical subresources failed to completely load for any reason (e.g. DNS error, HTTP
404 response, a connection being prematurely closed, unsupported Content-Type), queue a
task to fire a simple event named error
at
the style
element. Non-network errors in processing the style sheet or its
subresources (e.g. CSS parse errors, PNG decoding errors) are not failures for the purposes of
this paragraph.
The task source for these tasks is the DOM manipulation task source.
The element must delay the load event of the element's document until all the attempts to obtain the style sheet's critical subresources, if any, are complete.
This specification does not specify a style system, but CSS is expected to be supported by most Web browsers. [CSS]
The media
, type
and scoped
IDL attributes must reflect the
respective content attributes of the same name.
The disabled
IDL attribute behaves as
defined for the alternative style sheets DOM.
The LinkStyle
interface is also implemented by this element; the styling
processing model defines how. [CSSOM]
The following document has its stress emphasis styled as bright red text rather than italics text, while leaving titles of works and Latin words in their default italics. It shows how using appropriate elements enables easier restyling of documents.
<!DOCTYPE html> <html lang="en-US"> <head> <title>My favorite book</title> <style> body { color: black; background: white; } em { font-style: normal; color: red; } </style> </head> <body> <p>My <em>favorite</em> book of all time has <em>got</em> to be <cite>A Cat's Life</cite>. It is a book by P. Rahmel that talks about the <i lang="la">Felis Catus</i> in modern human society.</p> </body> </html>
The link
and style
elements can provide styling information for the
user agent to use when rendering the document. The CSS and CSSOM specifications specify what
styling information is to be used by the user agent and how it is to be used. [CSS] [CSSOM]
The style
and link
elements implement the LinkStyle
interface. [CSSOM]
For style
elements, if the user agent does not support the specified styling
language, then the sheet
attribute of the element's
LinkStyle
interface must return null. Similarly, link
elements that do
not represent external resource links that contribute to the styling
processing model (i.e. that do not have a stylesheet
keyword in their rel
attribute), for which the link is an
alternative stylesheet but whose title
content attribute is
absent or empty, or whose resource is CORS-cross-origin, must have their
LinkStyle
interface's sheet
attribute return
null.
Otherwise, the LinkStyle
interface's sheet
attribute must return null if the corresponding element
is not in a Document
,
and otherwise must return a StyleSheet
object with the following properties: [CSSOM]
The style sheet type must be the same as the style's specified type. For
style
elements, this is the same as the type
content attribute's value, or text/css
if that is omitted. For
link
elements, this is the Content-Type metadata of the
specified resource.
For link
elements, the location must be the result of resolving the URL given by the element's href
content attribute, relative to the element, or the empty
string if that fails. For style
elements, there is no location.
The media must be the same as the value of the element's media
content attribute, or the empty string, if the attribute is omitted.
The title must be the same as the value of the element's title
content attribute, if the attribute is present and has a non-empty
value. If the attribute is absent or its value is the empty string, then the style sheet does not
have a title (it is the empty string). The title is used for defining alternative style
sheet sets.
For link
elements, true if the link is an alternative
stylesheet. In all other cases, false.
The same object must be returned each time.
The disabled
IDL attribute on
link
and style
elements must return false and do nothing on setting, if
the sheet
attribute of their LinkStyle
interface is null. Otherwise, it must return the value of the StyleSheet
interface's
disabled
attribute on getting, and forward the new
value to that same attribute on setting.
The rules for handling alternative style sheets are defined in the CSS object model specification. [CSSOM]
Style sheets, whether added by a link
element, a style
element, an
<?xml-stylesheet>
PI, an HTTP Link:
header, or some
other mechanism, have a style sheet ready flag, which is initially unset.
When a style sheet is ready to be applied, its style sheet ready flag must be set.
If the style sheet referenced no other resources (e.g. it was an internal style sheet given by a
style
element with no @import
rules), then the style rules must
be synchronously made available to script; otherwise, the style rules must only be made available
to script once the event loop reaches its "update the rendering" step.
A style sheet in the context of the Document
of an HTML parser or
XML parser is said to be a style sheet that is blocking scripts if the
element was created by that Document
's parser, and the element is either a
style
element or a link
element that was an external resource link that contributes to the styling processing
model when the element was created by the parser, and the element's style sheet was enabled
when the element was created by the parser, and the element's style sheet ready flag
is not yet set, and, the last time the event loop reached step 1, the element was
in that Document
, and the user agent hasn't given
up on that particular style sheet yet. A user agent may give up on a style sheet at any time.
Giving up on a style sheet before the style sheet loads, if the style sheet eventually does still load, means that the script might end up operating with incorrect information. For example, if a style sheet sets the color of an element to green, but a script that inspects the resulting style is executed before the sheet is loaded, the script will find that the element is black (or whatever the default color is), and might thus make poor choices (e.g. deciding to use black as the color elsewhere on the page, instead of green). Implementors have to balance the likelihood of a script using incorrect information with the performance impact of doing nothing while waiting for a slow network request to finish.
A Document
has a style sheet that is blocking scripts if there is
either a style sheet that is blocking scripts in the context of that
Document
, or if that Document
is in a browsing context that
has a parent browsing context, and the active document of that
parent browsing context itself has a style sheet that is blocking
scripts.
A Document
has no style sheet that is blocking scripts if it does not
have a style sheet that is blocking
scripts as defined in the previous paragraph.
body
elementhtml
element.onafterprint
onbeforeprint
onbeforeunload
onhashchange
onmessage
onoffline
ononline
onpagehide
onpageshow
onpopstate
onstorage
onunload
body
element's start tag may be omitted if
the element is empty, or if the first thing inside the body
element is not a
space character or a comment, except if the
first thing inside the body
element is a meta
, link
, script
, style
, or template
element. body
element's end tag may be omitted if the
body
element is not immediately followed by a comment.document
role (default - do not set), application
.aria-*
attributes applicable to the allowed roles.interface HTMLBodyElement : HTMLElement { }; HTMLBodyElement implements WindowEventHandlers;
The body
element represents the
content of the document.
In conforming documents, there is only one body
element. The document.body
IDL attribute provides scripts with easy access to a document's
body
element.
Some DOM operations (for example, parts of the
drag and drop model) are defined in terms of "the
body element". This refers to a particular element in the
DOM, as per the definition of the term, and not any arbitrary
body
element.
The body
element exposes as event handler
content attributes a number of the event
handlers of the Window
object. It also mirrors
their event handler IDL attributes.
The onblur
, onerror
,
onfocus
, onload
, onresize
, and
onscroll
event handlers of the
Window
object, exposed on the body
element, replace the generic
event handlers with the same names normally supported by HTML elements.
Thus, for example, a bubbling error
event dispatched on a child of
the body element of a Document
would first
trigger the onerror
event
handler content attributes of that element, then that of the
root html
element, and only then would it
trigger the onerror
event handler content
attribute on the body
element. This is because
the event would bubble from the target, to the body
, to
the html
, to the Document
, to the
Window
, and the event
handler on the body
is watching the
Window
not the body
. A regular event
listener attached to the body
using addEventListener()
, however, would be run when the
event bubbled through the body
and not when it reaches
the Window
object.
This page updates an indicator to show whether or not the user is online:
<!DOCTYPE HTML> <html> <head> <title>Online or offline?</title> <script> function update(online) { document.getElementById('status').textContent = online ? 'Online' : 'Offline'; } </script> </head> <body ononline="update(true)" onoffline="update(false)" onload="update(navigator.onLine)"> <p>You are: <span id="status">(Unknown)</span></p> </body> </html>
article
elementmain
element descendants.article
(default - do not set), application
, document
or main
.aria-*
attributes applicable to the allowed roles.HTMLElement
.The article
element represents a complete, or self-contained,
composition in a document, page, application, or site and that is, in principle, independently
distributable or reusable, e.g. in syndication. This could be a forum post, a magazine or
newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any
other independent item of content.
When article
elements are nested, the inner article
elements
represent articles that are in principle related to the contents of the outer article. For
instance, a blog entry on a site that accepts user-submitted comments could represent the comments
as article
elements nested within the article
element for the blog
entry.
Author information associated with an article
element (q.v. the
address
element) does not apply to nested article
elements.
When used specifically with content to be redistributed in syndication, the
article
element is similar in purpose to the entry
element in
Atom. [ATOM]
The schema.org microdata vocabulary can be used to provide the publication date
for an article
element, using one of the CreativeWork subtypes.
When the main content of the page (i.e. excluding footers, headers, navigation blocks, and
sidebars) is all one single self-contained composition, the content should be marked up with a
main
element and the content may also be marked with an article
, but
it is technically redundant in this case (since it's self-evident that the page is a single
composition, as it is a single document).
This example shows a blog post using the article
element, with some schema.org
annotations:
<article itemscope itemtype="http://schema.org/BlogPosting"> <header> <h1 itemprop="headline">The Very First Rule of Life</h1> <p><time itemprop="datePublished" datetime="2009-10-09">3 days ago</time></p> <link itemprop="url" href="?comments=0"> </header> <p>If there's a microphone anywhere near you, assume it's hot and sending whatever you're saying to the world. Seriously.</p> <p>...</p> <footer> <a itemprop="discussionUrl" href="?comments=1">Show comments...</a> </footer> </article>
Here is that same blog post, but showing some of the comments:
<article itemscope itemtype="http://schema.org/BlogPosting"> <header> <h1 itemprop="headline">The Very First Rule of Life</h1> <p><time itemprop="datePublished" datetime="2009-10-09">3 days ago</time></p> <link itemprop="url" href="?comments=0"> </header> <p>If there's a microphone anywhere near you, assume it's hot and sending whatever you're saying to the world. Seriously.</p> <p>...</p> <section> <h1>Comments</h1> <article itemprop="comment" itemscope itemtype="http://schema.org/UserComments" id="c1"> <link itemprop="url" href="#c1"> <footer> <p>Posted by: <span itemprop="creator" itemscope itemtype="http://schema.org/Person"> <span itemprop="name">George Washington</span> </span></p> <p><time itemprop="commentTime" datetime="2009-10-10">15 minutes ago</time></p> </footer> <p>Yeah! Especially when talking about your lobbyist friends!</p> </article> <article itemprop="comment" itemscope itemtype="http://schema.org/UserComments" id="c2"> <link itemprop="url" href="#c2"> <footer> <p>Posted by: <span itemprop="creator" itemscope itemtype="http://schema.org/Person"> <span itemprop="name">George Hammond</span> </span></p> <p><time itemprop="commentTime" datetime="2009-10-10">5 minutes ago</time></p> </footer> <p>Hey, you have the same first name as me.</p> </article> </section> </article>
Notice the use of footer
to give the information for each comment (such as who
wrote it and when): the footer
element can appear at the start of its
section when appropriate, such as in this case. (Using header
in this case wouldn't
be wrong either; it's mostly a matter of authoring preference.)
section
elementregion
role (default - do not set), alert
, alertdialog
, application
, contentinfo
, dialog
, document
, log
, main
, marquee
, presentation
, search
or status
.aria-*
attributes applicable to the allowed roles.HTMLElement
.The section
element represents a generic section of a document or
application. A section, in this context, is a thematic grouping of content. The theme of each section
should be identified, typically by including a heading (h1
-h6
element) as
a child of the section
element.
Examples of sections would be chapters, the various tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A Web site's home page could be split into sections for an introduction, news items, and contact information.
Authors are encouraged to use the article
element instead of the
section
element when it would make sense to syndicate the contents of the
element.
The section
element is not a generic
container element. When an element is needed only for styling purposes or as a convenience for
scripting, authors are encouraged to use the div
element instead. A general rule is
that the section
element is appropriate only if the element's contents would be
listed explicitly in the document's outline.
In the following example, we see an article (part of a larger Web page) about apples, containing two short sections.
<article> <header> <h2>Apples</h2> <p>Tasty, delicious fruit!</p> </header> <p>The apple is the pomaceous fruit of the apple tree.</p> <section> <h3>Red Delicious</h3> <p>These bright red apples are the most common found in many supermarkets.</p> </section> <section> <h3>Granny Smith</h3> <p>These juicy, green apples make a great filling for apple pies.</p> </section> </article>
Here is a graduation programme with two sections, one for the list of people graduating, and one for the description of the ceremony. (The markup in this example features an uncommon style sometimes used to minimize the amount of inter-element whitespace.)
<!DOCTYPE Html> <Html ><Head ><Title >Graduation Ceremony Summer 2022</Title ></Head ><Body ><H1 >Graduation</H1 ><Section ><H2 >Ceremony</H2 ><P >Opening Procession</P ><P >Speech by Validactorian</P ><P >Speech by Class President</P ><P >Presentation of Diplomas</P ><P >Closing Speech by Headmaster</P ></Section ><Section ><H2 >Graduates</H2 ><Ul ><Li >Molly Carpenter</Li ><Li >Anastasia Luccio</Li ><Li >Ebenezar McCoy</Li ><Li >Karrin Murphy</Li ><Li >Thomas Raith</Li ><Li >Susan Rodriguez</Li ></Ul ></Section ></Body ></Html>
In this example, a book author has marked up some sections as chapters and some as appendices,
and uses CSS to style the headers in these two classes of section differently. The whole book is
wrapped in an article
element as part of an even larger document containing other
books.
<article class="book"> <style> section { border: double medium; margin: 2em; } section.chapter h1 { font: 2em Roboto, Helvetica Neue, sans-serif; } section.appendix h1 { font: small-caps 2em Roboto, Helvetica Neue, sans-serif; } </style> <header> <h2>My Book</h2> <p>A sample with not much content</p> <p><small>Published by Dummy Publicorp Ltd.</small></p> </header> <section class="chapter"> <h3>My First Chapter</h3> <p>This is the first of my chapters. It doesn't say much.</p> <p>But it has two paragraphs!</p> </section> <section class="chapter"> <h3>It Continutes: The Second Chapter</h3> <p>Bla dee bla, dee bla dee bla. Boom.</p> </section> <section class="chapter"> <h3>Chapter Three: A Further Example</h3> <p>It's not like a battle between brightness and earthtones would go unnoticed.</p> <p>But it might ruin my story.</p> </section> <section class="appendix"> <h3>Appendix A: Overview of Examples</h3> <p>These are demonstrations.</p> </section> <section class="appendix"> <h3>Appendix B: Some Closing Remarks</h3> <p>Hopefully this long example shows that you <em>can</em> style sections, so long as they are used to indicate actual sections.</p> </section> </article>
nav
elementmain
element descendants.navigation
role (default - do not set) or presentation
.aria-*
attributes applicable to the allowed roles.HTMLElement
.The nav
element represents a section of a page that links to other
pages or to parts within the page: a section with navigation links.
In cases where the content of a nav
element represents a list of items,
use list markup to aid understanding and navigation.
Not all groups of links on a page need to be in a nav
element —
the element is primarily intended for sections that consist of major navigation blocks. In
particular, it is common for footers to have a short list of links to various pages of a site,
such as the terms of service, the home page, and a copyright page. The footer
element
alone is sufficient for such cases; while a nav
element can be used in such cases, it
is usually unnecessary.
User agents (such as screen readers) that are targeted at users who can benefit from navigation information being omitted in the initial rendering, or who can benefit from navigation information being immediately available, can use this element as a way to determine what content on the page to initially skip or provide on request (or both).
In the following example, the page has several places where links are present, but only one of those places is considered a navigation section.
<body itemscope itemtype="http://schema.org/Blog"> <header> <h1>Wake up sheeple!</h1> <p><a href="news.html">News</a> - <a href="blog.html">Blog</a> - <a href="forums.html">Forums</a></p> <p>Last Modified: <span itemprop="dateModified">2009-04-01</span></p> <nav> <h1>Navigation</h1> <ul> <li><a href="articles.html">Index of all articles</a></li> <li><a href="today.html">Things sheeple need to wake up for today</a></li> <li><a href="successes.html">Sheeple we have managed to wake</a></li> </ul> </nav> </header> <main> <article itemprop="blogPosts" itemscope itemtype="http://schema.org/BlogPosting"> <header> <h1 itemprop="headline">My Day at the Beach</h1> </header> <div itemprop="articleBody"> <p>Today I went to the beach and had a lot of fun.</p> ...more content... </div> <footer> <p>Posted <time itemprop="datePublished" datetime="2009-10-10">Thursday</time>.</p> </footer> </article> ...more blog posts... </main> <footer> <p>Copyright © <span itemprop="copyrightYear">2010</span> <span itemprop="copyrightHolder">The Example Company</span> </p> <p><a href="about.html">About</a> - <a href="policy.html">Privacy Policy</a> - <a href="contact.html">Contact Us</a></p> </footer> </body>
Notice the main
element being used to wrap the
main content of the page. In this case, all content other than
the page header and footer.
You can also see microdata annotations in the above example that use the schema.org vocabulary to provide the publication date and other metadata about the blog post.
In the following example, there are two nav
elements, one for primary navigation
around the site, and one for secondary navigation around the page itself.
<body> <h1>The Wiki Center Of Exampland</h1> <nav> <ul> <li><a href="/">Home</a></li> <li><a href="/events">Current Events</a></li> ...more... </ul> </nav> <main> <header> <h1>Demos in Exampland</h1> <p>Written by A. N. Other.</p> </header> <nav> <ul> <li><a href="#public">Public demonstrations</a></li> <li><a href="#destroy">Demolitions</a></li> ...more... </ul> </nav> <div> <section id="public"> <h1>Public demonstrations</h1> <p>...more...</p> </section> <section id="destroy"> <h1>Demolitions</h1> <p>...more...</p> </section> ...more... </div> <footer> <p><a href="?edit">Edit</a> | <a href="?delete">Delete</a> | <a href="?Rename">Rename</a></p> </footer> </main> <footer> <p><small>© copyright 1998 Exampland Emperor</small></p> </footer> </body>
A nav
element doesn't have to contain a list, it can contain other kinds of
content as well. In this navigation block, links are provided in prose:
<nav> <h1>Navigation</h1> <p>You are on my home page. To the north lies <a href="/blog">my blog</a>, from whence the sounds of battle can be heard. To the east you can see a large mountain, upon which many <a href="/school">school papers</a> are littered. Far up thus mountain you can spy a little figure who appears to be me, desperately scribbling a <a href="/school/thesis">thesis</a>.</p> <p>To the west are several exits. One fun-looking exit is labeled <a href="http://games.example.com/">"games"</a>. Another more boring-looking exit is labeled <a href="http://isp.example.net/">ISP™</a>.</p> <p>To the south lies a dark and dank <a href="/about">contacts page</a>. Cobwebs cover its disused entrance, and at one point you see a rat run quickly out of the page.</p> </nav>
aside
elementmain
element descendants.complementary
role (default - do not set), note
, search
or presentation
.aria-*
attributes applicable to the allowed roles.HTMLElement
.The aside
element represents a section of a page that consists of
content that is tangentially related to the content around the aside
element, and
which could be considered separate from that content. Such sections are often represented as
sidebars in printed typography.
The element can be used for typographical effects like pull quotes or sidebars, for
advertising, for groups of nav
elements, and for other content that is considered
separate from the main content of the page.
It's not appropriate to use the aside
element just for
parentheticals, since those are part of the main flow of the document.
The following example shows how an aside is used to mark up background material on Switzerland in a much longer news story on Europe.
<aside> <h1>Switzerland</h1> <p>Switzerland, a land-locked country in the middle of geographic Europe, has not joined the geopolitical European Union, though it is a signatory to a number of European treaties.</p> </aside>
The following example shows how an aside is used to mark up a pull quote in a longer article.
... <p>He later joined a large company, continuing on the same work. <q>I love my job. People ask me what I do for fun when I'm not at work. But I'm paid to do my hobby, so I never know what to answer. Some people wonder what they would do if they didn't have to work... but I know what I would do, because I was unemployed for a year, and I filled that time doing exactly what I do now.</q></p> <aside> <q> People ask me what I do for fun when I'm not at work. But I'm paid to do my hobby, so I never know what to answer. </q> </aside> <p>Of course his work — or should that be hobby? — isn't his only passion. He also enjoys other pleasures.</p> ...
The following extract shows how aside
can be used for blogrolls and other side
content on a blog:
<body> <header> <h1>My wonderful blog</h1> <p>My tagline</p> </header> <aside> <!-- this aside contains two sections that are tangentially related to the page, namely, links to other blogs, and links to blog posts from this blog --> <nav> <h1>My blogroll</h1> <ul> <li><a href="http://blog.example.com/">Example Blog</a> </ul> </nav> <nav> <h1>Archives</h1> <ol reversed> <li><a href="/last-post">My last post</a> <li><a href="/first-post">My first post</a> </ol> </nav> </aside> <aside> <!-- this aside is tangentially related to the page also, it contains twitter messages from the blog author --> <h1>Twitter Feed</h1> <blockquote cite="http://twitter.example.net/t31351234"> I'm on vacation, writing my blog. </blockquote> <blockquote cite="http://twitter.example.net/t31219752"> I'm going to go on vacation soon. </blockquote> </aside> <article> <!-- this is a blog post --> <h1>My last post</h1> <p>This is my last post.</p> <footer> <p><a href="/last-post" rel=bookmark>Permalink</a> </footer> </article> <article> <!-- this is also a blog post --> <h1>My first post</h1> <p>This is my first post.</p> <aside> <!-- this aside is about the blog post, since it's inside the <article> element; it would be wrong, for instance, to put the blogroll here, since the blogroll isn't really related to this post specifically, only to the page as a whole --> <h1>Posting</h1> <p>While I'm thinking about it, I wanted to say something about posting. Posting is fun!</p> </aside> <footer> <p><a href="/first-post" rel=bookmark>Permalink</a> </footer> </article> <footer> <nav> <a href="/archives">Archives</a> — <a href="/about">About me</a> — <a href="/copyright">Copyright</a> </nav> </footer> </body>
h1
, h2
, h3
, h4
, h5
, and
h6
elementsheading
role (default - do not set), tab
or presentation
.aria-*
attributes applicable to the allowed roles.interface HTMLHeadingElement : HTMLElement {};
These elements represent headings for their sections.
The semantics and meaning of these elements are defined in the section on headings and sections.
These elements have a rank given by the number in their name. The h1
element is said to have the highest rank, the h6
element has the lowest rank, and two
elements with the same name have equal rank.
h1
–h6
elements must not be used to markup subheadings, subtitles, alternative titles and taglines unless intended to be the heading for a new section or subsection. Instead use the markup patterns in the Common idioms without dedicated elements section of the specification.
As far as their respective document outlines (their heading and section structures) are concerned, these two snippets are semantically equivalent:
<body> <h1>Let's call it a draw(ing surface)</h1> <h2>Diving in</h2> <h2>Simple shapes</h2> <h2>Canvas coordinates</h2> <h3>Canvas coordinates diagram</h3> <h2>Paths</h2> </body>
<body> <h1>Let's call it a draw(ing surface)</h1> <section> <h1>Diving in</h1> </section> <section> <h1>Simple shapes</h1> </section> <section> <h1>Canvas coordinates</h1> <section> <h1>Canvas coordinates diagram</h1> </section> </section> <section> <h1>Paths</h1> </section> </body>
Authors might prefer the former style for its terseness, or the latter style for its convenience in the face of heavy editing; which is best is purely an issue of preferred authoring style.
header
elementheader
, footer
, or main
element descendants.banner
role (default - do not set) or presentation
.aria-*
attributes applicable to the allowed roles.HTMLElement
.The header
element represents introductory content
for its nearest ancestor sectioning content or
sectioning root element. A header
typically contains a group of introductory or navigational
aids.
When the nearest ancestor sectioning content or sectioning root element is the body element, then it applies to the whole page.
A header
element is intended to usually contain the section's heading
(an h1
–h6
element), but this is
not required. The header
element can also be used to wrap a section's table of
contents, a search form, or any relevant logos.
Here are some sample headers. This first one is for a game:
<header> <p>Welcome to...</p> <h1>Voidwars!</h1> </header>
The following snippet shows how the element can be used to mark up a specification's header:
<header> <h1>Scalable Vector Graphics (SVG) 1.2</h1> <p>W3C Working Draft 27 October 2004</p> <dl> <dt>This version:</dt> <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20041027/">http://www.w3.org/TR/2004/WD-SVG12-20041027/</a></dd> <dt>Previous version:</dt> <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20040510/">http://www.w3.org/TR/2004/WD-SVG12-20040510/</a></dd> <dt>Latest version of SVG 1.2:</dt> <dd><a href="http://www.w3.org/TR/SVG12/">http://www.w3.org/TR/SVG12/</a></dd> <dt>Latest SVG Recommendation:</dt> <dd><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></dd> <dt>Editor:</dt> <dd>Dean Jackson, W3C, <a href="mailto:dean@w3.org">dean@w3.org</a></dd> <dt>Authors:</dt> <dd>See <a href="#authors">Author List</a></dd> </dl> <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notic ... </header>
The header
element is not sectioning content; it doesn't
introduce a new section.
In this example, the page has a page heading given by the h1
element, and two
subsections whose headings are given by h2
elements. The content after the
header
element is still part of the last subsection started in the
header
element, because the header
element doesn't take part in the
outline algorithm.
<body> <header> <h1>Little Green Guys With Guns</h1> <nav> <ul> <li><a href="/games">Games</a> <li><a href="/forum">Forum</a> <li><a href="/download">Download</a> </ul> </nav> <h2>Important News</h2> <!-- this starts a second subsection --> <!-- this is part of the subsection entitled "Important News" --> <p>To play today's games you will need to update your client.</p> <h2>Games</h2> <!-- this starts a third subsection --> </header> <p>You have three active games:</p> <!-- this is still part of the subsection entitled "Games" --> ...
footer
elementheader
, footer
, or main
element descendants.contentinfo
role (default - do not set) or presentation
.aria-*
attributes applicable to the allowed roles.HTMLElement
.The footer
element represents a footer
for its nearest ancestor sectioning content or
sectioning root element. A footer typically contains
information about its section such as who wrote it, links to related
documents, copyright data, and the like.
When the footer
element contains entire sections,
they represent appendices, indexes,
long colophons, verbose license agreements, and other such
content.
Contact information for the author or editor of a
section belongs in an address
element, possibly itself
inside a footer
. Bylines and other information that
could be suitable for both a header
or a
footer
can be placed in either (or neither). The
primary purpose of these elements is merely to help the author write
self-explanatory markup that is easy to maintain and style; they are
not intended to impose specific structures on authors.
Footers don't necessarily have to appear at the end of a section, though they usually do.
When the nearest ancestor sectioning content or sectioning root element is the body element, then it applies to the whole page.
The footer
element is not
sectioning content; it doesn't introduce a new
section.
Here is a page with two footers, one at the top and one at the bottom, with the same content:
<body> <footer><a href="../">Back to index...</a></footer> <div> <h1>Lorem ipsum</h1> <p>The ipsum of all lorems</p> </div> <p>A dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p> <footer><a href="../">Back to index...</a></footer> </body>
Here is an example which shows the footer
element
being used both for a site-wide footer and for a section
footer.
<!DOCTYPE HTML> <HTML><HEAD> <TITLE>The Ramblings of a Scientist</TITLE> <BODY> <H1>The Ramblings of a Scientist</H1> <MAIN> <ARTICLE> <H1>Episode 15</H1> <VIDEO SRC="/fm/015.ogv" CONTROLS PRELOAD> <P><A HREF="/fm/015.ogv">Download video</A>.</P> </VIDEO> <FOOTER> <!-- footer for article --> <P>Published <TIME DATETIME="2009-10-21T18:26-07:00">on 2009/10/21 at 6:26pm</TIME></P> </FOOTER> </ARTICLE> <ARTICLE> <H1>My Favorite Trains</H1> <P>I love my trains. My favorite train of all time is a Köf.</P> <P>It is fun to see them pull some coal cars because they look so dwarfed in comparison.</P> <FOOTER> <!-- footer for article --> <P>Published <TIME DATETIME="2009-09-15T14:54-07:00">on 2009/09/15 at 2:54pm</TIME></P> </FOOTER> </ARTICLE> </MAIN> <FOOTER> <!-- site wide footer --> <NAV> <P><A HREF="/credits.html">Credits</A> — <A HREF="/tos.html">Terms of Service</A> — <A HREF="/index.html">Blog Index</A></P> </NAV> <P>Copyright © 2009 Gordon Freeman</P> </FOOTER> </BODY> </HTML>
Some site designs have what is sometimes referred to as "fat footers" — footers that contain a lot of material, including images, links to other articles, links to pages for sending feedback, special offers... in some ways, a whole "front page" in the footer.
This fragment shows the bottom of a page on a site with a "fat footer":
... <footer> <nav> <section> <h1>Articles</h1> <p><img src="images/somersaults.jpeg" alt=""> Go to the gym with our somersaults class! Our teacher Jim takes you through the paces in this two-part article. <a href="articles/somersaults/1">Part 1</a> · <a href="articles/somersaults/2">Part 2</a></p> <p><img src="images/kindplus.jpeg"> Tired of walking on the edge of a clif<!-- sic -->? Our guest writer Lara shows you how to bumble your way through the bars. <a href="articles/kindplus/1">Read more...</a></p> <p><img src="images/crisps.jpeg"> The chips are down, now all that's left is a potato. What can you do with it? <a href="articles/crisps/1">Read more...</a></p> </section> <ul> <li> <a href="/about">About us...</a> <li> <a href="/feedback">Send feedback!</a> <li> <a href="/sitemap">Sitemap</a> </ul> </nav> <p><small>Copyright © 2015 The Snacker — <a href="/tos">Terms of Service</a></small></p> </footer> </body>
address
elementheader
, footer
, or
address
element descendants.contentinfo
role.aria-*
attributes applicable to the allowed roles.HTMLElement
.The address
element represents the
contact information for its nearest article
or
body
element ancestor. If that is the body
element, then the contact information applies to the document
as a whole.
For example, a page at the W3C Web site related to HTML might include the following contact information:
<ADDRESS> <A href="../People/Raggett/">Dave Raggett</A>, <A href="../People/Arnaud/">Arnaud Le Hors</A>, contact persons for the <A href="Activity">W3C HTML Activity</A> </ADDRESS>
The address
element must not be used to represent
arbitrary addresses (e.g. postal addresses), unless those addresses
are in fact the relevant contact information. (The p
element is the appropriate element for marking up postal addresses
in general.)
The address
element must not contain information
other than contact information.
For example, the following is non-conforming use of the
address
element:
<ADDRESS>Last Modified: 1999/12/24 23:37:50</ADDRESS>
Typically, the address
element would be included
along with other information in a footer
element.
The contact information for a node node is a
collection of address
elements defined by the first
applicable entry from the following list:
article
elementbody
elementThe contact information consists of all the
address
elements that have node
as an ancestor and do not have another body
or
article
element ancestor that is a descendant of node.
article
elementbody
elementThe contact information of node is the same
as the contact information of the nearest article
or
body
element ancestor, whichever is nearest.
Document
has a body elementThe contact information of node is the same
as the contact information of the body element of the
Document
.
There is no contact information for node.
User agents may expose the contact information of a node to the user, or use it for other purposes, such as indexing sections based on the sections' contact information.
In this example the footer contains contact information and a copyright notice.
<footer> <address> For more details, contact <a href="mailto:js@example.com">John Smith</a>. </address> <p><small>© copyright 2038 Example Corp.</small></p> </footer>
The h1
–h6
elements are headings.
The first element of heading content in an element of sectioning content represents the heading for that section. Subsequent headings of equal or higher rank start new (implied) sections, headings of lower rank start implied subsections that are part of the previous one. In both cases, the element represents the heading of the implied section.
h1
–h6
elements must not be used to markup subheadings, subtitles, alternative titles and taglines unless intended to be the heading for a new section or subsection. Instead use the markup patterns in the Common idioms without dedicated elements section of the specification.
Certain elements are said to be sectioning roots, including blockquote
and
td
elements. These elements can have their own
outlines, but the sections and headings inside these elements do not
contribute to the outlines of their ancestors.
Sectioning content elements are always considered subsections of their nearest ancestor sectioning root or their nearest ancestor element of sectioning content, whichever is nearest, regardless of what implied sections other headings may have created.
For the following fragment:
<body> <h1>Foo</h1> <h2>Bar</h2> <blockquote> <h3>Bla</h3> </blockquote> <p>Baz</p> <h2>Quux</h2> <section> <h3>Thud</h3> </section> <p>Grunt</p> </body>
...the structure would be:
body
section, containing the "Grunt" paragraph)
section
section)
Notice how the section
ends the earlier implicit
section so that a later paragraph ("Grunt") is back at the top
level.
Sections may contain headings of any rank, and authors are strongly encouraged to use headings of the appropriate rank for the section's nesting level.
Authors are also encouraged to explicitly wrap sections in elements of sectioning content, instead of relying on the implicit sections generated by having multiple headings in one element of sectioning content.
For example, the following is correct:
<body> <h4>Apples</h4> <p>Apples are fruit.</p> <section> <h2>Taste</h2> <p>They taste lovely.</p> <h6>Sweet</h6> <p>Red apples are sweeter than green ones.</p> <h1>Color</h1> <p>Apples come in various colors.</p> </section> </body>
However, the same document would be more clearly expressed as:
<body> <h1>Apples</h1> <p>Apples are fruit.</p> <section> <h2>Taste</h2> <p>They taste lovely.</p> <section> <h3>Sweet</h3> <p>Red apples are sweeter than green ones.</p> </section> </section> <section> <h2>Color</h2> <p>Apples come in various colors.</p> </section> </body>
Both of the documents above are semantically identical and would produce the same outline in compliant user agents.
This third example is also semantically identical, and might be easier to maintain (e.g. if sections are often moved around in editing):
<body> <h1>Apples</h1> <p>Apples are fruit.</p> <section> <h1>Taste</h1> <p>They taste lovely.</p> <section> <h1>Sweet</h1> <p>Red apples are sweeter than green ones.</p> </section> </section> <section> <h1>Color</h1> <p>Apples come in various colors.</p> </section> </body>
This final example would need explicit style rules to be rendered well in legacy browsers. Legacy browsers without CSS support would render all the headings as top-level headings.
This section defines an algorithm for creating an outline for a sectioning content element or a sectioning root element. It is defined in terms of a walk over the nodes of a DOM tree, in tree order, with each node being visited when it is entered and when it is exited during the walk.
The outline for a sectioning content element or a sectioning
root element consists of a list of one or more potentially nested sections. A section is a
container that corresponds to some nodes in the original DOM tree. Each section can have one
heading associated with it, and can contain any number of further nested sections. The algorithm for the outline also associates each node in the DOM tree with a
particular section and potentially a heading. (The sections in the outline aren't
section
elements, though some may correspond to such elements — they are merely
conceptual sections.)
The following markup fragment:
<body> <h1>A</h1> <p>B</p> <h2>C</h2> <p>D</p> <h2>E</h2> <p>F</p> </body>
...results in the following outline being created for the body
node (and thus the
entire document):
Section created for body
node.
Associated with heading "A".
Also associated with paragraph "B".
Nested sections:
The algorithm that must be followed during a walk of a DOM subtree rooted at a sectioning content element or a sectioning root element to determine that element's outline is as follows:
Let current outline target be null. (It holds the element whose outline is being created.)
Let current section be null. (It holds a pointer to a section, so that elements in the DOM can all be associated with a section.)
Create a stack to hold elements, which is used to handle nesting. Initialize this stack to empty.
Walk over the DOM in tree order, starting with the sectioning content element or sectioning root element at the root of the subtree for which an outline is to be created, and trigger the first relevant step below for each element as the walk enters and exits it.
The element being exited is a heading content element or an
element with a hidden
attribute.
Pop that element from the stack.
hidden
attributeDo nothing.
hidden
attributePush the element being entered onto the stack. (This causes the algorithm to skip that element and any descendants of the element.)
Run these steps:
If current outline target is not null, run these substeps:
If the current section has no heading, create an implied heading and let that be the heading for the current section.
Push current outline target onto the stack.
Let current outline target be the element that is being entered.
Let current section be a newly created section for the current outline target element.
Associate current outline target with current section.
Let there be a new outline for the new current outline target, initialized with just the new current section as the only section in the outline.
Run these steps:
If the current section has no heading, create an implied heading and let that be the heading for the current section.
Pop the top element from the stack, and let the current outline target be that element.
Let current section be the last section in the outline of the current outline target element.
Append the outline of the sectioning content element being exited to the current section. (This does not change which section is the last section in the outline.)
Run these steps:
If current outline target is not null, push current outline target onto the stack.
Let current outline target be the element that is being entered.
Let current outline target's parent section be current section.
Let current section be a newly created section for the current outline target element.
Let there be a new outline for the new current outline target, initialized with just the new current section as the only section in the outline.
Run these steps:
If the current section has no heading, create an implied heading and let that be the heading for the current section.
Let current section be current outline target's parent section.
Pop the top element from the stack, and let the current outline target be that element.
The current outline target is the element being exited, and it is the sectioning content element or a sectioning root element at the root of the subtree for which an outline is being generated.
If the current section has no heading, create an implied heading and let that be the heading for the current section.
Skip to the next step in the overall set of steps. (The walk is over.)
If the current section has no heading, let the element being entered be the heading for the current section.
Otherwise, if the element being entered has a rank equal to or higher than the heading of the last section of the outline of the current outline target, or if the heading of the last section of the outline of the current outline target is an implied heading, then create a new section and append it to the outline of the current outline target element, so that this new section is the new last section of that outline. Let current section be that new section. Let the element being entered be the new heading for the current section.
Otherwise, run these substeps:
Let candidate section be current section.
Heading loop: If the element being entered has a rank lower than the rank of the heading of the candidate section, then create a new section, and append it to candidate section. (This does not change which section is the last section in the outline.) Let current section be this new section. Let the element being entered be the new heading for the current section. Abort these substeps.
Let new candidate section be the section that contains candidate section in the outline of current outline target.
Let candidate section be new candidate section.
Return to the step labeled heading loop.
Push the element being entered onto the stack. (This causes the algorithm to skip any descendants of the element.)
Recall that h1
has the highest rank, and h6
has the lowest rank.
Do nothing.
In addition, whenever the walk exits a node, after doing the steps above, if the node is not associated with a section yet, associate the node with the section current section.
Associate all nodes with the heading of the section with which they are associated, if any.
The tree of sections created by the algorithm above, or a proper subset thereof, must be used when generating document outlines, for example when generating tables of contents.
The outline created for the body element of a Document
is the
outline of the entire document.
When creating an interactive table of contents, entries should jump the user to the relevant sectioning content element, if the section was created for a real element in the original document, or to the relevant heading content element, if the section in the tree was generated for a heading in the above process.
Selecting the first section of the document
therefore always takes the user to the top of the document, regardless of where the first heading
in the body
is to be found.
The outline depth of a heading content element associated with a section section is the number of sections that are ancestors of section in the
outermost outline that section finds itself in when the outlines of its Document
's elements are created, plus 1. The
outline depth of a heading content element not associated with a section is 1.
User agents should provide default headings for sections that do not have explicit section headings.
Consider the following snippet:
<body> <nav> <p><a href="/">Home</a></p> </nav> <p>Hello world.</p> <aside> <p>My cat is cute.</p> </aside> </body>
Although it contains no headings, this snippet has three sections: a document (the
body
) with two subsections (a nav
and an aside
). A user
agent could present the outline as follows:
These default headings ("Untitled document", "Navigation", "Sidebar") are not specified by this specification, and might vary with the user's language, the page's language, the user's preferences, the user agent implementor's preferences, etc.
The following JavaScript function shows how the tree walk could be implemented. The root argument is the root of the tree to walk (either a sectioning content element or a sectioning root element), and the enter and exit arguments are callbacks that are called with the nodes as they are entered and exited. [ECMA262]
function (root, enter, exit) { var node = root; start: while (node) { enter(node); if (node.firstChild) { node = node.firstChild; continue start; } while (node) { exit(node); if (node == root) { node = null; } else if (node.nextSibling) { node = node.nextSibling; continue start; } else { node = node.parentNode; } } } }
This section is non-normative.
The following document shows a straight-forward application of the outline algorithm. First, here is the document, which is a book with very short chapters and subsections:
<!DOCTYPE HTML> <title>The Tax Book (all in one page)</title> <h1>The Tax Book</h1> <h2>Earning money</h2> <p>Earning money is good.</p> <h3>Getting a job</h3> <p>To earn money you typically need a job.</p> <h2>Spending money</h2> <p>Spending is what money is mainly used for.</p> <h3>Cheap things</h3> <p>Buying cheap things often not cost-effective.</p> <h3>Expensive things</h3> <p>The most expensive thing is often not the most cost-effective either.</p> <h2>Investing money</h2> <p>You can lend your money to other people.</p> <h2>Losing money</h2> <p>If you spend money or invest money, sooner or later you will lose money. <h3>Poor judgement</h3> <p>Usually if you lose money it's because you made a mistake.</p>
This book would form the following outline:
Notice that the title
element does not participate in the outline.
Here is a similar document, but this time using section
elements to get the same
effect:
<!DOCTYPE HTML> <title>The Tax Book (all in one page)</title> <h1>The Tax Book</h1> <section> <h1>Earning money</h1> <p>Earning money is good.</p> <section> <h1>Getting a job</h1> <p>To earn money you typically need a job.</p> </section> </section> <section> <h1>Spending money</h1> <p>Spending is what money is mainly used for.</p> <section> <h1>Cheap things</h1> <p>Buying cheap things often not cost-effective.</p> </section> <section> <h1>Expensive things</h1> <p>The most expensive thing is often not the most cost-effective either.</p> </section> </section> <section> <h1>Investing money</h1> <p>You can lend your money to other people.</p> </section> <section> <h1>Losing money</h1> <p>If you spend money or invest money, sooner or later you will lose money. <section> <h1>Poor judgement</h1> <p>Usually if you lose money it's because you made a mistake.</p> </section> </section>
This book would form the same outline:
A document can contain multiple top-level headings:
<!DOCTYPE HTML> <title>Alphabetic Fruit</title> <h1>Apples</h1> <p>Pomaceous.</p> <h1>Bananas</h1> <p>Edible.</p> <h1>Carambola</h1> <p>Star.</p>
This would form the following simple outline consisting of three top-level sections:
Effectively, the body
element is split into three.
Mixing both the h1
–h6
model and the
section
/h1
model can lead to some unintuitive results.
Consider for example the following, which is just the previous example but with the contents
of the (implied) body
wrapped in a section
:
<!DOCTYPE HTML> <title>Alphabetic Fruit</title> <section> <h1>Apples</h1> <p>Pomaceous.</p> <h1>Bananas</h1> <p>Edible.</p> <h1>Carambola</h1> <p>Star.</p> </section>
The resulting outline would be:
This result is described as unintuitive because it results in three subsections even
though there's only one section
element. Effectively, the section
is
split into three, just like the implied body
element in the previous example.
(In this example, "(untitled page)" is the implied heading for the body
element, since it has no explicit heading.)
Headings never rise above other sections. Thus, in the following example, the first
h1
does not actually describe the page header; it describes the header for the
second half of the page:
<!DOCTYPE HTML> <title>Feathers on The Site of Encyclopedic Knowledge</title> <section> <h1>A plea from our caretakers</h1> <p>Please, we beg of you, send help! We're stuck in the server room!</p> </section> <h1>Feathers</h1> <p>Epidermal growths.</p>
The resulting outline would be:
Thus, when an article
element starts with a nav
block and only later
has its heading, the result is that the nav
block is not part of the same section as
the rest of the article
in the outline. For instance, take this document:
<!DOCTYPE HTML> <title>We're adopting a child! — Ray's blog</title> ... <h1>Ray's blog</h1> <main> <article> <header> <nav> <a href="?t=-1d">Yesterday</a>; <a href="?t=-7d">Last week</a>; <a href="?t=-1m">Last month</a> </nav> </header> <h2>We're adopting a child!</h2> <p>As of today, Janine and I have signed the papers to become the proud parents of baby Diane! We've been looking forward to this day for weeks.</p> </article> </main> ...
The resulting outline would be:
Also worthy of note in this example is that the header
and main
elements have no effect whatsoever on the document outline.
This section is non-normative.
Element | Purpose |
---|---|
Example | |
body
| |
<!DOCTYPE HTML> <html> <head> <title>Steve Hill's Home Page</title> </head> <body> <p>Hard Trance is My Life.</p> </body> </html> | |
article
| |
<article> <img src="/tumblr_masqy2s5yn1rzfqbpo1_500.jpg" alt="Yellow smiley face with the caption 'masif'"> <p>My fave Masif tee so far!</p> <footer>Posted 2 days ago</footer> </article> <article> <img src="/tumblr_m9tf6wSr6W1rzfqbpo1_500.jpg" alt=""> <p>Happy 2nd birthday Masif Saturdays!!!</p> <footer>Posted 3 weeks ago</footer> </article> | |
section
| |
<h1>Biography</h1> <section> <h1>The facts</h1> <p>1500+ shows, 14+ countries</p> </section> <section> <h1>2010/2011 figures per year</h1> <p>100+ shows, 8+ countries</p> </section> | |
nav
| |
<nav> <ul> <li><a href="/">Home</a> <li><a href="/biog.html">Bio</a> <li><a href="/discog.html">Discog</a> </ul> </nav> | |
aside
| |
<h1>Music</h1> <p>As any burner can tell you, the event has a lot of trance.</p> <aside>You can buy the music we played at our <a href="buy.html">playlist page</a>.</aside> <p>This year we played a kind of trance that originated in Belgium, Germany, and the Netherlands in the mid 90s.</p> | |
h1 –h6
| A section heading |
<h1>The Guide To Music On The Playa</h1> <h2>The Main Stage</h2> <p>If you want to play on a stage, you should bring one.</p> <h2>Amplified Music</h2> <p>Amplifiers up to 300W or 90dB are welcome.</p> | |
header
| |
<article> <header> <h1>Hard Trance is My Life</h1> <p>By DJ Steve Hill and Technikal</p> </header> <p>The album with the amusing punctuation has red artwork.</p> </article> | |
footer
| |
<article> <h1>Hard Trance is My Life</h1> <p>The album with the amusing punctuation has red artwork.</p> <footer> <p>Artists: DJ Steve Hill and Technikal</p> </footer> </article> |
This section is non-normative.
A section
forms part of something else. An article
is its own thing.
But how does one know which is which? Mostly the real answer is "it depends on author intent".
For example, one could imagine a book with a "Granny Smith" chapter that just said "These
juicy, green apples make a great filling for apple pies."; that would be a section
because there'd be lots of other chapters on (maybe) other kinds of apples.
On the other hand, one could imagine a tweet or reddit comment or tumblr post or newspaper
classified ad that just said "Granny Smith. These juicy, green apples make a great filling for
apple pies."; it would then be article
s because that was the whole thing.
A comment on an article is not part of the article
on which it is commenting,
therefore it is its own article
.
p
elementA p
element's end tag may be omitted if the
p
element is immediately followed by an address
, article
,
aside
, blockquote
, div
, dl
,
fieldset
, footer
, form
, h1
, h2
,
h3
, h4
, h5
, h6
, header
,
hgroup
, hr
, main
, nav
,
ol
, p
, pre
, section
, table
, or
ul
, element, or if there is no more content in the parent element and the parent
element is not an a
element.
aria-*
attributes applicable to the allowed roles.interface HTMLParagraphElement : HTMLElement {};
The p
element represents a paragraph.
While paragraphs are usually represented in visual media by blocks of text that are physically separated from adjacent blocks through blank lines, a style sheet or user agent would be equally justified in presenting paragraph breaks in a different manner, for instance using inline pilcrows (¶).
The following examples are conforming HTML fragments:
<p>The little kitten gently seated himself on a piece of carpet. Later in his life, this would be referred to as the time the cat sat on the mat.</p>
<fieldset> <legend>Personal information</legend> <p> <label>Name: <input name="n"></label> <label><input name="anon" type="checkbox"> Hide from other users</label> </p> <p><label>Address: <textarea name="a"></textarea></label></p> </fieldset>
<p>There was once an example from Femley,<br> Whose markup was of dubious quality.<br> The validator complained,<br> So the author was pained,<br> To move the error from the markup to the rhyming.</p>
The p
element should not be used when a more specific element is more
appropriate.
The following example is technically correct:
<section> <!-- ... --> <p>Last modified: 2001-04-23</p> <p>Author: fred@example.com</p> </section>
However, it would be better marked-up as:
<section> <!-- ... --> <footer>Last modified: 2001-04-23</footer> <address>Author: fred@example.com</address> </section>
Or:
<section> <!-- ... --> <footer> <p>Last modified: 2001-04-23</p> <address>Author: fred@example.com</address> </footer> </section>
List elements (in particular, ol
and ul
elements) cannot be children
of p
elements. When a sentence contains a bulleted list, therefore, one might wonder
how it should be marked up.
For instance, this fantastic sentence has bullets relating to
and is further discussed below.
The solution is to realise that a paragraph, in HTML terms, is not a logical concept, but a structural one. In the fantastic example above, there are actually five paragraphs as defined by this specification: one before the list, one for each bullet, and one after the list.
The markup for the above example could therefore be:
<p>For instance, this fantastic sentence has bullets relating to</p> <ul> <li>wizards, <li>faster-than-light travel, and <li>telepathy, </ul> <p>and is further discussed below.</p>
Authors wishing to conveniently style such "logical" paragraphs consisting of multiple
"structural" paragraphs can use the div
element instead of the p
element.
Thus for instance the above example could become the following:
<div>For instance, this fantastic sentence has bullets relating to <ul> <li>wizards, <li>faster-than-light travel, and <li>telepathy, </ul> and is further discussed below.</div>
This example still has five structural paragraphs, but now the author can style just the
div
instead of having to consider each part of the example separately.
hr
elementseparator
(default - do not set) or presentation
.aria-*
attributes applicable to the allowed roles.interface HTMLHRElement : HTMLElement {};
The hr
element represents a paragraph-level thematic
break, e.g. a scene change in a story, or a transition to another topic within a section of a
reference book.
The following fictional extract from a project manual shows two sections that use the
hr
element to separate topics within the section.
<section> <h1>Communication</h1> <p>There are various methods of communication. This section covers a few of the important ones used by the project.</p> <hr> <p>Communication stones seem to come in pairs and have mysterious properties:</p> <ul> <li>They can transfer thoughts in two directions once activated if used alone.</li> <li>If used with another device, they can transfer one's consciousness to another body.</li> <li>If both stones are used with another device, the consciousnesses switch bodies.</li> </ul> <hr> <p>Radios use the electromagnetic spectrum in the meter range and longer.</p> <hr> <p>Signal flares use the electromagnetic spectrum in the nanometer range.</p> </section> <section> <h1>Food</h1> <p>All food at the project is rationed:</p> <dl> <dt>Potatoes</dt> <dd>Two per day</dd> <dt>Soup</dt> <dd>One bowl per day</dd> </dl> <hr> <p>Cooking is done by the chefs on a set rotation.</p> </section>
There is no need for an hr
element between the
sections themselves, since the section
elements and
the h1
elements imply thematic changes themselves.
The following extract from Pandora's Star by Peter
F. Hamilton shows two paragraphs that precede a scene change and
the paragraph that follows it. The scene change, represented in the
printed book by a gap containing a solitary centered star between
the second and third paragraphs, is here represented using the
hr
element.
<p>Dudley was ninety-two, in his second life, and fast approaching
time for another rejuvenation. Despite his body having the physical
age of a standard fifty-year-old, the prospect of a long degrading
campaign within academia was one he regarded with dread. For a
supposedly advanced civilization, the Intersolar Commonwealth could be
appallingly backward at times, not to mention cruel.</p>
<p><i>Maybe it won't be that bad</i>, he told himself. The lie was
comforting enough to get him through the rest of the night's
shift.</p>
<hr>
<p>The Carlton AllLander drove Dudley home just after dawn. Like the
astronomer, the vehicle was old and worn, but perfectly capable of
doing its job. It had a cheap diesel engine, common enough on a
semi-frontier world like Gralmond, although its drive array was a
thoroughly modern photoneural processor. With its high suspension and
deep-tread tyres it could plough along the dirt track to the
observatory in all weather and seasons, including the metre-deep snow
of Gralmond's winters.</p>
The hr
element does not affect the
document's outline.
pre
elementaria-*
attributes applicable to the allowed roles.interface HTMLPreElement : HTMLElement {};
The pre
element represents a block of
preformatted text, in which structure is represented by typographic
conventions rather than by elements.
In the HTML syntax, a leading
newline character immediately following the pre
element
start tag is stripped.
Some examples of cases where the pre
element could
be used:
Authors are encouraged to consider how preformatted text will be experienced when the formatting is lost, as will be the case for users of speech synthesizers, braille displays, and the like. For cases like ASCII art, it is likely that an alternative presentation, such as a textual description, would be more universally accessible to the readers of the document.
To represent a block of computer code, the pre
element can be used with a code
element; to represent a
block of computer output the pre
element can be used
with a samp
element. Similarly, the kbd
element can be used within a pre
element to indicate
text that the user is to enter.
In the following snippet, a sample of computer code is presented.
<p>This is the <code>Panel</code> constructor:</p> <pre><code>function Panel(element, canClose, closeHandler) { this.element = element; this.canClose = canClose; this.closeHandler = function () { if (closeHandler) closeHandler() }; }</code></pre>
In the following snippet, samp
and kbd
elements are mixed in the contents of a pre
element to
show a session of Zork I.
<pre><samp>You are in an open field west of a big white house with a boarded front door. There is a small mailbox here. ></samp> <kbd>open mailbox</kbd> <samp>Opening the mailbox reveals: A leaflet. ></samp></pre>
The following shows a contemporary poem that uses the
pre
element to preserve its unusual formatting, which
forms an intrinsic part of the poem itself.
<pre> maxling it is with a heart heavy that i admit loss of a feline so loved a friend lost to the unknown (night) ~cdr 11dec07</pre>
blockquote
elementcite
- Link to the source of the quotation.aria-*
attributes applicable to the allowed roles.interface HTMLQuoteElement : HTMLElement { attribute DOMString cite; };
The HTMLQuoteElement
interface is
also used by the q
element.
The blockquote
element represents content that is quoted from another source, optionally with a citation which must be within a footer
or cite
element, and optionally
with in-line changes such as annotations and abbreviations.
Content inside a blockquote
other than citations and in-line changes must be quoted from another source, whose address, if it has one, may be cited in the cite
attribute.
In cases where a page contains contributions from multiple people, such as comments on a blog post, 'another source' can include text from the same page, written by another person.
If the cite
attribute is present, it must be a
valid URL potentially surrounded by spaces. To obtain the
corresponding citation link, the value of the attribute must be resolved relative to the element. User agents may allow users to follow such
citation links, but they are primarily intended for private use (e.g. by server-side scripts
collecting statistics about a site's use of quotations), not for readers.
The cite
IDL
attribute must reflect the element's cite
content attribute.
The content of a blockquote
may be abbreviated, may have context added or may have annotations. Any such additions or changes to quoted text must be indicated in the text (at the text level). This may mean the use of notational conventions or explicit remarks, such as "emphasis mine".
For example, in English, abbreviations are traditionally identified using square brackets. Consider a page with the sentence "Fred ate the cracker. He then said he liked apples and fish."; it could be quoted as follows:
<blockquote> <p>[Fred] then said he liked [...] fish.</p> </blockquote>
Quotation marks may be used to delineate between quoted text and annotations
within a blockquote
.
For example, an in-line note provided by the author:
<figure> <blockquote> "That monster custom, who all sense doth eat Of habit's devil," <abbr title="et cetera">&c.</abbr> not in Folio "What a falling off was there ! From me, whose love was of that dignity That it went hand in hand even with the vow I made to her in marriage, and to decline Upon a wretch." </blockquote> <footer> — <cite class="title">Shakespeare manual</cite> by <cite class="author">Frederick Gard Fleay</cite>, p19 (in Google Books) </footer> </figure>
In the example above, the citation is contained within the footer
of a figure
element,
this groups and associates the information, about the quote, with the quote. The figcaption
element was not
used, in this case, as a container for the citation as it is not a caption.
Attribution for the quotation, may be be placed inside the
blockquote
element, but must be within a cite
element for in-text attributions or within a footer
element.
For example, here the attribution is given in a footer
after
the quoted text, to clearly relate the quote to its attribution:
<blockquote> <p>I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.</p> <footer>— <cite>Stephen Roberts</cite></footer> </blockquote>
Here the attribution is given in a cite
element on the last line of the quoted text.
Note that a link to the author is also included.
<blockquote> The people recognize themselves in their commodities; they find their soul in their automobile, hi-fi set, split-level home, kitchen equipment. — <cite><a href="http://en.wikipedia.org/wiki/Herbert_Marcuse">Herbert Marcuse</a></cite> </blockquote>
Here the attribution is given in a footer
after
the quoted text, and metadata about the reference has been added using the
Microdata syntax
(note it could have equally been marked up using RDFA Lite).
<blockquote> <p>... she said she would not sign any deposition containing the word "amorous" instead of "advances". For her the difference was of crucial significance, and one of the reasons she had separated from her husband was that he had never been amorous but had consistently made advances.</p> <footer itemscope itemtype="http://schema.org/Book"> <span itemprop="author">Heinrich Böll</span>, <span itemprop="name">The Lost Honor of Katharina Blum</span>, <span itemprop="datePublished">January 1, 1974</span> </footer> </blockquote>
There is no formal method for indicating the markup in a blockquote
is from a quoted source. It is suggested that if the footer
or cite
elements are included and these elements are also being used within a blockquote
to identify citations, the elements from the quoted source could be annotated with metadata to identify their origin, for example by using the class
attribute (a defined extensibility mechanism).
In this example the source of a quote includes a cite
element, which is annotated using the class
attribute:
<blockquote> <p>My favorite book is <cite class="from-source">At Swim-Two-Birds</cite></p> <footer>- <cite>Mike[tm]Smith</cite></footer> </blockquote>
Here a blockquote
element is used in conjunction
with a figure
element and its figcaption
:
<figure> <blockquote> <p>The truth may be puzzling. It may take some work to grapple with. It may be counterintuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true. We have a method, and that method helps us to reach not absolute truth, only asymptotic approaches to the truth — never there, just closer and closer, always finding vast new oceans of undiscovered possibilities. Cleverly designed experiments are the key.</p> </blockquote> <figcaption><cite>Carl Sagan</cite>, in "<cite>Wonder and Skepticism</cite>", from the <cite>Skeptical Enquirer</cite> Volume 19, Issue 1 (January-February 1995)</figcaption> </figure>
This next example shows the use of cite
alongside
blockquote
:
<p>His next piece was the aptly named <cite>Sonnet 130</cite>:</p> <blockquote cite="http://quotes.example.org/s/sonnet130.html"> <p>My mistress' eyes are nothing like the sun,<br> Coral is far more red, than her lips red,<br> ...
This example shows how a forum post could use
blockquote
to show what post a user is replying
to. The article
element is used for each post, to mark
up the threading.
<article> <h1><a href="http://bacon.example.com/?blog=109431">Bacon on a crowbar</a></h1> <article> <header><strong>t3yw</strong> 12 points 1 hour ago</header> <p>I bet a narwhal would love that.</p> <footer><a href="?pid=29578">permalink</a></footer> <article> <header><strong>greg</strong> 8 points 1 hour ago</header> <blockquote><p>I bet a narwhal would love that.</p></blockquote> <p>Dude narwhals don't eat bacon.</p> <footer><a href="?pid=29579">permalink</a></footer> <article> <header><strong>t3yw</strong> 15 points 1 hour ago</header> <blockquote> <blockquote><p>I bet a narwhal would love that.</p></blockquote> <p>Dude narwhals don't eat bacon.</p> </blockquote> <p>Next thing you'll be saying they don't get capes and wizard hats either!</p> <footer><a href="?pid=29580">permalink</a></footer> <article> <article> <header><strong>boing</strong> -5 points 1 hour ago</header> <p>narwhals are worse than ceiling cat</p> <footer><a href="?pid=29581">permalink</a></footer> </article> </article> </article> </article> <article> <header><strong>fred</strong> 1 points 23 minutes ago</header> <blockquote><p>I bet a narwhal would love that.</p></blockquote> <p>I bet they'd love to peel a banana too.</p> <footer><a href="?pid=29582">permalink</a></footer> </article> </article> </article>
This example shows the use of a blockquote
for
short snippets, demonstrating that one does not have to use
p
elements inside blockquote
elements:
<p>He began his list of "lessons" with the following:</p> <blockquote>One should never assume that his side of the issue will be recognized, let alone that it will be conceded to have merits.</blockquote> <p>He continued with a number of similar points, ending with:</p> <blockquote>Finally, one should be prepared for the threat of breakdown in negotiations at any given moment and not be cowed by the possibility.</blockquote> <p>We shall now discuss these points...
Examples of how to
represent a conversation are shown in a later section; it is not
appropriate to use the cite
and blockquote
elements for this purpose.
ol
elementli
element: Palpable content.li
and script-supporting elements.reversed
- Number the list backwards.start
- Ordinal value of the first item type
- Kind of list marker.list
role (default - do not set), directory
, listbox
, menu
, menubar
, presentation
, tablist
, toolbar
or tree
.aria-*
attributes applicable to the allowed roles.interface HTMLOListElement : HTMLElement { attribute boolean reversed; attribute long start; attribute DOMString type; };
The ol
element represents a list of
items, where the items have been intentionally ordered, such that
changing the order would change the meaning of the document.
The items of the list are the li
element child nodes
of the ol
element, in tree order.
The reversed
attribute is a boolean attribute. If present, it
indicates that the list is a descending list (..., 3, 2, 1). If the
attribute is omitted, the list is an ascending list (1, 2, 3,
...).
The start
attribute, if present, must be a valid integer giving
the ordinal value of the first list item.
If the start
attribute is
present, user agents must parse it as an integer, in order to determine the
attribute's value. The default value, used if the attribute is
missing or if the value cannot be converted to a number according to
the referenced algorithm, is 1 if the element has no reversed
attribute, and is the
number of child li
elements otherwise.
The first item in the list has the ordinal value
given by the ol
element's start
attribute, unless that
li
element has a value
attribute with a value that can
be successfully parsed, in which case it has the ordinal
value given by that value
attribute.
Each subsequent item in the list has the ordinal
value given by its value
attribute, if it has one, or, if it doesn't, the ordinal
value of the previous item, plus one if the reversed
is absent, or minus one if
it is present.
The type
attribute
can be used to specify the kind of marker to use in the list, in the
cases where that matters (e.g. because items are to be referenced by
their number/letter). The attribute, if specified, must have a value
that is a case-sensitive match for one of the
characters given in the first cell of one of the rows of the
following table. The type
attribute represents the state
given in the cell in the second column of the row whose first cell
matches the attribute's value; if none of the cells match, or if the
attribute is omitted, then the attribute represents the decimal state.
Keyword | State | Description | Examples for values 1-3 and 3999-4001 | |||||||
---|---|---|---|---|---|---|---|---|---|---|
1 (U+0031)
| decimal | Decimal numbers | 1. | 2. | 3. | ... | 3999. | 4000. | 4001. | ... |
a (U+0061)
| lower-alpha | Lowercase latin alphabet | a. | b. | c. | ... | ewu. | ewv. | eww. | ... |
A (U+0041)
| upper-alpha | Uppercase latin alphabet | A. | B. | C. | ... | EWU. | EWV. | EWW. | ... |
i (U+0069)
| lower-roman | Lowercase roman numerals | i. | ii. | iii. | ... | mmmcmxcix. | i̅v̅. | i̅v̅i. | ... |
I (U+0049)
| upper-roman | Uppercase roman numerals | I. | II. | III. | ... | MMMCMXCIX. | I̅V̅. | I̅V̅I. | ... |
User agents should render the items of the list in a manner
consistent with the state of the type
attribute of the ol
element. Numbers less than or equal to zero should always use the
decimal system regardless of the type
attribute.
For CSS user agents, a mapping for this attribute to the 'list-style-type' CSS property is given in the rendering section (the mapping is straightforward: the states above have the same names as their corresponding CSS values).
The reversed
,
start
, and type
IDL attributes must
reflect the respective content attributes of the same
name. The start
IDL attribute has
the same default as its content attribute.
The following markup shows a list where the order matters, and
where the ol
element is therefore appropriate. Compare
this list to the equivalent list in the ul
section to
see an example of the same items using the ul
element.
<p>I have lived in the following countries (given in the order of when I first lived there):</p> <ol> <li>Switzerland <li>United Kingdom <li>United States <li>Norway </ol>
Note how changing the order of the list changes the meaning of the document. In the following example, changing the relative order of the first two items has changed the birthplace of the author:
<p>I have lived in the following countries (given in the order of when I first lived there):</p> <ol> <li>United Kingdom <li>Switzerland <li>United States <li>Norway </ol>
ul
elementli
element: Palpable content.li
and script-supporting elements.list
role (default - do not set), directory
, group
, listbox
, menu
, menubar
, presentation
, tablist
, toolbar
or tree
.aria-*
attributes applicable to the allowed roles.interface HTMLUListElement : HTMLElement {};
The ul
element represents a list of
items, where the order of the items is not important — that
is, where changing the order would not materially change the meaning
of the document.
The items of the list are the li
element child nodes
of the ul
element.
The following markup shows a list where the order does not
matter, and where the ul
element is therefore
appropriate. Compare this list to the equivalent list in the
ol
section to see an example of the same items using
the ol
element.
<p>I have lived in the following countries:</p> <ul> <li>Norway <li>Switzerland <li>United Kingdom <li>United States </ul>
Note that changing the order of the list does not change the meaning of the document. The items in the snippet above are given in alphabetical order, but in the snippet below they are given in order of the size of their current account balance in 2007, without changing the meaning of the document whatsoever:
<p>I have lived in the following countries:</p> <ul> <li>Switzerland <li>Norway <li>United Kingdom <li>United States </ul>
li
elementol
elements.ul
elements.ol
element: value
- Ordinal value of the list itemAn li
element's end tag may be omitted if the
li
element is immediately followed by another li
element or if there is
no more content in the parent element.
listitem
role (default - do not set), menuitem
, menuitemcheckbox
, menuitemradio
, option
, tab
, treeitem
or presentation
.aria-*
attributes applicable to the allowed roles.interface HTMLLIElement : HTMLElement { attribute long value; };
The li
element represents a list
item. If its parent element is an ol
, or ul
,
then the element is an item of the
parent element's list, as defined for those elements. Otherwise, the
list item has no defined list-related relationship to any other
li
element.
If the parent element is an ol
element, then the
li
element has an ordinal value.
The value
attribute, if present, must be a valid integer giving
the ordinal value of the list item.
If the value
attribute is
present, user agents must parse it as an integer, in order to determine the
attribute's value. If the attribute's value cannot be converted to a
number, the attribute must be treated as if it was absent. The
attribute has no default value.
The value
attribute is
processed relative to the element's parent ol
element
(q.v.), if there is one. If there is not, the attribute has no
effect.
The value
IDL
attribute must reflect the value of the value
content attribute.
The following example, the top ten movies are listed (in reverse
order). Note the way the list is given a title by using a
figure
element and its figcaption
element.
<figure> <figcaption>The top 10 movies of all time</figcaption> <ol> <li value="10"><cite>Josie and the Pussycats</cite>, 2001</li> <li value="9"><cite lang="sh">Црна мачка, бели мачор</cite>, 1998</li> <li value="8"><cite>A Bug's Life</cite>, 1998</li> <li value="7"><cite>Toy Story</cite>, 1995</li> <li value="6"><cite>Monsters, Inc</cite>, 2001</li> <li value="5"><cite>Cars</cite>, 2006</li> <li value="4"><cite>Toy Story 2</cite>, 1999</li> <li value="3"><cite>Finding Nemo</cite>, 2003</li> <li value="2"><cite>The Incredibles</cite>, 2004</li> <li value="1"><cite>Ratatouille</cite>, 2007</li> </ol> </figure>
The markup could also be written as follows, using the reversed
attribute on the
ol
element:
<figure> <figcaption>The top 10 movies of all time</figcaption> <ol reversed> <li><cite>Josie and the Pussycats</cite>, 2001</li> <li><cite lang="sh">Црна мачка, бели мачор</cite>, 1998</li> <li><cite>A Bug's Life</cite>, 1998</li> <li><cite>Toy Story</cite>, 1995</li> <li><cite>Monsters, Inc</cite>, 2001</li> <li><cite>Cars</cite>, 2006</li> <li><cite>Toy Story 2</cite>, 1999</li> <li><cite>Finding Nemo</cite>, 2003</li> <li><cite>The Incredibles</cite>, 2004</li> <li><cite>Ratatouille</cite>, 2007</li> </ol> </figure>
While it is conforming to include heading elements
(e.g. h1
) inside li
elements, it likely
does not convey the semantics that the author intended. A heading
starts a new section, so a heading in a list implicitly splits the
list into spanning multiple sections.
dl
elementdt
elements followed by one or more dd
elements, optionally intermixed with script-supporting elements.aria-*
attributes applicable to the allowed roles.interface HTMLDListElement : HTMLElement {};
The dl
element represents an
association list consisting of zero or more name-value groups (a
description list). A name-value group consists of one or more names
(dt
elements) followed by one or more values
(dd
elements), ignoring any nodes other than dt
and dd
elements. Within a single dl
element,
there should not be more than one dt
element for each
name.
Name-value groups may be terms and definitions, metadata topics and values, questions and answers, or any other groups of name-value data.
The values within a group are alternatives; multiple paragraphs
forming part of the same value must all be given within the same
dd
element.
The order of the list of groups, and of the names and values within each group, may be significant.
If a dl
element is empty, it contains no groups.
If a dl
element has one or more non-whitespace Text
node children, or has child elements that are neither
dt
nor dd
elements, all such
Text
nodes and elements, as well as their descendants
(including any dt
or dd
elements), do not
form part of any groups in that dl
.
If a dl
element has one or more dt
element children but no dd
element children, then it
consists of one group with names but no values.
If a dl
element has one or more dd
element children but no dt
element children, then it
consists of one group with values but no names.
If a dl
element's first dt
or
dd
element child is a dd
element, then the
first group has no associated name.
If a dl
element's last dt
or
dd
element child is a dt
element, then the
last group has no associated value.
When a dl
element doesn't match its
content model, it is often due to accidentally using dd
elements in the place of dt
elements and vice
versa. Conformance checkers can spot such mistakes and might be able
to advise authors how to correctly use the markup.
In the following example, one entry ("Authors") is linked to two values ("John" and "Luke").
<dl> <dt> Authors <dd> John <dd> Luke <dt> Editor <dd> Frank </dl>
In the following example, one definition is linked to two terms.
<dl> <dt lang="en-US"> <dfn>color</dfn> </dt> <dt lang="en-GB"> <dfn>colour</dfn> </dt> <dd> A sensation which (in humans) derives from the ability of the fine structure of the eye to distinguish three differently filtered analyses of a view. </dd> </dl>
The following example illustrates the use of the dl
element to mark up metadata
of sorts. At the end of the example, one group has two metadata labels ("Authors" and "Editors")
and two values ("Robert Rothman" and "Daniel Jackson").
<dl> <dt> Last modified time </dt> <dd> 2004-12-23T23:33Z </dd> <dt> Recommended update interval </dt> <dd> 60s </dd> <dt> Authors </dt> <dt> Editors </dt> <dd> Robert Rothman </dd> <dd> Daniel Jackson </dd> </dl>
The following example shows the dl
element used to give a set of instructions.
The order of the instructions here is important (in the other examples, the order of the blocks
was not important).
<p>Determine the victory points as follows (use the first matching case):</p> <dl> <dt> If you have exactly five gold coins </dt> <dd> You get five victory points </dd> <dt> If you have one or more gold coins, and you have one or more silver coins </dt> <dd> You get two victory points </dd> <dt> If you have one or more silver coins </dt> <dd> You get one victory point </dd> <dt> Otherwise </dt> <dd> You get no victory points </dd> </dl>
The following snippet shows a dl
element being used as a glossary. Note the use
of dfn
to indicate the word being defined.
<dl> <dt><dfn>Apartment</dfn>, n.</dt> <dd>An execution context grouping one or more threads with one or more COM objects.</dd> <dt><dfn>Flat</dfn>, n.</dt> <dd>A deflated tire.</dd> <dt><dfn>Home</dfn>, n.</dt> <dd>The user's login directory.</dd> </dl>
The dl
element is inappropriate for marking up dialogue. Examples of how to mark up dialogue are shown below.
dt
elementdd
or dt
elements inside dl
elements.header
, footer
, sectioning content, or heading content descendants.A dt
element's end tag may be omitted if the
dt
element is immediately followed by another dt
element or a
dd
element.
aria-*
attributes
applicable to the allowed roles.HTMLElement
.The dt
element represents the term, or name, part of a
term-description group in a description list (dl
element).
The dt
element itself, when used in a dl
element, does
not indicate that its contents are a term being defined, but this can be indicated using the
dfn
element.
This example shows a list of frequently asked questions (a FAQ) marked up using the
dt
element for questions and the dd
element for answers.
<article> <h1>FAQ</h1> <dl> <dt>What do we want?</dt> <dd>Our data.</dd> <dt>When do we want it?</dt> <dd>Now.</dd> <dt>Where is it?</dt> <dd>We are not sure.</dd> </dl> </article>
dd
elementdt
or dd
elements inside dl
elements.A dd
element's end tag may be omitted if the
dd
element is immediately followed by another dd
element or a
dt
element, or if there is no more content in the parent element.
aria-*
attributes
applicable to the allowed roles.HTMLElement
.The dd
element represents the description, definition, or value, part
of a term-description group in a description list (dl
element).
A dl
can be used to define a vocabulary list, like in a dictionary. In the
following example, each entry, given by a dt
with a dfn
, has several
dd
s, showing the various parts of the definition.
<dl> <dt><dfn>happiness</dfn></dt> <dd class="pronunciation">/'hæ p. nes/</dd> <dd class="part-of-speech"><i><abbr>n.</abbr></i></dd> <dd>The state of being happy.</dd> <dd>Good fortune; success. <q>Oh <b>happiness</b>! It worked!</q></dd> <dt><dfn>rejoice</dfn></dt> <dd class="pronunciation">/ri jois'/</dd> <dd><i class="part-of-speech"><abbr>v.intr.</abbr></i> To be delighted oneself.</dd> <dd><i class="part-of-speech"><abbr>v.tr.</abbr></i> To cause one to be delighted.</dd> </dl>
figure
elementfigcaption
element followed by flow content.figcaption
element.aria-*
attributes
applicable to the allowed roles.HTMLElement
.The figure
element represents some flow content,
optionally with a caption, that is self-contained (like a complete sentence) and is typically
referenced as a single unit from the main flow of the document.
Self-contained in this context does not necessarily mean independent. For example,
each sentence in a paragraph is self-contained; an image that is part of a sentence would be
inappropriate for figure
, but an entire sentence made of images would be fitting.
The element can thus be used to annotate illustrations, diagrams, photos, code listings, etc.
When a figure
is referred to from the main content of the document by identifying
it by its caption (e.g. by figure number), it enables such content to be easily moved away from
that primary content, e.g. to the side of the page, to dedicated pages, or to an appendix, without
affecting the flow of the document.
If a figure
element is referenced by its relative position, e.g. "in the
photograph above" or "as the next figure shows", then moving the figure would disrupt the page's
meaning. Authors are encouraged to consider using labels to refer to figures, rather than using
such relative references, so that the page can easily be restyled without affecting the page's
meaning.
The first figcaption
element child of the element, if
any, represents the caption of the figure
element's contents. If there is no child
figcaption
element, then there is no caption.
A figure
element's contents are part of the surrounding flow. If the purpose of
the page is to display the figure, for example a photograph on an image sharing site, the
figure
and figcaption
elements can be used to explicitly provide a
caption for that figure. For content that is only tangentially related, or that serves a separate
purpose than the surrounding flow, the aside
element should be used (and can itself
wrap a figure
). For example, a pull quote that repeats content from an
article
would be more appropriate in an aside
than in a
figure
, because it isn't part of the content, it's a repetition of the content for
the purposes of enticing readers or highlighting key topics.
This example shows the figure
element to mark up a code listing.
<p>In <a href="#l4">listing 4</a> we see the primary core interface API declaration.</p> <figure id="l4"> <figcaption>Listing 4. The primary core interface API declaration.</figcaption> <pre><code>interface PrimaryCore { boolean verifyDataLine(); void sendData(in sequence<byte> data); void initSelfDestruct(); }</code></pre> </figure> <p>The API is designed to use UTF-8.</p>
Here we see a figure
element to mark up a photo that is the main content of the
page (as in a gallery).
<!DOCTYPE HTML> <title>Bubbles at work — My Gallery™</title> <figure> <img src="bubbles-work.jpeg" alt="Bubbles, sitting in his office chair, works on his latest project intently."> <figcaption>Bubbles at work</figcaption> </figure> <nav><a href="19414.html">Prev</a> — <a href="19416.html">Next</a></nav>
In this example, we see an image that is not a figure, as well as an image and a
video that are. The first image is literally part of the example's second sentence, so it's not a
self-contained unit, and thus figure
would be inappropriate.
<h2>Malinko's comics</h2> <p>This case centered on some sort of "intellectual property" infringement related to a comic (see Exhibit A). The suit started after a trailer ending with these words: <blockquote> <img src="promblem-packed-action.png" alt="ROUGH COPY! Promblem-Packed Action!"> </blockquote> <p>...was aired. A lawyer, armed with a Bigger Notebook, launched a preemptive strike using snowballs. A complete copy of the trailer is included with Exhibit B. <figure> <img src="ex-a.png" alt="Two squiggles on a dirty piece of paper."> <figcaption>Exhibit A. The alleged <cite>rough copy</cite> comic.</figcaption> </figure> <figure> <video src="ex-b.mov"></video> <figcaption>Exhibit B. The <cite>Rough Copy</cite> trailer.</figcaption> </figure> <p>The case was resolved out of court.
Here, a part of a poem is marked up using figure
.
<figure> <p>'Twas brillig, and the slithy toves<br> Did gyre and gimble in the wabe;<br> All mimsy were the borogoves,<br> And the mome raths outgrabe.</p> <figcaption><cite>Jabberwocky</cite> (first verse). Lewis Carroll, 1832-98</figcaption> </figure>
In this example, which could be part of a much larger work discussing a castle, nested
figure
elements are used to provide both a group caption and individual captions for
each figure in the group:
<figure> <figcaption>The castle through the ages: 1423, 1858, and 1999 respectively.</figcaption> <figure> <figcaption>Etching. Anonymous, ca. 1423.</figcaption> <img src="castle1423.jpeg" alt="The castle has one tower, and a tall wall around it."> </figure> <figure> <figcaption>Oil-based paint on canvas. Maria Towle, 1858.</figcaption> <img src="castle1858.jpeg" alt="The castle now has two towers and two walls."> </figure> <figure> <figcaption>Film photograph. Peter Jankle, 1999.</figcaption> <img src="castle1999.jpeg" alt="The castle lies in ruins, the original tower all that remains in one piece."> </figure> </figure>
The figure is sometimes referenced only implicitly from the content:
<article> <h1>Fiscal negotiations stumble in Congress as deadline nears</h1> <figure> <img src="obama-reid.jpeg" alt="Obama and Reid sit together smiling in the Oval Office."> <figcaption>Barrak Obama and Harry Reid. White House press photograph.</figcaption> </figure> <p>Negotiations in Congress to end the fiscal impasse sputtered on Tuesday, leaving both chambers grasping for a way to reopen the government and raise the country's borrowing authority with a Thursday deadline drawing near.</p> ... </article>
figcaption
elementfigure
element.aria-*
attributes
applicable to the allowed roles.HTMLElement
.The figcaption
element represents a caption or legend for the rest of
the contents of the figcaption
element's parent figure
element, if any.
div
elementaria-*
attributes
applicable to the allowed roles.interface HTMLDivElement : HTMLElement {};
The div
element has no special meaning at all. It
represents its children. It can be used with the class
, lang
, and title
attributes to mark up semantics
common to a group of consecutive elements.
Authors are strongly encouraged to view the
div
element as an element of last resort, for when no
other element is suitable. Use of more appropriate elements instead
of the div
element leads to better accessibility for
readers and easier maintainability for authors.
For example, a blog post would be marked up using
article
, a chapter using section
, a
page's navigation aids using nav
, and a group of form
controls using fieldset
.
On the other hand, div
elements can be useful for
stylistic purposes or to wrap multiple paragraphs within a section
that are all to be annotated in a similar way. In the following
example, we see div
elements used as a way to set the
language of two paragraphs at once, instead of setting the language
on the two paragraph elements separately:
<article lang="en-US"> <h1>My use of language and my cats</h1> <p>My cat's behavior hasn't changed much since her absence, except that she plays her new physique to the neighbors regularly, in an attempt to get pets.</p> <div lang="en-GB"> <p>My other cat, coloured black and white, is a sweetie. He followed us to the pool today, walking down the pavement with us. Yesterday he apparently visited our neighbours. I wonder if he recognises that their flat is a mirror image of ours.</p> <p>Hm, I just noticed that in the last paragraph I used British English. But I'm supposed to write in American English. So I shouldn't say "pavement" or "flat" or "colour"...</p> </div> <p>I should say "sidewalk" and "apartment" and "color"!</p> </article>
main
elementarticle
, aside
,
footer
, header
or nav
element ancestors.main
role (default - do not set) or presentation
.aria-*
attributes
applicable to the allowed roles.HTMLElement
The main
element represents the main content of the body
of a document or application. The main content area consists of content that is directly related to or expands upon
the central topic of a document or central functionality of an application.
The main
element is not sectioning content and has no effect
on the document outline
The main content area of a document includes content that is unique to that document and excludes content that is repeated across a set of documents such as site navigation links, copyright information, site logos and banners and search forms (unless the document or applications main function is that of a search form).
User agents that support keyboard navigation of content are strongly encouraged to provide
a method to navigate to the main
element and once navigated to, ensure the next
element in the focus order is the first focusable element within the main
element.
This will provide a simple method for keyboard users to bypass blocks of content such as navigation links.
Authors must not include more than one main
element in a document.
Authors must not include the main
element as a descendant of an article
,
aside
, footer
, header
or nav
element.
The main
element is not suitable for use to identify the main content areas of sub sections of a
document or application. The simplest solution is to not mark up the main content of a sub section at all, and just leave it
as implicit, but an author could use a grouping content or sectioning content element as appropriate.
Authors are advised to use ARIA role="main"
attribute on the
main
element until user agents implement the required role mapping.
<main role="main"> ... </main>
In the following example, we see 2 articles about skateboards (the main topic of a
Web page) the main topic content is identified by the use of the main
element.
<!-- other content --> <main> <h1>Skateboards</h1> <p>The skateboard is the way cool kids get around</p> <article> <h2>Longboards</h2> <p>Longboards are a type of skateboard with a longer wheelbase and larger, softer wheels.</p> <p>... </p> <p>... </p> </article> <article> <h2>Electric Skateboards</h2> <p>These no longer require the propelling of the skateboard by means of the feet; rather an electric motor propels the board, fed by an electric battery.</p> <p>... </p> <p>... </p> </article> </main> <!-- other content -->
Here is a graduation programme the main content section is defined by the use of the main
element.
Note in this example the main
element contains a nav
element consisting of links to
sub sections of the main content.
<!DOCTYPE html> <html> <head>
<title>Graduation Ceremony Summer 2022</title> </head> <body> <header>The Lawson Academy: <nav> <ul> <li><a href="courses.html">Courses</a></li> <li><a href="fees.html">Fees</a></li> <li><a>Graduation</a></li> </ul> </nav> </header> <main> <h1>Graduation</h1> <nav> <ul> <li><a href="#ceremony">Ceremony</a></li> <li><a href="#graduates">Graduates</a></li> <li><a href="#awards">Awards</a></li> </ul> </nav> <H2 id="ceremony">Ceremony</H2> <p>Opening Procession</p> <p>Speech by Valedictorian</p> <p>Speech by Class President</p> <p>Presentation of Diplomas</p> <p>Closing Speech by Headmaster</p> <h2 id="graduates">Graduates</h2> <ul> <li>Eileen Williams</li> <li>Andy Maseyk</li> <li>Blanca Sainz Garcia</li> <li>Clara Faulkner</li> <li>Gez Lemon</li> <li>Eloisa Faulkner</li> </ul> <h2 id="awards">Awards</h2> <ul> <li>Clara Faulkner</li> <li>Eloisa Faulkner</li> <li>Blanca Sainz Garcia</li> </ul> </main> <footer> Copyright 2012 B.lawson</footer> </body> </html>
a
elementhref
- Address of the hyperlinktarget
- Default browsing context for hyperlink navigation and form submissiondownload
- Whether to download the resource instead of navigating to it, and its file name if sorel
- Relationship between the document containing the hyperlink and the destination resourcehreflang
- Language of the linked resourcetype
- Hint for the type of the referenced resourcelink
(default - do not set), button
, checkbox
, menuitem
, menuitemcheckbox
, menuitemradio
, tab
or treeitem
aria-*
attributes
applicable to the allowed roles.interface HTMLAnchorElement : HTMLElement { attribute DOMString target; attribute DOMString download; attribute DOMString rel; readonly attribute DOMTokenList relList; attribute DOMString hreflang; attribute DOMString type; attribute DOMString text; }; HTMLAnchorElement implements URLUtils;
If the a
element has an href
attribute,
then it represents a hyperlink (a hypertext anchor) labeled by its
contents.
If the a
element has no href
attribute,
then the element represents a placeholder for where a link might otherwise have been
placed, if it had been relevant, consisting of just the element's contents.
The target
,
download
,
rel
,
hreflang
, and
type
attributes must be omitted if the href
attribute is not
present.
If a site uses a consistent navigation toolbar on every page, then the link that would
normally link to the page itself could be marked up using an a
element:
<nav> <ul> <li> <a href="/">Home</a> </li> <li> <a href="/news">News</a> </li> <li> <a>Examples</a> </li> <li> <a href="/legal">Legal</a> </li> </ul> </nav>
The href
, target
, download
, and
attributes affect what happens when users follow
hyperlinks or download hyperlinks created using
the a
element. The rel
, hreflang
, and type
attributes may be used to indicate to the user the likely nature of the target resource before the
user follows the link.
The activation behavior of a
elements that create hyperlinks is to run the following steps:
If the a
element's Document
is not fully active, then abort these steps.
If either the a
element has a download
attribute and the algorithm is not allowed
to show a popup, or the element's target
attribute is present and applying the rules for choosing a browsing context given a
browsing context name, using the value of the target
attribute as the browsing context name, would result
in there not being a chosen browsing context, then run these substeps:
If there is an entry settings object, throw an
InvalidAccessError
exception.
Abort these steps without following the hyperlink.
If the target of the click
event is an img
element with an ismap
attribute specified, then server-side
image map processing must be performed, as follows:
click
event was a real pointing-device-triggered
click
event on the img
element, then let x be the distance in CSS pixels from the left edge of the image's left border,
if it has one, or the left edge of the image otherwise, to the location of the click, and let
y be the distance in CSS pixels from the top edge of the image's top
border, if it has one, or the top edge of the image otherwise, to the location of the click.
Otherwise, let x and y be zero.Finally, the user agent must follow the
hyperlink or download the hyperlink created by
the a
element, as determined by the download
attribute and any expressed user preference. If
the steps above defined a hyperlink suffix, then take that into account when following
or downloading the hyperlink.
text
Same as textContent
.
The IDL attributes download
,
target
,
rel
, hreflang
, and type
, must reflect the respective content
attributes of the same name.
The IDL attribute relList
must
reflect the rel
content attribute.
The text
IDL attribute, on getting, must return the
same value as the textContent
IDL attribute on the element, and on setting, must act
as if the textContent
IDL attribute on the element had been set to the new value.
The a
element also supports the URLUtils
interface. [URL]
When the element is created, and whenever the element's href
content attribute is set, changed, or removed, the user
agent must invoke the element's URLUtils
interface's set the input algorithm with the value of the href
content attribute, if any, or the empty string otherwise,
as the given value.
The element's URLUtils
interface's get the
base algorithm must simply return the element's base URL.
The element's URLUtils
interface's query
encoding is the document's character encoding.
When the element's URLUtils
interface invokes its update steps with a string value, the user
agent must set the element's href
content attribute to
the string value.
The a
element may be wrapped around entire paragraphs, lists, tables, and so
forth, even entire sections, so long as there is no interactive content within (e.g. buttons or
other links). This example shows how this can be used to make an entire advertising block into a
link:
<aside class="advertising"> <h1>Advertising</h1> <a href="http://ad.example.com/?adid=1929&pubid=1422"> <section> <h1>Mellblomatic 9000!</h1> <p>Turn all your widgets into mellbloms!</p> <p>Only $9.99 plus shipping and handling.</p> </section> </a> <a href="http://ad.example.com/?adid=375&pubid=1422"> <section> <h1>The Mellblom Browser</h1> <p>Web browsing at the speed of light.</p> <p>No other browser goes faster!</p> </section> </a> </aside>
em
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The em
element represents stress emphasis of its contents.
The level of stress that a particular piece of content has is given by its number of ancestor
em
elements.
The placement of stress emphasis changes the meaning of the sentence. The element thus forms an integral part of the content. The precise way in which stress is used in this way depends on the language.
These examples show how changing the stress emphasis changes the meaning. First, a general statement of fact, with no stress:
<p>Cats are cute animals.</p>
By emphasizing the first word, the statement implies that the kind of animal under discussion is in question (maybe someone is asserting that dogs are cute):
<p><em>Cats</em> are cute animals.</p>
Moving the stress to the verb, one highlights that the truth of the entire sentence is in question (maybe someone is saying cats are not cute):
<p>Cats <em>are</em> cute animals.</p>
By moving it to the adjective, the exact nature of the cats is reasserted (maybe someone suggested cats were mean animals):
<p>Cats are <em>cute</em> animals.</p>
Similarly, if someone asserted that cats were vegetables, someone correcting this might emphasize the last word:
<p>Cats are cute <em>animals</em>.</p>
By emphasizing the entire sentence, it becomes clear that the speaker is fighting hard to get the point across. This kind of stress emphasis also typically affects the punctuation, hence the exclamation mark here.
<p><em>Cats are cute animals!</em></p>
Anger mixed with emphasizing the cuteness could lead to markup such as:
<p><em>Cats are <em>cute</em> animals!</em></p>
The em
element isn't a generic "italics" element. Sometimes, text is intended to
stand out from the rest of the paragraph, as if it was in a different mood or voice. For this,
the i
element is more appropriate.
The em
element also isn't intended to convey importance; for that purpose, the
strong
element is more appropriate.
strong
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The strong
element represents strong importance, seriousness, or
urgency for its contents.
Importance: The strong
element can be used in a heading, caption,
or paragraph to distinguish the part that really matters from other parts of the that might be
more detailed, more jovial, or merely boilerplate.
For example, the first word of the previous paragraph is marked up with
strong
to distinguish it from the more detailed text in the rest of the
paragraph.
Seriousness: The strong
element can be used to mark up a warning
or caution notice.
Urgency: The strong
element can be used to denote contents that
the user needs to see sooner than other parts of the document.
The relative level of importance of a piece of content is given by its number of ancestor
strong
elements; each strong
element increases the importance of its
contents.
Changing the importance of a piece of text with the strong
element does not change
the meaning of the sentence.
Here, the word "chapter" and the actual chapter number are mere boilerplate, and the actual
name of the chapter is marked up with strong
:
<h1>Chapter 1: <strong>The Praxis</strong></h1>
In the following example, the name of the diagram in the caption is marked up with
strong
, to distinguish it from boilerplate text (before) and the description
(after):
<figcaption>Figure 1. <strong>Ant colony dynamics</strong>. The ants in this colony are affected by the heat source (upper left) and the food source (lower right).</figcaption>
In this example, the heading is really "Flowers, Bees, and Honey", but the author has added a
light-hearted addition to the heading. The strong
element is thus used to mark up
the first part to distinguish it from the latter part.
<h1><strong>Flowers, Bees, and Honey</strong> and other things I don't understand</h1>
Here is an example of a warning notice in a game, with the various parts marked up according to how important they are:
<p><strong>Warning.</strong> This dungeon is dangerous. <strong>Avoid the ducks.</strong> Take any gold you find. <strong><strong>Do not take any of the diamonds</strong>, they are explosive and <strong>will destroy anything within ten meters.</strong></strong> You have been warned.</p>
In this example, the strong
element is used to denote the part of the text that
the user is intended to read first.
<p>Welcome to Remy, the reminder system.</p> <p>Your tasks for today:</p> <ul> <li><p><strong>Turn off the oven.</strong></p></li> <li><p>Put out the trash.</p></li> <li><p>Do the laundry.</p></li> </ul>
small
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The small
element represents side comments such as small print.
Small print typically features disclaimers, caveats, legal restrictions, or copyrights. Small print is also sometimes used for attribution, or for satisfying licensing requirements.
The small
element does not "de-emphasize" or lower the importance of
text emphasized by the em
element or marked as important with the strong
element. To mark text as not emphasized or important, simply do not mark it up with the
em
or strong
elements respectively.
The small
element should not be used for extended spans of text, such as multiple
paragraphs, lists, or sections of text. It is only intended for short runs of text. The text of a
page listing terms of use, for instance, would not be a suitable candidate for the
small
element: in such a case, the text is not a side comment, it is the main content
of the page.
In this example, the small
element is used to indicate that value-added tax is
not included in a price of a hotel room:
<dl> <dt>Single room <dd>199 € <small>breakfast included, VAT not included</small> <dt>Double room <dd>239 € <small>breakfast included, VAT not included</small> </dl>
In this second example, the small
element is used for a side comment in an
article.
<p>Example Corp today announced record profits for the second quarter <small>(Full Disclosure: Foo News is a subsidiary of Example Corp)</small>, leading to speculation about a third quarter merger with Demo Group.</p>
This is distinct from a sidebar, which might be multiple paragraphs long and is removed from the main flow of text. In the following example, we see a sidebar from the same article. This sidebar also has small print, indicating the source of the information in the sidebar.
<aside> <h1>Example Corp</h1> <p>This company mostly creates small software and Web sites.</p> <p>The Example Corp company mission is "To provide entertainment and news on a sample basis".</p> <p><small>Information obtained from <a href="http://example.com/about.html">example.com</a> home page.</small></p> </aside>
In this last example, the small
element is marked as being important
small print.
<p><strong><small>Continued use of this service will result in a kiss.</small></strong></p>
s
elementHTMLElement
.The s
element represents contents that are no longer accurate or no
longer relevant.
The s
element is not appropriate when indicating document edits; to
mark a span of text as having been removed from a document, use the del
element.
In this example a recommended retail price has been marked as no longer relevant as the product in question has a new sale price.
<p>Buy our Iced Tea and Lemonade!</p> <p><s>Recommended retail price: $3.99 per bottle</s></p> <p><strong>Now selling for just $2.99 a bottle!</strong></p>
cite
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The cite
element represents a reference to a creative work. It must include the
title of the work or the name of the author(person, people or organization) or an URL reference, which may be in an abbreviated form as per the conventions used for the addition of citation metadata.
Creative works include a book, a paper, an essay, a poem, a score, a song, a script, a film, a TV show, a game, a sculpture, a painting, a theatre production, a play, an opera, a musical, an exhibition, a legal case report, a web site, a web page, a blog post or comment, a forum post or comment, a tweet, a written or oral statement, etc.
Here is an example of the author of a quote referenced using the cite
element:
<p>In the words of <cite>Charles Bukowski</cite> - <q>An intellectual says a simple thing in a hard way. An artist says a hard thing in a simple way.</q></p>
This second example identifies the author of a tweet by referencing the authors name using the cite
element:
<blockquote class="twitter-tweet"> <p>♥ Bukowski in <a href="https://twitter.com/search?q=%23HTML5&src=hash">#HTML5</a> spec examples <a href="http://t.co/0FIEiYN1pC">http://t.co/0FIEiYN1pC</a></p><cite>— karl dubost (@karlpro) <a href="https://twitter.com/karlpro/statuses/370905307293442048">August 23, 2013</a></cite> </blockquote>
In this example the cite
element is used to reference the title of a work
in a bibliography:
<p><cite>Universal Declaration of Human Rights</cite>, United Nations, December 1948. Adopted by General Assembly resolution 217 A (III).</p>
In this example the cite
element is used to reference the title of a television show:
<p>Who is your favorite doctor (in <cite>Doctor Who</cite>)?</p>
A very common use for the cite
element is to identify the author of a comment in a blog post or forum, as in this example:
<article id="comment-1"> Comment by <cite><a href="http://oli.jp">Oli Studholme</a></cite> <time datetime="2013-08-19T16:01">August 19th, 2013 at 4:01 pm</time> <p>Unfortunately I don't think adding names back into the definition of <code>cite</code> solves the problem: of the 12 blockquote examples in <a href="http://oli.jp/example/blockquote-metadata/">Examples of block quote metadata</a>, there's not even one that's <em>just</em> a person’s name.</p> <p>A subset of the problem, maybe…</p> </article>
Another common use for the cite
element is to reference the URL
of a search result, as in this example:
<div id="resultStats">About 416,000,000 results 0.33 seconds) </div> ... <p><a href="http://www.w3.org/html/wg/">W3C <i>HTML Working Group</i></a></p> <p><cite>www.w3.org/<b>html</b>/wg/</cite></p> <p>15 Apr 2013 - The <i>HTML Working Group</i> is currently chartered to continue its work through 31 December 2014. A Plan 2014 document published by the...</p> ...
A citation is not a quote (for
which the q
element is appropriate).
This is incorrect usage, because cite
is not for
quotes:
<p><cite>This is wrong!, said Hillary.</cite> is a quote from the popular daytime TV drama When Ian became Hillary.</p>
This is an example of the correct usage:
<p><q>This is correct, said Hillary.</q> is a quote from the popular daytime TV drama <cite>When Ian became Hillary</cite>.</p>
q
elementcite
- Link to the source of the quotation or more information about the editaria-*
attributes
applicable to the allowed roles.HTMLQuoteElement
.The q
element represents some phrasing content quoted from another
source.
Quotation punctuation (such as quotation marks) that is quoting
the contents of the element must not appear immediately before,
after, or inside q
elements; they will be inserted into
the rendering by the user agent.
Content inside a q
element must be quoted from
another source, whose address, if it has one, may be cited in the
cite
attribute. The
source may be fictional, as when quoting characters in a novel or
screenplay.
If the cite
attribute is present, it must be a valid URL
potentially surrounded by spaces. To obtain the corresponding citation
link, the value of the attribute must be resolved relative to
the element. User agents may allow users to follow such citation links, but they are
primarily intended for private use (e.g. by server-side scripts collecting statistics about a
site's use of quotations), not for readers.
The q
element must not be used in place of quotation
marks that do not represent quotes; for example, it is inappropriate
to use the q
element for marking up sarcastic
statements.
The use of q
elements to mark up quotations is
entirely optional; using explicit quotation punctuation without
q
elements is just as correct.
Here is a simple example of the use of the q
element:
<p>The man said <q>Things that are impossible just take longer</q>. I disagreed with him.</p>
Here is an example with both an explicit citation link in the
q
element, and an explicit citation outside:
<p>The W3C page <cite>About W3C</cite> says the W3C's mission is <q cite="http://www.w3.org/Consortium/">To lead the World Wide Web to its full potential by developing protocols and guidelines that ensure long-term growth for the Web</q>. I disagree with this mission.</p>
In the following example, the quotation itself contains a quotation:
<p>In <cite>Example One</cite>, he writes <q>The man said <q>Things that are impossible just take longer</q>. I disagreed with him</q>. Well, I disagree even more!</p>
In the following example, quotation marks are used instead of
the q
element:
<p>His best argument was ❝I disagree❞, which I thought was laughable.</p>
In the following example, there is no quote — the
quotation marks are used to name a word. Use of the q
element in this case would be inappropriate.
<p>The word "ineffable" could have been used to describe the disaster resulting from the campaign's mismanagement.</p>
dfn
elementdfn
element descendants.title
attribute has special semantics on this element.aria-*
attributes
applicable to the allowed roles.HTMLElement
.The dfn
element represents the defining
instance of a term. The paragraph,
description list group, or section that is the nearest
ancestor of the dfn
element must also contain the
definition(s) for the term given
by the dfn
element.
Defining term: If the dfn
element has a
title
attribute, then
the exact value of that attribute is the term being defined.
Otherwise, if it contains exactly one element child node and no
child Text
nodes, and that child
element is an abbr
element with a title
attribute, then the exact value
of that attribute is the term being defined. Otherwise, it
is the exact textContent
of the dfn
element that gives the term being defined.
If the title
attribute of the
dfn
element is present, then it must contain only the
term being defined.
The title
attribute
of ancestor elements does not affect dfn
elements.
An a
element that links to a dfn
element represents an instance of the term defined by the
dfn
element.
In the following fragment, the term "Garage Door Opener" is first defined in the first paragraph, then used in the second. In both cases, its abbreviation is what is actually displayed.
<p>The <dfn><abbr title="Garage Door Opener">GDO</abbr></dfn> is a device that allows off-world teams to open the iris.</p> <!-- ... later in the document: --> <p>Teal'c activated his <abbr title="Garage Door Opener">GDO</abbr> and so Hammond ordered the iris to be opened.</p>
With the addition of an a
element, the reference
can be made explicit:
<p>The <dfn id=gdo><abbr title="Garage Door Opener">GDO</abbr></dfn> is a device that allows off-world teams to open the iris.</p> <!-- ... later in the document: --> <p>Teal'c activated his <a href=#gdo><abbr title="Garage Door Opener">GDO</abbr></a> and so Hammond ordered the iris to be opened.</p>
abbr
elementtitle
attribute has special semantics on this element.aria-*
attributes
applicable to the allowed roles.HTMLElement
.The abbr
element represents an abbreviation or acronym, optionally
with its expansion. The title
attribute may be
used to provide an expansion of the abbreviation. The attribute, if specified, must contain an
expansion of the abbreviation, and nothing else.
The paragraph below contains an abbreviation marked up with the abbr
element.
This paragraph defines the term "Web Hypertext Application
Technology Working Group".
<p>The <dfn id=whatwg><abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr></dfn> is a loose unofficial collaboration of Web browser manufacturers and interested parties who wish to develop new technologies designed to allow authors to write and deploy Applications over the World Wide Web.</p>
An alternative way to write this would be:
<p>The <dfn id=whatwg>Web Hypertext Application Technology Working Group</dfn> (<abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr>) is a loose unofficial collaboration of Web browser manufacturers and interested parties who wish to develop new technologies designed to allow authors to write and deploy Applications over the World Wide Web.</p>
This paragraph has two abbreviations. Notice how only one is defined; the other, with no
expansion associated with it, does not use the abbr
element.
<p>The <abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr> started working on HTML5 in 2004.</p>
This paragraph links an abbreviation to its definition.
<p>The <a href="#whatwg"><abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr></a> community does not have much representation from Asia.</p>
This paragraph marks up an abbreviation without giving an expansion, possibly as a hook to apply styles for abbreviations (e.g. smallcaps).
<p>Philip` and Dashiva both denied that they were going to get the issue counts from past revisions of the specification to backfill the <abbr>WHATWG</abbr> issue graph.</p>
If an abbreviation is pluralized, the expansion's grammatical number (plural vs singular) must match the grammatical number of the contents of the element.
Here the plural is outside the element, so the expansion is in the singular:
<p>Two <abbr title="Working Group">WG</abbr>s worked on this specification: the <abbr>WHATWG</abbr> and the <abbr>HTMLWG</abbr>.</p>
Here the plural is inside the element, so the expansion is in the plural:
<p>Two <abbr title="Working Groups">WGs</abbr> worked on this specification: the <abbr>WHATWG</abbr> and the <abbr>HTMLWG</abbr>.</p>
Abbreviations do not have to be marked up using this element. It is expected to be useful in the following cases:
abbr
element with a title
attribute is an
alternative to including the expansion inline (e.g. in parentheses).abbr
element with a title
attribute or include the expansion inline in the text the first
time the abbreviation is used.abbr
element
can be used without a title
attribute.Providing an expansion in a title
attribute once
will not necessarily cause other abbr
elements in the same document with the same
contents but without a title
attribute to behave as if they had
the same expansion. Every abbr
element is independent.
data
elementvalue
- Machine-readable value aria-*
attributes
applicable to the allowed roles.interface HTMLDataElement : HTMLElement { attribute DOMString value; };
The data
element represents its
contents, along with a machine-readable form of those contents in
the value
attribute.
The value
attribute must be present. Its value must be a representation of the
element's contents in a machine-readable format.
When the value is date- or time-related, the more
specific time
element can be used instead.
The element can be used for several purposes.
When combined with microformats or
microdata,
the element serves to provide both a machine-readable
value for the purposes of data processors, and a human-readable value
for the purposes of rendering in a Web browser. In this case, the
format to be used in the value
attribute is determined by the microformats or microdata
vocabulary in use.
The element can also, however, be used in conjunction with
scripts in the page, for when a script has a literal value to store
alongside a human-readable value. In such cases, the format to be
used depends only on the needs of the script. (The data-*
attributes can also be useful in
such situations.)
The value
IDL
attribute must reflect the content attribute of the
same name.
time
elementdatetime
- Machine-readable valuearia-*
attributes
applicable to the allowed roles.interface HTMLTimeElement : HTMLElement { attribute DOMString dateTime; };
The time
element represents its contents, along with a
machine-readable form of those contents in the datetime
attribute. The kind of content is limited to various kinds of dates, times, time-zone offsets, and
durations, as described below.
The datetime
attribute may be present. If
present, its value must be a representation of the element's contents in a machine-readable
format.
A time
element that does not have a datetime
content attribute must not have any element
descendants.
The datetime value of a time
element is the value of the element's
datetime
content attribute, if it has one, or the
element's textContent
, if it does not.
The datetime value of a time
element must match one of the following
syntaxes.
<time>2011-11</time>
<time>2011-11-12</time>
<time>11-12</time>
<time>14:54</time>
<time>14:54:39</time>
<time>14:54:39.929</time>
<time>2011-11-12T14:54</time>
<time>2011-11-12T14:54:39</time>
<time>2011-11-12T14:54:39.929</time>
<time>2011-11-12 14:54</time>
<time>2011-11-12 14:54:39</time>
<time>2011-11-12 14:54:39.929</time>
Times with dates but without a time zone offset are useful for specifying events that are observed at the same specific time in each time zone, throughout a day. For example, the 2020 new year is celebrated at 2020-01-01 00:00 in each time zone, not at the same precise moment across all time zones. For events that occur at the same time across all time zones, for example a videoconference meeting, a valid global date and time string is likely more useful.
<time>Z</time>
<time>+0000</time>
<time>+00:00</time>
<time>-0800</time>
<time>-08:00</time>
For times without dates (or times referring to events that recur on multiple dates), specifying the geographic location that controls the time is usually more useful than specifying a time zone offset, because geographic locations change time zone offsets with daylight savings time. In some cases, geographic locations even change time zone, e.g. when the boundaries of those time zones are redrawn, as happened with Samoa at the end of 2011. There exists a time zone database that describes the boundaries of time zones and what rules apply within each such zone, known as the time zone database. [TZDATABASE]
<time>2011-11-12T14:54Z</time>
<time>2011-11-12T14:54:39Z</time>
<time>2011-11-12T14:54:39.929Z</time>
<time>2011-11-12T14:54+0000</time>
<time>2011-11-12T14:54:39+0000</time>
<time>2011-11-12T14:54:39.929+0000</time>
<time>2011-11-12T14:54+00:00</time>
<time>2011-11-12T14:54:39+00:00</time>
<time>2011-11-12T14:54:39.929+00:00</time>
<time>2011-11-12T06:54-0800</time>
<time>2011-11-12T06:54:39-0800</time>
<time>2011-11-12T06:54:39.929-0800</time>
<time>2011-11-12T06:54-08:00</time>
<time>2011-11-12T06:54:39-08:00</time>
<time>2011-11-12T06:54:39.929-08:00</time>
<time>2011-11-12 14:54Z</time>
<time>2011-11-12 14:54:39Z</time>
<time>2011-11-12 14:54:39.929Z</time>
<time>2011-11-12 14:54+0000</time>
<time>2011-11-12 14:54:39+0000</time>
<time>2011-11-12 14:54:39.929+0000</time>
<time>2011-11-12 14:54+00:00</time>
<time>2011-11-12 14:54:39+00:00</time>
<time>2011-11-12 14:54:39.929+00:00</time>
<time>2011-11-12 06:54-0800</time>
<time>2011-11-12 06:54:39-0800</time>
<time>2011-11-12 06:54:39.929-0800</time>
<time>2011-11-12 06:54-08:00</time>
<time>2011-11-12 06:54:39-08:00</time>
<time>2011-11-12 06:54:39.929-08:00</time>
Times with dates and a time zone offset are useful for specifying specific events, or recurring virtual events where the time is not anchored to a specific geographic location. For example, the precise time of an asteroid impact, or a particular meeting in a series of meetings held at 1400 UTC every day, regardless of whether any particular part of the world is observing daylight savings time or not. For events where the precise time varies by the local time zone offset of a specific geographic location, a valid local date and time string combined with that geographic location is likely more useful.
<time>2011-W46</time>
<time>2011</time>
<time>0001</time>
<time>PT4H18M3S</time>
<time>4h 18m 3s</time>
The machine-readable equivalent of the element's contents must be obtained from the element's datetime value by using the following algorithm:
If parsing a month string from the element's datetime value returns a month, that is the machine-readable equivalent; abort these steps.
If parsing a date string from the element's datetime value returns a date, that is the machine-readable equivalent; abort these steps.
If parsing a yearless date string from the element's datetime value returns a yearless date, that is the machine-readable equivalent; abort these steps.
If parsing a time string from the element's datetime value returns a time, that is the machine-readable equivalent; abort these steps.
If parsing a local date and time string from the element's datetime value returns a local date and time, that is the machine-readable equivalent; abort these steps.
If parsing a time-zone offset string from the element's datetime value returns a time-zone offset, that is the machine-readable equivalent; abort these steps.
If parsing a global date and time string from the element's datetime value returns a global date and time, that is the machine-readable equivalent; abort these steps.
If parsing a week string from the element's datetime value returns a week, that is the machine-readable equivalent; abort these steps.
If the element's datetime value consists of only ASCII digits, at least one of which is not "0" (U+0030), then the machine-readable equivalent is the base-ten interpretation of those digits, representing a year; abort these steps.
If parsing a duration string from the element's datetime value returns a duration, that is the machine-readable equivalent; abort these steps.
There is no machine-readable equivalent.
The algorithms referenced above are intended to be designed such that for any arbitrary string s, only one of the algorithms returns a value. A more efficient approach might be to create a single algorithm that parses all these data types in one pass; developing such an algorithm is left as an exercise to the reader.
The dateTime
IDL attribute must
reflect the element's datetime
content
attribute.
The time
element can be used to encode dates, for example in microformats. The
following shows a hypothetical way of encoding an event using a variant on hCalendar that uses
the time
element:
<div class="vevent"> <a class="url" href="http://www.web2con.com/">http://www.web2con.com/</a> <span class="summary">Web 2.0 Conference</span>: <time class="dtstart" datetime="2005-10-05">October 5</time> - <time class="dtend" datetime="2005-10-07">7</time>, at the <span class="location">Argent Hotel, San Francisco, CA</span> </div>
Here, a fictional microdata vocabulary based on the Atom vocabulary is used with the
time
element to mark up a blog post's publication date.
<article itemscope itemtype="http://n.example.org/rfc4287"> <h1 itemprop="title">Big tasks</h1> <footer>Published <time itemprop="published" datetime="2009-08-29">two days ago</time>.</footer> <p itemprop="content">Today, I went out and bought a bike for my kid.</p> </article>
In this example, another article's publication date is marked up using time
, this
time using the schema.org microdata vocabulary:
<article itemscope itemtype="http://schema.org/BlogPosting"> <h1 itemprop="headline">Small tasks</h1> <footer>Published <time itemprop="datePublished" datetime="2009-08-30">yesterday</time>.</footer> <p itemprop="articleBody">I put a bike bell on his bike.</p> </article>
In the following snippet, the time
element is used to encode a date in the
ISO8601 format, for later processing by a script:
<p>Our first date was <time datetime="2006-09-23">a Saturday</time>.</p>
In this second snippet, the value includes a time:
<p>We stopped talking at <time datetime="2006-09-24T05:00-07:00">5am the next morning</time>.</p>
A script loaded by the page (and thus privy to the page's internal convention of marking up
dates and times using the time
element) could scan through the page and look at all
the time
elements therein to create an index of dates and times.
For example, this element conveys the string "Tuesday" with the additional semantic that the 12th of November 2011 is the meaning that corresponds to "Tuesday":
Today is <time datetime="2011-11-12">Tuesday</time>.
In this example, a specific time in the Pacific Standard Time timezone is specified:
Your next meeting is at <time datetime="2011-11-12T15:00-08:00">3pm</time>.
code
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The code
element represents a fragment of computer code. This could
be an XML element name, a file name, a computer program, or any other string that a computer would
recognize.
There is no formal way to indicate the language of computer code being marked up. Authors who
wish to mark code
elements with the language used, e.g. so that syntax highlighting
scripts can use the right rules, can use the class
attribute, e.g.
by adding a class prefixed with "language-
" to the element.
The following example shows how the element can be used in a paragraph to mark up element names and computer code, including punctuation.
<p>The <code>code</code> element represents a fragment of computer code.</p> <p>When you call the <code>activate()</code> method on the <code>robotSnowman</code> object, the eyes glow.</p> <p>The example below uses the <code>begin</code> keyword to indicate the start of a statement block. It is paired with an <code>end</code> keyword, which is followed by the <code>.</code> punctuation character (full stop) to indicate the end of the program.</p>
The following example shows how a block of code could be marked up using the pre
and code
elements.
<pre><code class="language-pascal">var i: Integer; begin i := 1; end.</code></pre>
A class is used in that example to indicate the language used.
See the pre
element for more details.
var
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The var
element represents a variable.
This could be an actual variable in a mathematical expression or
programming context, an identifier representing a constant, a symbol
identifying a physical quantity, a function parameter, or just be a
term used as a placeholder in prose.
In the paragraph below, the letter "n" is being used as a variable in prose:
<p>If there are <var>n</var> pipes leading to the ice cream factory then I expect at <em>least</em> <var>n</var> flavors of ice cream to be available for purchase!</p>
For mathematics, in particular for anything beyond the simplest
of expressions, MathML is more appropriate. However, the
var
element can still be used to refer to specific
variables that are then mentioned in MathML expressions.
In this example, an equation is shown, with a legend that
references the variables in the equation. The expression itself is
marked up with MathML, but the variables are mentioned in the
figure's legend using var
.
<figure> <math> <mi>a</mi> <mo>=</mo> <msqrt> <msup><mi>b</mi><mn>2</mn></msup> <mi>+</mi> <msup><mi>c</mi><mn>2</mn></msup> </msqrt> </math> <figcaption> Using Pythagoras' theorem to solve for the hypotenuse <var>a</var> of a triangle with sides <var>b</var> and <var>c</var> </figcaption> </figure>
Here, the equation describing mass-energy equivalence is used in a sentence, and the
var
element is used to mark the variables and constants in that equation:
<p>Then he turned to the blackboard and picked up the chalk. After a few moment's thought, he wrote <var>E</var> = <var>m</var> <var>c</var><sup>2</sup>. The teacher looked pleased.</p>
samp
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The samp
element represents (sample) output from a program or
computing system.
See the pre
and kbd
elements for more details.
This example shows the samp
element being used
inline:
<p>The computer said <samp>Too much cheese in tray two</samp> but I didn't know what that meant.</p>
This second example shows a block of sample output. Nested samp
and
kbd
elements allow for the styling of specific elements of the sample output using a
style sheet. There's also a few parts of the samp
that are annotated with even more
detailed markup, to enable very precise styling. To achieve this, span
elements are
used.
<pre><samp><span class="prompt">jdoe@mowmow:~$</span> <kbd>ssh demo.example.com</kbd> Last login: Tue Apr 12 09:10:17 2005 from mowmow.example.com on pts/1 Linux demo 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189 #1 SMP Tue Feb 1 11:22:36 PST 2005 i686 unknown <span class="prompt">jdoe@demo:~$</span> <span class="cursor">_</span></samp></pre>
kbd
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The kbd
element represents user input (typically keyboard input,
although it may also be used to represent other input, such as voice commands).
When the kbd
element is nested inside a samp
element, it represents
the input as it was echoed by the system.
When the kbd
element contains a samp
element, it represents
input based on system output, for example invoking a menu item.
When the kbd
element is nested inside another kbd
element, it
represents an actual key or other single unit of input as appropriate for the input mechanism.
Here the kbd
element is used to indicate keys to press:
<p>To make George eat an apple, press <kbd><kbd>Shift</kbd>+<kbd>F3</kbd></kbd></p>
In this second example, the user is told to pick a particular menu item. The outer
kbd
element marks up a block of input, with the inner kbd
elements
representing each individual step of the input, and the samp
elements inside them
indicating that the steps are input based on something being displayed by the system, in this
case menu labels:
<p>To make George eat an apple, select <kbd><kbd><samp>File</samp></kbd>|<kbd><samp>Eat Apple...</samp></kbd></kbd> </p>
Such precision isn't necessary; the following is equally fine:
<p>To make George eat an apple, select <kbd>File | Eat Apple...</kbd></p>
sub
and sup
elementsaria-*
attributes
applicable to the allowed roles.HTMLElement
.The sup
element represents a superscript and the sub
element represents a subscript.
These elements must be used only to mark up typographical conventions with specific meanings,
not for typographical presentation for presentation's sake. For example, it would be inappropriate
for the sub
and sup
elements to be used in the name of the LaTeX
document preparation system. In general, authors should use these elements only if the
absence of those elements would change the meaning of the content.
In certain languages, superscripts are part of the typographical conventions for some abbreviations.
<p>The most beautiful women are <span lang="fr"><abbr>M<sup>lle</sup></abbr> Gwendoline</span> and <span lang="fr"><abbr>M<sup>me</sup></abbr> Denise</span>.</p>
The sub
element can be used inside a var
element, for variables that
have subscripts.
Here, the sub
element is used to represent the subscript that identifies the
variable in a family of variables:
<p>The coordinate of the <var>i</var>th point is (<var>x<sub><var>i</var></sub></var>, <var>y<sub><var>i</var></sub></var>). For example, the 10th point has coordinate (<var>x<sub>10</sub></var>, <var>y<sub>10</sub></var>).</p>
Mathematical expressions often use subscripts and superscripts. Authors are encouraged to use
MathML for marking up mathematics, but authors may opt to use sub
and
sup
if detailed mathematical markup is not desired. [MATHML]
<var>E</var>=<var>m</var><var>c</var><sup>2</sup>
f(<var>x</var>, <var>n</var>) = log<sub>4</sub><var>x</var><sup><var>n</var></sup>
i
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The i
element represents a span of text in an alternate voice or
mood, or otherwise offset from the normal prose in a manner indicating a different quality of
text, such as a taxonomic designation, a technical term, an idiomatic phrase from another
language, transliteration, a thought, or a ship name in Western texts.
Terms in languages different from the main text should be annotated with lang
attributes (or, in XML, lang
attributes in the XML namespace).
The examples below show uses of the i
element:
<p>The <i class="taxonomy">Felis silvestris catus</i> is cute.</p> <p>The term <i>prose content</i> is defined above.</p> <p>There is a certain <i lang="fr">je ne sais quoi</i> in the air.</p>
In the following example, a dream sequence is marked up using
i
elements.
<p>Raymond tried to sleep.</p> <p><i>The ship sailed away on Thursday</i>, he dreamt. <i>The ship had many people aboard, including a beautiful princess called Carey. He watched her, day-in, day-out, hoping she would notice him, but she never did.</i></p> <p><i>Finally one night he picked up the courage to speak with her—</i></p> <p>Raymond woke with a start as the fire alarm rang out.</p>
Authors can use the class
attribute on the i
element to identify why the element is being used, so that if the style of a particular use (e.g.
dream sequences as opposed to taxonomic terms) is to be changed at a later date, the author
doesn't have to go through the entire document (or series of related documents) annotating each
use.
Authors are encouraged to consider whether other elements might be more applicable than the
i
element, for instance the em
element for marking up stress emphasis,
or the dfn
element to mark up the defining instance of a term.
Style sheets can be used to format i
elements, just like any other
element can be restyled. Thus, it is not the case that content in i
elements will
necessarily be italicized.
b
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The b
element represents a span of text to which attention is being
drawn for utilitarian purposes without conveying any extra importance and with no implication of
an alternate voice or mood, such as key words in a document abstract, product names in a review,
actionable words in interactive text-driven software, or an article lede.
The following example shows a use of the b
element to highlight key words without
marking them up as important:
<p>The <b>frobonitor</b> and <b>barbinator</b> components are fried.</p>
In the following example, objects in a text adventure are highlighted as being special by use
of the b
element.
<p>You enter a small room. Your <b>sword</b> glows brighter. A <b>rat</b> scurries past the corner wall.</p>
Another case where the b
element is appropriate is in marking up the lede (or
lead) sentence or paragraph. The following example shows how a BBC article about
kittens adopting a rabbit as their own could be marked up:
<article> <h2>Kittens 'adopted' by pet rabbit</h2> <p><b class="lede">Six abandoned kittens have found an unexpected new mother figure — a pet rabbit.</b></p> <p>Veterinary nurse Melanie Humble took the three-week-old kittens to her Aberdeen home.</p> [...]
As with the i
element, authors can use the class
attribute on the b
element to identify why the element is being used, so that if the
style of a particular use is to be changed at a later date, the author doesn't have to go through
annotating each use.
The b
element should be used as a last resort when no other element is more
appropriate. In particular, headings should use the h1
to h6
elements,
stress emphasis should use the em
element, importance should be denoted with the
strong
element, and text marked or highlighted should use the mark
element.
The following would be incorrect usage:
<p><b>WARNING!</b> Do not frob the barbinator!</p>
In the previous example, the correct element to use would have been strong
, not
b
.
Style sheets can be used to format b
elements, just like any other
element can be restyled. Thus, it is not the case that content in b
elements will
necessarily be boldened.
u
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The u
element represents a span of text with an unarticulated, though
explicitly rendered, non-textual annotation, such as labeling the text as being a proper name in
Chinese text (a Chinese proper name mark), or labeling the text as being misspelt.
In most cases, another element is likely to be more appropriate: for marking stress emphasis,
the em
element should be used; for marking key words or phrases either the
b
element or the mark
element should be used, depending on the context;
for marking book titles, the cite
element should be used; for labeling text with explicit textual annotations, the
ruby
element should be used; for labeling ship names in Western texts, the
i
element should be used.
The default rendering of the u
element in visual presentations
clashes with the conventional rendering of hyperlinks (underlining). Authors are encouraged to
avoid using the u
element where it could be confused for a hyperlink.
mark
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The mark
element represents a run of text in one document marked or
highlighted for reference purposes, due to its relevance in another context. When used in a
quotation or other block of text referred to from the prose, it indicates a highlight that was not
originally present but which has been added to bring the reader's attention to a part of the text
that might not have been considered important by the original author when the block was originally
written, but which is now under previously unexpected scrutiny. When used in the main prose of a
document, it indicates a part of the document that has been highlighted due to its likely
relevance to the user's current activity.
This example shows how the mark
element can be used to bring attention to a
particular part of a quotation:
<p lang="en-US">Consider the following quote:</p> <blockquote lang="en-GB"> <p>Look around and you will find, no-one's really <mark>colour</mark> blind.</p> </blockquote> <p lang="en-US">As we can tell from the <em>spelling</em> of the word, the person writing this quote is clearly not American.</p>
(If the goal was to mark the element as misspelt, however, the u
element,
possibly with a class, would be more appropriate.)
Another example of the mark
element is highlighting parts of a document that are
matching some search string. If someone looked at a document, and the server knew that the user
was searching for the word "kitten", then the server might return the document with one paragraph
modified as follows:
<p>I also have some <mark>kitten</mark>s who are visiting me these days. They're really cute. I think they like my garden! Maybe I should adopt a <mark>kitten</mark>.</p>
In the following snippet, a paragraph of text refers to a specific part of a code fragment.
<p>The highlighted part below is where the error lies:</p> <pre><code>var i: Integer; begin i := <mark>1.1</mark>; end.</code></pre>
This is separate from syntax highlighting, for which span
is more
appropriate. Combining both, one would get:
<p>The highlighted part below is where the error lies:</p> <pre><code><span class=keyword>var</span> <span class=ident>i</span>: <span class=type>Integer</span>; <span class=keyword>begin</span> <span class=ident>i</span> := <span class=literal><mark>1.1</mark></span>; <span class=keyword>end</span>.</code></pre>
This is another example showing the use of mark
to highlight a part of quoted
text that was originally not emphasized. In this example, common typographic conventions have led
the author to explicitly style mark
elements in quotes to render in italics.
<article> <style scoped> blockquote mark, q mark { font: inherit; font-style: italic; text-decoration: none; background: transparent; color: inherit; } .bubble em { font: inherit; font-size: larger; text-decoration: underline; } </style> <h1>She knew</h1> <p>Did you notice the subtle joke in the joke on panel 4?</p> <blockquote> <p class="bubble">I didn't <em>want</em> to believe. <mark>Of course on some level I realized it was a known-plaintext attack.</mark> But I couldn't admit it until I saw for myself.</p> </blockquote> <p>(Emphasis mine.) I thought that was great. It's so pedantic, yet it explains everything neatly.</p> </article>
Note, incidentally, the distinction between the em
element in this example, which
is part of the original text being quoted, and the mark
element, which is
highlighting a part for comment.
The following example shows the difference between denoting the importance of a span
of text (strong
) as opposed to denoting the relevance of a span of text
(mark
). It is an extract from a textbook, where the extract has had the parts
relevant to the exam highlighted. The safety warnings, important though they may be, are
apparently not relevant to the exam.
<h3>Wormhole Physics Introduction</h3> <p><mark>A wormhole in normal conditions can be held open for a maximum of just under 39 minutes.</mark> Conditions that can increase the time include a powerful energy source coupled to one or both of the gates connecting the wormhole, and a large gravity well (such as a black hole).</p> <p><mark>Momentum is preserved across the wormhole. Electromagnetic radiation can travel in both directions through a wormhole, but matter cannot.</mark></p> <p>When a wormhole is created, a vortex normally forms. <strong>Warning: The vortex caused by the wormhole opening will annihilate anything in its path.</strong> Vortexes can be avoided when using sufficiently advanced dialing technology.</p> <p><mark>An obstruction in a gate will prevent it from accepting a wormhole connection.</mark></p>
ruby
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.
The ruby
element allows one or more spans of phrasing content to be marked with
ruby annotations. Ruby annotations are short runs of text presented alongside base text,
primarily used in East Asian typography as a guide for pronunciation or to include other
annotations. In Japanese, this form of typography is also known as furigana. Ruby text
can appear on either side, and sometimes both sides, of the base text, and it is possible to
control its position using CSS. A more complete introduction to ruby can be found in the
Use Cases & Exploratory Approaches for Ruby Markup document as well as in
CSS Ruby Module Level 1. [RUBY-UC] [CSSRUBY]
The content model of ruby
elements consists of one or more of the following
sequences:
rb
elements.
rt
or rtc
elements, each of which either immediately
preceded or followed by an rp
elements.
The ruby
, rb
, rtc
, and rt
elements can be
used for a variety of kinds of annotations, including in particular (though by no means limited
to) those described below. For more details on Japanese Ruby in particular, and how to render
Ruby for Japanese, see Requirements for Japanese Text Layout. [JLREQ] The rp
element can be used as fallback content when
ruby rendering is not supported.
Annotations (the ruby text) are associated individually with each ideographic character (the base text). In Japanese this is typically hiragana or katakana characters used to provide readings of kanji characters.
<ruby>base<rt>annotation</ruby>
When no rb
element is used, the base is implied, as above. But you can also
make it explicit. This can be useful notably for styling, or when consecutive bases are
to be treated as a group, as in the jukugo ruby example further down.
<ruby><rb>base<rt>annotation</ruby>
In the following example, notice how each annotation corresponds to a single base character.
<ruby>日<rt>に</rt></ruby><ruby>本<rt>ほん</rt></ruby> <ruby>語<rt>ご</rt></ruby>で<ruby>書<rt>か</rt></ruby> いた<ruby>作<rt>さく</rt></ruby><ruby>文<rt>ぶん</rt></ruby>です。
Ruby text interspersed in regular text provides structure akin to the following image:
This example can also be written as follows, using one ruby
element with
two segments of base text and two annotations (one for each) rather than two
back-to-back ruby
elements each with one base text segment and annotation
(as in the markup above):
<ruby>日<rt>に</rt>本<rt>ほん</rt>語<rt>ご</rt></ruby> で<ruby>書<rt>か</rt></ruby> いた<ruby>作<rt>さく</rt>文<rt>ぶん</rt></ruby>です。
Group ruby is often used where phonetic annotations don't map to discreet base characters, or for semantic glosses that span the whole base text. For example, the word "today" is written with the characters 今日, literally "this day". But it's pronounced きょう (kyou), which can't be broken down into a "this" part and a "day" part. In typical rendering, you can't split text that is annotated with group ruby; it has to wrap as a single unit onto the next line. When a ruby text annotation maps to a base that is comprised of more than one character, then that base is grouped.
The following group ruby:
Can be marked up as follows:
<ruby>今日<rt>きょう</ruby>
Jukugo refers to a Japanese compound noun, i.e. a word made up of more than one kanji character. Jukugo ruby is a term that is used not to describe ruby annotations over jukugo text, but rather to describe ruby with a behaviour slightly different from mono or group ruby. Jukugo ruby is similar to mono ruby, in that there is a strong association between ruby text and individual base characters, but the ruby text is typically rendered as grouped together over multiple ideographs when they are on the same line.
The distinction is captured in this example:
Which can be marked up as follows:
<ruby>法<rb>華<rb>経<rt>ほ<rt>け<rt>きょう</ruby>
In this example, each rt
element is paired with its respective
rb
element, the difference with an interleaved
rb
/rt
approach being that the sequences of both base text and
ruby annotations are implicitly placed in common containers so that the grouping
information is captured.
For more details on Jukugo Ruby rendering, see Appendix F in the Requirements for Japanese Text Layout and Use Case C: Jukugo ruby in the Use Cases & Exploratory Approaches for Ruby Markup. [JLREQ] [RUBY-UC]
In some contexts, for instance when the font size or line height are too small for ruby to be readable, it is desirable to inline the ruby annotation such that it appears in parentheses after the text it annotates. This also provides a convenient fallback strategy for user agents that do not support rendering ruby annotations.
Inlining takes grouping into account. For example, Tokyo is written with two kanji characters, 東, which is pronounced とう, and 京, which is pronounced きょう. Each base character should be annotated individually, but the fallback should be 東京(とうきょう) not 東(とう)京(きょう). This can be marked up as follows:
<ruby>東<rb>京<rt>とう<rt>きょう</ruby>
Note that the above markup will enable the usage of parentheses when inlining for
browsers that support ruby layout, but for those that don't it will fail to provide
parenthetical fallback. This is where the rp
element is useful. It can be
inserted into the above example to provide the appropriate fallback when ruby layout is
not supported:
<ruby>東<rb>京<rp>(<rt>とう<rt>きょう<rp>)</ruby>
Sometimes, ruby can be used to annotate a base twice.
In the following example, the Chinese word for San Francisco (旧金山, i.e. “old gold mountain”) is annotated both using pinyin to give the pronunciation, and with the original English.
Which is marked up as follows:
<ruby><rb>旧<rb>金<rb>山<rt>jiù<rt>jīn<rt>shān<rtc>San Francisco</ruby>
In this example, a single base run of three base characters is annotated with three
pinyin ruby text segments in a first (implicit) container, and an rtc
element is introduced in order to provide a second single ruby text annotation
being the city's English name.
We can also revisit our jukugo example above with 上手 ("skill") to show how it can be annotation in both kana and romaji phonetics while at the same time maintaining the pairing to bases and annotation grouping information.
Which is marked up as follows:
<ruby><rb>上<rb>手<rt>じよう<rt>ず<rtc><rt>jou<rt>zu</ruby>
Text that is a direct child of the rtc
element implicitly produces a ruby
text segment as if it were contained in an rt
element. In this contrived
example, this is shown with some symbols that are given names in English and French with
annotations intended to appear on either side of the base symbol.
<ruby> ♥<rt>Heart<rtc lang=fr>Cœur</rtc> ☘<rt>Shamrock<rtc lang=fr>Trèfle</rtc> ✶<rt>Star<rtc lang=fr>Étoile </ruby>
Similarly, text directly inside a ruby
element implicitly produces a ruby
base as if it were contained in an rb
element, and rt
children
of ruby
are implicitly contained in an rtc
container. In
effect, the above example is equivalent (in meaning, though not in the DOM it produces)
to the following:
<ruby> <rb>♥</rb><rtc><rt>Heart</rt></rtc><rtc lang=fr><rt>Cœur</rt></rtc> <rb>☘</rb><rtc><rt>Shamrock</rt></rtc><rtc lang=fr><rt>Trèfle</rt></rtc> <rb>✶</rb><rtc><rt>Star</rt></rtc><rtc lang=fr><rt>Étoile</rt></rtc> </ruby>
Within a ruby element, content is parcelled into a series of ruby segments. Each ruby segment is described by:
rb
element.
rtc
elements, or to sequences of rt
elements implicitly recognised as contained in an anonymous ruby text
container.
Each ruby text container is described by zero or more ruby text annotations each of which is a DOM range that may contain
phrasing content or an rt
element, and an annotations range that is a range
including all the annotations for that container. A ruby text container is also
known (primarily in a CSS context) as a ruby annotation container.
Furthermore, a ruby element contains ignored ruby content. Ignored ruby content
does not form part of the document's semantics. It consists of some inter-element
whitespace and rp
elements, the latter of which are used for legacy user
agents that do not support ruby at all.
The process of annotation pairing associates ruby annotations with ruby bases. Within each ruby segment, each ruby base in the ruby base container is paired with one ruby text annotation from the ruby text container, in order. If there are not enough ruby text annotations in a ruby annotation container, the last one is associated with any excess ruby bases. (If there are not any in the ruby annotation container, an anonymous empty one is assumed to exist.) If there are not enough ruby bases, any remaining ruby text annotations are assumed to be associated with empty, anonymous bases inserted at the end of the ruby base container.
Note that the terms ruby segment, ruby base, ruby text annotation, ruby text container, ruby base container, and ruby annotation container have their equivalents in CSS Ruby Module Level 1. [CSSRUBY]
Informally, the segmentation and categorisation algorithm below performs a simple set of
tasks. First it processes adjacent rb
elements, text nodes, and non-ruby
elements into a list of bases. Then it processes any number of rtc
elements or
sequences of rt
elements that are considered to automatically map to an
anonymous ruby text container. Put together these data items form a ruby
segment as detailed in the data model above. It will continue to produce such segments
until it reaches the end of the content of a given ruby
element. The complexity
of the algorithm below compared to this informal description stems from the need to support
an author-friendly syntax and being mindful of inter-element white space.
At any particular time, the segmentation and categorisation of content of a ruby
element
is the result that would be obtained from running the following algorithm:
ruby
element for which the algorithm is
being run.
ruby
element ancestor, then abort these
steps.
rp
element, then increment
index by one and jump to the step labelled process a ruby child. (Note
that this has the effect of including this element in any range that we are currently
processing. This is done intentionally so that misplaced rp
can be
processed correctly; semantically they are ignored all the same.)
rt
element, then run these substeps:
rtc
element, then run these
substeps:
rtc
element and a DOM range whose start is
the boundary point (root,
index) and whose end is the boundary point (root, index plus
one). Append this new ruby annotation container at the end of current
annotation containers.
rt
element, an
rtc
element, or an rp
element, then set
index to the value of lookahead index and jump to the step
labelled process a ruby child.
rb
element, then run these substeps:
When the steps above say to commit a ruby segment, it means to run the following steps at that point in the algorithm:
When the steps above say to commit the base range, it means to run the following steps at that point in the algorithm:
When the steps above say to commit current annotations, it means to run the following steps at that point in the algorithm:
When the steps above say to commit an automatic base, it means to run the following steps at that point in the algorithm:
rb
elementruby
element.An rb
element's end tag may be omitted
if the rb
element is immediately followed by an rb
, rt
,
rtc
or rp
element, or if there is no more content in the parent
element.
aria-*
attributes
applicable to the allowed roles.HTMLElement
.
The rb
element marks the base text component of a ruby annotation. When it is
the child of a ruby
element, it doesn't represent anything itself, but its parent ruby
element uses it as part of determining what it represents.
An rb
element that is not a child of a ruby
element
represents the same thing as its children.
rt
elementruby
or of an rtc
element.An rt
element's end tag may be omitted if the
rt
element is immediately followed by an rb
, rt
or
rp
element, or if there is no more content in the parent element.
aria-*
attributes
applicable to the allowed roles.HTMLElement
.
The rt
element marks the ruby text component of a ruby annotation. When it is
the child of a ruby
element or of an rtc
element that is itself
the child of a ruby
element, it doesn't represent anything itself, but its ancestor ruby
element uses it as part of determining what it represents.
An rt
element that is not a child of a ruby
element or of an
rtc
element that is itself the child of a ruby
element
represents the same thing as its children.
rtc
elementruby
element.An rtc
element's end tag may be omitted
if the rtc
element is immediately followed by an rb
, rt
,
rtc
or rp
element, or if there is no more content in the parent
element.
aria-*
attributes
applicable to the allowed roles.HTMLElement
.
The rtc
element marks a ruby text container for ruby text components
in a ruby annotation. When it is the child of a ruby
element it doesn't represent anything itself, but its parent ruby
element
uses it as part of determining what it represents.
An rtc
element that is not a child of a ruby
element
represents the same thing as its children.
When an rtc
element is processed as part of the segmentation and
categorisation of content for a ruby
element, the following algorithm
defines how to process an rtc
element:
rtc
element for which the algorithm is
being run.
rt
element, then run these substeps:
When the steps above say to commit an automatic annotation, it means to run the following steps at that point in the algorithm:
rp
elementruby
element, either immediately before or immediately
after an rt
or rtc
element.
An rb
element's end tag may be omitted
if the rb
element is immediately followed by an rb
, rt
,
rtc
or rp
element, or if there is no more content in the parent
element.
aria-*
attributes
applicable to the allowed roles.HTMLElement
.
The rp
element is used to provide fallback text to be shown by user agents that
don't support ruby annotations. One widespread convention is to provide parentheses around
the ruby text component of a ruby annotation.
The contents of the rp
elements are typically not displayed by user agents
which do support ruby annotations
An rp
element that is a child of a ruby
element represents nothing. An rp
element whose parent element is not a ruby
element represents its
children.
The example shown previously, in which each ideograph in the text 漢字 is annotated with its phonetic reading, could be expanded
to use rp
so that in legacy user agents the readings are in parentheses (please
note that white space has been introduced into this example in order to make it more
readable):
...
<ruby>
漢
<rb>字</rb>
<rp> (</rp>
<rt>かん</rt>
<rt>じ</rt>
<rp>) </rp>
</ruby>
...
In conforming user agents the rendering would be as above, but in user agents that do not support ruby, the rendering would be:
... 漢字 (かんじ) ...
When there are multiple annotations for a segment, rp
elements can also be
placed between the annotations. Here is another copy of an earlier contrived example showing
some symbols with names given in English and French using double-sided annotations, but this
time with rp
elements as well:
<ruby> ♥<rp>: </rp><rt>Heart</rt><rp>, </rp><rtc><rt lang=fr>Cœur</rt></rtc><rp>.</rp> ☘<rp>: </rp><rt>Shamrock</rt><rp>, </rp><rtc><rt lang=fr>Trèfle</rt></rtc><rp>.</rp> ✶<rp>: </rp><rt>Star</rt><rp>, </rp><rtc><rt lang=fr>Étoile</rt></rtc><rp>.</rp> </ruby>
This would make the example render as follows in non-ruby-capable user agents:
♥: Heart, Cœur. ☘: Shamrock, Trèfle. ✶: Star, Étoile.
bdi
elementdir
global attribute has special semantics on this element.aria-*
attributes
applicable to the allowed roles.HTMLElement
.The bdi
element represents a span of text that is to be isolated from
its surroundings for the purposes of bidirectional text formatting. [BIDI]
The dir
global attribute defaults to auto
on this element (it never inherits from the parent element like
with other elements).
This element is especially useful when embedding user-generated content with an unknown directionality.
In this example, usernames are shown along with the number of posts that the user has
submitted. If the bdi
element were not used, the username of the Arabic user would
end up confusing the text (the bidirectional algorithm would put the colon and the number "3"
next to the word "User" rather than next to the word "posts").
<ul> <li>User <bdi>jcranmer</bdi>: 12 posts. <li>User <bdi>hober</bdi>: 5 posts. <li>User <bdi>إيان</bdi>: 3 posts. </ul>
bdo
elementdir
global attribute has special semantics on this element.aria-*
attributes
applicable to the allowed roles.HTMLElement
.The bdo
element represents explicit text directionality formatting
control for its children. It allows authors to override the Unicode bidirectional algorithm by
explicitly specifying a direction override. [BIDI]
Authors must specify the dir
attribute on this element, with the
value ltr
to specify a left-to-right override and with the value rtl
to
specify a right-to-left override. The auto
value must not be specified.
span
elementaria-*
attributes
applicable to the allowed roles.interface HTMLSpanElement : HTMLElement {};
The span
element doesn't mean anything on its own,
but can be useful when used together with the global
attributes, e.g. class
, lang
, or dir
.
It represents its children.
In this example, a code fragment is marked up using
span
elements and class
attributes so that its keywords and
identifiers can be color-coded from CSS:
<pre><code class="lang-c"><span class="keyword">for</span> (<span class="ident">j</span> = 0; <span class="ident">j</span> < 256; <span class="ident">j</span>++) { <span class="ident">i_t3</span> = (<span class="ident">i_t3</span> & 0x1ffff) | (<span class="ident">j</span> << 17); <span class="ident">i_t6</span> = (((((((<span class="ident">i_t3</span> >> 3) ^ <span class="ident">i_t3</span>) >> 1) ^ <span class="ident">i_t3</span>) >> 8) ^ <span class="ident">i_t3</span>) >> 5) & 0xff; <span class="keyword">if</span> (<span class="ident">i_t6</span> == <span class="ident">i_t1</span>) <span class="keyword">break</span>; }</code></pre>
br
elementaria-*
attributes
applicable to the allowed roles.interface HTMLBRElement : HTMLElement {};
The br
element represents a line break.
While line breaks are usually represented in visual media by physically moving subsequent text to a new line, a style sheet or user agent would be equally justified in causing line breaks to be rendered in a different manner, for instance as green dots, or as extra spacing.
br
elements must be used only for line breaks that are actually part of the
content, as in poems or addresses.
The following example is correct usage of the br
element:
<p>P. Sherman<br> 42 Wallaby Way<br> Sydney</p>
br
elements must not be used for separating thematic groups in a paragraph.
The following examples are non-conforming, as they abuse the br
element:
<p><a ...>34 comments.</a><br> <a ...>Add a comment.</a></p>
<p><label>Name: <input name="name"></label><br> <label>Address: <input name="address"></label></p>
Here are alternatives to the above, which are correct:
<p><a ...>34 comments.</a></p> <p><a ...>Add a comment.</a></p>
<p><label>Name: <input name="name"></label></p> <p><label>Address: <input name="address"></label></p>
If a paragraph consists of nothing but a single br
element, it
represents a placeholder blank line (e.g. as in a template). Such blank lines must not be used for
presentation purposes.
Any content inside br
elements must not be considered part of the surrounding
text.
This element has rendering requirements involving the bidirectional algorithm.
wbr
elementaria-*
attributes
applicable to the allowed roles.HTMLElement
.The wbr
element represents a line break opportunity.
In the following example, someone is quoted as saying something which, for effect, is written
as one long word. However, to ensure that the text can be wrapped in a readable fashion, the
individual words in the quote are separated using a wbr
element.
<p>So then he pointed at the tiger and screamed "there<wbr>is<wbr>no<wbr>way<wbr>you<wbr>are<wbr>ever<wbr>going<wbr>to<wbr>catch<wbr>me"!</p>
Here, especially long lines of code in a program listing have suggested wrapping points given
using wbr
elements.
<pre>... Heading heading = Helm.HeadingFactory(HeadingCoordinates[1], <wbr>HeadingCoordinates[2], <wbr>HeadingCoordinates[3], <wbr>HeadingCoordinates[4]); Course course = Helm.CourseFactory(Heading, <wbr>Maps.MapFactoryFromHeading(heading), <wbr>Speeds.GetMaximumSpeed().ConvertToWarp()); ...</pre>
Any content inside wbr
elements must not be considered part of the surrounding
text.
This element has rendering requirements involving the bidirectional algorithm.
This section is non-normative.
Element | Purpose | Example |
---|---|---|
a
| Hyperlinks | Visit my <a href="drinks.html">drinks</a> page. |
em
| Stress emphasis | I must say I <em>adore</em> lemonade. |
strong
| Importance | This tea is <strong>very hot</strong>. |
small
| Side comments | These grapes are made into wine. <small>Alcohol is addictive.</small> |
s
| Inaccurate text | Price: <s>£4.50</s> £2.00! |
cite
| Titles of works | The case <cite>Hugo v. Danielle</cite> is relevant here. |
q
| Quotations | The judge said <q>You can drink water from the fish tank</q> but advised against it. |
dfn
| Defining instance | The term <dfn>organic food</dfn> refers to food produced without synthetic chemicals. |
abbr
| Abbreviations | Organic food in Ireland is certified by the <abbr title="Irish Organic Farmers and Growers Association">IOFGA</abbr>. |
data
| Machine-readable equivalent | Available starting today! <data value="UPC:022014640201">North Coast Organic Apple Cider</data> |
time
| Machine-readable equivalent of date- or time-related data | Available starting on <time datetime="2011-11-12">November 12th</time>! |
code
| Computer code | The <code>fruitdb</code> program can be used for tracking fruit production. |
var
| Variables | If there are <var>n</var> fruit in the bowl, at least <var>n</var>÷2 will be ripe. |
samp
| Computer output | The computer said <samp>Unknown error -3</samp>. |
kbd
| User input | Hit <kbd>F1</kbd> to continue. |
sub
| Subscripts | Water is H<sub>2</sub>O. |
sup
| Superscripts | The Hydrogen in heavy water is usually <sup>2</sup>H. |
i
| Alternative voice | Lemonade consists primarily of <i>Citrus limon</i>. |
b
| Keywords | Take a <b>lemon</b> and squeeze it with a <b>juicer</b>. |
u
| Annotations | The mixture of apple juice and <u class="spelling">eldeflower</u> juice is very pleasant. |
mark
| Highlight | Elderflower cordial, with one <mark>part</mark> cordial to ten <mark>part</mark>s water, stands a<mark>part</mark> from the rest. |
ruby , rb , rp , rt , rtc
| Ruby annotations | <ruby> <rb>OJ <rp>(<rtc><rt>Orange Juice</rtc><rp>)</ruby> |
bdi
| Text directionality isolation | The recommended restaurant is <bdi lang="">My Juice Café (At The Beach)</bdi>. |
bdo
| Text directionality formatting | The proposal is to write English, but in reverse order. "Juice" would become "<bdo dir=rtl>Juice</bdo>" |
span
| Other | In French we call it <span lang="fr">sirop de sureau</span>. |
br
| Line break | Simply Orange Juice Company<br>Apopka, FL 32703<br>U.S.A. |
wbr
| Line breaking opportunity | www.simply<wbr>orange<wbr>juice.com |
The ins
and del
elements represent edits to the document.
ins
elementcite
- Link to the source of the quotation or more information about the edit datetime
- Date and (optionally) time of the change aria-*
attributes
applicable to the allowed roles.HTMLModElement
interface.The ins
element represents an addition to the document.
The following represents the addition of a single paragraph:
<aside> <ins> <p> I like fruit. </p> </ins> </aside>
As does the following, because everything in the aside
element here counts as
phrasing content and therefore there is just one paragraph:
<aside> <ins> Apples are <em>tasty</em>. </ins> <ins> So are pears. </ins> </aside>
ins
elements should not cross implied paragraph
boundaries.
The following example represents the addition of two paragraphs, the second of which was
inserted in two parts. The first ins
element in this example thus crosses a
paragraph boundary, which is considered poor form.
<aside> <!-- don't do this --> <ins datetime="2005-03-16 00:00Z"> <p> I like fruit. </p> Apples are <em>tasty</em>. </ins> <ins datetime="2007-12-19 00:00Z"> So are pears. </ins> </aside>
Here is a better way of marking this up. It uses more elements, but none of the elements cross implied paragraph boundaries.
<aside> <ins datetime="2005-03-16 00:00Z"> <p> I like fruit. </p> </ins> <ins datetime="2005-03-16 00:00Z"> Apples are <em>tasty</em>. </ins> <ins datetime="2007-12-19 00:00Z"> So are pears. </ins> </aside>
del
elementcite
- Link to the source of the quotation or more information about the edit datetime
- Date and (optionally) time of the change aria-*
attributes
applicable to the allowed roles.HTMLModElement
interface.The del
element represents a removal from the document.
del
elements should not cross implied paragraph
boundaries.
The following shows a "to do" list where items that have been done are crossed-off with the date and time of their completion.
<h1>To Do</h1> <ul> <li>Empty the dishwasher</li> <li><del datetime="2009-10-11T01:25-07:00">Watch Walter Lewin's lectures</del></li> <li><del datetime="2009-10-10T23:38-07:00">Download more tracks</del></li> <li>Buy a printer</li> </ul>
ins
and del
elementsThe cite
attribute may be used to specify the
address of a document that explains the change. When that document is long, for instance the
minutes of a meeting, authors are encouraged to include a fragment identifier pointing to the
specific part of that document that discusses the change.
If the cite
attribute is present, it must be a valid
URL potentially surrounded by spaces that explains the change. To obtain
the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents may allow users to follow such
citation links, but they are primarily intended for private use (e.g. by server-side scripts
collecting statistics about a site's edits), not for readers.
The datetime
attribute may be used to specify
the time and date of the change.
If present, the datetime
attribute's value must be a
valid date string with optional time.
User agents must parse the datetime
attribute according
to the parse a date or time string algorithm. If that doesn't return a date or a global date and time,
then the modification has no associated timestamp (the value is non-conforming; it is not a
valid date string with optional time). Otherwise, the modification is marked as
having been made at the given date or global date and time. If the given value is a global date and time then user agents should use the associated
time-zone offset information to determine which time zone to present the given datetime in.
This value may be shown to the user, but it is primarily intended for private use.
The ins
and del
elements must implement the
HTMLModElement
interface:
interface HTMLModElement : HTMLElement { attribute DOMString cite; attribute DOMString dateTime; };
The cite
IDL attribute must reflect
the element's cite
content attribute. The dateTime
IDL attribute must reflect the
element's datetime
content attribute.
This section is non-normative.
Since the ins
and del
elements do not affect paragraphing, it is possible, in some cases where paragraphs are implied (without explicit p
elements), for an
ins
or del
element to span both an entire paragraph or other
non-phrasing content elements and part of another paragraph. For example:
<section> <ins> <p> This is a paragraph that was inserted. </p> This is another paragraph whose first sentence was inserted at the same time as the paragraph above. </ins> This is a second sentence, which was there all along. </section>
By only wrapping some paragraphs in p
elements, one can even get the end of one
paragraph, a whole second paragraph, and the start of a third paragraph to be covered by the same
ins
or del
element (though this is very confusing, and not considered
good practice):
<section> This is the first paragraph. <ins>This sentence was inserted. <p>This second paragraph was inserted.</p> This sentence was inserted too.</ins> This is the third paragraph in this example. <!-- (don't do this) --> </section>
However, due to the way implied paragraphs are defined, it is
not possible to mark up the end of one paragraph and the start of the very next one using the same
ins
or del
element. You instead have to use one (or two) p
element(s) and two ins
or del
elements, as for example:
<section> <p>This is the first paragraph. <del>This sentence was deleted.</del></p> <p><del>This sentence was deleted too.</del> That sentence needed a separate <del> element.</p> </section>
Partly because of the confusion described above, authors are strongly encouraged to always mark
up all paragraphs with the p
element, instead of having ins
or
del
elements that cross implied paragraphs
boundaries.
This section is non-normative.
The content models of the ol
and ul
elements do not allow
ins
and del
elements as children. Lists always represent all their
items, including items that would otherwise have been marked as deleted.
To indicate that an item is inserted or deleted, an ins
or del
element can be wrapped around the contents of the li
element. To indicate that an
item has been replaced by another, a single li
element can have one or more
del
elements followed by one or more ins
elements.
In the following example, a list that started empty had items added and removed from it over time. The bits in the example that have been emphasized show the parts that are the "current" state of the list. The list item numbers don't take into account the edits, though.
<h1>Stop-ship bugs</h1> <ol> <li><ins datetime="2008-02-12T15:20Z">Bug 225: Rain detector doesn't work in snow</ins></li> <li><del datetime="2008-03-01T20:22Z"><ins datetime="2008-02-14T12:02Z">Bug 228: Water buffer overflows in April</ins></del></li> <li><ins datetime="2008-02-16T13:50Z">Bug 230: Water heater doesn't use renewable fuels</ins></li> <li><del datetime="2008-02-20T21:15Z"><ins datetime="2008-02-16T14:25Z">Bug 232: Carbon dioxide emissions detected after startup</ins></del></li> </ol>
In the following example, a list that started with just fruit was replaced by a list with just colors.
<h1>List of <del>fruits</del><ins>colors</ins></h1> <ul> <li><del>Lime</del><ins>Green</ins></li> <li><del>Apple</del></li> <li>Orange</li> <li><del>Pear</del></li> <li><ins>Teal</ins></li> <li><del>Lemon</del><ins>Yellow</ins></li> <li>Olive</li> <li><ins>Purple</ins></li> </ul>
This section is non-normative.
The elements that form part of the table model have complicated content model requirements that
do not allow for the ins
and del
elements, so indicating edits to a
table can be difficult.
To indicate that an entire row or an entire column has been added or removed, the entire
contents of each cell in that row or column can be wrapped in ins
or del
elements (respectively).
Here, a table's row has been added:
<table> <thead> <tr> <th> Game name <th> Game publisher <th> Verdict <tbody> <tr> <td> Diablo 2 <td> Blizzard <td> 8/10 <tr> <td> Portal <td> Valve <td> 10/10 <tr> <td> <ins>Portal 2</ins> <td> <ins>Valve</ins> <td> <ins>10/10</ins> </table>
Here, a column has been removed (the time at which it was removed is given also, as is a link to the page explaining why):
<table> <thead> <tr> <th> Game name <th> Game publisher <th> <del cite="/edits/r192" datetime="2011-05-02 14:23Z">Verdict</del> <tbody> <tr> <td> Diablo 2 <td> Blizzard <td> <del cite="/edits/r192" datetime="2011-05-02 14:23Z">8/10</del> <tr> <td> Portal <td> Valve <td> <del cite="/edits/r192" datetime="2011-05-02 14:23Z">10/10</del> <tr> <td> Portal 2 <td> Valve <td> <del cite="/edits/r192" datetime="2011-05-02 14:23Z">10/10</del> </table>
Generally speaking, there is no good way to indicate more complicated edits (e.g. that a cell was removed, moving all subsequent cells up or to the left).
img
elementusemap
attribute: Interactive content.alt
- Replacement text for use when images are not availablesrc
- Address of the resourcecrossorigin
- How the element handles crossorigin requestsusemap
- Name of image map to use ismap
- Whether the image is a server-side image mapwidth
- Horizontal dimensionheight
- Vertical dimensionpresentation
role only, for an
img
element whose alt
attribute's value is empty (alt=""
), otherwise
any role value.aria-*
attributes
applicable to the allowed roles.[NamedConstructor=Image(optional unsigned long width, optional unsigned long height)] interface HTMLImageElement : HTMLElement { attribute DOMString alt; attribute DOMString src; attribute DOMString crossOrigin; attribute DOMString useMap; attribute boolean isMap; attribute unsigned long width; attribute unsigned long height; readonly attribute unsigned long naturalWidth; readonly attribute unsigned long naturalHeight; readonly attribute boolean complete; };
An img
element represents an image.
The image given by the src
attributes is the embedded content; the value of
the alt
attribute provides equivalent content for
those who cannot process images or who have image loading disabled.
The requirements on the alt
attribute's value are described
in the next section.
The src
attribute must be present, and must contain a
valid non-empty URL potentially surrounded by spaces referencing a non-interactive,
optionally animated, image resource that is neither paged nor scripted.
The requirements above imply that images can be static bitmaps (e.g. PNGs, GIFs, JPEGs), single-page vector documents (single-page PDFs, XML files with an SVG root element), animated bitmaps (APNGs, animated GIFs), animated vector graphics (XML files with an SVG root element that use declarative SMIL animation), and so forth. However, these definitions preclude SVG files with script, multipage PDF files, interactive MNG files, HTML documents, plain text documents, and so forth. [PNG] [GIF] [JPEG] [PDF] [XML] [APNG] [SVG] [MNG]
The img
element must not be used as a layout tool. In particular, img
elements should not be used to display transparent images, as such images rarely convey meaning and
rarely add anything useful to the document.
The crossorigin
attribute is a CORS
settings attribute. Its purpose is to allow images from third-party sites that allow
cross-origin access to be used with canvas
.
An img
is always in one of the following states:
When an img
element is either in the partially
available state or in the completely available state, it is
said to be available.
An img
element is initially unavailable.
When an img
element is available, it
provides a paint source whose width is the image's intrinsic width, whose height is
the image's intrinsic height, and whose appearance is the intrinsic appearance of the image.
In a browsing context where scripting is disabled, user agents may obtain images immediately or on demand. In a browsing context where scripting is enabled, user agents must obtain images immediately.
A user agent that obtains images immediately must synchronously update the image
data of an img
element whenever that element is created with a src
attribute.
A user agent that obtains images immediately must also synchronously
update the image data of an img
element whenever that element has its
src
or crossorigin
attribute set, changed, or removed.
A user agent that obtains images on demand must update the image data of an
img
element whenever it needs the image data (i.e. on demand), but only if the
img
element has a src
attribute, and only if the img
element is in the
unavailable state. When an img
element's src
or crossorigin
attribute set, changed, or removed, if the user
agent only obtains images on demand, the img
element must return to the unavailable state.
Each img
element has a last selected source, which must initially be
null, and a current pixel density, which must initially be undefined.
When an img
element has a current pixel density that is not 1.0, the
element's image data must be treated as if its resolution, in device pixels per CSS pixels, was
the current pixel density.
For example, if the current pixel density is 3.125, that means that there are 300 device pixels per CSS inch, and thus if the image data is 300x600, it has an intrinsic dimension of 96 CSS pixels by 192 CSS pixels.
Each Document
object must have a list of available images. Each image
in this list is identified by a tuple consisting of an absolute URL, a CORS
settings attribute mode, and, if the mode is not No
CORS, an origin. User agents may copy entries from one Document
object's list of available images to another at any time (e.g. when the
Document
is created, user agents can add to it all the images that are loaded in
other Document
s), but must not change the keys of entries copied in this way when
doing so. User agents may also remove images from such lists at any time (e.g. to save
memory).
When the user agent is to update the image data of an img
element, it
must run the following steps:
Return the img
element to the unavailable
state.
If an instance of the fetching algorithm is still running for this element, then abort that algorithm, discarding any pending tasks generated by that algorithm.
Forget the img
element's current image data, if any.
If the user agent cannot support images, or its support for images has been disabled, then abort these steps.
src
attribute specified and
its value is not the empty string, let selected source be the value of the
element's src
attribute, and selected pixel
density be 1.0. Otherwise, let selected source be null and selected pixel density be undefined.
Let the img
element's last selected source be selected source and the img
element's current pixel
density be selected pixel density.
If selected source is not null, run these substeps:
Resolve selected source, relative to the element. If that is not successful, abort these steps.
Let key be a tuple consisting of the resulting absolute
URL, the img
element's crossorigin
attribute's mode, and, if that mode is not No CORS,
the Document
object's origin.
If the list of available images contains an entry for key, then set the img
element to the completely
available state, update the presentation of the image appropriately, queue a
task to fire a simple event named load
at the
img
element, and abort these steps.
Asynchronously await a stable state, allowing the task that invoked this algorithm to continue. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
⌛ If another instance of this algorithm for this img
element was started
after this instance (even if it aborted and is no longer running), then abort these steps.
Only the last instance takes effect, to avoid multiple requests when, for
example, the src
and crossorigin
attributes are all set in
succession.
⌛ If selected source is null, then set the element to the broken state, queue a task to fire a simple
event named error
at the img
element, and
abort these steps.
⌛ Queue a task to fire a progress event named loadstart
at
the img
element.
⌛ Do a potentially CORS-enabled fetch of the absolute
URL that resulted from the earlier step, with the mode being the current state of the
element's crossorigin
content attribute, the origin being the origin of the img
element's
Document
, and the default origin behaviour set to taint.
The resource obtained in this fashion, if any, is the img
element's image data.
It can be either CORS-same-origin or CORS-cross-origin; this affects
the origin of the image itself (e.g. when used on a canvas
).
Fetching the image must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run.
This, unfortunately, can be used to perform a rudimentary port scan of the user's local network (especially in conjunction with scripting, though scripting isn't actually necessary to carry out such an attack). User agents may implement cross-origin access control policies that are stricter than those described above to mitigate this attack, but unfortunately such policies are typically not compatible with existing Web content.
If the resource is CORS-same-origin, each task
that is queued by the networking task source
while the image is being fetched must fire a progress
event named progress
at the img
element.
End the synchronous section, continuing the remaining steps asynchronously, but without missing any data from the fetch algorithm.
As soon as possible, jump to the first applicable entry from the following list:
multipart/x-mixed-replace
The next task that is queued by the networking task source while the image is being fetched must set the img
element's state to partially available.
Each task that is queued by the networking task source while the image is being fetched must update the presentation of the image, but as each new
body part comes in, it must replace the previous image. Once one body part has been completely
decoded, the user agent must set the img
element to the completely available state and queue a task to fire
a simple event named load
at the img
element.
The progress
and loadend
events are not fired for
multipart/x-mixed-replace
image streams.
The next task that is queued by the networking task source while the image is being fetched must set the img
element's state to partially available.
That task, and each subsequent task, that is queued by the networking task source while the image is being fetched must update the presentation of the image appropriately (e.g. if the image is a progressive JPEG, each packet can improve the resolution of the image).
Furthermore, the last task that is queued by the networking task source once the resource has been fetched must additionally run the steps for the matching entry in the following list:
Set the img
element to the completely
available state.
Add the image to the list of available images using the key key.
If the resource is CORS-same-origin: fire a progress event
named load
at the img
element.
If the resource is CORS-cross-origin: fire a simple event named
load
at the img
element.
If the resource is CORS-same-origin: fire a progress event
named loadend
at the img
element.
If the resource is CORS-cross-origin: fire a simple event named
loadend
at the img
element.
If the resource is CORS-same-origin: fire a progress event
named load
at the img
element.
If the resource is CORS-cross-origin: fire a simple event named
load
at the img
element.
If the resource is CORS-same-origin: fire a progress event
named loadend
at the img
element.
If the resource is CORS-cross-origin: fire a simple event named
loadend
at the img
element.
Either the image data is corrupted in some fatal way such that the image dimensions cannot
be obtained, or the image data is not in a supported file format; the user agent must set the
img
element to the broken state, abort the fetching algorithm, discarding any pending tasks generated by that algorithm, and then queue a
task to first fire a simple event named error
at the img
element and then fire a simple
event named loadend
at the img
element.
While a user agent is running the above algorithm for an element x, there
must be a strong reference from the element's Document
to the element x, even if that element is not in its
Document
.
When an img
element is in the completely available
state and the user agent can decode the media data without errors, then the
img
element is said to be fully decodable.
Whether the image is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the image's type and whether it is a valid image.
This allows servers to return images with error responses, and have them displayed.
The user agent should apply the image sniffing rules to determine the type of the image, with the image's associated Content-Type headers giving the official type. If these rules are not applied, then the type of the image must be the type given by the image's associated Content-Type headers.
User agents must not support non-image resources with the img
element (e.g. XML
files whose root element is an HTML element). User agents must not run executable code (e.g.
scripts) embedded in the image resource. User agents must only display the first page of a
multipage resource (e.g. a PDF file). User agents must not allow the resource to act in an
interactive fashion, but should honor any animation in the resource.
This specification does not specify which image types are to be supported.
What an img
element represents depends on the src
attribute and the alt
attribute.
src
attribute is set and the alt
attribute is set to the empty stringThe image is either decorative or supplemental to the rest of the content, redundant with some other information in the document.
If the image is available and the user agent is configured to display that image, then the element represents the element's image data.
Otherwise, the element represents nothing, and may be omitted completely from the rendering. User agents may provide the user with a notification that an image is present but has been omitted from the rendering.
src
attribute is set and the alt
attribute is set to a value that isn't emptyThe image is a key part of the content; the alt
attribute
gives a textual equivalent or replacement for the image.
If the image is available and the user agent is configured to display that image, then the element represents the element's image data.
Otherwise, the element represents the text given by the alt
attribute. User agents may provide the user with a notification
that an image is present but has been omitted from the rendering.
src
attribute is set and the alt
attribute is notThere is no textual equivalent of the image available.
If the image is available and the user agent is configured to display that image, then the element represents the element's image data.
Otherwise, the user agent should display some sort of indicator that there is an image that is not being rendered, and may, if requested by the user, or if so configured, or when required to provide contextual information in response to navigation, provide caption information for the image, derived as follows:
If the image is a descendant of a figure
element that has a child
figcaption
element, and, ignoring the figcaption
element and its
descendants, the figure
element has no Text
node descendants other
than inter-element whitespace, and no embedded content descendant
other than the img
element, then the contents of the first such
figcaption
element are the caption information; abort these steps.
There is no caption information.
src
attribute is not set and either the alt
attribute is set to the empty string or the alt
attribute is not set at allThe element represents nothing.
The element represents the text given by the alt
attribute.
The alt
attribute does not represent advisory information.
User agents must not present the contents of the alt
attribute
in the same way as content of the title
attribute.
While user agents are encouraged to repair cases of missing alt
attributes, authors must not rely on such behavior. Requirements for providing text to act as an alternative for images are described
in detail below.
The contents of img
elements, if any, are ignored for the purposes of
rendering.
The usemap
attribute,
if present, can indicate that the image has an associated
image map.
The ismap
attribute, when used on an element that is a descendant of an
a
element with an href
attribute, indicates by its
presence that the element provides access to a server-side image
map. This affects how events are handled on the corresponding
a
element.
The ismap
attribute is a
boolean attribute. The attribute must not be specified
on an element that does not have an ancestor a
element
with an href
attribute.
The img
element supports dimension
attributes.
The alt
, src
IDL attributes must reflect the
respective content attributes of the same name.
The crossOrigin
IDL attribute must
reflect the crossorigin
content attribute,
limited to only known values.
The useMap
IDL attribute must
reflect the usemap
content attribute.
The isMap
IDL attribute must reflect
the ismap
content attribute.
width
[ = value ]height
[ = value ]These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known.
They can be set, to change the corresponding content attributes.
naturalWidth
naturalHeight
These attributes return the intrinsic dimensions of the image, or zero if the dimensions are not known.
complete
Returns true if the image has been completely downloaded or if no image is specified; otherwise, returns false.
Image
( [ width [, height ] ] )Returns a new img
element, with the width
and height
attributes set to the values
passed in the relevant arguments, if applicable.
The IDL attributes width
and height
must return the rendered width and height of the
image, in CSS pixels, if the image is being rendered, and is being rendered to a
visual medium; or else the intrinsic width and height of the image, in CSS pixels, if the image is
available but not being rendered to a visual medium; or else 0, if
the image is not available. [CSS]
On setting, they must act as if they reflected the respective content attributes of the same name.
The IDL attributes naturalWidth
and naturalHeight
must return the intrinsic width and
height of the image, in CSS pixels, if the image is available, or
else 0. [CSS]
The IDL attribute complete
must return true if
any of the following conditions is true:
src
attribute and the srcset
attribute are omitted.
srcset
attribute is omitted and the src
attribute's value is the empty string.
img
element is completely available.
img
element is broken.
Otherwise, the attribute must return false.
The value of complete
can thus change while
a script is executing.
A constructor is provided for creating HTMLImageElement
objects (in addition to
the factory methods from DOM such as createElement()
): Image(width, height)
.
When invoked as a constructor, this must return a new HTMLImageElement
object (a new
img
element). If the width argument is present, the new object's
width
content attribute must be set to width. If the height argument is also present, the new object's
height
content attribute must be set to height. The element's document must be the active document of the
browsing context of the Window
object on which the interface object of
the invoked constructor is found.
Text alternatives, [WCAG] are a primary way of making visual information accessible, because they can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. Providing text alternatives allows the information to be rendered in a variety of ways by a variety of user agents. For example, a person who cannot see a picture can have the text alternative read aloud using synthesized speech.
The alt
attribute on images is a very important accessibility attribute
(it is supported by all browsers, most authoring tools and is the most well known accessibility
technique among authors). Useful alt
attribute content enables users who are unable
to view images on a page to comprehend and make use of that page as much as those who can.
Except where otherwise specified, the alt
attribute must be specified and its value must not be empty;
the value must be an appropriate functional replacement for the image. The specific requirements for the alt
attribute content
depend on the image's function in the page, as described in the following sections.
To determine an appropriate text alternative it is important to think about why an image is being included in a page. What is its purpose? Thinking like this will help you to understand what is important about the image for the intended audience. Every image has a reason for being on a page, because it provides useful information, performs a function, labels an interactive element, enhances aesthetics or is purely decorative. Therefore, knowing what the image is for, makes writing an appropriate text alternative easier.
When an a
element that is a hyperlink, or a button
element, has no text content
but contains one or more images, include text in the alt
attribute(s) that together convey the purpose of the link or button.
In this example, a user is asked to pick her preferred color
from a list of three. Each color is given by an image, but for
users who cannot view the images,
the color names are included within the alt
attributes of the images:
<ul> <li><a href="red.html"><img src="red.jpeg" alt="Red"></a></li> <li><a href="green.html"><img src="green.jpeg" alt="Green"></a></li> <li><a href="blue.html"><img src="blue.jpeg" alt="Blue"></a></li> </ul>
In this example, a link contains a logo. The link points to the W3C web site from an external site. The text alternative is a brief description of the link target.
<a href="http://w3.org"> <img src="images/w3c_home.png" width="72" height="48" alt="W3C web site"> </a>
This example is the same as the previous example, except that the link is on the W3C web site. The text alternative is a brief description of the link target.
<a href="http://w3.org"> <img src="images/w3c_home.png" width="72" height="48" alt="W3C home"> </a>
In this example, a link contains a print preview icon. The link points to a version of the page with a print stylesheet applied. The text alternative is a brief description of the link target.
<a href="preview.html"> <img src="images/preview.png" width="32" height="30" alt="Print preview."> </a>
In this example, a button contains a search icon. The button submits a search form. The text alternative is a brief description of what the button does.
<button> <img src="images/search.png" width="74" height="29" alt="Search"> </button>
In this example, a company logo for the PIP Corporation has been split into the following two images,
the first containing the word PIP and the second with the abbreviated word CO. The images are the
sole content of a link to the PIPCO home page. In this case a brief description of the link target is provided.
As the images are presented to the user as a single entity the text alternative PIP CO home is in the
alt
attribute of the first image.
<a href="pipco-home.html"> <img src="pip.gif" alt="PIP CO home"><img src="co.gif" alt=""> </a>
Users can benefit when content is presented in graphical form, for example as a flowchart, a diagram, a graph, or a map showing directions. Users also benefit when content presented in a graphical form is also provided in a textual format, these users include those who are unable to view the image (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or because they have a visual impairment and use an assistive technology to render the text to speech).
In the following example we have an image of a pie chart, with text in the alt
attribute
representing the data shown in the pie chart:
<img src="piechart.gif" alt="Pie chart: Browser Share - Internet Explorer 25%, Firefox 40%, Chrome 25%, Safari 6% and Opera 4%.">
In the case where an image repeats the previous paragraph in graphical form. The alt
attribute content labels the image.
<p>According to a recent study Firefox has a 40% browser share, Internet Explorer has 25%, Chrome has 25%, Safari has 6% and Opera has 4%.</p> <p><img src="piechart.gif" alt="Pie chart representing the data in the previous paragraph."></p>
It can be seen that when the image is not available, for example because the src
attribute value is incorrect, the text alternative provides the user with a brief description of the image content:
In cases where the text alternative is lengthy, more than a sentence or two, or would benefit from
the use of structured markup, provide a brief description or label using the alt
attribute, and an associated text alternative.
Here's an example of a flowchart image, with a short text alternative
included in the alt
attribute, in this case the text alternative is a description of the link target
as the image is the sole content of a link. The link points to a description, within the same document, of the
process represented in the flowchart.
<a href="#desc"><img src="flowchart.gif" alt="Flowchart: Dealing with a broken lamp."></a> ... ... <div id="desc"> <h2>Dealing with a broken lamp</h2> <ol> <li>Check if it's plugged in, if not, plug it in.</li> <li>If it still doesn't work; check if the bulb is burned out. If it is, replace the bulb.</li> <li>If it still doesn't work; buy a new lamp.</li> </ol> </div>
In this example, there is an image of a chart. It would be inappropriate to provide the information depicted in
the chart as a plain text alternative in an alt
attribute as the information is a data set. Instead a
structured text alternative is provided below the image in the form of a data table using the data that is represented
in the chart image.
Indications of the highest and lowest rainfall for each season have been included in the table, so trends easily identified in the chart are also available in the data table.
United Kingdom | Japan | Australia | |
---|---|---|---|
Spring | 5.3 (highest) | 2.4 | 2 (lowest) |
Summer | 4.5 (highest) | 3.4 | 2 (lowest) |
Autumn | 3.5 (highest) | 1.8 | 1.5 (lowest) |
Winter | 1.5 (highest) | 1.2 | 1 (lowest) |
<img src="rainchart.gif" alt="Bar chart: Average rainfall in millimetres by Country and Season."> <table> <caption>Rainfall in millimetres by Country and Season.</caption> <tr><td><th scope="col">UK <th scope="col">Japan<th scope="col">Australia</tr> <tr><th scope="row">Spring <td>5.5 (highest)<td>2.4 <td>2 (lowest)</tr> <tr><th scope="row">Summer <td>4.5 (highest)<td>3.4<td>2 (lowest)</tr> <tr><th scope="row">Autumn <td>3.5 (highest) <td>1.8 <td>1.5 (lowest)</tr> <tr><th scope="row">Winter <td>1.5 (highest) <td>1.2 <td>1 lowest</tr> </table>
Sometimes, an image only contains text, and the purpose of the image
is to display text using visual effects and /or fonts. It is strongly
recommended that text styled using CSS be used, but if this is not possible, provide
the same text in the alt
attribute as is in the image.
This example shows an image of the text "Get Happy!" written in a fancy multi colored freehand style. The image makes up the content of a heading. In this case the text alternative for the image is "Get Happy!".
<h1><img src="gethappy.gif" alt="Get Happy!"></h1>
In this example we have an advertising image consisting of text, the phrase "The BIG sale" is repeated 3 times, each time the text gets smaller and fainter, the last line reads "...ends Friday" In the context of use, as an advertisement, it is recommended that the image's text alternative only include the text "The BIG sale" once as the repetition is for visual effect and the repetition of the text for users who cannot view the image is unnecessary and could be confusing.
<p><img src="sale.gif" alt="The BIG sale ...ends Friday."></p>
In situations where there is also a photo or other graphic along with the image of text, ensure that the words in the image text are included in the text alternative, along with any other description of the image that conveys meaning to users who can view the image, so the information is also available to users who cannot view the image.
When an image is used to represent a character that cannot otherwise be represented in Unicode, for example gaiji, itaiji, or new characters such as novel currency symbols, the text alternative should be a more conventional way of writing the same thing, e.g. using the phonetic hiragana or katakana to give the character's pronunciation.
In this example from 1997, a new-fangled currency symbol that looks like a curly E with two bars in the middle instead of one is represented using an image. The alternative text gives the character's pronunication.
Only 5.99!
<p>Only <img src="euro.png" alt="euro ">5.99!
An image should not be used if Unicode characters would serve an identical purpose. Only when the text cannot be directly represented using Unicode, e.g. because of decorations or because the character is not in the Unicode character set (as in the case of gaiji), would an image be appropriate.
If an author is tempted to use an image because their default system font does not support a given character, then Web Fonts are a better solution than images.
An illuminated manuscript might use graphics for some of its letters. The text alternative in such a situation is just the character that the image represents.
nce upon a time and a long long time ago...
<p><img src="initials/fancyO.png" alt="O">nce upon a time and a long long time ago...
Sometimes, an image consists of a graphics such as a chart and associated text. In this case it is recommended that the text in the image is included in the text alternative.
Consider an image containing a pie chart and associated text. It is recommended wherever possible to provide any associated text as text, not an image of text. If this is not possible include the text in the text alternative along with the pertinent information conveyed in the image.
<p><img src="figure1.gif" alt="Figure 1. Distribution of Articles by Journal Category. Pie chart: Language=68%, Education=14% and Science=18%."></p>
Here's another example of the same pie chart image,
showing a short text alternative included in the alt
attribute
and a longer text alternative in text. The figure
and figcaption
elements are used to associate the longer text alternative with the image. The alt
attribute is used
to label the image.
<figure> <img src="figure1.gif" alt="Figure 1"> <figcaption><strong>Figure 1.</strong> Distribution of Articles by Journal Category. Pie chart: Language=68%, Education=14% and Science=18%.</figcaption> </figure>
The advantage of this method over the previous example is that the text alternative
is available to all users at all times. It also allows structured mark up to be used in the text
alternative, where as a text alternative provided using the alt
attribute does not.
An image that isn't discussed directly by the surrounding text but still has
some relevance can be included in a page using the img
element. Such images
are more than mere decoration, they may augment the themes or subject matter of the page
content and so still form part of the content. In these cases, it is recommeneded that a
text alternative be provided.
Here is an example of an image closely related to the subject matter of the page content
but not directly discussed. An image of a painting inspired by a poem, on a page reciting that poem.
The following snippet shows an example. The image is a painting titled the "Lady of Shallot", it is
inspired by the poem and its subject matter is derived from the poem. Therefore it is strongly
recommended that a text alternative is provided. There is a short description of the content of
the image in the alt
attribute and
a link below the image to a longer description located at the bottom of the document. At the end
of the longer description there is also a link to further information about the painting.
<header> <h1>The Lady of Shalott</h1> <p>A poem by Alfred Lord Tennyson</p> </header> <img src="shalott.jpeg" alt="Painting of a young woman with long hair, sitting in a wooden boat. "> <p><a href="#des">Description of the painting</a>.</p> <!-- Full Recitation of Alfred, Lord Tennyson's Poem. --> ... ... ... <p id="des">The woman in the painting is wearing a flowing white dress. A large piece of intricately patterned fabric is draped over the side. In her right hand she holds the chain mooring the boat. Her expression is mournful. She stares at a crucifix lying in front of her. Beside it are three candles. Two have blown out. <a href="http://bit.ly/5HJvVZ">Further information about the painting</a>.</p>
In many cases, the image is actually just supplementary, and its presence merely reinforces the
surrounding text. In these cases, the alt
attribute must be
present but its value must be the empty string.
In general, an image falls into this category if removing the image doesn't make the page any less useful, but including the image makes it a lot easier for users of visual browsers to understand the concept.
It is not always easy to write a useful text alternative for an image, another option is to provide a link to a description or further information about the image when one is available.
In this example of the same image, there is a short text alternative included in the alt
attribute, and
there is a link after the image. The link points to a page containing information about the painting.
The Lady of Shalott
A poem by Alfred Lord Tennyson.
Full recitation of Alfred, Lord Tennyson's poem.
<header><h1>The Lady of Shalott</h1> <p>A poem by Alfred Lord Tennyson</p></header> <figure> <img src="shalott.jpeg" alt="Painting of a woman in a white flowing dress, sitting in a small boat."> <p><a href="http://bit.ly/5HJvVZ">About this painting.</a></p> </figure> <!-- Full Recitation of Alfred, Lord Tennyson's Poem. -->
Purely decorative images are visual enhancements, decorations or embellishments that provide no function or information beyond aesthetics to users who can view the images.
Mark up purely decorative images so they can be ignored by assistive technology by using an empty alt
attribute (alt=""
). While it is not unacceptable to include decorative images inline,
it is recommended if they are purely decorative to include the image using CSS.
Here's an example of an image being used as a decorative banner for a person's blog, the image offers no information
and so an empty alt
attribute is used.
Clara's Blog
Welcome to my blog...
<header> <div><img src="border.gif" alt="" width="400" height="30"></div> <h1>Clara's Blog</h1> </header> <p>Welcome to my blog...</p>
When images are used inline as part of the flow of text in a sentence, provide a word or phrase as a text alternative which makes sense in the context of the sentence it is apart of.
I you.
I <img src="heart.png" alt="love"> you.
My breaks.
My <img src="heart.png" alt="heart"> breaks.
When a picture has been sliced into smaller image files that are then displayed
together to form the complete picture again, include a text alternative for one
of the images using the alt
attribute as per the relevant relevant
guidance for the picture as a whole, and then include an empty alt
attribute on the other images.
In this example, a picture representing a company logo for the PIP Corporation
has been split into two pieces, the first containing the letters "PIP" and the second with the word "CO".
The text alternatve PIP CO is in the alt
attribute of the first image.
<img src="pip.gif" alt="PIP CO"><img src="co.gif" alt="">
In the following example, a rating is shown as three filled
stars and two empty stars. While the text alternative could have
been "★★★☆☆", the author has
instead decided to more helpfully give the rating in the form "3
out of 5". That is the text alternative of the first image, and the
rest have empty alt
attributes.
<p>Rating: <meter max=5 value=3> <img src="1" alt="3 out of 5"> <img src="1" alt=""><img src="1" alt=""> <img src="0" alt=""><img src="0" alt=""> </meter></p>
img
element has a usemap
attribute which references a map
element containing
area
elements that have href
attributes, the img
is considered to be interactive content.
In such cases, always provide a text alternative for the image using the alt
attribute.
Consider the following image which is a map of Katoomba, it has 2 interactive regions corresponding to the areas of North and South Katoomba:
The text alternative is a brief description of the image. The alt
attribute on each
of the area
elements provides text describing the content of the target page of each linked region:
<p>View houses for sale in North Katoomba or South Katoomba:</p> <p><img src="imagemap.png" width="209" alt="Map of Katoomba" height="249" usemap="#Map"> <map name="Map"> <area shape="poly" coords="78,124,124,10,189,29,173,93,168,132,136,151,110,130" href="north.html" alt="Houses in North Katoomba"> <area shape="poly" coords="66,63,80,135,106,138,137,154,167,137,175,133,144,240,49,223,17,137,17,61" alt="Houses in South Katoomba" href="south.html"> </map>
Generally, image maps should be used instead of slicing an image for links.
Sometimes, when you create a composite picture from multiple images, you may wish to
link one or more of the images. Provide an alt
attribute
for each linked image to describe the purpose of the link.
In the following example, a composite picture is used to represent a "crocoduck"; a fictional creature which defies evolutionary principles by being part crocodile and part duck. You are asked to interact with the crocoduck, but you need to exercise caution...
<h1>The crocoduck</h1> <p>You encounter a strange creature called a "crocoduck". The creature seems angry! Perhaps some friendly stroking will help to calm it, but be careful not to stroke any crocodile parts. This would just enrage the beast further.</p> <a href="?stroke=head"><img src="crocoduck1.png" alt="Stroke crocodile's angry, chomping head"></a> <a href="?stroke=body"><img src="crocoduck2.png" alt="Stroke duck's soft, feathery body"></a>
Images of pictures or graphics include visual representations of objects, people, scenes, abstractions, etc. This non-text content, [WCAG] can convey a significant amount of information visually or provide a specific sensory experience, [WCAG] to a sighted person. Examples include photographs, paintings, drawings and artwork.
An appropriate text alternative for a picture is a brief description, or name [WCAG]. As in all text alternative authoring decisions, writing suitable text alternatives for pictures requires
human judgment. The text value is subjective to the context where the image is used and the page author's writing style. Therefore,
there is no single 'right' or 'correct' piece of alt
text for any particular image. In addition to providing a short text
alternative that gives a brief description of the non-text content, also providing supplemental content through another means when
appropriate may be useful.
This first example shows an image uploaded to a photo-sharing site. The photo is of a cat, sitting in the bath. The image has a
text alternative provided using the img
element's alt
attribute. It also has a caption provided by including
the img
element in a figure
element and using a figcaption
element to identify the caption text.
Lola prefers a bath to a shower.
<figure> <img src="664aef.jpg" alt="Lola the cat sitting under an umbrella in the bath tub."> <figcaption>Lola prefers a bath to a shower.</figcaption> </figure>
This example is of an image that defies a complete description, as the subject of the image is open to interpretation.
The image has a text alternative in the alt
attribute which gives users who cannot view the image a sense
of what the image is. It also has a caption provided by including the img
element in a figure
element and using a figcaption
element to identify the caption text.
The first of the ten cards in the Rorschach test.
<figure> <img src="Rorschach1.jpg" alt="An abstract, freeform, vertically symmetrical, black inkblot on a light background."> <figcaption>The first of the ten cards in the Rorschach test.</figcaption> </figure>
Webcam images are static images that are automatically updated periodically. Typically the images are from a fixed viewpoint, the images may update on the page automatically as each new image is uploaded from the camera or the user may be required to refresh the page to view an updated image. Examples include traffic and weather cameras.
This example is fairly typical; the title and a time stamp are included in the image, automatically generated
by the webcam software. It would be better if the text information was not included in the image, but as it is part
of the image, include it part of the text alternative. A caption is also provided using the figure
and figcaption
elements. As the image is provided to give a visual indication of the current weather near a building,
a link to a local weather forecast is provided, as with automatically generated and uploaded webcam images it may be impractical to
provide such information as a text alternative.
The text of the alt
attribute includes a prose version of the timestamp, designed to make the text more
understandable when announced by text to speech software. The text alternative also includes a description of some aspects
of what can be seen in the image which are unchanging, although weather conditions and time of day change.
View from the top of Sopwith house, looking towards North Kingston. This image is updated every hour.
View the latest weather details for Kingston upon Thames.
<figure> <img src="webcam1.jpg" alt="Sopwith house weather cam. Taken on the 21/04/10 at 11:51 and 34 seconds. In the foreground are the safety rails on the flat part of the roof. Nearby there are low rise industrial buildings, beyond are blocks of flats. In the distance there's a church steeple."> <figcaption>View from Sopwith house, looking towards north Kingston. This image is updated every hour.</figcaption> </figure> <p>View the <a href="http://news.bbc.co.uk/weather/forecast/4296?area=Kingston">latest weather details</a> for Kingston upon Thames.</p>
In some cases an image is included in a published document, but the author is unable to provide an appropriate text alternative.
In such cases the minimum requirement is to provide a caption for the image using the figure
and figcaption
elements under the following conditions:
img
element is in a figure
element
figure
element contains a figcaption
element
figcaption
element contains content other than inter-element whitespace
figcaption
element and its descendants, the figure
element has no Text
node descendants other than inter-element whitespace, and no
embedded content descendant other than the img
element.
In other words, the only content of the figure
is an img
element and a figcaption
element, and the figcaption
element must include (caption) content.
Such cases are to be kept to an absolute
minimum. If there is even the slightest possibility of the author
having the ability to provide real alternative text, then it would
not be acceptable to omit the alt
attribute.
In this example, a person uploads a photo, as part of a bulk upoad of many images, to a photo sharing site. The user has not provided a text alternative or a caption for the image. The site's authoring tool inserts a caption automatically using whatever useful information it has for the image. In this case it's the file name and date the photo was taken.
clara.jpg, taken on 12/11/2010.
<figure> <img src="clara.jpg"> <figcaption>clara.jpg, taken on 12/11/2010.</figcaption> </figure>
Notice that even in this example, as much useful information
as possible is still included in the figcaption
element.
In this second example, a person uploads a photo to a photo sharing site. She has provided
a caption for the image but not a text alternative. This may be because the site does not provide users with the ability
to add a text alternative in the alt
attribute.
Eloisa with Princess Belle
<figure> <img src="elo.jpg"> <figcaption>Eloisa with Princess Belle</figcaption> </figure>
Sometimes the entire point of the image is that a textual description is not available, and the user is to provide the description. For example, software that displays images and asks for alternative text precisely for the purpose of then writing a page with correct alternative text. Such a page could have a table of images, like this:
<table> <tr><tr> <th> Image <th> Description<tr> <td> <figure> <img src="2421.png"> <figcaption>Image 640 by 100, filename 'banner.gif'</figcaption> </figure> <td> <input name="alt2421"> <tr> <td> <figure> <img src="2422.png"> <figcaption>Image 200 by 480, filename 'ad3.gif'</figcaption> </figure> <td> <input name="alt2422"> </table>
Since some users cannot use images at all (e.g. because they are blind) the
alt
attribute is only allowed to be omitted when no text
alternative is available and none can be made available, as in the above examples.
Generally authors should avoid using img
elements
for purposes other than showing images.
If an img
element is being used for purposes other
than showing an image, e.g. as part of a service to count page
views, use an empty alt
attribute.
An example of an img
element used to collect web page statistics.
The alt
attribute is empty as the image has no meaning.
<img src="http://server3.stats.com/count.pl?NeonMeatDream.com" width="0" height="0" alt="">
It is recommended for the example use above the width
and
height
attributes be set to zero.
Another example use is when an image such as a spacer.gif is used to aid positioning of content.
The alt
attribute is empty as the image has no meaning.
<img src="spacer.gif" width="10" height="10" alt="">
It is recommended that that CSS be used to position content instead of img
elements.
An icon is usually a simple picture representing a program, action, data file or a concept. Icons are intended to help users of visual browsers to recognize features at a glance.
Use an empty alt
attribute when an icon is supplemental to
text conveying the same meaning.
In this example, we have a link pointing to a site's home page, the link contains a
house icon image and the text "home". The image has an empty alt
text.
Where images are used in this way, it would also be appropriate to add the image using CSS
<a href="home.html"><img src="home.gif" width="15" height="15" alt="">Home</a>
#home:before { content: url(home.png); } <a href="home.html" id="home">Home</a>
In this example, there is a warning message, with a warning icon. The word "Warning!" is in emphasized
text next to the icon. As the information conveyed by the icon is redundant the img
element is given an an empty alt
attribute.
Warning! Your session is about to expire.
<p><img src="warning.png" width="15" height="15" alt=""> <strong>Warning!</strong> Your session is about to expire</p>
When an icon conveys additional information not available in text, provide a text alternative.
In this example, there is a warning message, with a warning icon. The icon emphasizes the importance of the message and identifies it as a particular type of content.
Your session is about to expire.
<p><img src="warning.png" width="15" height="15" alt="Warning!"> Your session is about to expire</p>
Many pages include logos, insignia, flags, or emblems, which stand for a company, organization, project, band, software package, country, or other entity. What can be considered as an appropriate text alternative depends upon, like all images, the context in which the image is being used and what function it serves in the given context.
If a logo is the sole content of a link, provide a brief description of the link target in the alt
attribute.
This example illustrates the use of the HTML5 logo as the sole content of a link to the HTML specification.
<a href="http://dev.w3.org/html5/spec/spec.html"> <img src="HTML5_Logo.png" alt="HTML 5.1 specification"></a>
If a logo is being used to represent the entity, e.g. as a page heading, provide the name of the entity being represented by the logo as the text alternative.
This example illustrates the use of the WebPlatform.org logo being used to represent itself.
and other developer resources
<h2><img src="images/webplatform.png" alt="WebPlatform.org"> and other developer resources<h2>
If a logo is being used next to the name of the what that it represents, then the logo is supplemental.
Include an empty alt
attribute as the text alternative is already provided.
This example illustrates the use of a logo next to the name of the organization it represents.
WebPlatform.org
<img src="images/webplatform1.png" alt=""> WebPlatform.org
If the logo is used alongside text discussing the subject or entity the logo represents, then provide a text alternative which describes the logo.
This example illustrates the use of a logo next to text discussing the subject the logo represents.
HTML5 is a language for structuring and presenting content for the World Wide Web, a core technology of the Internet. It is the latest revision of the HTML standard (originally created in 1990 and most recently standardized as HTML4 in 1997) and currently remains under development. Its core aims have been to improve the language with support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers and devices (web browsers, parsers etc.).
<p><img src="HTML5_Logo.png" alt="HTML5 logo: Shaped like a shield with the text 'HTML' above and the numeral '5' prominent on the face of the shield."></p> Information about HTML5
CAPTCHA stands for "Completely Automated Public Turing test to tell Computers and Humans Apart". CAPTCHA images are used for security purposes to confirm that content is being accessed by a person rather than a computer. This authentication is done through visual verification of an image. CAPTCHA typically presents an image with characters or words in it that the user is to re-type. The image is usually distorted and has some noise applied to it to make the characters difficult to read.
To improve the accessibility of CAPTCHA provide text alternatives that identify and describe the purpose of the image, and provide alternative forms of the CAPTCHA using output modes for different types of sensory perception. For instance provide an audio alternative along with the visual image. Place the audio option right next to the visual one. This helps but is still problematic for people without sound cards, the deaf-blind, and some people with limited hearing. Another method is to include a form that asks a question along with the visual image. This helps but can be problematic for people with cognitive impairments.
It is strongly recommended that alternatives to CAPTCHA be used, as all forms of CAPTCHA introduce unacceptable barriers to entry for users with disabilities. Further information is available in Inaccessibility of CAPTCHA.
This example shows a CAPTCHA test which uses a distorted image of text. The text alternative in the
alt
attribute provides instructions for a user in the case where she cannot access the image content.
Example code:
<img src="captcha.png" alt="If you cannot view this image an audio challenge is provided."> <!-- audio CAPTCHA option that allows the user to listen and type the word --> <!-- form that asks a question -->
Markup generators (such as WYSIWYG authoring tools) should, wherever possible, obtain a text alternative from their users. However, it is recognized that in many cases, this will not be possible.
For images that are the sole contents of links, markup generators should examine the link target to determine the title of the target, or the URL of the target, and use information obtained in this manner as the text alternative.
For images that have captions, markup generators should use the
figure
and figcaption
elements to provide the
image's caption.
As a last resort, implementors should either set the alt
attribute to the empty string, under
the assumption that the image is a purely decorative image that
doesn't add any information but is still specific to the surrounding
content, or omit the alt
attribute
altogether, under the assumption that the image is a key part of the
content.
Markup generators may specify a generator-unable-to-provide-required-alt
attribute on img
elements for which they have been
unable to obtain a text alternative and for which they have therefore
omitted the alt
attribute. The
value of this attribute must be the empty string. Documents
containing such attributes are not conforming, but conformance
checkers will silently
ignore this error.
This is intended to avoid markup generators from
being pressured into replacing the error of omitting the alt
attribute with the even more
egregious error of providing phony text alternatives, because
state-of-the-art automated conformance checkers cannot distinguish
phony text alternatives from correct text alternatives.
Markup generators should generally avoid using the image's own file name as the text alternative. Similarly, markup generators should avoid generating text alternatives from any content that will be equally available to presentation user agents (e.g. Web browsers).
This is because once a page is generated, it will typically not be updated, whereas the browsers that later read the page can be updated by the user, therefore the browser is likely to have more up-to-date and finely-tuned heuristics than the markup generator did when generating the page.
A conformance checker must report the lack of an alt
attribute as an error unless one of
the conditions listed below applies:
The img
element is in a figure
element that satisfies the
conditions described above.
The img
element has a (non-conforming) generator-unable-to-provide-required-alt
attribute whose value is the empty string. A conformance checker
that is not reporting the lack of an alt
attribute as an error must also not
report the presence of the empty generator-unable-to-provide-required-alt
attribute as an error. (This case does not represent a case where
the document is conforming, only that the generator could not
determine appropriate alternative text — validators are not
required to show an error in this case, because such an error might
encourage markup generators to include bogus alternative text
purely in an attempt to silence validators. Naturally, conformance
checkers may report the lack of an alt
attribute as an error even in the
presence of the generator-unable-to-provide-required-alt
attribute; for example, there could be a user option to report
all conformance errors even those that might be the more
or less inevitable result of using a markup generator.)
iframe
elementsrc
- Address of the resourcesrcdoc
- A document to render in the iframe
name
- Name of nested browsing contextsandbox
- Security rules for nested contentseamless
- Whether to apply the document's styles to the nested contentwidth
- Horizontal dimensionheight
- Vertical dimessionapplication
,
document
, img
or
presentation
.aria-*
attributes
applicable to the allowed roles.interface HTMLIFrameElement : HTMLElement {
attribute DOMString src;
attribute DOMString srcdoc;
attribute DOMString name;
[PutForwards=value] readonly attribute DOMSettableTokenList sandbox;
attribute boolean seamless;
attribute DOMString width;
attribute DOMString height;
readonly attribute Document? contentDocument;
readonly attribute WindowProxy? contentWindow;
};
The iframe
element represents a nested browsing
context.
The src
attribute gives the address of a page
that the nested browsing context is to contain. The attribute, if present, must be a
valid non-empty URL potentially surrounded by spaces.
The srcdoc
attribute gives the content of
the page that the nested browsing context is to contain. The value of the attribute
is the source of an iframe
srcdoc
document.
For iframe
elements in HTML documents, the srcdoc
attribute, if present, must have a value using the
HTML syntax that consists of the following syntactic components, in the given order:
html
element.For iframe
elements in XML documents, the srcdoc
attribute, if present, must have a value that matches the
production labeled document
in the XML specification. [XML]
Here a blog uses the srcdoc
attribute in conjunction
with the sandbox
and seamless
attributes described below to provide users of user
agents that support this feature with an extra layer of protection from script injection in the
blog post comments:
<article> <h1>I got my own magazine!</h1> <p>After much effort, I've finally found a publisher, and so now I have my own magazine! Isn't that awesome?! The first issue will come out in September, and we have articles about getting food, and about getting in boxes, it's going to be great!</p> <footer> <p>Written by <a href="/users/cap">cap</a>, 1 hour ago. </footer> <article> <footer> Thirteen minutes ago, <a href="/users/ch">ch</a> wrote: </footer> <iframe seamless sandbox srcdoc="<p>did you get a cover picture yet?"></iframe> </article> <article> <footer> Nine minutes ago, <a href="/users/cap">cap</a> wrote: </footer> <iframe seamless sandbox srcdoc="<p>Yeah, you can see it <a href="/gallery?mode=cover&amp;page=1">in my gallery</a>."></iframe> </article> <article> <footer> Five minutes ago, <a href="/users/ch">ch</a> wrote: </footer> <iframe seamless sandbox srcdoc="<p>hey that's earl's table. <p>you should get earl&amp;me on the next cover."></iframe> </article>
Notice the way that quotes have to be escaped (otherwise the srcdoc
attribute would end prematurely), and the way raw
ampersands (e.g. in URLs or in prose) mentioned in the sandboxed content have to be
doubly escaped — once so that the ampersand is preserved when originally parsing
the srcdoc
attribute, and once more to prevent the
ampersand from being misinterpreted when parsing the sandboxed content.
Furthermore, notice that since the DOCTYPE is optional in
iframe
srcdoc
documents, and the html
,
head
, and body
elements have optional
start and end tags, and the title
element is also optional in iframe
srcdoc
documents, the markup in a srcdoc
attribute can be
relatively succint despite representing an entire document, since only the contents of the
body
element need appear literally in the syntax. The other elements are still
present, but only by implication.
In the HTML syntax, authors need only remember to use """ (U+0022) characters to wrap the attribute contents and then to escape all """ (U+0022) and U+0026 AMPERSAND (&) characters, and to specify the sandbox
attribute, to ensure safe embedding of content.
Due to restrictions of the XHTML syntax, in XML the "<" (U+003C) character needs to be escaped as well. In order to prevent attribute-value normalization, some of XML's whitespace characters — specifically "tab" (U+0009), "LF" (U+000A), and "CR" (U+000D) — also need to be escaped. [XML]
If the src
attribute and the srcdoc
attribute are both specified together, the srcdoc
attribute takes priority. This allows authors to provide
a fallback URL for legacy user agents that do not support the srcdoc
attribute.
When an iframe
element is inserted
into a document, the user agent must create a nested browsing context, and
then process the iframe
attributes for the "first time".
When an iframe
element is removed
from a document, the user agent must discard the nested browsing context.
This happens without any unload
events firing
(the nested browsing context and its Document
are discarded, not unloaded).
Whenever an iframe
element with a nested browsing context has its
srcdoc
attribute set, changed, or removed, the user agent
must process the iframe
attributes.
Similarly, whenever an iframe
element with a nested browsing context
but with no srcdoc
attribute specified has its src
attribute set, changed, or removed, the user agent must
process the iframe
attributes.
When the user agent is to process the iframe
attributes, it must run
the first appropriate steps from the following list:
srcdoc
attribute is specifiedNavigate the element's child browsing context
to a resource whose Content-Type is text/html
, whose URL
is about:srcdoc
, and whose data consists of the value of the attribute. The
resulting Document
must be considered an iframe
srcdoc
document.
src
attribute
specified, and the user agent is processing the iframe
's attributes for the "first
time"Queue a task to run the iframe load event steps.
The task source for this task is the DOM manipulation task source.
If the value of the src
attribute is missing, or its value is the empty string,
let url be the string "about:blank
".
Otherwise, resolve the value of the src
attribute, relative to the iframe
element.
If that is not successful, then let url be the string
"about:blank
". Otherwise, let url be the resulting
absolute URL.
If there exists an ancestor browsing context whose active document's address, ignoring fragment identifiers, is equal to url, then abort these steps.
Navigate the element's child browsing context to url.
Any navigation required of the user agent in the process
the iframe
attributes algorithm must be completed as an explicit
self-navigation override and with the iframe
element's document's
browsing context as the source browsing context.
Furthermore, if the active document of the element's child browsing context before such a navigation was not completely loaded at the time of the new navigation, then the navigation must be completed with replacement enabled.
Similarly, if the child browsing context's session history contained
only one Document
when the process the iframe
attributes
algorithm was invoked, and that was the about:blank
Document
created
when the child browsing context was created, then any navigation required of the user agent in that algorithm must be completed
with replacement enabled.
When a Document
in an iframe
is marked as completely
loaded, the user agent must synchronously run the iframe load event steps.
A load
event is also fired at the
iframe
element when it is created if no other data is loaded in it.
Each Document
has an iframe load in progress flag and a mute
iframe load flag. When a Document
is created, these flags must be unset for
that Document
.
The iframe load event steps are as follows:
Let child document be the active document of the
iframe
element's nested browsing context.
If child document has its mute iframe load flag set, abort these steps.
Set child document's iframe load in progress flag.
Fire a simple event named load
at the
iframe
element.
Unset child document's iframe load in progress flag.
This, in conjunction with scripting, can be used to probe the URL space of the local network's HTTP servers. User agents may implement cross-origin access control policies that are stricter than those described above to mitigate this attack, but unfortunately such policies are typically not compatible with existing Web content.
When the iframe
's browsing context's active document is
not ready for post-load tasks, and when anything in the iframe
is delaying the load event of the iframe
's
browsing context's active document, and when the iframe
's
browsing context is in the delaying load
events
mode, the iframe
must delay the load event of its document.
If, during the handling of the load
event, the
browsing context in the iframe
is again navigated, that will further delay the load event.
If, when the element is created, the srcdoc
attribute is not set, and the src
attribute is either also not set or set but its value cannot be
resolved, the browsing context will remain at the initial
about:blank
page.
If the user navigates away from this page, the
iframe
's corresponding WindowProxy
object will proxy new
Window
objects for new Document
objects, but the src
attribute will not change.
The name
attribute, if present, must be a
valid browsing context name. The given value is used to name the nested
browsing context. When the browsing context is created, if the attribute
is present, the browsing context name must be set to the value of this attribute;
otherwise, the browsing context name must be set to the empty string.
Whenever the name
attribute is set, the nested
browsing context's name must be changed to
the new value. If the attribute is removed, the browsing context name must be set to
the empty string.
The sandbox
attribute, when specified,
enables a set of extra restrictions on any content hosted by the iframe
. Its value
must be an unordered set of unique space-separated tokens that are ASCII
case-insensitive. The allowed values are allow-forms
, allow-pointer-lock
, allow-popups
, allow-same-origin
, allow-scripts
, and allow-top-navigation
.
When the attribute is set, the content is treated as being from a unique origin,
forms, scripts, and various potentially annoying APIs are disabled, links are prevented from
targeting other browsing contexts, and plugins are secured.
The allow-same-origin
keyword causes
the content to be treated as being from its real origin instead of forcing it into a unique
origin; the allow-top-navigation
keyword allows the content to navigate its top-level browsing context;
and the allow-forms
, allow-pointer-lock
, allow-popups
and allow-scripts
keywords re-enable forms, the
pointer lock API, popups, and scripts respectively. [POINTERLOCK]
Setting both the allow-scripts
and allow-same-origin
keywords together when the
embedded page has the same origin as the page containing the iframe
allows the embedded page to simply remove the sandbox
attribute and then reload itself, effectively breaking out of the sandbox altogether.
These flags only take effect when the nested browsing context of
the iframe
is navigated. Removing them, or removing the
entire sandbox
attribute, has no effect on an
already-loaded page.
Potentially hostile files should not be served from the same server as the file
containing the iframe
element. Sandboxing hostile content is of minimal help if an
attacker can convince the user to just visit the hostile content directly, rather than in the
iframe
. To limit the damage that can be caused by hostile HTML content, it should be
served from a separate dedicated domain. Using a different domain ensures that scripts in the
files are unable to attack the site, even if the user is tricked into visiting those pages
directly, without the protection of the sandbox
attribute.
When an iframe
element with a sandbox
attribute has its nested browsing context created (before the initial
about:blank
Document
is created), and when an iframe
element's sandbox
attribute is set or changed while it
has a nested browsing context, the user agent must parse the sandboxing directive using the attribute's value as the input, and the iframe
element's nested browsing context's
iframe
sandboxing flag set as the output.
When an iframe
element's sandbox
attribute is removed while it has a nested browsing context, the user agent must
empty the iframe
element's nested browsing context's
iframe
sandboxing flag set as the output.
In this example, some completely-unknown, potentially hostile, user-provided HTML content is embedded in a page. Because it is served from a separate domain, it is affected by all the normal cross-site restrictions. In addition, the embedded page has scripting disabled, plugins disabled, forms disabled, and it cannot navigate any frames or windows other than itself (or any frames or windows it itself embeds).
<p>We're not scared of you! Here is your content, unedited:</p> <iframe sandbox src="http://usercontent.example.net/getusercontent.cgi?id=12193"></iframe>
It is important to use a separate domain so that if the attacker convinces the user to visit that page directly, the page doesn't run in the context of the site's origin, which would make the user vulnerable to any attack found in the page.
In this example, a gadget from another site is embedded. The gadget has scripting and forms enabled, and the origin sandbox restrictions are lifted, allowing the gadget to communicate with its originating server. The sandbox is still useful, however, as it disables plugins and popups, thus reducing the risk of the user being exposed to malware and other annoyances.
<iframe sandbox="allow-same-origin allow-forms allow-scripts" src="http://maps.example.com/embedded.html"></iframe>
Suppose a file A contained the following fragment:
<iframe sandbox="allow-same-origin allow-forms" src=B></iframe>
Suppose that file B contained an iframe also:
<iframe sandbox="allow-scripts" src=C></iframe>
Further, suppose that file C contained a link:
<a href=D>Link</a>
For this example, suppose all the files were served as text/html
.
Page C in this scenario has all the sandboxing flags set. Scripts are disabled, because the
iframe
in A has scripts disabled, and this overrides the allow-scripts
keyword set on the
iframe
in B. Forms are also disabled, because the inner iframe
(in B)
does not have the allow-forms
keyword
set.
Suppose now that a script in A removes all the sandbox
attributes in A and B.
This would change nothing immediately. If the user clicked the link in C, loading page D into the
iframe
in B, page D would now act as if the iframe
in B had the allow-same-origin
and allow-forms
keywords set, because that was the
state of the nested browsing context in the iframe
in A when page B was
loaded.
Generally speaking, dynamically removing or changing the sandbox
attribute is ill-advised, because it can make it quite
hard to reason about what will be allowed and what will not.
The seamless
attribute is a boolean
attribute. When specified, it indicates that the iframe
element's
browsing context is to be rendered in a manner that makes it appear to be part of the
containing document (seamlessly included in the parent document).
An HTML inclusion is effected using this attribute as in the following example. In this case, the inclusion is of a site-wide navigation bar.
<!DOCTYPE HTML> <title>Mirror Mirror — MovieInfo™</title> <header> <h1>Mirror Mirror</h1> <p>Part of the MovieInfo™ Database</p> <nav> <iframe seamless src="nav.inc"></iframe> </nav> </header> ...
An iframe
element is said to be in seamless mode when all of the
following conditions are met:
seamless
attribute is set on the
iframe
element, and
iframe
element's owner Document
's active sandboxing flag
set does not have the sandboxed seamless iframes flag set, and
iframe
element's Document
, or
iframe
element's Document
, or
iframe
srcdoc
document.
When an iframe
element is in seamless mode, the following
requirements apply:
The user agent must set the seamless browsing context flag to true for that
browsing context. This will cause links to open in the
parent browsing context unless an explicit self-navigation override is used
(target="_self"
).
Media queries in the context of the iframe
's browsing context
(e.g. on media
attributes of style
elements in
Document
s in that iframe
) must be evaluated with respect to the nearest
ancestor browsing context that is not itself being nested through an iframe
that is in seamless
mode. [MQ]
In a CSS-supporting user agent: the user agent must add all the style sheets that apply to
the iframe
element to the cascade of the active document of the
iframe
element's nested browsing context, at the appropriate cascade
levels, before any style sheets specified by the document itself.
In a CSS-supporting user agent: the user agent must, for the purpose of CSS property
inheritance only, treat the root element of the active document of the
iframe
element's nested browsing context as being a child of the
iframe
element. (Thus inherited properties on the root element of the document in
the iframe
will inherit the computed values of those properties on the
iframe
element instead of taking their initial values.)
In visual media, in a CSS-supporting user agent: the user agent should set the intrinsic
width of the iframe
to the width that the element would have if it was a
non-replaced block-level element with 'width: auto', unless that width would be zero (e.g. if the
element is floating or absolutely positioned), in which case the user agent should set the
intrinsic width of the iframe
to the shrink-to-fit width of the root element (if
any) of the content rendered in the iframe
.
In visual media, in a CSS-supporting user agent: the user agent should set the intrinsic
height of the iframe
to the shortest height that would make the content rendered in
the iframe
at its current width (as given in the previous bullet point) have no
scrollable overflow at its bottom edge. Scrollable overflow is any overflow that would increase the range to
which a scrollbar or other scrolling mechanism can scroll.
In visual media, in a CSS-supporting user agent: the user agent must force the height of the
initial containing block of the active document of the nested browsing
context of the iframe
to zero.
This is intended to get around the otherwise circular dependency of percentage dimensions that depend on the height of the containing block, thus affecting the height of the document's bounding box, thus affecting the height of the viewport, thus affecting the size of the initial containing block.
In speech media, the user agent should render the nested browsing context without announcing that it is a separate document.
User agents should, in general, act as if the active document of the
iframe
's nested browsing context was part of the document that the
iframe
is in, if any.
For example if the user agent supports listing all the links in a document, links in "seamlessly" nested documents would be included in that list without being significantly distinguished from links in the document itself.
The nested browsing context's Window
object's
cross-boundary event parent is the browsing context container. [DOM]
If the attribute is not specified, or if the origin conditions listed above are not met, then the user agent should render the nested browsing context in a manner that is clearly distinguishable as a separate browsing context, and the seamless browsing context flag must be set to false for that browsing context.
It is important that user agents recheck the above conditions whenever the
active document of the nested browsing context of the
iframe
changes, such that the seamless browsing context flag gets unset
if the nested browsing context is navigated to another
origin.
The attribute can be set or removed dynamically, with the rendering updating in tandem.
In this example, the site's navigation is embedded using a client-side include using an
iframe
. Any links in the iframe
will, in new user agents, be
automatically opened in the iframe
's parent browsing context; for legacy user
agents, the site could also include a base
element with a target
attribute with the value _parent
.
Similarly, in new user agents the styles of the parent page will be automatically applied to the
contents of the frame, but to support legacy user agents authors might wish to include the styles
explicitly.
<nav><iframe seamless src="nav.include.html"></iframe></nav>
The contenteditable
attribute does not
propagate into seamless
iframe
s.
The iframe
element supports dimension attributes for cases where the
embedded content has specific dimensions (e.g. ad units have well-defined dimensions).
An iframe
element never has fallback content, as it will always
create a nested browsing context, regardless of whether the specified initial
contents are successfully used.
Descendants of iframe
elements represent nothing. (In legacy user agents that do
not support iframe
elements, the contents would be parsed as markup that could act as
fallback content.)
When used in HTML documents, the allowed content model
of iframe
elements is text, except that invoking the HTML fragment parsing
algorithm with the iframe
element as the context element and the text contents as the input must result in a list of nodes that are all phrasing content,
with no parse errors having occurred, with no script
elements being anywhere in the list or as descendants of elements in the list, and with all the
elements in the list (including their descendants) being themselves conforming.
The iframe
element must be empty in XML documents.
The HTML parser treats markup inside iframe
elements as
text.
The IDL attributes src
, srcdoc
, name
, sandbox
, and seamless
must reflect the respective
content attributes of the same name.
The contentDocument
IDL attribute
must return the Document
object of the active document of the
iframe
element's nested browsing context, if any and if its
effective script origin is the same origin as the effective script
origin specified by the incumbent settings object, or null otherwise.
The contentWindow
IDL attribute must
return the WindowProxy
object of the iframe
element's nested
browsing context, if any, or null otherwise.
Here is an example of a page using an iframe
to include advertising from an
advertising broker:
<iframe src="http://ads.example.com/?customerid=923513721&format=banner" width="468" height="60"></iframe>
embed
elementsrc
type
width
height
interface HTMLEmbedElement : HTMLElement { attribute DOMString src; attribute DOMString type; attribute DOMString width; attribute DOMString height; legacycaller any (any... arguments); };
Depending on the type of content instantiated by the
embed
element, the node may also support other
interfaces.
The embed
element provides an integration point for an external (typically
non-HTML) application or interactive content.
The src
attribute gives the address of the
resource being embedded. The attribute, if present, must contain a valid non-empty URL
potentially surrounded by spaces.
The type
attribute, if present, gives the
MIME type by which the plugin to instantiate is selected. The value must be a
valid MIME type. If both the type
attribute and
the src
attribute are present, then the type
attribute must specify the same type as the explicit Content-Type metadata of the resource given by the src
attribute.
When the element is created with neither a src
attribute
nor a type
attribute, and when attributes are removed such
that neither attribute is present on the element anymore, and when the element has a media
element ancestor, and when the element has an ancestor object
element that is
not showing its fallback content, any plugin instantiated for
the element must be removed, and the embed
element then represents nothing.
An embed
element is said to be potentially
active when the following conditions are all met simultaneously:
Document
or was in a Document
the last time the event loop
reached step 1.Document
is fully active.src
attribute set or a type
attribute set (or both).src
attribute is either absent or its value
is not the empty string.object
element that is not showing its
fallback content.Whenever an embed
element that was not potentially active becomes potentially active, and whenever a potentially active embed
element that is
remaining potentially active and has its src
attribute set, changed, or removed or its type
attribute set, changed, or removed, the user agent must
queue a task using the embed task source to run the
embed
element setup steps.
The embed
element setup steps are as follows:
If another task has since been queued to run the
embed
element setup steps for this element, then abort these steps.
src
attribute setThe user agent must resolve the value of the element's
src
attribute, relative to the element. If that is
successful, the user agent should fetch the resulting absolute
URL, from the element's browsing context scope origin if it has one. The task that
is queued by the networking task source once
the resource has been fetched must run the following steps:
If another task has since been queued to run
the embed
element setup steps for this element, then abort these
steps.
Determine the type of the content being embedded, as follows (stopping at the first substep that determines the type):
If the element has a type
attribute, and that
attribute's value is a type that a plugin supports, then the value of the
type
attribute is the content's type.
Otherwise, if applying the URL parser algorithm to the URL of the specified resource (after any redirects) results in a parsed URL whose path component matches a pattern that a plugin supports, then the content's type is the type that that plugin can handle.
For example, a plugin might say that it can handle resources with path components that end with the four character string
".swf
".
Otherwise, if the specified resource has explicit Content-Type metadata, then that is the content's type.
Otherwise, the content has no type and there can be no appropriate plugin for it.
If the previous step determined that the content's
type is image/svg+xml
, then run the following substeps:
If the embed
element is not associated with a nested browsing
context, associate the element with a newly created nested browsing
context, and, if the element has a name
attribute, set the browsing context name of the element's nested
browsing context to the value of this attribute.
Navigate the nested browsing context to
the fetched resource, with replacement enabled, and with the
embed
element's document's browsing context as the source
browsing context. (The src
attribute of the
embed
element doesn't get updated if the browsing context gets further
navigated to other locations.)
The embed
element now represents its associated
nested browsing context.
Otherwise, find and instantiate an appropriate plugin based on the content's type, and hand that plugin the
content of the resource, replacing any previously instantiated plugin for the element. The
embed
element now represents this plugin instance.
Whether the resource is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the content's type and when handing the resource to the plugin.
This allows servers to return data for plugins even with error responses (e.g. HTTP 500 Internal Server Error codes can still contain plugin data).
Fetching the resource must delay the load event of the element's document.
src
attribute setThe user agent should find and instantiate an appropriate plugin based on the
value of the type
attribute. The embed
element now represents this plugin instance.
The embed
element has no fallback content. If the user agent can't
find a suitable plugin when attempting to find and instantiate one for the algorithm above, then
the user agent must use a default plugin. This default could be as simple as saying "Unsupported
Format".
Whenever an embed
element that was potentially
active stops being potentially active, any
plugin that had been instantiated for that element must be unloaded.
When a plugin is to be instantiated but it cannot be secured and the sandboxed plugins browsing context
flag is set on the embed
element's Document
's active
sandboxing flag set, then the user agent must not instantiate the plugin, and
must instead render the embed
element in a manner that conveys that the
plugin was disabled. The user agent may offer the user the option to override the
sandbox and instantiate the plugin anyway; if the user invokes such an option, the
user agent must act as if the conditions above did not apply for the purposes of this element.
Plugins that cannot be secured are disabled in sandboxed browsing contexts because they might not honor the restrictions imposed by the sandbox (e.g. they might allow scripting even when scripting in the sandbox is disabled). User agents should convey the danger of overriding the sandbox to the user if an option to do so is provided.
Any namespace-less attribute other than name
, align
, hspace
, and vspace
may be
specified on the embed
element, so long as its name is XML-compatible
and contains no uppercase ASCII letters. These attributes are then passed as
parameters to the plugin.
All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents.
The four exceptions are to exclude legacy attributes that have side-effects beyond just sending parameters to the plugin.
The user agent should pass the names and values of all the attributes of the embed
element that have no namespace to the plugin used, when one is instantiated.
The HTMLEmbedElement
object representing the element must expose the scriptable
interface of the plugin instantiated for the embed
element, if any. At a
minimum, this interface must implement the legacy caller
operation. (It is suggested that the default behavior of this legacy caller operation, e.g.
the behavior of the default plugin's legacy caller operation, be to throw a
NotSupportedError
exception.)
The embed
element supports dimension attributes.
The IDL attributes src
and type
each must reflect the respective
content attributes of the same name.
Here's a way to embed a resource that requires a proprietary plugin, like Flash:
<embed src="catgame.swf">
If the user does not have the plugin (for example if the plugin vendor doesn't support the user's platform), then the user will be unable to use the resource.
To pass the plugin a parameter "quality" with the value "high", an attribute can be specified:
<embed src="catgame.swf" quality="high">
This would be equivalent to the following, when using an object
element
instead:
<object data="catgame.swf"> <param name="quality" value="high"> </object>
object
elementusemap
attribute: Interactive content.param
elements, then, transparent.data
type
typemustmatch
name
usemap
form
width
height
interface HTMLObjectElement : HTMLElement { attribute DOMString data; attribute DOMString type; attribute boolean typeMustMatch; attribute DOMString name; attribute DOMString useMap; readonly attribute HTMLFormElement? form; attribute DOMString width; attribute DOMString height; readonly attribute Document? contentDocument; readonly attribute WindowProxy? contentWindow; readonly attribute boolean willValidate; readonly attribute ValidityState validity; readonly attribute DOMString validationMessage; boolean checkValidity(); boolean reportValidity(); void setCustomValidity(DOMString error); legacycaller any (any... arguments); };
Depending on the type of content instantiated by the
object
element, the node also supports other
interfaces.
The object
element can represent an external resource, which, depending on the
type of the resource, will either be treated as an image, as a nested browsing
context, or as an external resource to be processed by a plugin.
The data
attribute, if present, specifies the
address of the resource. If present, the attribute must be a valid non-empty URL potentially
surrounded by spaces.
Authors who reference resources from other origins
that they do not trust are urged to use the typemustmatch
attribute defined below. Without that
attribute, it is possible in certain cases for an attacker on the remote host to use the plugin
mechanism to run arbitrary scripts, even if the author has used features such as the Flash
"allowScriptAccess" parameter.
The type
attribute, if present, specifies the
type of the resource. If present, the attribute must be a valid MIME type.
At least one of either the data
attribute or the type
attribute must be present.
The typemustmatch
attribute is a
boolean attribute whose presence indicates that the resource specified by the data
attribute is only to be used if the value of the type
attribute and the Content-Type of the
aforementioned resource match.
The typemustmatch
attribute must not be
specified unless both the data
attribute and the type
attribute are present.
The name
attribute, if present, must be a
valid browsing context name. The given value is used to name the nested
browsing context, if applicable.
Whenever one of the following conditions occur:
Document
changes whether it is fully active,
object
elements changes to or from showing its
fallback content,
classid
attribute is set, changed, or removed,
classid
attribute is not present, and
its data
attribute is set, changed, or removed,
classid
attribute nor its
data
attribute are present, and its type
attribute is set, changed, or removed,
...the user agent must queue a task to run the following steps to (re)determine
what the object
element represents. The task source for this task is the DOM manipulation task source. This task being queued or actively
running must delay the load event of the element's document.
If the user has indicated a preference that this object
element's fallback
content be shown instead of the element's usual behavior, then jump to the step below labeled fallback.
For example, a user could ask for the element's fallback content to be shown because that content uses a format that the user finds more accessible.
If the element has an ancestor media element, or has an ancestor
object
element that is not showing its fallback content, or
if the element is not in a Document
with a
browsing context, or if the element's Document
is not fully
active, or if the element is still in the stack of open elements of an
HTML parser or XML parser, or if the element is not being
rendered, then jump to the step below labeled fallback.
If the classid
attribute is present, and has a value
that isn't the empty string, then: if the user agent can find a plugin suitable
according to the value of the classid
attribute, and
either plugins aren't being sandboxed or that
plugin can be secured, then that
plugin should be used, and the value of the data
attribute, if any, should be passed to the
plugin. If no suitable plugin can be found, or if the
plugin reports an error, jump to the step below labeled fallback.
If the data
attribute is present and its value is
not the empty string, then:
If the type
attribute is present and its value is
not a type that the user agent supports, and is not a type that the user agent can find a
plugin for, then the user agent may jump to the step below labeled fallback
without fetching the content to examine its real type.
Resolve the URL specified by the data
attribute, relative to the element.
If that failed, fire a simple event named error
at the element, then jump to the step below labeled
fallback.
Fetch the resulting absolute URL, from the element's browsing context scope origin if it has one.
Fetching the resource must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined next) has been run.
For the purposes of the application cache networking model, this fetch operation is not for a child browsing context (though it might end up being used for one after all, as defined below).
If the resource is not yet available (e.g. because the resource was not available in the cache, so that loading the resource required making a request over the network), then jump to the step below labeled fallback. The task that is queued by the networking task source once the resource is available must restart this algorithm from this step. Resources can load incrementally; user agents may opt to consider a resource "available" whenever enough data has been obtained to begin processing the resource.
If the load failed (e.g. there was an HTTP 404 error, there was a DNS error), fire
a simple event named error
at the element, then jump to
the step below labeled fallback.
Determine the resource type, as follows:
Let the resource type be unknown.
If the object
element has a type
attribute and a typemustmatch
attribute, and
the resource has associated Content-Type metadata, and the
type specified in the resource's Content-Type metadata is
an ASCII case-insensitive match for the value of the element's type
attribute, then let resource type
be that type and jump to the step below labeled handler.
If the object
element has a typemustmatch
attribute, jump to the step below
labeled handler.
If the user agent is configured to strictly obey Content-Type headers for this resource, and the resource has associated Content-Type metadata, then let the resource type be the type specified in the resource's Content-Type metadata, and jump to the step below labeled handler.
This can introduce a vulnerability, wherein a site is trying to embed a resource that uses a particular plugin, but the remote site overrides that and instead furnishes the user agent with a resource that triggers a different plugin with different security characteristics.
If there is a type
attribute present on the
object
element, and that attribute's value is not a type that the user agent
supports, but it is a type that a plugin supports, then let the resource type be the type specified in that type
attribute, and jump to the step below labeled
handler.
Run the appropriate set of steps from the following list:
Let binary be false.
If the type specified in the resource's Content-Type
metadata is "text/plain
", and the result of applying the rules for distinguishing if a resource is
text or binary to the resource is that the resource is not
text/plain
, then set binary to true.
If the type specified in the resource's Content-Type
metadata is "application/octet-stream
", then set binary to true.
If binary is false, then let the resource type be the type specified in the resource's Content-Type metadata, and jump to the step below labeled handler.
If there is a type
attribute present on the
object
element, and its value is not application/octet-stream
,
then run the following steps:
If the attribute's value is a type that a plugin supports, or the
attribute's value is a type that starts with "image/
" that is not also an
XML MIME type, then let the resource type be the type
specified in that type
attribute.
Jump to the step below labeled handler.
If there is a type
attribute present on the
object
element, then let the tentative type be the type
specified in that type
attribute.
Otherwise, let tentative type be the sniffed type of the resource.
If tentative type is not
application/octet-stream
, then let resource type be
tentative type and jump to the step below labeled
handler.
If applying the URL parser algorithm to the URL of the specified resource (after any redirects) results in a parsed URL whose path component matches a pattern that a plugin supports, then let resource type be the type that that plugin can handle.
For example, a plugin might say that it can handle resources with path components that end with the four character string
".swf
".
It is possible for this step to finish, or for one of the substeps above to jump straight to the next step, with resource type still being unknown. In both cases, the next step will trigger fallback.
Handler: Handle the content as given by the first of the following cases that matches:
If plugins are being sandboxed and the plugin that supports resource type cannot be secured, jump to the step below labeled fallback.
Otherwise, the user agent should use the plugin that supports resource type and pass the content of the resource to that plugin. If the plugin reports an error, then jump to the step below labeled fallback.
image/
"The object
element must be associated with a newly created nested
browsing context, if it does not already have one.
If the URL of the given resource is not about:blank
, the
element's nested browsing context must then be navigated to that resource, with
replacement enabled, and with the object
element's document's
browsing context as the source browsing context. (The data
attribute of the object
element doesn't
get updated if the browsing context gets further navigated to other locations.)
If the URL of the given resource is about:blank
, then,
instead, the user agent must queue a task to fire a simple event
named load
at the object
element. No load
event is fired at the
about:blank
document itself.
The object
element represents the nested browsing
context.
If the name
attribute is present, the
browsing context name must be set to the value of this attribute; otherwise,
the browsing context name must be set to the empty string.
In certain situations, e.g. if the resource was fetched from an application cache but it is an HTML file
with a manifest
attribute that points to a different
application cache manifest, the navigation of the browsing context will be restarted so
as to load the resource afresh from the network or a different application
cache. Even if the resource is then found to have a different type, it is still used
as part of a nested browsing context: only the navigate algorithm
is restarted, not this object
algorithm.
image/
", and support
for images has not been disabledApply the image sniffing rules to determine the type of the image.
The object
element represents the specified image. The image is
not a nested browsing context.
If the image cannot be rendered, e.g. because it is malformed or in an unsupported format, jump to the step below labeled fallback.
The given resource type is not supported. Jump to the step below labeled fallback.
If the previous step ended with the resource type being unknown, this is the case that is triggered.
The element's contents are not part of what the object
element
represents.
Once the resource is completely loaded, queue a task to fire a simple
event named load
at the element.
The task source for this task is the DOM manipulation task source.
If the data
attribute is absent but the type
attribute is present, and the user agent can find a
plugin suitable according to the value of the type
attribute, and either plugins
aren't being sandboxed or the plugin can be secured, then that plugin should be used. If these conditions cannot be met, or if the
plugin reports an error, jump to the step below labeled fallback.
Fallback: The object
element represents the element's
children, ignoring any leading param
element children. This is the element's
fallback content. If the element has an instantiated plugin, then
unload it.
When the algorithm above instantiates a plugin, the user agent
should pass to the plugin used the names and values of all the attributes on the
element, in the order they were added to the element, with the attributes added by the parser
being ordered in source order, followed by a parameter named "PARAM" whose value is null, followed
by all the names and values of parameters given by
param
elements that are children of the object
element, in tree
order. If the plugin supports a scriptable interface, the
HTMLObjectElement
object representing the element should expose that interface. The
object
element represents the plugin. The
plugin is not a nested browsing context.
Plugins are considered sandboxed for the purpose of an
object
element if the sandboxed plugins browsing context flag is set on
the object
element's Document
's active sandboxing flag
set.
Due to the algorithm above, the contents of object
elements act as fallback
content, used only when referenced resources can't be shown (e.g. because it returned a 404
error). This allows multiple object
elements to be nested inside each other,
targeting multiple user agents with different capabilities, with the user agent picking the first
one it supports.
Whenever the name
attribute is set, if the
object
element has a nested browsing context, its name must be changed to the new value. If the attribute is removed, if the
object
element has a browsing context, the browsing context
name must be set to the empty string.
The usemap
attribute, if present while the
object
element represents an image, can indicate that the object has an associated
image map. The attribute must be ignored if the
object
element doesn't represent an image.
The form
attribute is used to explicitly associate the
object
element with its form owner.
Constraint validation: object
elements are always barred
from constraint validation.
The object
element supports dimension attributes.
The IDL attributes data
, type
and name
each must reflect the respective
content attributes of the same name. The typeMustMatch
IDL attribute must
reflect the typemustmatch
content
attribute. The useMap
IDL attribute must
reflect the usemap
content attribute.
The contentDocument
IDL attribute
must return the Document
object of the active document of the
object
element's nested browsing context, if any and if its
effective script origin is the same origin as the effective script
origin specified by the incumbent settings object, or null otherwise.
The contentWindow
IDL attribute must
return the WindowProxy
object of the object
element's nested
browsing context, if it has one; otherwise, it must return null.
The willValidate
, validity
, and validationMessage
attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The form
IDL attribute
is part of the element's forms API.
All object
elements have a legacy caller
operation. If the object
element has an instantiated plugin that
supports a scriptable interface that defines a legacy caller operation, then that must be the
behavior of the object's legacy caller operation. Otherwise, the object's legacy caller operation
must be to throw a NotSupportedError
exception.
In the following example, a Java applet is embedded in a page using the object
element. (Generally speaking, it is better to avoid using applets like these and instead use
native JavaScript and HTML to provide the functionality, since that way the application will work
on all Web browsers without requiring a third-party plugin. Many devices, especially embedded
devices, do not support third-party technologies like Java.)
<figure> <object type="application/x-java-applet"> <param name="code" value="MyJavaClass"> <p>You do not have Java available, or it is disabled.</p> </object> <figcaption>My Java Clock</figcaption> </figure>
In this example, an HTML page is embedded in another using the object
element.
<figure> <object data="clock.html"></object> <figcaption>My HTML Clock</figcaption> </figure>
The following example shows how a plugin can be used in HTML (in this case the Flash plugin,
to show a video file). Fallback is provided for users who do not have Flash enabled, in this case
using the video
element to show the video for those using user agents that support
video
, and finally providing a link to the video for those who have neither Flash
nor a video
-capable browser.
<p>Look at my video: <object type="application/x-shockwave-flash"> <param name=movie value="http://video.example.com/library/watch.swf"> <param name=allowfullscreen value=true> <param name=flashvars value="http://video.example.com/vids/315981"> <video controls src="http://video.example.com/vids/315981"> <a href="http://video.example.com/vids/315981">View video</a>. </video> </object> </p>
param
elementobject
element, before any flow content.name
value
interface HTMLParamElement : HTMLElement { attribute DOMString name; attribute DOMString value; };
The param
element defines parameters for plugins invoked by object
elements. It does not represent anything on its own.
The name
attribute gives the name of the
parameter.
The value
attribute gives the value of the
parameter.
Both attributes must be present. They may have any value.
If both attributes are present, and if the parent element of the param
is an
object
element, then the element defines a parameter with the given name-value pair.
If either the name or value of a parameter defined
by a param
element that is the child of an object
element that
represents an instantiated plugin changes, and if that
plugin is communicating with the user agent using an API that features the ability to
update the plugin when the name or value of a parameter so changes, then the user agent must
appropriately exercise that ability to notify the plugin of the change.
The IDL attributes name
and value
must both reflect the respective
content attributes of the same name.
The following example shows how the param
element can be used to pass a parameter
to a plugin, in this case the O3D plugin.
<!DOCTYPE HTML> <html lang="en"> <head> <title>O3D Utah Teapot</title> </head> <body> <p> <object type="application/vnd.o3d.auto"> <param name="o3d_features" value="FloatingPointTextures"> <img src="o3d-teapot.png" title="3D Utah Teapot illustration rendered using O3D." alt="When O3D renders the Utah Teapot, it appears as a squat teapot with a shiny metallic finish on which the surroundings are reflected, with a faint shadow caused by the lighting."> <p>To see the teapot actually rendered by O3D on your computer, please download and install the <a href="http://code.google.com/apis/o3d/docs/gettingstarted.html#install">O3D plugin</a>.</p> </object> <script src="o3d-teapot.js"></script> </p> </body> </html>
video
elementcontrols
attribute: Interactive content.src
attribute:
zero or more track
elements, then
transparent, but with no media element descendants.src
attribute: zero or more source
elements, then
zero or more track
elements, then
transparent, but with no media element descendants.src
crossorigin
poster
preload
autoplay
mediagroup
loop
muted
controls
width
height
interface HTMLVideoElement : HTMLMediaElement { attribute unsigned long width; attribute unsigned long height; readonly attribute unsigned long videoWidth; readonly attribute unsigned long videoHeight; attribute DOMString poster; };
A video
element is used for playing videos or movies, and audio files with
captions.
Content may be provided inside the video
element. User agents
should not show this content to the user; it is intended for older Web browsers which do
not support video
, so that legacy video plugins can be tried, or to show text to the
users of these older browsers informing them of how to access the video contents.
In particular, this content is not intended to address accessibility concerns. To
make video content accessible to the partially sighted, the blind, the hard-of-hearing, the deaf,
and those with other physical or cognitive disabilities, a variety of features are available.
Captions can be provided, either embedded in the video stream or as external files using the
track
element. Sign-language tracks can be provided, again either embedded in the
video stream or by synchronizing multiple video
elements using the mediagroup
attribute or a MediaController
object. Audio descriptions can be provided, either as a separate track embedded in the video
stream, or a separate audio track in an audio
element slaved to the same controller as the video
element(s), or in text
form using a WebVTT file referenced using the track
element and
synthesized into speech by the user agent. WebVTT can also be used to provide chapter titles. For
users who would rather not use a media element at all, transcripts or other textual alternatives
can be provided by simply linking to them in the prose near the video
element. [WEBVTT]
The video
element is a media element whose media data is
ostensibly video data, possibly with associated audio data.
The src
, preload
,
autoplay
, mediagroup
, loop
, muted
, and controls
attributes are the attributes common to all media
elements.
The poster
attribute gives the address of an
image file that the user agent can show while no video data is available. The attribute, if
present, must contain a valid non-empty URL potentially surrounded by spaces.
If the specified resource is to be used, then, when the element is created or when the poster
attribute is set, changed, or removed, the user agent must
run the following steps to determine the element's poster frame (regardless of the
value of the element's show poster flag):
If there is an existing instance of this algorithm running for this video
element, abort that instance of this algorithm without changing the poster
frame.
If the poster
attribute's value is the empty string
or if the attribute is absent, then there is no poster frame; abort these
steps.
Resolve the poster
attribute's value relative to the element. If this fails,
then there is no poster frame; abort these steps.
Fetch the resulting absolute URL, from the element's
Document
's origin. This must delay the load event of the
element's document.
If an image is thus obtained, the poster frame is that image. Otherwise, there is no poster frame.
The image given by the poster
attribute,
the poster frame, is intended to be a representative frame of the video (typically one of
the first non-blank frames) that gives the user an idea of what the video is like.
A video
element represents what is given for the first matching condition in the
list below:
readyState
attribute is either HAVE_NOTHING
, or HAVE_METADATA
but no video data has yet been obtained at
all, or the element's readyState
attribute is any
subsequent value but the media resource does not have a video channel)video
element represents its poster frame, if any,
or else transparent black with no intrinsic dimensions.video
element is paused, the current playback position is the first frame of video,
and the element's show poster flag is setvideo
element represents its poster frame, if any,
or else the first frame of the video.video
element is paused, and the
frame of video corresponding to the current playback
position is not available (e.g. because the video is seeking or buffering)video
element is neither potentially playing nor paused (e.g. when seeking or stalled)video
element represents the last frame of the video to have
been rendered.video
element is pausedvideo
element represents the frame of video corresponding to
the current playback position.video
element has a video channel and is potentially
playing)video
element represents the frame of video at the continuously
increasing "current" position. When the
current playback position changes such that the last frame rendered is no longer the
frame corresponding to the current playback position in the video, the new frame
must be rendered.Which frame in a video stream corresponds to a particular playback position is defined by the video stream's format.
The video
element also represents any text track cues whose text track cue active flag is set and whose
text track is in the showing mode, and any
audio from the media resource, at the current playback position.
Any audio associated with the media resource must, if played, be played synchronized with the current playback position, at the element's effective media volume.
In addition to the above, the user agent may provide messages to the user (such as "buffering", "no video loaded", "error", or more detailed information) by overlaying text or icons on the video or other areas of the element's playback area, or in another appropriate manner.
User agents that cannot render the video may instead make the element represent a link to an external video playback utility or to the video data itself.
When a video
element's media resource has a video channel, the
element provides a paint source whose width is the media resource's
intrinsic width, whose height is the
media resource's intrinsic
height, and whose appearance is the frame of video corresponding to the current playback position, if that is available, or else
(e.g. when the video is seeking or buffering) its previous appearance, if any, or else (e.g.
because the video is still loading the first frame) blackness.
videoWidth
videoHeight
These attributes return the intrinsic dimensions of the video, or zero if the dimensions are not known.
The intrinsic width and intrinsic height of the media resource are the dimensions of the resource in CSS pixels after taking into account the resource's dimensions, aspect ratio, clean aperture, resolution, and so forth, as defined for the format used by the resource. If an anamorphic format does not define how to apply the aspect ratio to the video data's dimensions to obtain the "correct" dimensions, then the user agent must apply the ratio by increasing one dimension and leaving the other unchanged.
The videoWidth
IDL attribute must return
the intrinsic width of the video in CSS pixels.
The videoHeight
IDL attribute must return
the intrinsic height of the video in CSS
pixels. If the element's readyState
attribute is HAVE_NOTHING
, then the attributes must return 0.
Whenever the intrinsic width
or intrinsic height of the video changes
(including, for example, because the selected video
track was changed), if the element's readyState
attribute is not HAVE_NOTHING
, the user agent must
queue a task to fire a simple event named resize
at the media element.
The video
element supports dimension attributes.
In the absence of style rules to the contrary, video content should be rendered inside the element's playback area such that the video content is shown centered in the playback area at the largest possible size that fits completely within it, with the video content's aspect ratio being preserved. Thus, if the aspect ratio of the playback area does not match the aspect ratio of the video, the video will be shown letterboxed or pillarboxed. Areas of the element's playback area that do not contain the video represent nothing.
In user agents that implement CSS, the above requirement can be implemented by using the style rule suggested in the rendering section.
The intrinsic width of a video
element's playback area is the intrinsic width of
the poster frame, if that is available and the element currently
represents its poster frame; otherwise, it is the intrinsic width of the video resource, if that is
available; otherwise the intrinsic width is missing.
The intrinsic height of a video
element's playback area is the intrinsic height of
the poster frame, if that is available and the element currently
represents its poster frame; otherwise it is the intrinsic height of the video resource, if that is
available; otherwise the intrinsic height is missing.
The default object size is a width of 300 CSS pixels and a height of 150 CSS pixels. [CSSIMAGES]
User agents should provide controls to enable or disable the display of closed captions, audio description tracks, and other additional data associated with the video stream, though such features should, again, not interfere with the page's normal rendering.
User agents may allow users to view the video content in manners more suitable to the user
(e.g. full-screen or in an independent resizable window). As for the other user interface
features, controls to enable this should not interfere with the page's normal rendering unless the
user agent is exposing a user interface.
In such an independent context, however, user agents may make full user interfaces visible, with,
e.g., play, pause, seeking, and volume controls, even if the controls
attribute is absent.
User agents may allow video playback to affect system features that could interfere with the user's experience; for example, user agents could disable screensavers while video playback is in progress.
The poster
IDL attribute must
reflect the poster
content attribute.
This example shows how to detect when a video has failed to play correctly:
<script> function failed(e) { // video playback failed - show a message saying why switch (e.target.error.code) { case e.target.error.MEDIA_ERR_ABORTED: alert('You aborted the video playback.'); break; case e.target.error.MEDIA_ERR_NETWORK: alert('A network error caused the video download to fail part-way.'); break; case e.target.error.MEDIA_ERR_DECODE: alert('The video playback was aborted due to a corruption problem or because the video used features your browser did not support.'); break; case e.target.error.MEDIA_ERR_SRC_NOT_SUPPORTED: alert('The video could not be loaded, either because the server or network failed or because the format is not supported.'); break; default: alert('An unknown error occurred.'); break; } } </script> <p><video src="tgif.vid" autoplay controls onerror="failed(event)"></video></p> <p><a href="tgif.vid">Download the video file</a>.</p>
audio
elementcontrols
attribute: Interactive content.controls
attribute: Palpable content.src
attribute:
zero or more track
elements, then
transparent, but with no media element descendants.src
attribute: zero or more source
elements, then
zero or more track
elements, then
transparent, but with no media element descendants.src
crossorigin
preload
autoplay
mediagroup
loop
muted
controls
[NamedConstructor=Audio(optional DOMString src)] interface HTMLAudioElement : HTMLMediaElement {};
An audio
element represents a sound or audio stream.
Content may be provided inside the audio
element. User agents
should not show this content to the user; it is intended for older Web browsers which do
not support audio
, so that legacy audio plugins can be tried, or to show text to the
users of these older browsers informing them of how to access the audio contents.
In particular, this content is not intended to address accessibility concerns. To
make audio content accessible to the deaf or to those with other physical or cognitive
disabilities, a variety of features are available. If captions or a sign language video are
available, the video
element can be used instead of the audio
element to
play the audio, allowing users to enable the visual alternatives. Chapter titles can be provided
to aid navigation, using the track
element and a WebVTT file. And,
naturally, transcripts or other textual alternatives can be provided by simply linking to them in
the prose near the audio
element. [WEBVTT]
The audio
element is a media element whose media data is
ostensibly audio data.
The src
, preload
,
autoplay
, mediagroup
, loop
, muted
, and controls
attributes are the attributes common to all media
elements.
When an audio
element is potentially playing, it must have its audio
data played synchronized with the current playback position, at the element's
effective media volume.
When an audio
element is not potentially playing, audio must not play
for the element.
Audio
( [ url ] )Returns a new audio
element, with the src
attribute set to the value passed in the argument, if applicable.
A constructor is provided for creating HTMLAudioElement
objects (in addition to
the factory methods from DOM such as createElement()
): Audio(src)
. When invoked as a
constructor, it must return a new HTMLAudioElement
object (a new audio
element). The element must have its preload
attribute set
to the literal value "auto
". If the src argument is present, the object created must have its src
content attribute set to the provided value, and the user agent
must invoke the object's resource selection
algorithm before returning. The element's document must be the active document
of the browsing context of the Window
object on which the interface
object of the invoked constructor is found.
source
elementtrack
elements.src
type
media
interface HTMLSourceElement : HTMLElement { attribute DOMString src; attribute DOMString type; attribute DOMString media; };
The source
element allows authors to specify multiple alternative media resources for media
elements. It does not represent anything on its own.
The src
attribute gives the address of the
media resource. The value must be a valid non-empty URL potentially surrounded
by spaces. This attribute must be present.
Dynamically modifying a source
element and its attribute when the
element is already inserted in a video
or audio
element will have no
effect. To change what is playing, just use the src
attribute
on the media element directly, possibly making use of the canPlayType()
method to pick from amongst available
resources. Generally, manipulating source
elements manually after the document has
been parsed is an unnecessarily complicated approach.
The type
attribute gives the type of the
media resource, to help the user agent determine if it can play this media
resource before fetching it. If specified, its value must be a valid MIME
type. The codecs
parameter, which certain MIME types define, might be
necessary to specify exactly how the resource is encoded. [RFC4281]
The following list shows some examples of how to use the codecs=
MIME
parameter in the type
attribute.
<source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>
<source src='video.mp4' type='video/mp4; codecs="avc1.58A01E, mp4a.40.2"'>
<source src='video.mp4' type='video/mp4; codecs="avc1.4D401E, mp4a.40.2"'>
<source src='video.mp4' type='video/mp4; codecs="avc1.64001E, mp4a.40.2"'>
<source src='video.mp4' type='video/mp4; codecs="mp4v.20.8, mp4a.40.2"'>
<source src='video.mp4' type='video/mp4; codecs="mp4v.20.240, mp4a.40.2"'>
<source src='video.3gp' type='video/3gpp; codecs="mp4v.20.8, samr"'>
<source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'>
<source src='video.ogv' type='video/ogg; codecs="theora, speex"'>
<source src='audio.ogg' type='audio/ogg; codecs=vorbis'>
<source src='audio.spx' type='audio/ogg; codecs=speex'>
<source src='audio.oga' type='audio/ogg; codecs=flac'>
<source src='video.ogv' type='video/ogg; codecs="dirac, vorbis"'>
The media
attribute gives the intended media
type of the media resource, to help the user agent determine if this media
resource is useful to the user before fetching it. Its value must be a valid media
query.
The resource
selection algorithm is defined in such a way that when the media
attribute is omitted the user agent acts the same as if the
value was "all
", i.e. by default the media resource is suitable
for all media.
If a source
element is inserted as a child of a media element that
has no src
attribute and whose networkState
has the value NETWORK_EMPTY
, the user agent must invoke the media
element's resource selection
algorithm.
The IDL attributes src
, type
, and media
must reflect the respective content
attributes of the same name.
If the author isn't sure if user agents will all be able to render the media resources
provided, the author can listen to the error
event on the last
source
element and trigger fallback behavior:
<script> function fallback(video) { // replace <video> with its contents while (video.hasChildNodes()) { if (video.firstChild instanceof HTMLSourceElement) video.removeChild(video.firstChild); else video.parentNode.insertBefore(video.firstChild, video); } video.parentNode.removeChild(video); } </script> <video controls autoplay> <source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'> <source src='video.ogv' type='video/ogg; codecs="theora, vorbis"' onerror="fallback(parentNode)"> ... </video>
track
elementkind
src
srclang
label
default
interface HTMLTrackElement : HTMLElement { attribute DOMString kind; attribute DOMString src; attribute DOMString srclang; attribute DOMString label; attribute boolean default; const unsigned short NONE = 0; const unsigned short LOADING = 1; const unsigned short LOADED = 2; const unsigned short ERROR = 3; readonly attribute unsigned short readyState; readonly attribute TextTrack track; };
The track
element allows authors to specify explicit external timed text tracks for media elements. It
does not represent anything on its own.
The kind
attribute is an enumerated
attribute. The following table lists the keywords defined for this attribute. The keyword
given in the first cell of each row maps to the state given in the second cell.
Keyword | State | Brief description |
---|---|---|
subtitles
| Subtitles | Transcription or translation of the dialogue, suitable for when the sound is available but not understood (e.g. because the user does not understand the language of the media resource's audio track). Overlaid on the video. |
captions
| Captions | Transcription or translation of the dialogue, sound effects, relevant musical cues, and other relevant audio information, suitable for when sound is unavailable or not clearly audible (e.g. because it is muted, drowned-out by ambient noise, or because the user is deaf). Overlaid on the video; labeled as appropriate for the hard-of-hearing. |
descriptions
| Descriptions | Textual descriptions of the video component of the media resource, intended for audio synthesis when the visual component is obscured, unavailable, or not usable (e.g. because the user is interacting with the application without a screen while driving, or because the user is blind). Synthesized as audio. |
chapters
| Chapters | Chapter titles, intended to be used for navigating the media resource. Displayed as an interactive (potentially nested) list in the user agent's interface. |
metadata
| Metadata | Tracks intended for use from script. Not displayed by the user agent. |
The attribute may be omitted. The missing value default is the subtitles state.
The src
attribute gives the address of the text
track data. The value must be a valid non-empty URL potentially surrounded by spaces.
This attribute must be present.
If the element has a src
attribute whose value is not the
empty string and whose value, when the attribute was set, could be successfully resolved relative to the element, then the element's track
URL is the resulting absolute URL. Otherwise, the element's track
URL is the empty string.
If the element's track URL identifies a WebVTT resource, and the
element's kind
attribute is not in the metadata state, then the WebVTT file must be
a WebVTT file using cue text. [WEBVTT]
Furthermore, if the element's track URL identifies a WebVTT resource,
and the element's kind
attribute is in the chapters state, then the WebVTT file must be
both a WebVTT file using chapter title text and a WebVTT file using only nested
cues. [WEBVTT]
The srclang
attribute gives the language of
the text track data. The value must be a valid BCP 47 language tag. This attribute must be present
if the element's kind
attribute is in the subtitles state. [BCP47]
If the element has a srclang
attribute whose value is
not the empty string, then the element's track language is the value of the attribute.
Otherwise, the element has no track language.
The label
attribute gives a user-readable
title for the track. This title is used by user agents when listing subtitle, caption, and audio description tracks in their user interface.
The value of the label
attribute, if the attribute is
present, must not be the empty string. Furthermore, there must not be two track
element children of the same media element whose kind
attributes are in the same state, whose srclang
attributes are both missing or have values that
represent the same language, and whose label
attributes are
again both missing or both have the same value.
If the element has a label
attribute whose value is not
the empty string, then the element's track label is the value of the attribute.
Otherwise, the element's track label is an empty string.
The default
attribute is a boolean
attribute, which, if specified, indicates that the track is to be enabled if the user's
preferences do not indicate that another track would be more appropriate.
Each media element must have no more than one track
element child
whose kind
attribute is in the subtitles or captions state and whose default
attribute is specified.
Each media element must have no more than one track
element child
whose kind
attribute is in the description state and whose default
attribute is specified.
Each media element must have no more than one track
element child
whose kind
attribute is in the chapters state and whose default
attribute is specified.
There is no limit on the number of track
elements whose kind
attribute is in the metadata state and whose default
attribute is specified.
readyState
Returns the text track readiness state, represented by a number from the following list:
NONE
(0)The text track not loaded state.
LOADING
(1)The text track loading state.
LOADED
(2)The text track loaded state.
ERROR
(3)The text track failed to load state.
track
Returns the TextTrack
object corresponding to the text track of the track
element.
The readyState
attribute must return the
numeric value corresponding to the text track readiness state of the
track
element's text track, as defined by the following list:
NONE
(numeric value 0)LOADING
(numeric value 1)LOADED
(numeric value 2)ERROR
(numeric value 3)The track
IDL attribute must, on getting,
return the track
element's text track's corresponding
TextTrack
object.
The src
, srclang
, label
, and default
IDL attributes must reflect the
respective content attributes of the same name. The kind
IDL attribute must reflect the content
attribute of the same name, limited to only known values.
This video has subtitles in several languages:
<video src="brave.webm"> <track kind=subtitles src=brave.en.vtt srclang=en label="English"> <track kind=captions src=brave.en.hoh.vtt srclang=en label="English for the Hard of Hearing"> <track kind=subtitles src=brave.fr.vtt srclang=fr lang=fr label="Français"> <track kind=subtitles src=brave.de.vtt srclang=de lang=de label="Deutsch"> </video>
(The lang
attributes on the last two describe the language of
the label
attribute, not the language of the subtitles
themselves. The language of the subtitles is given by the srclang
attribute.)
Media elements (audio
and video
, in
this specification) implement the following interface:
enum CanPlayTypeEnum { "" /* empty string */, "maybe", "probably" };
interface HTMLMediaElement : HTMLElement {
// error state
readonly attribute MediaError? error;
// network state
attribute DOMString src;
readonly attribute DOMString currentSrc;
attribute DOMString crossOrigin;
const unsigned short NETWORK_EMPTY = 0;
const unsigned short NETWORK_IDLE = 1;
const unsigned short NETWORK_LOADING = 2;
const unsigned short NETWORK_NO_SOURCE = 3;
readonly attribute unsigned short networkState;
attribute DOMString preload;
readonly attribute TimeRanges buffered;
void load();
CanPlayTypeEnum canPlayType(DOMString type);
// ready state
const unsigned short HAVE_NOTHING = 0;
const unsigned short HAVE_METADATA = 1;
const unsigned short HAVE_CURRENT_DATA = 2;
const unsigned short HAVE_FUTURE_DATA = 3;
const unsigned short HAVE_ENOUGH_DATA = 4;
readonly attribute unsigned short readyState;
readonly attribute boolean seeking;
// playback state
attribute double currentTime;
readonly attribute unrestricted double duration;
Date getStartDate();
readonly attribute boolean paused;
attribute double defaultPlaybackRate;
attribute double playbackRate;
readonly attribute TimeRanges played;
readonly attribute TimeRanges seekable;
readonly attribute boolean ended;
attribute boolean autoplay;
attribute boolean loop;
void play();
void pause();
// media controller
attribute DOMString mediaGroup;
attribute MediaController? controller;
// controls
attribute boolean controls;
attribute double volume;
attribute boolean muted;
attribute boolean defaultMuted;
// tracks
readonly attribute AudioTrackList audioTracks;
readonly attribute VideoTrackList videoTracks;
readonly attribute TextTrackList textTracks;
TextTrack addTextTrack(TextTrackKind kind, optional DOMString label = "", optional DOMString language = "");
};
The media element attributes, src
, crossorigin
, preload
, autoplay
,
mediagroup
, loop
,
muted
, and controls
, apply to all media
elements. They are defined in this section.
Media elements are used to present audio data, or video and audio data, to the user. This is referred to as media data in this section, since this section applies equally to media elements for audio or for video. The term media resource is used to refer to the complete set of media data, e.g. the complete video file, or complete audio file.
A media resource can have multiple audio and video tracks. For the purposes of a
media element, the video data of the media resource is only that of the
currently selected track (if any) given by the element's videoTracks
attribute, and the audio data of the media
resource is the result of mixing all the currently enabled tracks (if any) given by the
element's audioTracks
attribute.
Both audio
and video
elements can be used for both audio
and video. The main difference between the two is simply that the audio
element has
no playback area for visual content (such as video or captions), whereas the video
element does.
Except where otherwise explicitly specified, the task source for all the tasks queued in this section and its subsections is the media element event task source.
error
Returns a MediaError
object representing the current error state of the
element.
Returns null if there is no error.
All media elements have an associated error status, which
records the last error the element encountered since its resource selection algorithm was last invoked. The
error
attribute, on getting, must return the
MediaError
object created for this last error, or null if there has not been an
error.
interface MediaError { const unsigned short MEDIA_ERR_ABORTED = 1; const unsigned short MEDIA_ERR_NETWORK = 2; const unsigned short MEDIA_ERR_DECODE = 3; const unsigned short MEDIA_ERR_SRC_NOT_SUPPORTED = 4; readonly attribute unsigned short code; };
error
. code
Returns the current error's error code, from the list below.
The code
attribute of a
MediaError
object must return the code for the error, which must be one of the
following:
MEDIA_ERR_ABORTED
(numeric value 1)MEDIA_ERR_NETWORK
(numeric value 2)MEDIA_ERR_DECODE
(numeric value 3)MEDIA_ERR_SRC_NOT_SUPPORTED
(numeric value 4)src
attribute was not suitable.The src
content attribute on media elements gives the address of the media resource (video, audio) to show. The
attribute, if present, must contain a valid non-empty URL potentially surrounded by
spaces.
The crossorigin
content attribute on
media elements is a CORS settings attribute.
If a src
attribute of a media element is set
or changed, the user agent must invoke the media element's media element load
algorithm. (Removing the src
attribute does
not do this, even if there are source
elements present.)
The src
IDL attribute on media elements must reflect the content attribute of the same
name.
The crossOrigin
IDL attribute must
reflect the crossorigin
content
attribute, limited to only known values.
currentSrc
Returns the address of the current media resource.
Returns the empty string when there is no media resource.
The currentSrc
IDL attribute is initially
the empty string. Its value is changed by the resource
selection algorithm defined below.
There are two ways to specify a media resource, the src
attribute, or source
elements. The attribute
overrides the elements.
A media resource can be described in terms of its type, specifically a
MIME type, in some cases with a codecs
parameter. (Whether the
codecs
parameter is allowed or not depends on the MIME type.) [RFC4281]
Types are usually somewhat incomplete descriptions; for example "video/mpeg
" doesn't say anything except what the container type is, and even a
type like "video/mp4; codecs="avc1.42E01E, mp4a.40.2"
" doesn't
include information like the actual bitrate (only the maximum bitrate). Thus, given a type, a user
agent can often only know whether it might be able to play media of that type (with
varying levels of confidence), or whether it definitely cannot play media of that
type.
A type that the user agent knows it cannot render is one that describes a resource that the user agent definitely does not support, for example because it doesn't recognize the container type, or it doesn't support the listed codecs.
The MIME type "application/octet-stream
" with no parameters is never
a type that the user agent knows it cannot render. User agents must treat that type
as equivalent to the lack of any explicit Content-Type metadata
when it is used to label a potential media resource.
Only the MIME type "application/octet-stream
" with no
parameters is special-cased here; if any parameter appears with it, it will be treated just like
any other MIME type. This is a deviation from the rule that unknown MIME type parameters should be ignored.
canPlayType
(type)Returns the empty string (a negative response), "maybe", or "probably" based on how confident the user agent is that it can play media resources of the given type.
The canPlayType(type)
method must return the
empty string if type is a type that the user agent knows it cannot
render or is the type "application/octet-stream
"; it must return "probably
" if the user agent is confident
that the type represents a media resource that it can render if used in with this
audio
or video
element; and it must return "maybe
" otherwise. Implementors are encouraged
to return "maybe
" unless the type can be
confidently established as being supported or not. Generally, a user agent should never return
"probably
" for a type that allows the codecs
parameter if that parameter is not present.
This script tests to see if the user agent supports a (fictional) new format to dynamically
decide whether to use a video
element or a plugin:
<section id="video"> <p><a href="playing-cats.nfv">Download video</a></p> </section> <script> var videoSection = document.getElementById('video'); var videoElement = document.createElement('video'); var support = videoElement.canPlayType('video/x-new-fictional-format;codecs="kittens,bunnies"'); if (support != "probably" && "New Fictional Video Plugin" in navigator.plugins) { // not confident of browser support // but we have a plugin // so use plugin instead videoElement = document.createElement("embed"); } else if (support == "") { // no support from browser and no plugin // do nothing videoElement = null; } if (videoElement) { while (videoSection.hasChildNodes()) videoSection.removeChild(videoSection.firstChild); videoElement.setAttribute("src", "playing-cats.nfv"); videoSection.appendChild(videoElement); } </script>
The type
attribute of the
source
element allows the user agent to avoid downloading resources that use formats
it cannot render.
networkState
Returns the current state of network activity for the element, from the codes in the list below.
As media elements interact with the network, their current
network activity is represented by the networkState
attribute. On getting, it must
return the current network state of the element, which must be one of the following values:
NETWORK_EMPTY
(numeric value 0)NETWORK_IDLE
(numeric value 1)NETWORK_LOADING
(numeric value 2)NETWORK_NO_SOURCE
(numeric value 3)The resource selection algorithm defined
below describes exactly when the networkState
attribute changes value and what events fire to indicate changes in this state.
load
()Causes the element to reset and start selecting and loading a new media resource from scratch.
All media elements have an autoplaying flag, which must begin in the true state, and a delaying-the-load-event flag, which must begin in the false state. While the delaying-the-load-event flag is true, the element must delay the load event of its document.
When the load()
method on a media
element is invoked, the user agent must run the media element load
algorithm.
The media element load algorithm consists of the following steps.
Abort any already-running instance of the resource selection algorithm for this element.
If there are any tasks from the media element's media element event task source in one of the task queues, then remove those tasks.
If there are any tasks that were queued by the resource selection algorithm (including the algorithms that it itself invokes) for this same media element from the DOM manipulation task source in one of the task queues, then remove those tasks.
Basically, pending events and callbacks for the media element are discarded when the media element starts loading a new resource.
If the media element's networkState
is set to NETWORK_LOADING
or NETWORK_IDLE
, queue a task to fire a
simple event named abort
at the media
element.
If the media element's networkState
is not set to NETWORK_EMPTY
, then run these
substeps:
Queue a task to fire a simple event named emptied
at the media element.
If a fetching process is in progress for the media element, the user agent should stop it.
If readyState
is not set to HAVE_NOTHING
, then set it to that state.
If the paused
attribute is false, then set it to
true.
If seeking
is true, set it to false.
Set the current playback position to 0.
Set the official playback position to 0.
If this changed the official playback position, then queue a task
to fire a simple event named timeupdate
at the media element.
Set the initial playback position to 0.
Set the timeline offset to Not-a-Number (NaN).
Update the duration
attribute to Not-a-Number
(NaN).
The user agent will not fire a durationchange
event for this particular change of
the duration.
Set the playbackRate
attribute to the value of
the defaultPlaybackRate
attribute.
Set the error
attribute to null and the
autoplaying flag to true.
Invoke the media element's resource selection algorithm.
Playback of any previously playing media resource for this element stops.
The resource selection algorithm for a media element is as follows. This algorithm is always invoked synchronously, but one of the first steps in the algorithm is to return and continue running the remaining steps asynchronously, meaning that it runs in the background with scripts and other tasks running in parallel. In addition, this algorithm interacts closely with the event loop mechanism; in particular, it has synchronous sections (which are triggered as part of the event loop algorithm). Steps in such sections are marked with ⌛.
Set the element's networkState
attribute to
the NETWORK_NO_SOURCE
value.
Set the element's show poster flag to true.
Set the media element's delaying-the-load-event flag to true (this delays the load event).
Asynchronously await a stable state, allowing the task that invoked this algorithm to continue. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
⌛ If the media element's blocked-on-parser flag is false, then populate the list of pending text tracks.
⌛ If the media element has a src
attribute, then let mode be attribute.
⌛ Otherwise, if the media element does not have a src
attribute but has a source
element child, then
let mode be children and let candidate
be the first such source
element child in tree order.
⌛ Otherwise the media element has neither a src
attribute nor a source
element child: set the
networkState
to NETWORK_EMPTY
, and abort these steps; the
synchronous section ends.
⌛ Set the media element's networkState
to NETWORK_LOADING
.
⌛ Queue a task to fire a simple event named loadstart
at the media element.
If mode is attribute, then run these substeps:
⌛ If the src
attribute's value is the empty string, then end the synchronous section, and jump
down to the failed with attribute step below.
⌛ Let absolute URL be the absolute URL that
would have resulted from resolving the URL
specified by the src
attribute's value relative to the
media element when the src
attribute was last
changed.
⌛ If absolute URL was obtained successfully, set the currentSrc
attribute to absolute
URL.
End the synchronous section, continuing the remaining steps asynchronously.
If absolute URL was obtained successfully, run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed.
Failed with attribute: Reaching this step indicates that the media resource failed to load or that the given URL could not be resolved. Queue a task to run the following steps, using the DOM manipulation task source:
Set the error
attribute to a new
MediaError
object whose code
attribute
is set to MEDIA_ERR_SRC_NOT_SUPPORTED
.
Set the element's networkState
attribute
to the NETWORK_NO_SOURCE
value.
Set the element's show poster flag to true.
Fire a simple event named error
at
the media element.
Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
Wait for the task queued by the previous step to have executed.
Abort these steps. Until the load()
method is
invoked or the src
attribute is changed, the element won't
attempt to load another resource.
Otherwise, the source
elements will be used; run these substeps:
⌛ Let pointer be a position defined by two adjacent nodes in the media element's child list, treating the start of the list (before the first child in the list, if any) and end of the list (after the last child in the list, if any) as nodes in their own right. One node is the node before pointer, and the other node is the node after pointer. Initially, let pointer be the position between the candidate node and the next node, if there are any, or the end of the list, if it is the last node.
As nodes are inserted and removed into the media element, pointer must be updated as follows:
Other changes don't affect pointer.
⌛ Process candidate: If candidate does not have a
src
attribute, or if its src
attribute's value is the empty string, then end the
synchronous section, and jump down to the failed with elements step
below.
⌛ Let absolute URL be the absolute URL that
would have resulted from resolving the URL
specified by candidate's src
attribute's value relative to the candidate when the src
attribute was last changed.
⌛ If absolute URL was not obtained successfully, then end the synchronous section, and jump down to the failed with elements step below.
⌛ If candidate has a type
attribute whose value, when parsed as a MIME
type (including any codecs described by the codecs
parameter, for
types that define that parameter), represents a type that the user agent knows it cannot
render, then end the synchronous section, and jump down to the failed with elements step below.
⌛ If candidate has a media
attribute whose value does not match the environment, then end the synchronous section, and
jump down to the failed with elements step below.
⌛ Set the currentSrc
attribute to absolute URL.
End the synchronous section, continuing the remaining steps asynchronously.
Run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed.
Failed with elements: Queue a task, using the DOM
manipulation task source, to fire a simple event named error
at the candidate element.
Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
⌛ Forget the media element's media-resource-specific tracks.
⌛ Find next candidate: Let candidate be null.
⌛ Search loop: If the node after pointer is the end of the list, then jump to the waiting step below.
⌛ If the node after pointer is a source
element,
let candidate be that element.
⌛ Advance pointer so that the node before pointer is now the node that was after pointer, and the node after pointer is the node after the node that used to be after pointer, if any.
⌛ If candidate is null, jump back to the search loop step. Otherwise, jump back to the process candidate step.
⌛ Waiting: Set the element's networkState
attribute to the NETWORK_NO_SOURCE
value.
⌛ Set the element's show poster flag to true.
⌛ Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
End the synchronous section, continuing the remaining steps asynchronously.
Wait until the node after pointer is a node other than the end of the list. (This step might wait forever.)
Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
⌛ Set the element's delaying-the-load-event flag back to true (this delays the load event again, in case it hasn't been fired yet).
⌛ Set the networkState
back to NETWORK_LOADING
.
⌛ Jump back to the find next candidate step above.
The resource fetch algorithm for a media element and a given absolute URL is as follows:
Let the current media resource be the resource given by the absolute URL passed to this algorithm. This is now the element's media resource.
Remove all media-resource-specific text tracks from the media element's list of pending text tracks, if any.
Optionally, run the following substeps. This is the expected behavior if the user agent
intends to not attempt to fetch the resource until the user requests it explicitly (e.g. as a way
to implement the preload
attribute's none
keyword).
Set the networkState
to NETWORK_IDLE
.
Queue a task to fire a simple event named suspend
at the element, using the DOM manipulation
task source.
Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
Wait for the task to be run.
Wait for an implementation-defined event (e.g. the user requesting that the media element begin playback).
Set the element's delaying-the-load-event flag back to true (this delays the load event again, in case it hasn't been fired yet).
Set the networkState
to NETWORK_LOADING
.
Perform a potentially CORS-enabled fetch of the current media resource's absolute URL, with the mode being
the state of the media element's crossorigin
content attribute, the origin
being the origin of the media element's Document
, and the
default origin behaviour set to taint.
The resource obtained in this fashion, if any, contains the media data. It can
be CORS-same-origin or CORS-cross-origin; this affects whether
subtitles referenced in the media data are exposed in the API and, for
video
elements, whether a canvas
gets tainted when the video is drawn
on it.
While the load is not suspended (see below), every 350ms (±200ms) or for every byte
received, whichever is least frequent, queue a task to fire a simple
event named progress
at the element.
The stall timeout is a user-agent defined length of time, which should be about
three seconds. When a media element that is actively attempting to obtain
media data has failed to receive any data for a duration equal to the stall
timeout, the user agent must queue a task to fire a simple
event named stalled
at the element.
User agents may allow users to selectively block or slow media data downloads. When a media element's download has been blocked altogether, the user agent must act as if it was stalled (as opposed to acting as if the connection was closed). The rate of the download may also be throttled automatically by the user agent, e.g. to balance the download with other connections sharing the same bandwidth.
User agents may decide to not download more content at any time, e.g.
after buffering five minutes of a one hour media resource, while waiting for the user to decide
whether to play the resource or not, while waiting for user input in an interactive resource, or
when the user navigates away from the page. When a media element's download has
been suspended, the user agent must queue a task, using the DOM manipulation
task source, to set the networkState
to NETWORK_IDLE
and fire a simple event named
suspend
at the element. If and when downloading of the
resource resumes, the user agent must queue a task to set the networkState
to NETWORK_LOADING
. Between the queuing of these tasks,
the load is suspended (so progress
events don't fire,
as described above).
The preload
attribute provides a hint
regarding how much buffering the author thinks is advisable, even in the absence of the autoplay
attribute.
When a user agent decides to completely stall a download, e.g. if it is waiting until the user starts playback before downloading any further content, the element's delaying-the-load-event flag must be set to false. This stops delaying the load event.
The user agent may use whatever means necessary to fetch the resource (within the constraints put forward by this and other specifications); for example, reconnecting to the server in the face of network errors, using HTTP range retrieval requests, or switching to a streaming protocol. The user agent must consider a resource erroneous only if it has given up trying to fetch it.
This specification does not currently say whether or how to check the MIME types of the media resources, or whether or how to perform file type sniffing using the actual file data. Implementors differ in their intentions on this matter and it is therefore unclear what the right solution is. In the absence of any requirement here, the HTTP specification's strict requirement to follow the Content-Type header prevails ("Content-Type specifies the media type of the underlying data." ... "If and only if the media type is not given by a Content-Type field, the recipient MAY attempt to guess the media type via inspection of its content and/or the name extension(s) of the URI used to identify the resource.").
The networking task source tasks to process the data as it is being fetched must, when appropriate, include the relevant substeps from the following list:
DNS errors, HTTP 4xx and 5xx errors (and equivalents in other protocols), and other fatal network errors that occur before the user agent has established whether the current media resource is usable, as well as the file using an unsupported container format, or using unsupported codecs for all the data, must cause the user agent to execute the following steps:
The user agent should cancel the fetching process.
Abort this subalgorithm, returning to the resource selection algorithm.
Create an AudioTrack
object to represent the audio track.
Update the media element's audioTracks
attribute's AudioTrackList
object with the new AudioTrack
object.
Fire a trusted event with the name addtrack
, that does not bubble and is not cancelable, and
that uses the TrackEvent
interface, with the track
attribute initialized to the new
AudioTrack
object, at this AudioTrackList
object.
Create a VideoTrack
object to represent the video track.
Update the media element's videoTracks
attribute's VideoTrackList
object with the new VideoTrack
object.
Fire a trusted event with the name addtrack
, that does not bubble and is not cancelable, and that
uses the TrackEvent
interface, with the track
attribute initialized to the new
VideoTrack
object, at this VideoTrackList
object.
This indicates that the resource is usable. The user agent must follow these substeps:
Establish the media timeline for the purposes of the current playback position, the earliest possible position, and the initial playback position, based on the media data.
Update the timeline offset to the date and time that corresponds to the zero time in the media timeline established in the previous step, if any. If no explicit time and date is given by the media resource, the timeline offset must be set to Not-a-Number (NaN).
Set the current playback position and the official playback position to the earliest possible position.
Update the duration
attribute with the time of
the last frame of the resource, if known, on the media timeline established
above. If it is not known (e.g. a stream that is in principle infinite), update the duration
attribute to the value positive Infinity.
The user agent will queue a task
to fire a simple event named durationchange
at the element at this point.
For video
elements, set the videoWidth
and videoHeight
attributes, and queue a task
to fire a simple event named resize
at
the media element.
Further resize
events will be fired
if the dimensions subsequently change.
Set the readyState
attribute to HAVE_METADATA
.
A loadedmetadata
DOM event
will be fired as part of setting the readyState
attribute to a new value.
Let jumped be false.
If the media element's default playback start position is greater than zero, then seek to that time, and let jumped be true.
Let the media element's default playback start position be zero.
If either the media resource or the address of the current media resource indicate a particular start time, then set the initial playback position to that time and, if jumped is still false, seek to that time and let jumped be true.
For example, with media formats that support the Media Fragments URI fragment identifier syntax, the fragment identifier can be used to indicate a start position. [MEDIAFRAG]
If either the media resource or the address of the current
media resource indicate a particular set of audio or video tracks to enable, then the
selected audio tracks must be enabled in the element's audioTracks
object, and, of the selected video tracks,
the one that is listed first in the element's videoTracks
object must be selected. All other tracks
must be disabled.
Again, this could be done, for example, using the Media Fragments URI fragment identifier syntax. [MEDIAFRAG]
If the media element has a current media controller, then: if jumped is true and the initial playback position, relative to the current media controller's timeline, is greater than the current media controller's media controller position, then seek the media controller to the media element's initial playback position, relative to the current media controller's timeline; otherwise, seek the media element to the media controller position, relative to the media element's timeline.
Once the readyState
attribute reaches HAVE_CURRENT_DATA
, after
the loadeddata
event has been fired, set the
element's delaying-the-load-event flag to false. This stops delaying the load event.
A user agent that is attempting to reduce network usage while still fetching
the metadata for each media resource would also stop buffering at this point,
following the rules described previously, which involve the
networkState
attribute switching to the NETWORK_IDLE
value and a suspend
event firing.
The user agent is required to determine the duration of the media resource and go through this step before playing.
Fire a simple event named progress
at the media element.
Set the networkState
to NETWORK_IDLE
and fire a simple event named
suspend
at the media element.
If the user agent ever discards any media data and then needs to resume the
network activity to obtain it again, then it must queue a task to set the networkState
to NETWORK_LOADING
.
If the user agent can keep the media resource loaded, then the algorithm will continue to its final step below, which aborts the algorithm.
Fatal network errors that occur after the user agent has established whether the current media resource is usable (i.e. once the media element's
readyState
attribute is no longer HAVE_NOTHING
) must cause the user agent to execute the
following steps:
The user agent should cancel the fetching process.
Set the error
attribute to a new
MediaError
object whose code
attribute
is set to MEDIA_ERR_NETWORK
.
Fire a simple event named error
at
the media element.
Set the element's networkState
attribute
to the NETWORK_IDLE
value.
Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
Abort the overall resource selection algorithm.
Fatal errors in decoding the media data that occur after the user agent has established whether the current media resource is usable must cause the user agent to execute the following steps:
The user agent should cancel the fetching process.
Set the error
attribute to a new
MediaError
object whose code
attribute
is set to MEDIA_ERR_DECODE
.
Fire a simple event named error
at
the media element.
If the media element's readyState
attribute has a value equal to HAVE_NOTHING
, set
the element's networkState
attribute to the
NETWORK_EMPTY
value, set the element's
show poster flag to true, and fire a simple event named emptied
at the element.
Otherwise, set the element's networkState
attribute to the NETWORK_IDLE
value.
Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
Abort the overall resource selection algorithm.
The fetching process is aborted by the user, e.g. because the user
pressed a "stop" button, the user agent must execute the following steps. These steps are not
followed if the load()
method itself is invoked while
these steps are running, as the steps above handle that particular kind of abort.
The user agent should cancel the fetching process.
Set the error
attribute to a new
MediaError
object whose code
attribute
is set to MEDIA_ERR_ABORTED
.
Fire a simple event named abort
at
the media element.
If the media element's readyState
attribute has a value equal to HAVE_NOTHING
, set
the element's networkState
attribute to the
NETWORK_EMPTY
value, set the element's
show poster flag to true, and fire a simple event named emptied
at the element.
Otherwise, set the element's networkState
attribute to the NETWORK_IDLE
value.
Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
Abort the overall resource selection algorithm.
The server returning data that is partially usable but cannot be optimally rendered must cause the user agent to render just the bits it can handle, and ignore the rest.
If the media data is CORS-same-origin, run the steps to expose a media-resource-specific text track with the relevant data.
Cross-origin videos do not expose their subtitles, since that would allow attacks such as hostile sites reading subtitles from confidential videos on a user's intranet.
When the networking task source has queued the last task as part of fetching the media resource (i.e. once the download has completed), if the fetching process completes without errors, including decoding the media data, and if all of the data is available to the user agent without network access, then, the user agent must move on to the next step. This might never happen, e.g. when streaming an infinite resource such as Web radio, or if the resource is longer than the user agent's ability to cache data.
While the user agent might still need network access to obtain parts of the media resource, the user agent must remain on this step.
For example, if the user agent has discarded the first half of a video, the
user agent will remain at this step even once the playback has
ended, because there is always the chance the user will seek back to the start. In fact,
in this situation, once playback has ended, the user agent
will end up firing a suspend
event, as described
earlier.
If the user agent ever reaches this step (which can only happen if the entire resource gets loaded and kept available): abort the overall resource selection algorithm.
When a media element is to forget the media element's media-resource-specific
tracks, the user agent must remove from the media element's list of text
tracks all the media-resource-specific
text tracks, then empty the media element's audioTracks
attribute's AudioTrackList
object,
then empty the media element's videoTracks
attribute's VideoTrackList
object. No events (in particular, no removetrack
events) are fired as part of this; the error
and emptied
events, fired by the algorithms that invoke this one, can be used instead.
The preload
attribute is an enumerated
attribute. The following table lists the keywords and states for the attribute — the
keywords in the left column map to the states in the cell in the second column on the same row as
the keyword. The attribute can be changed even once the media resource is being
buffered or played; the descriptions in the table below are to be interpreted with that in
mind.
Keyword | State | Brief description |
---|---|---|
none
| None | Hints to the user agent that either the author does not expect the user to need the media resource, or that the server wants to minimize unnecessary traffic. This state does not provide a hint regarding how aggressively to actually download the media resource if buffering starts anyway (e.g. once the user hits "play"). |
metadata
| Metadata | Hints to the user agent that the author does not expect the user to need the media resource, but that fetching the resource metadata (dimensions, track list, duration, etc), and maybe even the first few frames, is reasonable. If the user agent precisely fetches no more than the metadata, then the media element will end up with its readyState attribute set to HAVE_METADATA ; typically though, some frames will be obtained as well and it will probably be HAVE_CURRENT_DATA or HAVE_FUTURE_DATA .
When the media resource is playing, hints to the user agent that bandwidth is to be considered scarce, e.g. suggesting throttling the download so that the media data is obtained at the slowest possible rate that still maintains consistent playback.
|
auto
| Automatic | Hints to the user agent that the user agent can put the user's needs first without risk to the server, up to and including optimistically downloading the entire resource. |
The empty string is also a valid keyword, and maps to the Automatic state. The attribute's missing value default is user-agent defined, though the Metadata state is suggested as a compromise between reducing server load and providing an optimal user experience.
Authors might switch the attribute from "none
" or "metadata
" to "auto
" dynamically once the user begins playback. For
example, on a page with many videos this might be used to indicate that the many videos are not to
be downloaded unless requested, but that once one is requested it is to be downloaded
aggressively.
The preload
attribute is intended to provide a hint to
the user agent about what the author thinks will lead to the best user experience. The attribute
may be ignored altogether, for example based on explicit user preferences or based on the
available connectivity.
The preload
IDL attribute must
reflect the content attribute of the same name, limited to only known
values.
The autoplay
attribute can override the
preload
attribute (since if the media plays, it naturally
has to buffer first, regardless of the hint given by the preload
attribute). Including both is not an error, however.
buffered
Returns a TimeRanges
object that represents the ranges of the media
resource that the user agent has buffered.
The buffered
attribute must return a new
static normalized TimeRanges
object that represents the ranges of the
media resource, if any, that the user agent has buffered, at the time the attribute
is evaluated. Users agents must accurately determine the ranges available, even for media streams
where this can only be determined by tedious inspection.
Typically this will be a single range anchored at the zero point, but if, e.g. the user agent uses HTTP range requests in response to seeking, then there could be multiple ranges.
User agents may discard previously buffered data.
Thus, a time position included within a range of the objects return by the buffered
attribute at one time can end up being not included in
the range(s) of objects returned by the same attribute at later times.
duration
Returns the length of the media resource, in seconds, assuming that the start of the media resource is at time zero.
Returns NaN if the duration isn't available.
Returns Infinity for unbounded streams.
currentTime
[ = value ]Returns the official playback position, in seconds.
Can be set, to seek to the given time.
Will throw an InvalidStateError
exception if there is no selected media
resource or if there is a current media controller.
A media resource has a media timeline that maps times (in seconds) to positions in the media resource. The origin of a timeline is its earliest defined position. The duration of a timeline is its last defined position.
Establishing the media
timeline: If the media resource somehow specifies an explicit timeline whose
origin is not negative (i.e. gives each frame a specific time offset and gives the first frame a
zero or positive offset), then the media timeline should be that timeline. (Whether
the media resource can specify a timeline or not depends on the media resource's format.) If the media resource specifies an
explicit start time and date, then that time and date should be considered the zero point
in the media timeline; the timeline offset will be the time and date,
exposed using the getStartDate()
method.
If the media resource has a discontinuous timeline, the user agent must extend the timeline used at the start of the resource across the entire resource, so that the media timeline of the media resource increases linearly starting from the earliest possible position (as defined below), even if the underlying media data has out-of-order or even overlapping time codes.
For example, if two clips have been concatenated into one video file, but the video format exposes the original times for the two clips, the video data might expose a timeline that goes, say, 00:15..00:29 and then 00:05..00:38. However, the user agent would not expose those times; it would instead expose the times as 00:15..00:29 and 00:29..01:02, as a single video.
In the rare case of a media resource that does not have an explicit timeline, the
zero time on the media timeline should correspond to the first frame of the
media resource. In the even rarer case of a media resource with no
explicit timings of any kind, not even frame durations, the user agent must itself determine the
time for each frame in a user-agent-defined manner.
An example of a file format with no explicit timeline but with explicit frame
durations is the Animated GIF format. An example of a file format with no explicit timings at all
is the JPEG-push format (multipart/x-mixed-replace
with JPEG frames, often
used as the format for MJPEG streams).
If, in the case of a resource with no timing information, the user agent will nonetheless be able to seek to an earlier point than the first frame originally provided by the server, then the zero time should correspond to the earliest seekable time of the media resource; otherwise, it should correspond to the first frame received from the server (the point in the media resource at which the user agent began receiving the stream).
At the time of writing, there is no known format that lacks explicit frame time offsets yet still supports seeking to a frame before the first frame sent by the server.
Consider a stream from a TV broadcaster, which begins streaming on a sunny Friday afternoon in
October, and always sends connecting user agents the media data on the same media timeline, with
its zero time set to the start of this stream. Months later, user agents connecting to this
stream will find that the first frame they receive has a time with millions of seconds. The getStartDate()
method would always return the date that the
broadcast started; this would allow controllers to display real times in their scrubber (e.g.
"2:30pm") rather than a time relative to when the broadcast began ("8 months, 4 hours, 12
minutes, and 23 seconds").
Consider a stream that carries a video with several concatenated fragments, broadcast by a
server that does not allow user agents to request specific times but instead just streams the
video data in a predetermined order, with the first frame delivered always being identified as
the frame with time zero. If a user agent connects to this stream and receives fragments defined
as covering timestamps 2010-03-20 23:15:00 UTC to 2010-03-21 00:05:00 UTC and 2010-02-12 14:25:00
UTC to 2010-02-12 14:35:00 UTC, it would expose this with a media timeline starting
at 0s and extending to 3,600s (one hour). Assuming the streaming server disconnected at the end
of the second clip, the duration
attribute would then
return 3,600. The getStartDate()
method would return a
Date
object with a time corresponding to 2010-03-20 23:15:00 UTC. However, if a
different user agent connected five minutes later, it would (presumably) receive
fragments covering timestamps 2010-03-20 23:20:00 UTC to 2010-03-21 00:05:00 UTC and 2010-02-12
14:25:00 UTC to 2010-02-12 14:35:00 UTC, and would expose this with a media timeline
starting at 0s and extending to 3,300s (fifty five minutes). In this case, the getStartDate()
method would return a Date
object
with a time corresponding to 2010-03-20 23:20:00 UTC.
In both of these examples, the seekable
attribute
would give the ranges that the controller would want to actually display in its UI; typically, if
the servers don't support seeking to arbitrary times, this would be the range of time from the
moment the user agent connected to the stream up to the latest frame that the user agent has
obtained; however, if the user agent starts discarding earlier information, the actual range
might be shorter.
In any case, the user agent must ensure that the earliest possible position (as defined below) using the established media timeline, is greater than or equal to zero.
The media timeline also has an associated clock. Which clock is used is user-agent defined, and may be media resource-dependent, but it should approximate the user's wall clock.
All the media elements that share current media controller use the same clock for their media timeline.
Media elements have a current playback position, which must initially (i.e. in the absence of media data) be zero seconds. The current playback position is a time on the media timeline.
Media elements also have an official playback position, which must initially be set to zero seconds. The official playback position is an approximation of the current playback position that is kept stable while scripts are running.
Media elements also have a default playback start position, which must initially be set to zero seconds. This time is used to allow the element to be seeked even before the media is loaded.
Each media element has a show poster flag. When a media
element is created, this flag must be set to true. This flag is used to control when the
user agent is to show a poster frame for a video
element instead of showing the video
contents.
The currentTime
attribute must, on
getting, return the media element's default playback start position,
unless that is zero, in which case it must return the element's official playback
position. The returned value must be expressed in seconds. On setting, if the media
element has a current media controller, then the user agent must throw an
InvalidStateError
exception; otherwise, if the media element's readyState
is HAVE_NOTHING
, then it must set the media
element's default playback start position to the new value; otherwise, it must
set the official playback position to the new value and then seek to the new value. The new value must be interpreted as being in
seconds.
Media elements have an initial playback position, which must initially (i.e. in the absence of media data) be zero seconds. The initial playback position is updated when a media resource is loaded. The initial playback position is a time on the media timeline.
If the media resource is a streaming resource, then the user agent might be unable to obtain certain parts of the resource after it has expired from its buffer. Similarly, some media resources might have a media timeline that doesn't start at zero. The earliest possible position is the earliest position in the stream or resource that the user agent can ever obtain again. It is also a time on the media timeline.
The earliest possible position is not explicitly exposed in the API;
it corresponds to the start time of the first range in the seekable
attribute's TimeRanges
object, if any, or
the current playback position otherwise.
When the earliest possible position changes, then: if the current playback
position is before the earliest possible position, the user agent must seek to the earliest possible position; otherwise, if
the user agent has not fired a timeupdate
event at the
element in the past 15 to 250ms and is not still running event handlers for such an event, then
the user agent must queue a task to fire a simple event named timeupdate
at the element.
Because of the above requirement and the requirement in the resource fetch algorithm that kicks in when the metadata of the clip becomes known, the current playback position can never be less than the earliest possible position.
If at any time the user agent learns that an audio or video track has ended and all media
data relating to that track corresponds to parts of the media timeline that
are before the earliest possible position, the user agent may queue a
task to first remove the track from the audioTracks
attribute's AudioTrackList
object or the videoTracks
attribute's VideoTrackList
object as
appropriate and then fire a trusted event with the name removetrack
, that does not bubble and is not cancelable, and that
uses the TrackEvent
interface, with the track
attribute initialized to the AudioTrack
or
VideoTrack
object representing the track, at the media element's
aforementioned AudioTrackList
or VideoTrackList
object.
The duration
attribute must return the time
of the end of the media resource, in seconds, on the media timeline. If
no media data is available, then the attributes must return the Not-a-Number (NaN)
value. If the media resource is not known to be bounded (e.g. streaming radio, or a
live event with no announced end time), then the attribute must return the positive Infinity
value.
The user agent must determine the duration of the media resource before playing
any part of the media data and before setting readyState
to a value equal to or greater than HAVE_METADATA
, even if doing so requires fetching multiple
parts of the resource.
When the length of the media resource changes to a known value
(e.g. from being unknown to known, or from a previously established length to a new length) the
user agent must queue a task to fire a simple event named durationchange
at the media element. (The
event is not fired when the duration is reset as part of loading a new media resource.) If the
duration is changed such that the current playback position ends up being greater
than the time of the end of the media resource, then the user agent must also seek to the time of the end of the media resource.
If an "infinite" stream ends for some reason, then the duration would change
from positive Infinity to the time of the last frame or sample in the stream, and the durationchange
event would be fired. Similarly, if the
user agent initially estimated the media resource's duration instead of determining
it precisely, and later revises the estimate based on new information, then the duration would
change and the durationchange
event would be
fired.
Some video files also have an explicit date and time corresponding to the zero time in the media timeline, known as the timeline offset. Initially, the timeline offset must be set to Not-a-Number (NaN).
The getStartDate()
method must return a new Date
object representing the current
timeline offset.
The loop
attribute is a boolean
attribute that, if specified, indicates that the media element is to seek back
to the start of the media resource upon reaching the end.
The loop
attribute has no effect while the element has a
current media controller.
The loop
IDL attribute must reflect
the content attribute of the same name.
readyState
Returns a value that expresses the current state of the element with respect to rendering the current playback position, from the codes in the list below.
Media elements have a ready state, which describes to what degree they are ready to be rendered at the current playback position. The possible values are as follows; the ready state of a media element at any particular time is the greatest value describing the state of the element:
HAVE_NOTHING
(numeric value 0)No information regarding the media resource is available. No data for the
current playback position is available. Media
elements whose networkState
attribute are set
to NETWORK_EMPTY
are always in the HAVE_NOTHING
state.
HAVE_METADATA
(numeric value 1)Enough of the resource has been obtained that the duration of the resource is available.
In the case of a video
element, the dimensions of the video are also available. The
API will no longer throw an exception when seeking. No media data is available for
the immediate current playback position.
HAVE_CURRENT_DATA
(numeric value 2)Data for the immediate current playback position is available, but either not
enough data is available that the user agent could successfully advance the current
playback position in the direction of playback at all without immediately
reverting to the HAVE_METADATA
state, or there is no
more data to obtain in the direction of playback. For example, in video this
corresponds to the user agent having data from the current frame, but not the next frame, when
the current playback position is at the end of the current frame; and to when playback has ended.
HAVE_FUTURE_DATA
(numeric value 3)Data for the immediate current playback position is available, as well as
enough data for the user agent to advance the current playback position in the
direction of playback at least a little without immediately reverting to the HAVE_METADATA
state, and the text tracks are
ready. For example, in video this corresponds to the user agent having data for at least
the current frame and the next frame when the current playback position is at the
instant in time between the two frames, or to the user agent having the video data for the
current frame and audio data to keep playing at least a little when the current playback
position is in the middle of a frame. The user agent cannot be in this state if playback has ended, as the current playback position
can never advance in this case.
HAVE_ENOUGH_DATA
(numeric value 4)All the conditions described for the HAVE_FUTURE_DATA
state are met, and, in addition,
either of the following conditions is also true:
In practice, the difference between HAVE_METADATA
and HAVE_CURRENT_DATA
is negligible. Really the only time
the difference is relevant is when painting a video
element onto a
canvas
, where it distinguishes the case where something will be drawn (HAVE_CURRENT_DATA
or greater) from the case where
nothing is drawn (HAVE_METADATA
or less). Similarly,
the difference between HAVE_CURRENT_DATA
(only
the current frame) and HAVE_FUTURE_DATA
(at least
this frame and the next) can be negligible (in the extreme, only one frame). The only time that
distinction really matters is when a page provides an interface for "frame-by-frame"
navigation.
When the ready state of a media element whose networkState
is not NETWORK_EMPTY
changes, the user agent must follow the steps
given below:
Apply the first applicable set of substeps from the following list:
HAVE_NOTHING
,
and the new ready state is HAVE_METADATA
Queue a task to fire a simple event named loadedmetadata
at the element.
Before this task is run, as part of the event loop mechanism, the
rendering will have been updated to resize the video
element if appropriate.
HAVE_METADATA
and the new ready state is HAVE_CURRENT_DATA
or greaterIf this is the first time this occurs for this media
element since the load()
algorithm was last
invoked, the user agent must queue a task to fire a simple event
named loadeddata
at the element.
If the new ready state is HAVE_FUTURE_DATA
or HAVE_ENOUGH_DATA
, then the relevant steps
below must then be run also.
HAVE_FUTURE_DATA
or more, and the new ready state is
HAVE_CURRENT_DATA
or lessIf the media element was potentially
playing before its readyState
attribute
changed to a value lower than HAVE_FUTURE_DATA
, and the element has not
ended playback, and playback has not stopped due to errors,
paused for user interaction, or paused for in-band content, the user
agent must queue a task to fire a simple event named timeupdate
at the element, and queue a task
to fire a simple event named waiting
at
the element.
HAVE_CURRENT_DATA
or less, and the new ready state
is HAVE_FUTURE_DATA
The user agent must queue a task to fire a simple event named
canplay
at the element.
If the element's paused
attribute is false, the user
agent must queue a task to fire a simple event named playing
at the element.
HAVE_ENOUGH_DATA
If the previous ready state was HAVE_CURRENT_DATA
or less, the user agent must
queue a task to fire a simple event named canplay
at the element, and, if the element's paused
attribute is false, queue a task to
fire a simple event named playing
at the element.
If the autoplaying flag is true, and the paused
attribute is true, and the media element
has an autoplay
attribute specified, and the
media element's Document
's active sandboxing flag set
does not have the sandboxed automatic features browsing context flag set, then
the user agent may also run the following substeps:
paused
attribute to false.play
at the element.playing
at the element.User agents do not need to support autoplay, and it is suggested that user
agents honor user preferences on the matter. Authors are urged to use the autoplay
attribute rather than using script to force the
video to play, so as to allow the user to override the behavior if so desired.
In any case, the user agent must finally queue a task to fire a simple
event named canplaythrough
at the element.
If the media element has a current media controller, then report the controller state for the media element's current media controller.
It is possible for the ready state of a media element to jump between these states
discontinuously. For example, the state of a media element can jump straight from HAVE_METADATA
to HAVE_ENOUGH_DATA
without passing through the HAVE_CURRENT_DATA
and HAVE_FUTURE_DATA
states.
The readyState
IDL attribute must, on
getting, return the value described above that describes the current ready state of the
media element.
The autoplay
attribute is a boolean
attribute. When present, the user agent (as described in the algorithm
described herein) will automatically begin playback of the media resource as
soon as it can do so without stopping.
Authors are urged to use the autoplay
attribute rather than using script to trigger automatic playback, as this allows the user to
override the automatic playback when it is not desired, e.g. when using a screen reader. Authors
are also encouraged to consider not using the automatic playback behavior at all, and instead to
let the user agent wait for the user to start playback explicitly.
The autoplay
IDL attribute must
reflect the content attribute of the same name.
paused
Returns true if playback is paused; false otherwise.
ended
Returns true if playback has reached the end of the media resource.
defaultPlaybackRate
[ = value ]Returns the default rate of playback, for when the user is not fast-forwarding or reversing through the media resource.
Can be set, to change the default rate of playback.
The default rate has no direct effect on playback, but if the user switches to a fast-forward mode, when they return to the normal playback mode, it is expected that the rate of playback will be returned to the default rate of playback.
When the element has a current media controller, the defaultPlaybackRate
attribute is ignored and the
current media controller's defaultPlaybackRate
is used instead.
playbackRate
[ = value ]Returns the current rate playback, where 1.0 is normal speed.
Can be set, to change the rate of playback.
When the element has a current media controller, the playbackRate
attribute is ignored and the current
media controller's playbackRate
is
used instead.
played
Returns a TimeRanges
object that represents the ranges of the media
resource that the user agent has played.
play
()Sets the paused
attribute to false, loading the
media resource and beginning playback if necessary. If the playback had ended, will
restart it from the start.
pause
()Sets the paused
attribute to true, loading the
media resource if necessary.
The paused
attribute represents whether the
media element is paused or not. The attribute must initially be true.
A media element is a blocked media element if its readyState
attribute is in the HAVE_NOTHING
state, the HAVE_METADATA
state, or the HAVE_CURRENT_DATA
state, or if the element has
paused for user interaction or paused for in-band content.
A media element is said to be potentially playing when its paused
attribute is false, the element has not ended
playback, playback has not stopped due to errors, the element either has no
current media controller or has a current media controller but is not
blocked on its media controller, and the element is not a blocked media
element.
A waiting
DOM event can be fired as a result of an element that is
potentially playing stopping playback due to its readyState
attribute changing to a value lower than HAVE_FUTURE_DATA
.
A media element is said to have ended playback when:
readyState
attribute is HAVE_METADATA
or greater, and
Either:
loop
attribute specified, or the media element has
a current media controller.
Or:
The ended
attribute must return true if, the
last time the event loop reached step 1, the media element had
ended playback and the direction of playback was forwards, and false
otherwise.
A media element is said to have stopped due to errors when the
element's readyState
attribute is HAVE_METADATA
or greater, and the user agent encounters a non-fatal error during the processing of the
media data, and due to that error, is not able to play the content at the
current playback position.
A media element is said to have paused for user interaction when its
paused
attribute is false, the readyState
attribute is either HAVE_FUTURE_DATA
or HAVE_ENOUGH_DATA
and the user agent has reached a point
in the media resource where the user has to make a selection for the resource to
continue. If the media element has a current media controller when this
happens, then the user agent must report the controller state for the media
element's current media controller. If the media element has a
current media controller when the user makes a selection, allowing playback to
resume, the user agent must similarly report the controller state for the media
element's current media controller.
It is possible for a media element to have both ended playback and paused for user interaction at the same time.
When a media element that is potentially playing stops playing
because it has paused for user interaction, the user agent must queue a
task to fire a simple event named timeupdate
at the element.
A media element is said to have paused for in-band content when its
paused
attribute is false, the readyState
attribute is either HAVE_FUTURE_DATA
or HAVE_ENOUGH_DATA
and the user agent has suspended
playback of the media resource in order to play content that is temporally anchored
to the media resource and has a non-zero length, or to play content that is
temporally anchored to a segment of the media resource but has a length longer than
that segment. If the media element has a current media controller when
this happens, then the user agent must report the controller state for the
media element's current media controller. If the media
element has a current media controller when the user agent unsuspends
playback, the user agent must similarly report the controller state for the
media element's current media controller.
One example of when a media element would be paused for in-band content is when the user agent is playing audio descriptions from an external WebVTT file, and the synthesized speech generated for a cue is longer than the time between the text track cue start time and the text track cue end time.
When the current playback position reaches the end of the media resource when the direction of playback is forwards, then the user agent must follow these steps:
If the media element has a loop
attribute specified and does not have a current media controller, then seek to the earliest possible position of the
media resource and abort these steps.
As defined above, the ended
IDL attribute starts
returning true once the event loop's current task
ends.
Queue a task to fire a simple event named timeupdate
at the media element.
Queue a task that, if the media element does not have a
current media controller, and the media element has still ended
playback, and the direction of playback is still forwards, and paused is false, changes paused to true and fires a
simple event named pause
at the media
element.
Queue a task to fire a simple event named ended
at the media element.
If the media element has a current media controller, then report the controller state for the media element's current media controller.
When the current playback position reaches the earliest possible
position of the media resource when the direction of playback is
backwards, then the user agent must only queue a task to fire a simple
event named timeupdate
at the element.
The defaultPlaybackRate
attribute
gives the desired speed at which the media resource is to play, as a multiple of its
intrinsic speed. The attribute is mutable: on getting it must return the last value it was set to,
or 1.0 if it hasn't yet been set; on setting the attribute must be set to the new value.
The defaultPlaybackRate
is used
by the user agent when it exposes a user
interface to the user.
The playbackRate
attribute gives the
effective playback rate (assuming there is no current media controller
overriding it), which is the speed at which the media resource plays, as a multiple
of its intrinsic speed. If it is not equal to the defaultPlaybackRate
, then the implication is that the
user is using a feature such as fast forward or slow motion playback. The attribute is mutable: on
getting it must return the last value it was set to, or 1.0 if it hasn't yet been set; on setting
the attribute must be set to the new value, and the playback will change speed (if the element is
potentially playing and there is no current media controller).
When the defaultPlaybackRate
or playbackRate
attributes change value (either by
being set by script or by being changed directly by the user agent, e.g. in response to user
control) the user agent must queue a task to fire a simple event named
ratechange
at the media element.
The defaultPlaybackRate
and
playbackRate
attributes have no effect when the
media element has a current media controller; the namesake attributes on
the MediaController
object are used instead in that situation.
The played
attribute must return a new static
normalized TimeRanges
object that represents the ranges of points on the
media timeline of the media resource reached through the usual monotonic
increase of the current playback position during normal playback, if any, at the time
the attribute is evaluated.
When the play()
method on a media
element is invoked, the user agent must run the following steps.
If the media element's networkState
attribute has the value NETWORK_EMPTY
, invoke the media element's
resource selection algorithm.
If the playback has ended and the direction of playback is forwards, and the media element does not have a current media controller, seek to the earliest possible position of the media resource.
This will cause the user agent to queue a
task to fire a simple event named timeupdate
at the media element.
If the media element has a current media controller, then bring the media element up to speed with its new media controller.
If the media element's paused
attribute is
true, run the following substeps:
Change the value of paused
to false.
If the show poster flag is true, set the element's show poster flag to false and run the time marches on steps.
Queue a task to fire a simple event named play
at the element.
If the media element's readyState
attribute has the value HAVE_NOTHING
, HAVE_METADATA
, or HAVE_CURRENT_DATA
, queue a task to
fire a simple event named waiting
at the
element.
Otherwise, the media element's readyState
attribute has the value HAVE_FUTURE_DATA
or HAVE_ENOUGH_DATA
: queue a task to
fire a simple event named playing
at the
element.
Set the media element's autoplaying flag to false.
If the media element has a current media controller, then report the controller state for the media element's current media controller.
When the pause()
method is invoked, and when
the user agent is required to pause the media element, the user agent must run the
following steps:
If the media element's networkState
attribute has the value NETWORK_EMPTY
, invoke the media element's
resource selection algorithm.
Set the media element's autoplaying flag to false.
If the media element's paused
attribute
is false, run the following steps:
Change the value of paused
to true.
Queue a task to fire a simple
event named timeupdate
at the
element.
Queue a task to fire a simple
event named pause
at the element.
Set the official playback position to the current playback position.
If the media element has a current media controller, then report the controller state for the media element's current media controller.
The effective playback rate is not necessarily the element's playbackRate
. When a media element has a
current media controller, its effective playback rate is the
MediaController
's media controller playback rate. Otherwise, the
effective playback rate is just the element's playbackRate
. Thus, the current media
controller overrides the media element.
If the effective playback rate is positive or zero, then the direction of playback is forwards. Otherwise, it is backwards.
When a media element is potentially playing and
its Document
is a fully active Document
, its current
playback position must increase monotonically at effective playback rate units
of media time per unit time of the media timeline's clock. (This specification always
refers to this as an increase, but that increase could actually be a decrease if
the effective playback rate is negative.)
The effective playback rate can be 0.0, in which case the
current playback position doesn't move, despite playback not being paused (paused
doesn't become true, and the pause
event doesn't fire).
This specification doesn't define how the user agent achieves the appropriate playback rate — depending on the protocol and media available, it is plausible that the user agent could negotiate with the server to have the server provide the media data at the appropriate rate, so that (except for the period between when the rate is changed and when the server updates the stream's playback rate) the client doesn't actually have to drop or interpolate any frames.
Any time the user agent provides a stable state, the official playback position must be set to the current playback position.
When the direction of playback is backwards, any corresponding audio must be muted. When the effective playback rate is so low or so high that the user agent cannot play audio usefully, the corresponding audio must also be muted. If the effective playback rate is not 1.0, the user agent may apply pitch adjustments to the audio as necessary to render it faithfully.
Media elements that are potentially playing
while not in a Document
must not play any video, but should play any
audio component. Media elements must not stop playing just because all references to them have
been removed; only once a media element is in a state where no further audio could ever be played
by that element may the element be garbage collected.
It is possible for an element to which no explicit references exist to play audio, even if such an element is not still actively playing: for instance, it could have a current media controller that still has references and can still be unpaused, or it could be unpaused but stalled waiting for content to buffer.
Each media element has a list of newly introduced cues, which must be initially empty. Whenever a text track cue is added to the list of cues of a text track that is in the list of text tracks for a media element, that cue must be added to the media element's list of newly introduced cues. Whenever a text track is added to the list of text tracks for a media element, all of the cues in that text track's list of cues must be added to the media element's list of newly introduced cues. When a media element's list of newly introduced cues has new cues added while the media element's show poster flag is not set, then the user agent must run the time marches on steps.
When a text track cue is removed from the list of cues of a text track that is in the list of text tracks for a media element, and whenever a text track is removed from the list of text tracks of a media element, if the media element's show poster flag is not set, then the user agent must run the time marches on steps.
When the current playback position of a media element changes (e.g. due to playback or seeking), the user agent must run the time marches on steps. If the current playback position changes while the steps are running, then the user agent must wait for the steps to complete, and then must immediately rerun the steps. (These steps are thus run as often as possible or needed — if one iteration takes a long time, this can cause certain cues to be skipped over as the user agent rushes ahead to "catch up".)
The time marches on steps are as follows:
Let current cues be a list of cues, initialized to contain all the cues of all the hidden or showing text tracks of the media element (not the disabled ones) whose start times are less than or equal to the current playback position and whose end times are greater than the current playback position.
Let other cues be a list of cues, initialized to contain all the cues of hidden and showing text tracks of the media element that are not present in current cues.
Let last time be the current playback position at the time this algorithm was last run for this media element, if this is not the first time it has run.
If the current playback position has, since the last time this algorithm was run, only changed through its usual monotonic increase during normal playback, then let missed cues be the list of cues in other cues whose start times are greater than or equal to last time and whose end times are less than or equal to the current playback position. Otherwise, let missed cues be an empty list.
Remove all the cues in missed cues that are also in the media element's list of newly introduced cues, and then empty the element's list of newly introduced cues.
If the time was reached through the usual monotonic increase of the current playback
position during normal playback, and if the user agent has not fired a timeupdate
event at the element in the past 15 to 250ms and
is not still running event handlers for such an event, then the user agent must queue a
task to fire a simple event named timeupdate
at the element. (In the other cases, such as
explicit seeks, relevant events get fired as part of the overall process of changing the
current playback position.)
The event thus is not to be fired faster than about 66Hz or slower than 4Hz (assuming the event handlers don't take longer than 250ms to run). User agents are encouraged to vary the frequency of the event based on the system load and the average cost of processing the event each time, so that the UI updates are not any more frequent than the user agent can comfortably handle while decoding the video.
If all of the cues in current cues have their text track cue active flag set, none of the cues in other cues have their text track cue active flag set, and missed cues is empty, then abort these steps.
If the time was reached through the usual monotonic increase of the current playback position during normal playback, and there are cues in other cues that have their text track cue pause-on-exit flag set and that either have their text track cue active flag set or are also in missed cues, then immediately pause the media element.
In the other cases, such as explicit seeks, playback is not paused by going past the end time of a cue, even if that cue has its text track cue pause-on-exit flag set.
Let events be a list of tasks, initially empty. Each task in this list will be associated with a text track, a text track cue, and a time, which are used to sort the list before the tasks are queued.
Let affected tracks be a list of text tracks, initially empty.
When the steps below say to prepare an event named event for a text track cue target with a time time, the user agent must run these substeps:
Let track be the text track with which the text track cue target is associated.
Create a task to fire a simple event named event at target.
Add the newly created task to events, associated with the time time, the text track track, and the text track cue target.
Add track to affected tracks.
For each text track cue in missed
cues, prepare an event named enter
for the
TextTrackCue
object with the text track cue start time.
For each text track cue in other
cues that either has its text track cue active flag set or is in missed cues, prepare an event named exit
for the TextTrackCue
object with the later of the
text track cue end time and the text track cue start time.
For each text track cue in current
cues that does not have its text track cue active flag set, prepare an
event named enter
for the TextTrackCue
object with the text track cue start time.
Sort the tasks in events in ascending time order (tasks with earlier times first).
Further sort tasks in events that have the same time by the relative text track cue order of the text track cues associated with these tasks.
Finally, sort tasks in events that have
the same time and same text track cue order by placing tasks that fire enter
events before
those that fire exit
events.
Sort affected tracks in the same order as the text tracks appear in the media element's list of text tracks, and remove duplicates.
For each text track in affected tracks, in the list
order, queue a task to fire a simple event named cuechange
at the TextTrack
object, and, if the
text track has a corresponding track
element, to then fire a
simple event named cuechange
at the
track
element as well.
Set the text track cue active flag of all the cues in the current cues, and unset the text track cue active flag of all the cues in the other cues.
Run the rules for updating the text track rendering of each of the text tracks in affected tracks that are showing. For example, for text tracks based on WebVTT, the rules for updating the display of WebVTT text tracks. [WEBVTT]
For the purposes of the algorithm above, a text track cue is considered to be part of a text track only if it is listed in the text track list of cues, not merely if it is associated with the text track.
If the media element's Document
stops being a
fully active document, then the playback will stop
until the document is active again.
When a media element is removed
from a Document
, the user agent must run the following steps:
Asynchronously await a stable state, allowing the task that removed the media element from the
Document
to continue. The synchronous section consists of all the
remaining steps of this algorithm. (Steps in the synchronous section are marked with
⌛.)
⌛ If the media element is in a Document
,
abort these steps.
⌛ If the media element's networkState
attribute has the value NETWORK_EMPTY
, abort these steps.
⌛ Pause the media element.
seeking
Returns true if the user agent is currently seeking.
seekable
Returns a TimeRanges
object that represents the ranges of the media
resource to which it is possible for the user agent to seek.
The seeking
attribute must initially have the
value false.
When the user agent is required to seek to a particular new playback position in the media resource, optionally with the approximate-for-speed flag set, it means that the user agent must run the following steps. This algorithm interacts closely with the event loop mechanism; in particular, it has a synchronous section (which is triggered as part of the event loop algorithm). Steps in that section are marked with ⌛.
Set the media element's show poster flag to false.
If the media element's readyState
is HAVE_NOTHING
, abort these steps.
If the element's seeking
IDL attribute is true,
then another instance of this algorithm is already running. Abort that other instance of the
algorithm without waiting for the step that it is running to complete.
Set the seeking
IDL attribute to true.
If the seek was in response to a DOM method call or setting of an IDL attribute, then continue the script. The remainder of these steps must be run asynchronously. With the exception of the steps marked with ⌛, they could be aborted at any time by another instance of this algorithm being invoked.
If the new playback position is later than the end of the media resource, then let it be the end of the media resource instead.
If the new playback position is less than the earliest possible position, let it be that position instead.
If the (possibly now changed) new playback position is not in one of
the ranges given in the seekable
attribute, then let it
be the position in one of the ranges given in the seekable
attribute that is the nearest to the new
playback position. If two positions both satisfy that constraint (i.e. the new playback position is exactly in the middle between two ranges in the seekable
attribute) then use the position that is closest to
the current playback position. If there are no ranges given in the seekable
attribute then set the seeking
IDL attribute to false and abort these steps.
If the approximate-for-speed flag is set, adjust the new playback position to a value that will allow for playback to resume promptly. If new playback position before this step is before current playback position, then the adjusted new playback position must also be before the current playback position. Similarly, if the new playback position before this step is after current playback position, then the adjusted new playback position must also be after the current playback position.
For example, the user agent could snap to the nearest key frame, so that it doesn't have to spend time decoding then discarding intermediate frames before resuming playback.
Queue a task to fire a simple event named seeking
at the element.
Set the current playback position to the given new playback position.
If the media element was potentially playing
immediately before it started seeking, but seeking caused its readyState
attribute to change to a value lower than HAVE_FUTURE_DATA
, then a waiting
will be
fired at the element.
The currentTime
attribute does not
get updated asynchronously, as it returns the official playback position, not the
current playback position.
Wait until the user agent has established whether or not the media data for the new playback position is available, and, if it is, until it has decoded enough data to play back that position.
Await a stable state. The synchronous section consists of all the remaining steps of this algorithm. (Steps in the synchronous section are marked with ⌛.)
⌛ Set the seeking
IDL attribute to
false.
⌛ Run the time marches on steps.
⌛ Queue a task to fire a simple event
named timeupdate
at the element.
⌛ Queue a task to fire a simple event named seeked
at the element.
The seekable
attribute must return a new
static normalized TimeRanges
object that represents the ranges of the
media resource, if any, that the user agent is able to seek to, at the time the
attribute is evaluated.
If the user agent can seek to anywhere in the media resource, e.g.
because it is a simple movie file and the user agent and the server support HTTP Range requests,
then the attribute would return an object with one range, whose start is the time of the first
frame (the earliest possible position, typically zero), and whose end is the same as
the time of the first frame plus the duration
attribute's
value (which would equal the time of the last frame, and might be positive Infinity).
The range might be continuously changing, e.g. if the user agent is buffering a sliding window on an infinite stream. This is the behavior seen with DVRs viewing live TV, for instance.
Media resources might be internally scripted or interactive. Thus, a media element could play in a non-linear fashion. If this happens, the user agent must act as if the algorithm for seeking was used whenever the current playback position changes in a discontinuous fashion (so that the relevant events fire). If the media element has a current media controller, then the user agent must seek the media controller appropriately instead.
A media resource can have multiple embedded audio and video tracks. For example, in addition to the primary video and audio tracks, a media resource could have foreign-language dubbed dialogues, director's commentaries, audio descriptions, alternative angles, or sign-language overlays.
audioTracks
Returns an AudioTrackList
object representing the audio tracks available in the
media resource.
videoTracks
Returns a VideoTrackList
object representing the video tracks available in the
media resource.
The audioTracks
attribute of a
media element must return a live AudioTrackList
object
representing the audio tracks available in the media element's media
resource. The same object must be returned each time.
The videoTracks
attribute of a
media element must return a live VideoTrackList
object
representing the video tracks available in the media element's media
resource. The same object must be returned each time.
There are only ever one AudioTrackList
object and one
VideoTrackList
object per media element, even if another media
resource is loaded into the element: the objects are reused. (The AudioTrack
and VideoTrack
objects are not, though.)
In this example, a script defines a function that takes a URL to a video and a reference to an element where the video is to be placed. That function then tries to load the video, and, once it is loaded, checks to see if there is a sign-language track available. If there is, it also displays that track. Both tracks are just placed in the given container; it's assumed that styles have been applied to make this work in a pretty way!
<script> function loadVideo(url, container) { var controller = new MediaController(); var video = document.createElement('video'); video.src = url; video.autoplay = true; video.controls = true; video.controller = controller; container.appendChild(video); video.onloadedmetadata = function (event) { for (var i = 0; i < video.videoTracks.length; i += 1) { if (video.videoTracks[i].kind == 'sign') { var sign = document.createElement('video'); sign.src = url + '#track=' + video.videoTracks[i].id; sign.autoplay = true; sign.controller = controller; container.appendChild(sign); return; } } }; } </script>
AudioTrackList
and VideoTrackList
objectsThe AudioTrackList
and VideoTrackList
interfaces are used by
attributes defined in the previous section.
interface AudioTrackList : EventTarget { readonly attribute unsigned long length; getter AudioTrack (unsigned long index); AudioTrack? getTrackById(DOMString id); attribute EventHandler onchange; attribute EventHandler onaddtrack; attribute EventHandler onremovetrack; }; interface AudioTrack { readonly attribute DOMString id; readonly attribute DOMString kind; readonly attribute DOMString label; readonly attribute DOMString language; attribute boolean enabled; }; interface VideoTrackList : EventTarget { readonly attribute unsigned long length; getter VideoTrack (unsigned long index); VideoTrack? getTrackById(DOMString id); readonly attribute long selectedIndex; attribute EventHandler onchange; attribute EventHandler onaddtrack; attribute EventHandler onremovetrack; }; interface VideoTrack { readonly attribute DOMString id; readonly attribute DOMString kind; readonly attribute DOMString label; readonly attribute DOMString language; attribute boolean selected; };
audioTracks
. length
videoTracks
. length
Returns the number of tracks in the list.
audioTracks
[index]videoTracks
[index]Returns the specified AudioTrack
or VideoTrack
object.
audioTracks
. getTrackById
( id )videoTracks
. getTrackById
( id )Returns the AudioTrack
or VideoTrack
object with the given identifier, or null if no track has that identifier.
id
id
Returns the ID of the given track. This is the ID that can be used with a fragment identifier
if the format supports the Media Fragments URI syntax, and that can be used with
the getTrackById()
method. [MEDIAFRAG]
kind
kind
Returns the category the given track falls into. The possible track categories are given below.
label
label
Returns the label of the given track, if known, or the empty string otherwise.
language
language
Returns the language of the given track, if known, or the empty string otherwise.
enabled
[ = value ]Returns true if the given track is active, and false otherwise.
Can be set, to change whether the track is enabled or not. If multiple audio tracks are enabled simultaneously, they are mixed.
videoTracks
. selectedIndex
Returns the index of the currently selected track, if any, or −1 otherwise.
selected
[ = value ]Returns true if the given track is active, and false otherwise.
Can be set, to change whether the track is selected or not. Either zero or one video track is selected; selecting a new track while a previous one is selected will unselect the previous one.
An AudioTrackList
object represents a dynamic list of zero or more audio tracks,
of which zero or more can be enabled at a time. Each audio track is represented by an
AudioTrack
object.
A VideoTrackList
object represents a dynamic list of zero or more video tracks, of
which zero or one can be selected at a time. Each video track is represented by a
VideoTrack
object.
Tracks in AudioTrackList
and VideoTrackList
objects must be
consistently ordered. If the media resource is in a format that defines an order,
then that order must be used; otherwise, the order must be the relative order in which the tracks
are declared in the media resource. The order used is called the natural order
of the list.
Each track in a TrackList
thus has an index; the first has the index
0, and each subsequent track is numbered one higher than the previous one. If a media
resource dynamically adds or removes audio or video tracks, then the indices of the tracks
will change dynamically. If the media resource changes entirely, then all the
previous tracks will be removed and replaced with new tracks.
The AudioTrackList.length
and VideoTrackList.length
attributes must return
the number of tracks represented by their objects at the time of getting.
The supported property indices of AudioTrackList
and
VideoTrackList
objects at any instant are the numbers from zero to the number of
tracks represented by the respective object minus one, if any tracks are represented. If an
AudioTrackList
or VideoTrackList
object represents no tracks, it has no
supported property indices.
To determine the value of an indexed property for a given index index in an AudioTrackList
or VideoTrackList
object list, the user agent must return the AudioTrack
or
VideoTrack
object that represents the indexth track in list.
The AudioTrackList.getTrackById(id)
and VideoTrackList.getTrackById(id)
methods must return the first AudioTrack
or
VideoTrack
object (respectively) in the AudioTrackList
or
VideoTrackList
object (respectively) whose identifier is equal to the value of the
id argument (in the natural order of the list, as defined above). When no
tracks match the given argument, the methods must return null.
The AudioTrack
and VideoTrack
objects represent specific tracks of a
media resource. Each track can have an identifier, category, label, and language.
These aspects of a track are permanent for the lifetime of the track; even if a track is removed
from a media resource's AudioTrackList
or VideoTrackList
objects, those aspects do not change.
In addition, AudioTrack
objects can each be enabled or disabled; this is the audio
track's enabled state. When an AudioTrack
is created, its enabled state
must be set to false (disabled). The resource fetch
algorithm can override this.
Similarly, a single VideoTrack
object per VideoTrackList
object can
be selected, this is the video track's selection state. When a VideoTrack
is
created, its selection state must be set to false (not selected). The resource fetch algorithm can override this.
The AudioTrack.id
and VideoTrack.id
attributes must return the identifier
of the track, if it has one, or the empty string otherwise. If the media resource is
in a format that supports the Media Fragments URI fragment identifier syntax, the
identifier returned for a particular track must be the same identifier that would enable the track
if used as the name of a track in the track dimension of such a fragment identifier. [MEDIAFRAG]
For example, in Ogg files, this would be the Name header field of the track. [OGGSKELETONHEADERS]
The AudioTrack.kind
and VideoTrack.kind
attributes must return the category
of the track, if it has one, or the empty string otherwise.
The category of a track is the string given in the first column of the table below that is the
most appropriate for the track based on the definitions in the table's second and third columns,
as determined by the metadata included in the track in the media resource. The cell
in the third column of a row says what the category given in the cell in the first column of that
row applies to; a category is only appropriate for an audio track if it applies to audio tracks,
and a category is only appropriate for video tracks if it applies to video tracks. Categories must
only be returned for AudioTrack
objects if they are appropriate for audio, and must
only be returned for VideoTrack
objects if they are appropriate for video.
For Ogg files, the Role header field of the track gives the relevant metadata. For DASH media
resources, the Role
element conveys the information. For WebM, only the
FlagDefault
element currently maps to a value. [OGGSKELETONHEADERS] [DASH] [WEBMCG]
Category | Definition | Applies to... | Examples |
---|---|---|---|
"alternative "
| A possible alternative to the main track, e.g. a different take of a song (audio), or a different angle (video). | Audio and video. | Ogg: "audio/alternate" or "video/alternate"; DASH: "alternate" without "main" and "commentary" roles, and, for audio, without the "dub" role (other roles ignored). |
"captions "
| A version of the main video track with captions burnt in. (For legacy content; new content would use text tracks.) | Video only. | DASH: "caption" and "main" roles together (other roles ignored). |
"descriptions "
| An audio description of a video track. | Audio only. | Ogg: "audio/audiodesc". |
"main "
| The primary audio or video track. | Audio and video. | Ogg: "audio/main" or "video/main"; WebM: the "FlagDefault" element is set; DASH: "main" role without "caption", "subtitle", and "dub" roles (other roles ignored). |
"main-desc "
| The primary audio track, mixed with audio descriptions. | Audio only. | AC3 audio in MPEG-2 TS: bsmod=2 and full_svc=1. |
"sign "
| A sign-language interpretation of an audio track. | Video only. | Ogg: "video/sign". |
"subtitles "
| A version of the main video track with subtitles burnt in. (For legacy content; new content would use text tracks.) | Video only. | DASH: "subtitle" and "main" roles together (other roles ignored). |
"translation "
| A translated version of the main audio track. | Audio only. | Ogg: "audio/dub". DASH: "dub" and "main" roles together (other roles ignored). |
"commentary "
| Commentary on the primary audio or video track, e.g. a director's commentary. | Audio and video. | DASH: "commentary" role without "main" role (other roles ignored). |
" " (empty string)
| No explicit kind, or the kind given by the track's metadata is not recognised by the user agent. | Audio and video. | Any other track type, track role, or combination of track roles not described above. |
The AudioTrack.label
and VideoTrack.label
attributes must return the label
of the track, if it has one, or the empty string otherwise.
The AudioTrack.language
and VideoTrack.language
attributes must return the
BCP 47 language tag of the language of the track, if it has one, or the empty string otherwise. If
the user agent is not able to express that language as a BCP 47 language tag (for example because
the language information in the media resource's format is a free-form string without
a defined interpretation), then the method must return the empty string, as if the track had no
language.
The AudioTrack.enabled
attribute, on
getting, must return true if the track is currently enabled, and false otherwise. On setting, it
must enable the track if the new value is true, and disable it otherwise. (If the track is no
longer in an AudioTrackList
object, then the track being enabled or disabled has no
effect beyond changing the value of the attribute on the AudioTrack
object.)
Whenever an audio track in an AudioTrackList
is enabled or disabled, the user
agent must queue a task to fire a simple event named change
at the AudioTrackList
object.
The VideoTrackList.selectedIndex
attribute
must return the index of the currently selected track, if any. If the VideoTrackList
object does not currently represent any tracks, or if none of the tracks are selected, it must
instead return −1.
The VideoTrack.selected
attribute, on
getting, must return true if the track is currently selected, and false otherwise. On setting, it
must select the track if the new value is true, and unselect it otherwise. If the track is in a
VideoTrackList
, then all the other VideoTrack
objects in that list must
be unselected. (If the track is no longer in a VideoTrackList
object, then the track
being selected or unselected has no effect beyond changing the value of the attribute on the
VideoTrack
object.)
Whenever a track in a VideoTrackList
that was previously not selected is selected,
the user agent must queue a task to fire a simple event named change
at the VideoTrackList
object. This task must be queued before the
task that fires the resize
event, if any.
The following are the event handlers (and their corresponding event handler event types) that must be supported, as event handler IDL attributes,
by all objects implementing the AudioTrackList
and VideoTrackList
interfaces:
Event handler | Event handler event type |
---|---|
onchange | change
|
onaddtrack | addtrack
|
onremovetrack | removetrack
|
The task source for the tasks listed in this section is the DOM manipulation task source.
The audioTracks
and videoTracks
attributes allow scripts to select which track
should play, but it is also possible to select specific tracks declaratively, by specifying
particular tracks in the fragment identifier of the URL of the media
resource. The format of the fragment identifier depends on the MIME type of
the media resource. [RFC2046] [URL]
In this example, a video that uses a format that supports the Media Fragments URI fragment identifier syntax is embedded in such a way that the alternative angles labeled "Alternative" are enabled instead of the default video track. [MEDIAFRAG]
<video src="myvideo#track=Alternative"></video>
Each media element can have a MediaController
. A
MediaController
is an object that coordinates the playback of multiple media elements, for instance so that a sign-language interpreter
track can be overlaid on a video track, with the two being kept in sync.
By default, a media element has no MediaController
. An implicit
MediaController
can be assigned using the mediagroup
content attribute. An explicit
MediaController
can be assigned directly using the controller
IDL attribute.
Media elements with a MediaController
are said
to be slaved to their controller. The MediaController
modifies the playback
rate and the playback volume of each of the media elements
slaved to it, and ensures that when any of its slaved media
elements unexpectedly stall, the others are stopped at the same time.
When a media element is slaved to a MediaController
, its playback
rate is fixed to that of the other tracks in the same MediaController
, and any
looping is disabled.
enum MediaControllerPlaybackState { "waiting", "playing", "ended" }; [Constructor] interface MediaController : EventTarget { readonly attribute unsigned short readyState; // uses HTMLMediaElement.readyState's values readonly attribute TimeRanges buffered; readonly attribute TimeRanges seekable; readonly attribute unrestricted double duration; attribute double currentTime; readonly attribute boolean paused; readonly attribute MediaControllerPlaybackState playbackState; readonly attribute TimeRanges played; void pause(); void unpause(); void play(); // calls play() on all media elements as well attribute double defaultPlaybackRate; attribute double playbackRate; attribute double volume; attribute boolean muted; attribute EventHandler onemptied; attribute EventHandler onloadedmetadata; attribute EventHandler onloadeddata; attribute EventHandler oncanplay; attribute EventHandler oncanplaythrough; attribute EventHandler onplaying; attribute EventHandler onended; attribute EventHandler onwaiting; attribute EventHandler ondurationchange; attribute EventHandler ontimeupdate; attribute EventHandler onplay; attribute EventHandler onpause; attribute EventHandler onratechange; attribute EventHandler onvolumechange; };
MediaController
()Returns a new MediaController
object.
controller
[ = controller ]Returns the current MediaController
for the media element, if any;
returns null otherwise.
Can be set, to set an explicit MediaController
. Doing so removes the mediagroup
attribute, if any.
readyState
Returns the state that the MediaController
was in the last time it fired events
as a result of reporting the controller state.
The values of this attribute are the same as for the readyState
attribute of media
elements.
buffered
Returns a TimeRanges
object that represents the intersection of the time ranges
for which the user agent has all relevant media data for all the slaved media elements.
seekable
Returns a TimeRanges
object that represents the intersection of the time ranges
into which the user agent can seek for all the slaved media
elements.
duration
Returns the difference between the earliest playable moment and the latest playable moment (not considering whether the data in question is actually buffered or directly seekable, but not including time in the future for infinite streams). Will return zero if there is no media.
currentTime
[ = value ]Returns the current playback position, in seconds, as a position between zero
time and the current duration
.
Can be set, to seek to the given time.
paused
Returns true if playback is paused; false otherwise. When this attribute is true, any media element slaved to this controller will be stopped.
playbackState
Returns the state that the MediaController
was in the last time it fired events
as a result of reporting the controller state.
The value of this attribute is either "playing
", indicating that the media is actively
playing, "ended
", indicating that the media is
not playing because playback has reached the end of all the slaved media elements,
or "waiting
", indicating that the media is not
playing for some other reason (e.g. the MediaController
is paused).
pause
()Sets the paused
attribute to true.
unpause
()Sets the paused
attribute to false.
play
()Sets the paused
attribute to false and
invokes the play()
method of each slaved media element.
played
Returns a TimeRanges
object that represents the union of the time ranges in all
the slaved media elements that have been played.
defaultPlaybackRate
[ = value ]Returns the default rate of playback.
Can be set, to change the default rate of playback.
This default rate has no direct effect on playback, but if the user switches to a
fast-forward mode, when they return to the normal playback mode, it is expected that rate of
playback (playbackRate
) will be returned
to this default rate.
playbackRate
[ = value ]Returns the current rate of playback.
Can be set, to change the rate of playback.
volume
[ = value ]Returns the current playback volume multiplier, as a number in the range 0.0 to 1.0, where 0.0 is the quietest and 1.0 the loudest.
Can be set, to change the volume multiplier.
Throws an IndexSizeError
exception if the new value is not in the range 0.0 .. 1.0.
muted
[ = value ]Returns true if all audio is muted (regardless of other attributes either on the controller or on any media elements slaved to this controller), and false otherwise.
Can be set, to change whether the audio is muted or not.
A media element can have a current media controller, which is a
MediaController
object. When a media element is created without a mediagroup
attribute, it does not have a current media
controller. (If it is created with such an attribute, then that attribute
initializes the current media controller, as defined below.)
The slaved media elements of a MediaController
are the media elements whose current media controller is that
MediaController
. All the slaved media elements of a
MediaController
must use the same clock for their definition of their media
timeline's unit time. When the user agent is required to act on each slaved media element in turn, they must be processed in the order that they
were last associated with the MediaController
.
The controller
attribute on a media
element, on getting, must return the element's current media controller, if
any, or null otherwise. On setting, the user agent must run the following steps:
Let m be the media element in question.
Let old controller be m's current media controller, if it currently has one, and null otherwise.
Let new controller be null.
Let m have no current media controller, if it currently has one.
Remove the element's mediagroup
content
attribute, if any.
If the new value is null, then jump to the update controllers step below.
Let m's current media controller be the new value.
Let new controller be m's current media controller.
Bring the media element up to speed with its new media controller.
Update controllers: If old controller and new controller are the same (whether both null or both the same controller) then abort these steps.
If old controller is not null and still has one or more slaved media elements, then report the controller state for old controller.
If new controller is not null, then report the controller state for new controller.
The MediaController()
constructor, when
invoked, must return a newly created MediaController
object.
The readyState
attribute must
return the value to which it was most recently set. When the MediaController
object
is created, the attribute must be set to the value 0 (HAVE_NOTHING
). The value is updated by the report the
controller state algorithm below.
The seekable
attribute must return
a new static normalized TimeRanges
object that represents the
intersection of the ranges of the media resources of the
slaved media elements that the user agent is able to seek to, at the time the
attribute is evaluated.
The buffered
attribute must return
a new static normalized TimeRanges
object that represents the
intersection of the ranges of the media resources of the
slaved media elements that the user agent has buffered, at the time the attribute is
evaluated. Users agents must accurately determine the ranges available, even for media streams
where this can only be determined by tedious inspection.
The duration
attribute must return
the media controller duration.
Every 15 to 250ms, or whenever the MediaController
's media controller
duration changes, whichever happens least often, the user agent must queue a
task to fire a simple event named durationchange
at the
MediaController
. If the MediaController
's media controller
duration decreases such that the media controller position is greater than the
media controller duration, the user agent must immediately seek the media
controller to media controller duration.
The currentTime
attribute must
return the media controller position on getting, and on setting must seek the
media controller to the new value.
Every 15 to 250ms, or whenever the MediaController
's media controller
position changes, whichever happens least often, the user agent must queue a
task to fire a simple event named timeupdate
at the
MediaController
.
When a MediaController
is created it is a playing media controller. It
can be changed into a paused media controller and back either via the user agent's user
interface (when the element is exposing a user
interface to the user) or by script using the APIs defined in this section (see below).
The paused
attribute must return
true if the MediaController
object is a paused media controller, and
false otherwise.
When the pause()
method is invoked,
if the MediaController
is a playing media controller then the user agent
must change the MediaController
into a paused media controller,
queue a task to fire a simple event named pause
at the MediaController
, and then
report the controller state of the MediaController
.
When the unpause()
method is
invoked, if the MediaController
is a paused media controller, the user
agent must change the MediaController
into a playing media controller,
queue a task to fire a simple event named play
at the MediaController
, and then
report the controller state of the MediaController
.
When the play()
method is invoked, the
user agent must invoke the play()
method of each slaved media element in turn, and then invoke the unpause
method of the MediaController
.
The playbackState
attribute
must return the value to which it was most recently set. When the MediaController
object is created, the attribute must be set to the value "waiting
". The value is updated by the report the
controller state algorithm below.
The played
attribute must return a
new static normalized TimeRanges
object that represents the union of the
ranges of points on the media timelines of the media resources of the slaved media elements that the
user agent has so far reached through the usual monotonic increase of their current playback positions during normal playback, at the time the
attribute is evaluated.
A MediaController
has a media controller default playback rate and a
media controller playback rate, which must both be set to 1.0 when the
MediaController
object is created.
The defaultPlaybackRate
attribute, on getting, must return the MediaController
's media controller
default playback rate, and on setting, must set the MediaController
's
media controller default playback rate to the new value, then queue a
task to fire a simple event named ratechange
at the
MediaController
.
The playbackRate
attribute, on
getting, must return the MediaController
's media controller playback
rate, and on setting, must set the MediaController
's media controller
playback rate to the new value, then queue a task to fire a simple
event named ratechange
at the
MediaController
.
A MediaController
has a media controller volume multiplier, which must
be set to 1.0 when the MediaController
object is created, and a media controller
mute override, much must initially be false.
The volume
attribute, on getting,
must return the MediaController
's media controller volume multiplier,
and on setting, if the new value is in the range 0.0 to 1.0 inclusive, must set the
MediaController
's media controller volume multiplier to the new value
and queue a task to fire a simple event named volumechange
at the
MediaController
. If the new value is outside the range 0.0 to 1.0 inclusive, then, on
setting, an IndexSizeError
exception must be thrown instead.
The muted
attribute, on getting, must
return the MediaController
's media controller mute override, and on
setting, must set the MediaController
's media controller mute override
to the new value and queue a task to fire a simple event named volumechange
at the
MediaController
.
The media resources of all the slaved media
elements of a MediaController
have a defined temporal relationship which
provides relative offsets between the zero time of each such media resource: for
media resources with a timeline offset, their
relative offsets are the difference between their timeline offset; the zero times of
all the media resources without a timeline offset
are not offset from each other (i.e. the origins of their timelines are cotemporal); and finally,
the zero time of the media resource with the earliest timeline offset
(if any) is not offset from the zero times of the media
resources without a timeline offset (i.e. the origins of media resources without a timeline offset are further cotemporal
with the earliest defined point on the timeline of the media resource with the
earliest timeline offset).
The media resource end position of a media resource in a media element is defined as follows: if the media resource has a finite and known duration, the media resource end position is the duration of the media resource's timeline (the last defined position on that timeline); otherwise, the media resource's duration is infinite or unknown, and the media resource end position is the time of the last frame of media data currently available for that media resource.
Each MediaController
also has its own defined timeline. On this timeline, all the
media resources of all the slaved media elements
of the MediaController
are temporally aligned according to their defined offsets. The
media controller duration of that MediaController
is the time from the
earliest earliest possible position, relative to this MediaController
timeline, of any of the media resources of the slaved
media elements of the MediaController
, to the time of the latest media
resource end position of the media resources of the
slaved media elements of the MediaController
, again relative to this
MediaController
timeline.
Each MediaController
has a media controller position. This is the time
on the MediaController
's timeline at which the user agent is trying to play the
slaved media elements. When a MediaController
is created, its
media controller position is initially zero.
When the user agent is to bring a media element up to speed with its new media controller, it must seek that media element to the
MediaController
's media controller position relative to the media
element's timeline.
When the user agent is to seek the media controller to a particular new playback position, it must follow these steps:
If the new playback position is less than zero, then set it to zero.
If the new playback position is greater than the media controller duration, then set it to the media controller duration.
Set the media controller position to the new playback position.
Seek each slaved media element to the new playback position relative to the media element timeline.
A MediaController
is a restrained media controller if the
MediaController
is a playing media controller, and none of its
slaved media elements are blocked media
elements, but either at least one of its slaved media elements whose
autoplaying flag is true still has its paused
attribute set to true, or, all of its slaved media elements have their paused
attribute set to true.
A MediaController
is a blocked media controller if the
MediaController
is a paused media controller, or if any of its
slaved media elements are blocked media
elements, or if any of its slaved media elements whose autoplaying
flag is true still have their paused
attribute set to
true, or if all of its slaved media elements have their paused
attribute set to true.
A media element is blocked on its media controller if the
MediaController
is a blocked media controller, or if its media
controller position is either before the media resource's earliest
possible position relative to the MediaController
's timeline or after the end
of the media resource relative to the MediaController
's timeline.
When a MediaController
is not a blocked media
controller and it has at least one slaved media
element whose Document
is a fully active Document
,
the MediaController
's media controller position must increase
monotonically at media controller playback rate units of time on the
MediaController
's timeline per unit time of the clock used by its slaved media
elements.
When the zero point on the timeline of a MediaController
moves relative to the
timelines of the slaved media elements by a time difference ΔT, the MediaController
's media controller
position must be decremented by ΔT.
In some situations, e.g. when playing back a live stream without buffering anything, the media controller position would increase monotonically as described above at the same rate as the ΔT described in the previous paragraph decreases it, with the end result that for all intents and purposes, the media controller position would appear to remain constant (probably with the value 0).
A MediaController
has a most recently reported readiness state, which
is a number from 0 to 4 derived from the numbers used for the media element readyState
attribute, and a most recently reported
playback state, which is either playing, waiting, or ended.
When a MediaController
is created, its most recently reported readiness
state must be set to 0, and its most recently reported playback state must be
set to waiting.
When a user agent is required to report the controller state for a
MediaController
, the user agent must run the following steps:
If the MediaController
has no slaved media elements, let new readiness state be 0.
Otherwise, let it have the lowest value of the readyState
IDL attributes of all of its slaved media
elements.
If the MediaController
's most recently reported readiness state is
less than the new readiness state, then run these substeps:
Let next state be the MediaController
's most
recently reported readiness state.
Loop: Increment next state by one.
Queue a task to run the following steps:
Set the MediaController
's readyState
attribute to the value next state.
Fire a simple event at the MediaController
object, whose
name is the event name corresponding to the value of next state given in
the table below.
If next state is less than new readiness state, then return to the step labeled loop.
Otherwise, if the MediaController
's most recently reported readiness
state is greater than new readiness state then queue a
task to fire a simple event at the MediaController
object,
whose name is the event name corresponding to the value of new readiness
state given in the table below.
Value of new readiness state | Event name |
---|---|
0 | emptied
|
1 | loadedmetadata
|
2 | loadeddata
|
3 | canplay
|
4 | canplaythrough
|
Let the MediaController
's most recently reported readiness state
be new readiness state.
Initialize new playback state by setting it to the state given for the first matching condition from the following list:
MediaController
has no slaved media elementsMediaController
's slaved media elements have
ended playback and the media controller playback rate is positive or
zeroMediaController
is a blocked media controllerIf the MediaController
's most recently reported playback state
is not equal to new playback state and the new playback
state is ended, then queue a task that, if the
MediaController
object is a playing media controller, and all of the
MediaController
's slaved media elements have still ended
playback, and the media controller playback rate is still positive or zero,
changes the MediaController
object to a paused media controller and
then fires a simple event named pause
at the MediaController
object.
If the MediaController
's most recently reported playback state is
not equal to new playback state then queue a task to run the
following steps:
Set the MediaController
's playbackState
attribute to the value given in
the second column of the row of the following table whose first column contains the new playback state.
Fire a simple event at the MediaController
object, whose name
is the value given in the third column of the row of the following table whose first column
contains the new playback state.
New playback state | New value for playbackState
| Event name |
---|---|---|
playing | "playing "
| playing
|
waiting | "waiting "
| waiting
|
ended | "ended "
| ended
|
Let the MediaController
's most recently reported playback state
be new playback state.
The following are the event handlers (and their corresponding event handler event types) that must be supported, as event handler IDL attributes,
by all objects implementing the MediaController
interface:
Event handler | Event handler event type |
---|---|
onemptied | emptied
|
onloadedmetadata | loadedmetadata
|
onloadeddata | loadeddata
|
oncanplay | canplay
|
oncanplaythrough | canplaythrough
|
onplaying | playing
|
onended | ended
|
onwaiting | waiting
|
ondurationchange | durationchange
|
ontimeupdate | timeupdate
|
onplay | play
|
onpause | pause
|
onratechange | ratechange
|
onvolumechange | volumechange
|
The task source for the tasks listed in this section is the DOM manipulation task source.
The mediagroup
content attribute on media elements can be used to link multiple media elements together by implicitly creating a MediaController
. The
value is text; media elements with the same value are
automatically linked by the user agent.
When a media element is created with a mediagroup
attribute, and when a media element's
mediagroup
attribute is set, changed, or removed, the
user agent must run the following steps:
Let m be the media element in question.
Let old controller be m's current media controller, if it currently has one, and null otherwise.
Let new controller be null.
Let m have no current media controller, if it currently has one.
If m's mediagroup
attribute
is being removed, then jump to the update controllers step below.
If there is another media element whose Document
is the same as
m's Document
(even if one or both of these elements are not
actually in the Document
), and which
also has a mediagroup
attribute, and whose mediagroup
attribute has the same value as the new value of
m's mediagroup
attribute, then
let controller be that media element's current media
controller.
Otherwise, let controller be a newly created
MediaController
.
Let m's current media controller be controller.
Let new controller be m's current media controller.
Bring the media element up to speed with its new media controller.
Update controllers: If old controller and new controller are the same (whether both null or both the same controller) then abort these steps.
If old controller is not null and still has one or more slaved media elements, then report the controller state for old controller.
If new controller is not null, then report the controller state for new controller.
The mediaGroup
IDL attribute on media elements must reflect the mediagroup
content attribute.
Multiple media elements referencing the same media
resource will share a single network request. This can be used to efficiently play two
(video) tracks from the same media resource in two different places on the screen.
Used with the mediagroup
attribute, these elements can
also be kept synchronised.
In this example, a sign-languge interpreter track from a movie file is overlaid on the primary
video track of that same video file using two video
elements, some CSS, and an
implicit MediaController
:
<article> <style scoped> div { margin: 1em auto; position: relative; width: 400px; height: 300px; } video { position; absolute; bottom: 0; right: 0; } video:first-child { width: 100%; height: 100%; } video:last-child { width: 30%; } </style> <div> <video src="movie.vid#track=Video&track=English" autoplay controls mediagroup=movie></video> <video src="movie.vid#track=sign" autoplay mediagroup=movie></video> </div> </article>
A media element can have a group of associated text tracks, known as the media element's list of text tracks. The text tracks are sorted as follows:
track
element
children of the media element, in tree order.addTextTrack()
method, in the order they were added, oldest
first.A text track consists of:
This decides how the track is handled by the user agent. The kind is represented by a string. The possible strings are:
subtitles
captions
descriptions
chapters
metadata
The kind of track can change dynamically, in the case of
a text track corresponding to a track
element.
This is a human-readable string intended to identify the track for the user.
The label of a track can change dynamically, in the
case of a text track corresponding to a track
element.
When a text track label is the empty string, the user agent should automatically generate an appropriate label from the text track's other properties (e.g. the kind of text track and the text track's language) for use in its user interface. This automatically-generated label is not exposed in the API.
This is a string extracted from the media resource specifically for in-band metadata tracks to enable such tracks to be dispatched to different scripts in the document.
For example, a traditional TV station broadcast streamed on the Web and augmented with Web-specific interactive features could include text tracks with metadata for ad targeting, trivia game data during game shows, player states during sports games, recipe information during food programs, and so forth. As each program starts and ends, new tracks might be added or removed from the stream, and as each one is added, the user agent could bind them to dedicated script modules using the value of this attribute.
Other than for in-band metadata text tracks, the in-band metadata track dispatch type is the empty string. How this value is populated for different media formats is described in steps to expose a media-resource-specific text track.
This is a string (a BCP 47 language tag) representing the language of the text track's cues. [BCP47]
The language of a text track can change dynamically,
in the case of a text track corresponding to a track
element.
One of the following:
Indicates that the text track's cues have not been obtained.
Indicates that the text track is loading and there have been no fatal errors encountered so far. Further cues might still be added to the track by the parser.
Indicates that the text track has been loaded with no fatal errors.
Indicates that the text track was enabled, but when the user agent attempted to obtain it, this failed in some way (e.g. URL could not be resolved, network error, unknown text track format). Some or all of the cues are likely missing and will not be obtained.
The readiness state of a text track changes dynamically as the track is obtained.
One of the following:
Indicates that the text track is not active. Other than for the purposes of exposing the track in the DOM, the user agent is ignoring the text track. No cues are active, no events are fired, and the user agent will not attempt to obtain the track's cues.
Indicates that the text track is active, but that the user agent is not actively displaying the cues. If no attempt has yet been made to obtain the track's cues, the user agent will perform such an attempt momentarily. The user agent is maintaining a list of which cues are active, and events are being fired accordingly.
Indicates that the text track is active. If no attempt has yet been made to obtain the
track's cues, the user agent will perform such an attempt momentarily. The user agent is
maintaining a list of which cues are active, and events are being fired accordingly. In
addition, for text tracks whose kind is subtitles
or captions
, the cues are being overlaid on the video
as appropriate; for text tracks whose kind is descriptions
, the user agent is making the
cues available to the user in a non-visual fashion; and for text tracks whose kind is chapters
, the user agent is making available to
the user a mechanism by which the user can navigate to any point in the media
resource by selecting a cue.
A list of text track cues, along with rules for updating the text track rendering. For example, for WebVTT, the rules for updating the display of WebVTT text tracks. [WEBVTT]
The list of cues of a text track can change dynamically, either because the text track has not yet been loaded or is still loading, or due to DOM manipulation.
Each text track has a corresponding TextTrack
object.
Each media element has a list of pending text tracks, which must initially be empty, a blocked-on-parser flag, which must initially be false, and a did-perform-automatic-track-selection flag, which must also initially be false.
When the user agent is required to populate the list of pending text tracks of a media element, the user agent must add to the element's list of pending text tracks each text track in the element's list of text tracks whose text track mode is not disabled and whose text track readiness state is loading.
Whenever a track
element's parent node changes, the user agent must remove the
corresponding text track from any list of pending text tracks that it is
in.
Whenever a text track's text track readiness state changes to either loaded or failed to load, the user agent must remove it from any list of pending text tracks that it is in.
When a media element is created by an HTML parser or XML parser, the user agent must set the element's blocked-on-parser flag to true. When a media element is popped off the stack of open elements of an HTML parser or XML parser, the user agent must honor user preferences for automatic text track selection, populate the list of pending text tracks, and set the element's blocked-on-parser flag to false.
The text tracks of a media element are ready when both the element's list of pending text tracks is empty and the element's blocked-on-parser flag is false.
Each media element has a pending text track change notification flag, which must initially be unset.
Whenever a text track that is in a media element's list of text tracks has its text track mode change value, the user agent must run the following steps for the media element:
If the media element's pending text track change notification flag is set, abort these steps.
Set the media element's pending text track change notification flag.
Queue a task that runs the following substeps:
Unset the media element's pending text track change notification flag.
Fire a simple event named change
at
the media element's textTracks
attribute's TextTrackList
object.
If the media element's show poster flag is not set, run the time marches on steps.
The task source for the tasks listed in this section is the DOM manipulation task source.
A text track cue is the unit of time-sensitive data in a text track, corresponding for instance for subtitles and captions to the text that appears at a particular time and disappears at another time.
Each text track cue consists of:
An arbitrary string.
The time, in seconds and fractions of a second, that describes the beginning of the range of the media data to which the cue applies.
The time, in seconds and fractions of a second, that describes the end of the range of the media data to which the cue applies.
A boolean indicating whether playback of the media resource is to pause when the end of the range to which the cue applies is reached.
Additional fields, as needed for the format. For example, WebVTT has a text track cue writing direction and so forth. [WEBVTT]
The raw data of the cue, and rules for rendering the cue in isolation.
The precise nature of this data is defined by the format. For example, WebVTT uses text.
The text track cue start time and text track cue end time can be negative. (The current playback position can never be negative, though, so cues entirely before time zero cannot be active.)
Each text track cue has a corresponding TextTrackCue
object (or more
specifically, an object that inherits from TextTrackCue
— for example, WebVTT
cues use the VTTCue
interface). A text track cue's in-memory
representation can be dynamically changed through this TextTrackCue
API. [WEBVTT]
A text track cue is associated with rules for updating the text track
rendering, as defined by the specification for the specific kind of text track
cue. These rules are used specifically when the object representing the cue is added to a
TextTrack
object using the addCue()
method.
In addition, each text track cue has two pieces of dynamic information:
This flag must be initially unset. The flag is used to ensure events are fired appropriately when the cue becomes active or inactive, and to make sure the right cues are rendered.
The user agent must synchronously unset this flag whenever the text track cue is
removed from its text track's text track list of cues; whenever the
text track itself is removed from its media element's list of
text tracks or has its text track mode changed to disabled; and whenever the media element's readyState
is changed back to HAVE_NOTHING
. When the flag is unset in this way for one
or more cues in text tracks that were showing prior to the relevant incident, the user agent must, after having unset
the flag for all the affected cues, apply the rules for updating the text track
rendering of those text tracks. For example, for text tracks based on WebVTT, the rules for updating
the display of WebVTT text tracks. [WEBVTT]
This is used as part of the rendering model, to keep cues in a consistent position. It must initially be empty. Whenever the text track cue active flag is unset, the user agent must empty the text track cue display state.
The text track cues of a media element's text tracks are ordered relative to each other in the text track cue order, which is determined as follows: first group the cues by their text track, with the groups being sorted in the same order as their text tracks appear in the media element's list of text tracks; then, within each group, cues must be sorted by their start time, earliest first; then, any cues with the same start time must be sorted by their end time, latest first; and finally, any cues with identical end times must be sorted in the order they were last added to their respective text track list of cues, oldest first (so e.g. for cues from a WebVTT file, that would initially be the order in which the cues were listed in the file). [WEBVTT]
A media-resource-specific text track is a text track that corresponds to data found in the media resource.
Rules for processing and rendering such data are defined by the relevant specifications, e.g. the specification of the video format if the media resource is a video.
When a media resource contains data that the user agent recognises and supports as being equivalent to a text track, the user agent runs the steps to expose a media-resource-specific text track with the relevant data, as follows.
Associate the relevant data with a new text track and its corresponding new
TextTrack
object. The text track is a media-resource-specific
text track.
Set the new text track's kind, label, and language based on the semantics of the relevant data, as defined by the relevant specification. If there is no label in that data, then the label must be set to the empty string.
Associate the text track list of cues with the rules for updating the text track rendering appropriate for the format in question.
If the new text track's kind is metadata
, then set the text track in-band
metadata track dispatch type as follows, based on the type of the media
resource:
CodecID
element. [WEBMCG]stsd
box of the
first stbl
box of the
first minf
box of the
first mdia
box of the
text track's trak
box in the
first moov
box
of the file be the stsd box, if any.
If the file has no stsd box, or if the stsd box has neither a mett
box nor a metx
box, then the text track
in-band metadata track dispatch type must be set to the empty string.
Otherwise, if the stsd box has a mett
box then the text
track in-band metadata track dispatch type must be set to the concatenation of the
string "mett
", a U+0020 SPACE character, and the value of the first mime_format
field of the first mett
box of the stsd
box, or the empty string if that field is absent in that box.
Otherwise, if the stsd box has no mett
box but has a metx
box then the text track in-band metadata track dispatch type
must be set to the concatenation of the string "metx
", a U+0020 SPACE
character, and the value of the first namespace
field of the first metx
box of the stsd box, or the empty string if that field is absent in
that box.
[MPEG4]
Populate the new text track's list of cues with the cues parsed so far, following the guidelines for exposing cues, and begin updating it dynamically as necessary.
Set the new text track's readiness state to loaded.
Set the new text track's mode to the mode consistent with the user's preferences and the requirements of the relevant specification for the data.
Add the new text track to the media element's list of text tracks.
Fire a trusted event with the name addtrack
, that does not bubble and is not cancelable, and that uses
the TrackEvent
interface, with the track
attribute initialized to the text track's TextTrack
object, at the
media element's textTracks
attribute's
TextTrackList
object.
When a track
element is created, it must be associated with a new text
track (with its value set as defined below) and its corresponding new
TextTrack
object.
The text track kind is determined from the state of the element's kind
attribute according to the following table; for a state given
in a cell of the first column, the kind is the string given
in the second column:
State | String |
---|---|
Subtitles | subtitles
|
Captions | captions
|
Descriptions | descriptions
|
Chapters | chapters
|
Metadata | metadata
|
The text track label is the element's track label.
The text track language is the element's track language, if any, or the empty string otherwise.
As the kind
, label
,
and srclang
attributes are set, changed, or removed, the
text track must update accordingly, as per the definitions above.
Changes to the track URL are handled in the algorithm below.
The text track readiness state is initially not loaded, and the text track mode is initially disabled.
The text track list of cues is initially empty. It is dynamically modified when the referenced file is parsed. Associated with the list are the rules for updating the text track rendering appropriate for the format in question; for WebVTT, this is the rules for updating the display of WebVTT text tracks. [WEBVTT]
When a track
element's parent element changes and the new parent is a media
element, then the user agent must add the track
element's corresponding
text track to the media element's list of text tracks, and
then queue a task to fire a trusted event with the name addtrack
, that does not bubble and is not cancelable, and that uses
the TrackEvent
interface, with the track
attribute initialized to the text track's TextTrack
object, at the
media element's textTracks
attribute's
TextTrackList
object.
When a track
element's parent element changes and the old parent was a media
element, then the user agent must remove the track
element's corresponding
text track from the media element's list of text tracks,
and then queue a task to fire a trusted event with the name removetrack
, that does not bubble and is not cancelable, and that
uses the TrackEvent
interface, with the track
attribute initialized to the text track's
TextTrack
object, at the media element's textTracks
attribute's TextTrackList
object.
When a text track corresponding to a track
element is added to a
media element's list of text tracks, the user agent must queue a
task to run the following steps for the media element:
If the element's blocked-on-parser flag is true, abort these steps.
If the element's did-perform-automatic-track-selection flag is true, abort these steps.
Honor user preferences for automatic text track selection for this element.
When the user agent is required to honor user preferences for automatic text track selection for a media element, the user agent must run the following steps:
Perform automatic text track selection for subtitles
and captions
.
If there are any text tracks in the media
element's list of text tracks whose text track kind is metadata
that correspond to track
elements with a default
attribute set whose text
track mode is set to disabled, then set the
text track mode of all such tracks to hidden
Set the element's did-perform-automatic-track-selection flag to true.
When the steps above say to perform automatic text track selection for one or more text track kinds, it means to run the following steps:
Let candidates be a list consisting of the text tracks in the media element's list of text tracks whose text track kind is one of the kinds that were passed to the algorithm, if any, in the order given in the list of text tracks.
If candidates is empty, then abort these steps.
If any of the text tracks in candidates have a text track mode set to showing, abort these steps.
If the user has expressed an interest in having a track from candidates enabled based on its text track kind, text track language, and text track label, then set its text track mode to showing.
For example, the user could have set a browser preference to the effect of "I want French captions whenever possible", or "If there is a subtitle track with 'Commentary' in the title, enable it", or "If there are audio description tracks available, enable one, ideally in Swiss German, but failing that in Standard Swiss German or Standard German".
Otherwise, if there are any text tracks in candidates that correspond to track
elements with a default
attribute set whose text track mode is
set to disabled, then set the text track
mode of the first such track to showing.
When a text track corresponding to a track
element experiences any of
the following circumstances, the user agent must start the track
processing
model for that text track and its track
element:
track
element is created.track
element's parent element changes and the new parent is a media
element.When a user agent is to start the track
processing model for a
text track and its track
element, it must run the following algorithm.
This algorithm interacts closely with the event loop mechanism; in particular, it has
a synchronous section (which is triggered as part of the event loop
algorithm). The steps in that section are marked with ⌛.
If another occurrence of this algorithm is already running for this text
track and its track
element, abort these steps, letting that other algorithm
take care of this element.
If the text track's text track mode is not set to one of hidden or showing, abort these steps.
If the text track's track
element does not have a media
element as a parent, abort these steps.
Run the remainder of these steps asynchronously, allowing whatever caused these steps to run to continue.
Top: Await a stable state. The synchronous section consists of the following steps. (The steps in the synchronous section are marked with ⌛.)
⌛ Set the text track readiness state to loading.
⌛ If the track
element's parent is a media element then
let CORS mode be the state of the parent media element's crossorigin
content attribute. Otherwise, let CORS mode be No CORS.
End the synchronous section, continuing the remaining steps asynchronously.
If URL is not the empty string, perform a potentially CORS-enabled
fetch of URL, with the mode being CORS mode, the origin being the origin of the
track
element's Document
, and the default origin behaviour set
to fail.
The resource obtained in this fashion, if any, contains the text track data. If any data is obtained, it is by definition CORS-same-origin (cross-origin resources that are not suitably CORS-enabled do not get this far).
The tasks queued by the fetching algorithm on the networking task source to process the data as it is being fetched must determine the type of the resource. If the type of the resource is not a supported text track format, the load will fail, as described below. Otherwise, the resource's data must be passed to the appropriate parser (e.g. the WebVTT parser) as it is received, with the text track list of cues being used for that parser's output. [WEBVTT]
The appropriate parser will synchronously (during these networking task source tasks) and incrementally (as each such task is run with whatever data has been received from the network) update the text track list of cues.
This specification does not currently say whether or how to check the MIME types of text tracks, or whether or how to perform file type sniffing using the actual file data. Implementors differ in their intentions on this matter and it is therefore unclear what the right solution is. In the absence of any requirement here, the HTTP specification's strict requirement to follow the Content-Type header prevails ("Content-Type specifies the media type of the underlying data." ... "If and only if the media type is not given by a Content-Type field, the recipient MAY attempt to guess the media type via inspection of its content and/or the name extension(s) of the URI used to identify the resource.").
If the fetching algorithm fails for any reason (network error, the server returns an error code, a cross-origin check fails, etc), if URL is the empty string, or if the type of the resource is not a supported text track format, then run these steps:
Queue a task to first change the text track readiness state to
failed to load and then fire a simple
event named error
at the track
element.
Wait until the text track readiness state is no longer set to loading.
Wait until the track URL is no longer equal to URL, at the same time as the text track mode is set to hidden or showing.
Jump to the step labeled top.
If the fetching algorithm does not fail, then the final task that is queued by the networking task source must run the following steps after it has tried to parse the data:
Change the text track readiness state to loaded.
If the file was successfully processed, fire a simple event named load
at the track
element.
Otherwise, the file was not successfully processed (e.g. the format in question is an XML
format and the file contained a well-formedness error that the XML specification requires be
detected and reported to the application); fire a simple event named error
at the track
element.
Wait until the track URL is no longer equal to URL, at the same time as the text track mode is set to hidden or showing.
Jump back to the step labeled top.
If, while the fetching algorithm is active, either:
...then the user agent must run the following steps:
Abort the fetching algorithm, discarding any pending tasks generated by that algorithm (and in particular, not adding any cues to the text track list of cues after the moment the URL changed).
Jump back to the step labeled top.
Until one of the above circumstances occurs, the user agent must remain on this step.
Whenever a track
element has its src
attribute
set, changed, or removed, the user agent must synchronously empty the element's text
track's text track list of cues. (This also causes the algorithm above to stop
adding cues from the resource being obtained using the previously given URL, if any.)
How a specific format's text track cues are to be interpreted for the purposes of processing by an HTML user agent is defined by that format. In the absence of such a specification, this section provides some constraints within which implementations can attempt to consistently expose such formats.
To support the text track model of HTML, each unit of timed data is converted to a text track cue. Where the mapping of the format's features to the aspects of a text track cue as defined in this specification are not defined, implementations must ensure that the mapping is consistent with the definitions of the aspects of a text track cue as defined above, as well as with the following constraints:
Should be set to the empty string if the format has no obvious analogue to a per-cue identifier.
Should be set to false.
For media-resource-specific text tracks
of kind metadata
,
text track cues are exposed using the DataCue
object
unless there is a more appropriate TextTrackCue
interface available.
For example, if the media-resource-specific text track format is WebVTT,
then VTTCue
is more appropriate.
interface TextTrackList : EventTarget { readonly attribute unsigned long length; getter TextTrack (unsigned long index); TextTrack? getTrackById(DOMString id); attribute EventHandler onchange; attribute EventHandler onaddtrack; attribute EventHandler onremovetrack; };
textTracks
. length
Returns the number of text tracks associated with the media element (e.g. from track
elements). This is the number of text tracks in the media element's list of text tracks.
textTracks[
n ]
Returns the TextTrack
object representing the nth text track in the media element's list of text tracks.
textTracks
. getTrackById
( id )Returns the TextTrack
object with the given identifier, or null if no track has that identifier.
track
Returns the TextTrack
object representing the track
element's text track.
A TextTrackList
object represents a dynamically updating list of text tracks in a given order.
The textTracks
attribute of media elements must return a TextTrackList
object
representing the TextTrack
objects of the text tracks
in the media element's list of text tracks, in the same order as in the
list of text tracks. The same object must be returned each time the attribute is
accessed. [WEBIDL]
The length
attribute of a
TextTrackList
object must return the number of text
tracks in the list represented by the TextTrackList
object.
The supported property indices of a TextTrackList
object at any
instant are the numbers from zero to the number of text tracks in
the list represented by the TextTrackList
object minus one, if any. If there are no
text tracks in the list, there are no supported property
indices.
To determine the value of an indexed property of a TextTrackList
object for a given index index, the user agent must return the indexth text track in the list represented by the
TextTrackList
object.
The getTrackById(id)
method must return the first TextTrack
in the
TextTrackList
object whose id
IDL attribute
would return a value equal to the value of the id argument. When no tracks
match the given argument, the method must return null.
enum TextTrackMode { "disabled", "hidden", "showing" }; enum TextTrackKind { "subtitles", "captions", "descriptions", "chapters", "metadata" }; interface TextTrack : EventTarget { readonly attribute TextTrackKind kind; readonly attribute DOMString label; readonly attribute DOMString language; readonly attribute DOMString id; readonly attribute DOMString inBandMetadataTrackDispatchType; attribute TextTrackMode mode; readonly attribute TextTrackCueList? cues; readonly attribute TextTrackCueList? activeCues; void addCue(TextTrackCue cue); void removeCue(TextTrackCue cue); attribute EventHandler oncuechange; };
addTextTrack
( kind [, label [, language ] ] )Creates and returns a new TextTrack
object, which is also added to the
media element's list of text tracks.
kind
Returns the text track kind string.
label
Returns the text track label, if there is one, or the empty string otherwise (indicating that a custom label probably needs to be generated from the other attributes of the object if the object is exposed to the user).
language
Returns the text track language string.
id
Returns the ID of the given track.
For in-band tracks, this is the ID that can be used with a fragment identifier if the format
supports the Media Fragments URI syntax, and that can be used with the getTrackById()
method. [MEDIAFRAG]
For TextTrack
objects corresponding to track
elements, this is the
ID of the track
element.
inBandMetadataTrackDispatchType
Returns the text track in-band metadata track dispatch type string.
mode
[ = value ]Returns the text track mode, represented by a string from the following list:
disabled
"The text track disabled mode.
hidden
"The text track hidden mode.
showing
"The text track showing mode.
Can be set, to change the mode.
cues
Returns the text track list of cues, as a TextTrackCueList
object.
activeCues
Returns the text track cues from the text track
list of cues that are currently active (i.e. that start before the current playback
position and end after it), as a TextTrackCueList
object.
addCue
( cue )Adds the given cue to textTrack's text track list of cues.
removeCue
( cue )Removes the given cue from textTrack's text track list of cues.
The addTextTrack(kind, label, language)
method of media elements, when invoked, must run the following steps:
Create a new TextTrack
object.
Create a new text track corresponding to the new object, and set its text track kind to kind, its text track label to label, its text track language to language, its text track readiness state to the text track loaded state, its text track mode to the text track hidden mode, and its text track list of cues to an empty list.
Initially, the text track list of cues is not associated with any rules for updating the text track rendering. When a text track cue is added to it, the text track list of cues has its rules permanently set accordingly.
Add the new text track to the media element's list of text tracks.
Queue a task to fire a trusted event with the name addtrack
, that does not bubble and is not cancelable, and
that uses the TrackEvent
interface, with the track
attribute initialized to the new text
track's TextTrack
object, at the media element's textTracks
attribute's TextTrackList
object.
Return the new TextTrack
object.
The kind
attribute must return the
text track kind of the text track that the TextTrack
object
represents.
The label
attribute must return the
text track label of the text track that the TextTrack
object represents.
The language
attribute must return the
text track language of the text track that the TextTrack
object represents.
The id
attribute returns the track's
identifier, if it has one, or the empty string otherwise. For tracks that correspond to
track
elements, the track's identifier is the value of the element's id
attribute, if any. For in-band tracks, the track's identifier is
specified by the media resource. If the media resource is in a format
that supports the Media Fragments URI fragment identifier syntax, the identifier
returned for a particular track must be the same identifier that would enable the track if used as
the name of a track in the track dimension of such a fragment identifier. [MEDIAFRAG]
The inBandMetadataTrackDispatchType
attribute must return the text track in-band metadata track dispatch type of the
text track that the TextTrack
object represents.
The mode
attribute, on getting, must return
the string corresponding to the text track mode of the text track that
the TextTrack
object represents, as defined by the following list:
disabled
"hidden
"showing
"On setting, if the new value isn't equal to what the attribute would currently return, the new value must be processed as follows:
disabled
"Set the text track mode of the text track that the
TextTrack
object represents to the text track disabled mode.
hidden
"Set the text track mode of the text track that the
TextTrack
object represents to the text track hidden mode.
showing
"Set the text track mode of the text track that the
TextTrack
object represents to the text track showing mode.
If the text track mode of the text track that the
TextTrack
object represents is not the text track disabled mode, then
the cues
attribute must return a
live TextTrackCueList
object that represents the subset of the
text track list of cues of the text track that the
TextTrack
object represents whose end
times occur at or after the earliest possible position when the script
started, in text track cue order. Otherwise, it must return null. When an
object is returned, the same object must be returned each time.
The earliest possible position when the script started is whatever the earliest possible position was the last time the event loop reached step 1.
If the text track mode of the text track that the
TextTrack
object represents is not the text track disabled mode, then
the activeCues
attribute must return a
live TextTrackCueList
object that represents the subset of the
text track list of cues of the text track that the
TextTrack
object represents whose active flag was set when the script
started, in text track cue order. Otherwise, it must return null. When an
object is returned, the same object must be returned each time.
A text track cue's active flag was set when the script started if its text track cue active flag was set the last time the event loop reached step 1.
The addCue(cue)
method
of TextTrack
objects, when invoked, must run the following steps:
If the text track list of cues does not yet have any associated rules for updating the text track rendering, then associate the text track list of cues with the rules for updating the text track rendering appropriate to cue.
If text track list of cues' associated rules for updating the text
track rendering are not the same rules for updating the text track rendering
as appropriate for cue, then throw an InvalidStateError
exception and abort these steps.
If the given cue is in a text track list of cues, then remove cue from that text track list of cues.
Add cue to the method's TextTrack
object's text
track's text track list of cues.
The removeCue(cue)
method of TextTrack
objects, when invoked, must run the following steps:
If the given cue is not currently listed in the method's
TextTrack
object's text track's text track list of cues,
then throw a NotFoundError
exception and abort these steps.
Remove cue from the method's TextTrack
object's
text track's text track list of cues.
In this example, an audio
element is used to play a specific sound-effect from a
sound file containing many sound effects. A cue is used to pause the audio, so that it ends
exactly at the end of the clip, even if the browser is busy running some script. If the page had
relied on script to pause the audio, then the start of the next clip might be heard if the
browser was not able to run the script at the exact time specified.
var sfx = new Audio('sfx.wav'); var sounds = sfx.addTextTrack('metadata'); // add sounds we care about function addFX(start, end, name) { var cue = new VTTCue(start, end, ''); cue.id = name; cue.pauseOnExit = true; sounds.addCue(cue); } addFX(12.783, 13.612, 'dog bark'); addFX(13.612, 15.091, 'kitten mew')) function playSound(id) { sfx.currentTime = sounds.getCueById(id).startTime; sfx.play(); } // play a bark as soon as we can sfx.oncanplaythrough = function () { playSound('dog bark'); } // meow when the user tries to leave window.onbeforeunload = function () { playSound('kitten mew'); return 'Are you sure you want to leave this awesome page?'; }
interface TextTrackCueList { readonly attribute unsigned long length; getter TextTrackCue (unsigned long index); TextTrackCue? getCueById(DOMString id); };
length
Returns the number of cues in the list.
Returns the text track cue with index index in the list. The cues are sorted in text track cue order.
getCueById
( id )Returns the first text track cue (in text track cue order) with text track cue identifier id.
Returns null if none of the cues have the given identifier or if the argument is the empty string.
A TextTrackCueList
object represents a dynamically updating list of text track cues in a given order.
The length
attribute must return
the number of cues in the list represented by the
TextTrackCueList
object.
The supported property indices of a TextTrackCueList
object at any
instant are the numbers from zero to the number of cues in the
list represented by the TextTrackCueList
object minus one, if any. If there are no
cues in the list, there are no supported property
indices.
To determine the value of an indexed property for a given index index, the user agent must return the indexth text track
cue in the list represented by the TextTrackCueList
object.
The getCueById(id)
method, when called with an argument other than the empty string,
must return the first text track cue in the list represented by the
TextTrackCueList
object whose text track cue identifier is id, if any, or null otherwise. If the argument is the empty string, then the method
must return null.
interface TextTrackCue : EventTarget { attribute DOMString id; attribute double startTime; attribute double endTime; attribute boolean pauseOnExit; attribute EventHandler onenter; attribute EventHandler onexit; };
Returns the TextTrack
object to which this
text track cue belongs, if any, or null
otherwise.
Returns the text track cue identifier.
Can be set.
Returns the text track cue start time, in seconds.
Can be set.
Returns the text track cue end time, in seconds.
Can be set.
Returns true if the text track cue pause-on-exit flag is set, false otherwise.
Can be set.
The track
attribute, on getting, must
return the TextTrack
object of the text track in whose list of cues the text track cue that the
TextTrackCue
object represents finds itself, if any; or null otherwise.
The id
attribute, on getting, must return
the text track cue identifier of the text track cue that the
TextTrackCue
object represents. On setting, the text track cue
identifier must be set to the new value.
The startTime
attribute, on getting,
must return the text track cue start time of the text track cue that the
TextTrackCue
object represents, in seconds. On setting, the text track cue
start time must be set to the new value, interpreted in seconds; then, if the
TextTrackCue
object's text track cue is in a text track's
list of cues, and that text track is in
a media element's list of text tracks, and the media
element's show poster flag is not set, then run the time marches on
steps for that media element.
The endTime
attribute, on getting,
must return the text track cue end time of the text track cue that the
TextTrackCue
object represents, in seconds. On setting, the text track cue end
time must be set to the new value, interpreted in seconds; then, if the
TextTrackCue
object's text track cue is in a text track's
list of cues, and that text track is in
a media element's list of text tracks, and the media
element's show poster flag is not set, then run the time marches on
steps for that media element.
The pauseOnExit
attribute, on
getting, must return true if the text track cue pause-on-exit flag of the text
track cue that the TextTrackCue
object represents is set; or false otherwise.
On setting, the text track cue pause-on-exit flag must be set if the new value is
true, and must be unset otherwise.
Media resources often contain one or more media-resource-specific text tracks containing data that browsers don't render, but want to expose to script to allow being dealt with.
If the browser is unable to identify a TextTrackCue
interface that is more
appropriate to expose the data in the cues of a media-resource-specific text track,
the DataCue object is used.
[Constructor(double startTime, double endTime, ArrayBuffer data)]
interface DataCue : TextTrackCue {
attribute ArrayBuffer data;
readonly attribute DOMString text;
};
DataCue
( [ startTime, endTime, data ] )Returns a new DataCue
object, for use with the addCue()
method.
The startTime argument sets the text track cue start time.
The endTime argument sets the text track cue end time.
The data argument sets the raw data of the text track cue.
Returns the text track cue data in raw unparsed form.
Can be set.
Returns the text track cue data as UTF-16 text converted from data.
The data
attribute, on getting, must
return the raw text track cue data of the text track cue that the
TextTrackCue
object represents. On setting, the text track cue data must
be set to the new value.
The text
attribute, on getting, must
return UTF-16 text converted from data
of the text track cue that the
TextTrackCue
object represents. If a conversion of the content in data
is not possible, e.g. because the UA is unable to identify the encoding, it must return null.
The UA will use DataCue to expose only text track cue objects that belong to a text track that has a text track kind of metadata.
If a DataCue is added to a TextTrack via the
addCue()
method but the text track
does not have its text track kind set to
metadata, throw a InvalidNodeTypeError
exception and don't add the cue to the TextTrackList of the TextTrack.
DataCue has a constructor to allow script to create DataCue objects in cases where generic metadata needs to be managed for a text track.
Chapters are segments of a media resource with a given title. Chapters can be nested, in the same way that sections in a document outline can have subsections.
Each text track cue in a text track being used for describing chapters has three key features: the text track cue start time, giving the start time of the chapter, the text track cue end time, giving the end time of the chapter, and the text track cue data giving the chapter title.
The rules for constructing the chapter tree from a text track are as follows. They produce a potentially nested list of chapters, each of which have a start time, end time, title, and a list of nested chapters. This algorithm discards cues that do not correctly nest within each other, or that are out of order.
Let list be a copy of the list of cues of the text track being processed.
Remove from list any text track cue whose text track cue end time is before its text track cue start time.
Let output be an empty list of chapters, where a chapter is a record consisting of a start time, an end time, a title, and a (potentially empty) list of nested chapters. For the purpose of this algorithm, each chapter also has a parent chapter.
Let current chapter be a stand-in chapter whose start time is negative infinity, whose end time is positive infinity, and whose list of nested chapters is output. (This is just used to make the algorithm easier to describe.)
Loop: If list is empty, jump to the step labeled end.
Let current cue be the first cue in list, and then remove it from list.
If current cue's text track cue start time is less than the start time of current chapter, then return to the step labeled loop.
While current cue's text track cue start time is greater than or equal to current chapter's end time, let current chapter be current chapter's parent chapter.
If current cue's text track cue end time is greater than the end time of current chapter, then return to the step labeled loop.
Create a new chapter new chapter, whose start time is current cue's text track cue start time, whose end time is current cue's text track cue end time, whose title is current cue's text track cue data interpreted according to its rules for rendering the cue in isolation, and whose list of nested chapters is empty.
For WebVTT, the rules for rendering the cue in isolation are the rules for interpreting WebVTT cue text. [WEBVTT]
Append new chapter to current chapter's list of nested chapters, and let current chapter be new chapter's parent.
Let current chapter be new chapter.
Return to the step labeled loop.
End: Return output.
The following snippet of a WebVTT file shows how nested chapters can be marked up. The file describes three 50-minute chapters, "Astrophysics", "Computational Physics", and "General Relativity". The first has three subchapters, the second has four, and the third has two. [WEBVTT]
WEBVTT 00:00:00.000 --> 00:50:00.000 Astrophysics 00:00:00.000 --> 00:10:00.000 Introduction to Astrophysics 00:10:00.000 --> 00:45:00.000 The Solar System 00:00:00.000 --> 00:10:00.000 Coursework Description 00:50:00.000 --> 01:40:00.000 Computational Physics 00:50:00.000 --> 00:55:00.000 Introduction to Programming 00:55:00.000 --> 01:30:00.000 Data Structures 01:30:00.000 --> 01:35:00.000 Answers to Last Exam 01:35:00.000 --> 01:40:00.000 Coursework Description 01:40:00.000 --> 02:30:00.000 General Relativity 01:40:00.000 --> 02:00:00.000 Tensor Algebra 02:00:00.000 --> 02:30:00.000 The General Relativistic Field Equations
The following are the event handlers that (and their corresponding event handler event types) must be supported, as event handler IDL
attributes, by all objects implementing the TextTrackList
interface:
Event handler | Event handler event type |
---|---|
onchange | change
|
onaddtrack | addtrack
|
onremovetrack | removetrack
|
The following are the event handlers that (and their corresponding event handler event types) must be supported, as event handler IDL
attributes, by all objects implementing the TextTrack
interface:
Event handler | Event handler event type |
---|---|
oncuechange | cuechange
|
The following are the event handlers that (and their corresponding event handler event types) must be supported, as event handler IDL
attributes, by all objects implementing the TextTrackCue
interface:
Event handler | Event handler event type |
---|---|
onenter | enter
|
onexit | exit
|
The controls
attribute is a boolean
attribute. If present, it indicates that the author has not provided a scripted controller
and would like the user agent to provide its own set of controls.
If the attribute is present, or if scripting is disabled for the media element, then the user agent should expose a user interface to the user. This user interface should include features to begin playback, pause playback, seek to an arbitrary position in the content (if the content supports arbitrary seeking), change the volume, change the display of closed captions or embedded sign-language tracks, select different audio tracks or turn on audio descriptions, and show the media content in manners more suitable to the user (e.g. full-screen video or in an independent resizable window). Other controls may also be made available.
If the media element has a current media controller, then the user
agent should expose audio tracks from all the slaved media elements (although
avoiding duplicates if the same media resource is being used several times). If a
media resource's audio track exposed in this way has no known name, and it is the
only audio track for a particular media element, the user agent should use the
element's title
attribute, if any, as the name (or as part of the
name) of that track.
Even when the attribute is absent, however, user agents may provide controls to affect playback
of the media resource (e.g. play, pause, seeking, and volume controls), but such features should
not interfere with the page's normal rendering. For example, such features could be exposed in the
media element's context menu. The user agent may implement this simply by exposing a user interface to the user as
described above (as if the controls
attribute was
present).
If the user agent exposes a user interface to
the user by displaying controls over the media element, then the user agent
should suppress any user interaction events while the user agent is interacting with this
interface. (For example, if the user clicks on a video's playback control, mousedown
events and so forth would not simultaneously be fired at
elements on the page.)
Where possible (specifically, for starting, stopping, pausing, and unpausing playback, for seeking, for changing the rate of playback, for fast-forwarding or rewinding, for listing, enabling, and disabling text tracks, and for muting or changing the volume of the audio), user interface features exposed by the user agent must be implemented in terms of the DOM API described above, so that, e.g., all the same events fire.
When a media element has a current media controller, the user agent's
user interface for pausing and unpausing playback, for seeking, for changing the rate of playback,
for fast-forwarding or rewinding, and for muting or changing the volume of audio of the entire
group must be implemented in terms of the MediaController
API exposed on that
current media controller. When a media element has a current media
controller, and all the slaved media elements of that
MediaController
are paused, the user agent should also unpause all the slaved
media elements when the user invokes a user agent interface control for beginning
playback.
The "play" function in the user agent's interface must set the playbackRate
attribute to the value of the defaultPlaybackRate
attribute before invoking the play()
method. When a media element has a current media controller, the
attributes and method with those names on that MediaController
object must be used.
Otherwise, the attributes and method with those names on the media element itself
must be used.
Features such as fast-forward or rewind must be implemented by only changing the playbackRate
attribute (and not the defaultPlaybackRate
attribute). Again, when a media element has a current media controller,
the attributes with those names on that MediaController
object must be used;
otherwise, the attributes with those names on the media element itself must be used.
When a media element has a current media controller, seeking must be
implemented in terms of the currentTime
attribute on that MediaController
object. Otherwise, the user agent must directly
seek to the requested position in the media
element's media timeline. For media resources where seeking to an arbitrary
position would be slow, user agents are encouraged to use the approximate-for-speed flag
when seeking in response to the user manipulating an approximate position interface such as a seek
bar.
When a media element has a current media controller, user agents may
additionally provide the user with controls that directly manipulate an individual media
element without affecting the MediaController
, but such features are
considered relatively advanced and unlikely to be useful to most users.
The activation behavior of a media element that is exposing a user interface to the user must be to run the following steps:
If the media element has a current media controller, and that
current media controller is a restrained media controller, then invoke
the play()
method of the
MediaController
.
Otherwise, if the media element has a current media controller,
and that current media controller is a paused media controller, then
invoke the unpause()
method of the
MediaController
.
Otherwise, if the media element has a current media controller,
then that current media controller is a playing media controller;
invoke the pause()
method of the
MediaController
.
Otherwise, the media element has no current media controller; if
the media element's paused
attribute is true,
then invoke the play()
method on the media
element.
Otherwise, the media element has no current media controller,
and the media element's paused
attribute is
false; invoke the pause()
method on the media
element.
For the purposes of listing chapters in the media resource, only text tracks in the media element's list of text tracks
that are showing and whose text track kind is
chapters
should be used. Such tracks must be
interpreted according to the rules for constructing the chapter tree from a text
track. When seeking in response to a user maniplating a chapter selection interface, user
agents should not use the approximate-for-speed flag.
The controls
IDL attribute must
reflect the content attribute of the same name.
volume
[ = value ]Returns the current playback volume, as a number in the range 0.0 to 1.0, where 0.0 is the quietest and 1.0 the loudest.
Can be set, to change the volume.
Throws an IndexSizeError
exception if the new value is not in the range 0.0 .. 1.0.
muted
[ = value ]Returns true if audio is muted, overriding the volume
attribute, and false if the volume
attribute is being
honored.
Can be set, to change whether the audio is muted or not.
The volume
attribute must return the playback
volume of any audio portions of the media element, in the range 0.0 (silent) to 1.0
(loudest). Initially, the volume should be 1.0, but user agents may remember the last set value
across sessions, on a per-site basis or otherwise, so the volume may start at other values. On
setting, if the new value is in the range 0.0 to 1.0 inclusive, the playback volume of any audio
portions of the media element must be set to the new value. If the new value is
outside the range 0.0 to 1.0 inclusive, then, on setting, an IndexSizeError
exception
must be thrown instead.
The muted
attribute must return true if the
audio output is muted and false otherwise. Initially, the audio output should not be muted
(false), but user agents may remember the last set value across sessions, on a per-site basis or
otherwise, so the muted state may start as muted (true). On setting, if the new value is true then
the audio output should be muted and if the new value is false it should be unmuted.
Whenever either of the values that would be returned by the volume
and muted
attributes
change, the user agent must queue a task to fire a simple event named
volumechange
at the media element.
An element's effective media volume is determined as follows:
If the user has indicated that the user agent is to override the volume of the element, then the element's effective media volume is the volume desired by the user. Abort these steps.
If the element's audio output is muted, the element's effective media volume is zero. Abort these steps.
If the element has a current media controller and that
MediaController
object's media controller mute override is true, the
element's effective media volume is zero. Abort these steps.
Let volume be the playback volume of the audio portions of the media element, in range 0.0 (silent) to 1.0 (loudest).
If the element has a current media controller, multiply volume by that MediaController
object's media controller volume
multiplier.
The element's effective media volume is volume, interpreted relative to the range 0.0 to 1.0, with 0.0 being silent, and 1.0 being the loudest setting, values in between increasing in loudness. The range need not be linear. The loudest setting may be lower than the system's loudest possible setting; for example the user could have set a maximum volume.
The muted
attribute on media elements is a boolean attribute that controls the default state
of the audio output of the media resource, potentially overriding user
preferences.
When a media element is created, if it has a muted
attribute specified, the user agent must mute the
media element's audio output, overriding any user preference.
The defaultMuted
IDL attribute must
reflect the muted
content attribute.
This attribute has no dynamic effect (it only controls the default state of the element).
This video (an advertisement) autoplays, but to avoid annoying users, it does so without sound, and allows the user to turn the sound on.
<video src="adverts.cgi?kind=video" controls autoplay loop muted></video>
Objects implementing the TimeRanges
interface
represent a list of ranges (periods) of time.
interface TimeRanges { readonly attribute unsigned long length; double start(unsigned long index); double end(unsigned long index); };
length
Returns the number of ranges in the object.
start
(index)Returns the time for the start of the range with the given index.
Throws an IndexSizeError
exception if the index is out of range.
end
(index)Returns the time for the end of the range with the given index.
Throws an IndexSizeError
exception if the index is out of range.
The length
IDL attribute must return the
number of ranges represented by the object.
The start(index)
method must return the position of the start of the indexth range represented
by the object, in seconds measured from the start of the timeline that the object covers.
The end(index)
method
must return the position of the end of the indexth range represented by the
object, in seconds measured from the start of the timeline that the object covers.
These methods must throw IndexSizeError
exceptions if called with an index argument greater than or equal to the number of ranges represented by the
object.
When a TimeRanges
object is said to be a normalized TimeRanges
object, the ranges it represents must obey the following criteria:
In other words, the ranges in such an object are ordered, don't overlap, aren't empty, and don't touch (adjacent ranges are folded into one bigger range).
Ranges in a TimeRanges
object must be inclusive.
Thus, the end of a range would be equal to the start of a following adjacent (touching but not overlapping) range. Similarly, a range covering a whole timeline anchored at zero would have a start equal to zero and an end equal to the duration of the timeline.
The timelines used by the objects returned by the buffered
, seekable
and
played
IDL attributes of media
elements must be that element's media timeline.
[Constructor(DOMString type, optional TrackEventInit eventInitDict)] interface TrackEvent : Event { readonly attribute (VideoTrack or AudioTrack or TextTrack) track; }; dictionary TrackEventInit : EventInit { (VideoTrack or AudioTrack or TextTrack) track; };
track
Returns the track object (TextTrack
, AudioTrack
, or
VideoTrack
) to which the event relates.
The track
attribute must return the value
it was initialized to. When the object is created, this attribute must be initialized to null. It
represents the context information for the event.
This section is non-normative.
The following events fire on media elements as part of the processing model described above:
Event name | Interface | Fired when... | Preconditions |
---|---|---|---|
loadstart
| Event
| The user agent begins looking for media data, as part of the resource selection algorithm. | networkState equals NETWORK_LOADING
|
progress
| Event
| The user agent is fetching media data. | networkState equals NETWORK_LOADING
|
suspend
| Event
| The user agent is intentionally not currently fetching media data. | networkState equals NETWORK_IDLE
|
abort
| Event
| The user agent stops fetching the media data before it is completely downloaded, but not due to an error. | error is an object with the code MEDIA_ERR_ABORTED . networkState equals either NETWORK_EMPTY or NETWORK_IDLE , depending on when the download was aborted.
|
error
| Event
| An error occurs while fetching the media data. | error is an object with the code MEDIA_ERR_NETWORK or higher. networkState equals either NETWORK_EMPTY or NETWORK_IDLE , depending on when the download was aborted.
|
emptied
| Event
| A media element whose networkState
was previously not in the NETWORK_EMPTY state has
just switched to that state (either because of a fatal error during load that's about to be
reported, or because the load() method was invoked while
the resource selection algorithm was already
running).
| networkState is NETWORK_EMPTY ; all the IDL attributes are in their
initial states.
|
stalled
| Event
| The user agent is trying to fetch media data, but data is unexpectedly not forthcoming. | networkState is NETWORK_LOADING .
|
loadedmetadata
| Event
| The user agent has just determined the duration and dimensions of the media resource and the text tracks are ready. | readyState is newly equal to HAVE_METADATA or greater for the first time.
|
loadeddata
| Event
| The user agent can render the media data at the current playback position for the first time. | readyState newly increased to HAVE_CURRENT_DATA or greater for the first time.
|
canplay
| Event
| The user agent can resume playback of the media data, but estimates that if playback were to be started now, the media resource could not be rendered at the current playback rate up to its end without having to stop for further buffering of content. | readyState newly increased to HAVE_FUTURE_DATA or greater.
|
canplaythrough
| Event
| The user agent estimates that if playback were to be started now, the media resource could be rendered at the current playback rate all the way to its end without having to stop for further buffering. | readyState is newly equal to HAVE_ENOUGH_DATA .
|
playing
| Event
| Playback is ready to start after having been paused or delayed due to lack of media data. | readyState is newly equal to or greater than
HAVE_FUTURE_DATA and paused is false, or paused is newly false and readyState is equal to or greater than HAVE_FUTURE_DATA . Even if this event fires, the
element might still not be potentially playing, e.g. if the element is
blocked on its media controller (e.g. because the current media
controller is paused, or another slaved media
element is stalled somehow, or because the media resource has no data
corresponding to the media controller position), or the element is paused
for user interaction or paused for in-band content.
|
waiting
| Event
| Playback has stopped because the next frame is not available, but the user agent expects that frame to become available in due course. | readyState is equal to or less than HAVE_CURRENT_DATA , and paused is false. Either seeking is true, or the current playback position
is not contained in any of the ranges in buffered . It
is possible for playback to stop for other reasons without paused being false, but those reasons do not fire this event
(and when those situations resolve, a separate playing
event is not fired either): e.g. the element is newly blocked on its media
controller, or playback ended, or playback
stopped due to errors, or the element has paused for user interaction
or paused for in-band content.
|
seeking
| Event
| The seeking IDL attribute changed to true, and the user agent has started seeking to a new position.
| |
seeked
| Event
| The seeking IDL attribute changed to false after the current playback position was changed.
| |
ended
| Event
| Playback has stopped because the end of the media resource was reached. | currentTime equals the end of the media
resource; ended is true.
|
durationchange
| Event
| The duration attribute has just been updated.
| |
timeupdate
| Event
| The current playback position changed as part of normal playback or in an especially interesting way, for example discontinuously. | |
play
| Event
| The element is no longer paused. Fired after the play()
method has returned, or when the autoplay attribute
has caused playback to begin.
| paused is newly false.
|
pause
| Event
| The element has been paused. Fired after the pause()
method has returned.
| paused is newly true.
|
ratechange
| Event
| Either the defaultPlaybackRate or the
playbackRate attribute has just been updated.
| |
resize
| Event
| One or both of the videoWidth and videoHeight attributes have just been updated.
| Media element is a video element; readyState is not HAVE_NOTHING
|
volumechange
| Event
| Either the volume attribute or the muted attribute has changed. Fired after the relevant
attribute's setter has returned.
|
The following events fire on MediaController
objects:
Event name | Interface | Fired when... |
---|---|---|
emptied
| Event
| All the slaved media elements newly have readyState set to HAVE_NOTHING or greater, or there are no longer any
slaved media elements.
|
loadedmetadata
| Event
| All the slaved media elements newly have readyState set to HAVE_METADATA or greater.
|
loadeddata
| Event
| All the slaved media elements newly have readyState set to HAVE_CURRENT_DATA or greater.
|
canplay
| Event
| All the slaved media elements newly have readyState set to HAVE_FUTURE_DATA or greater.
|
canplaythrough
| Event
| All the slaved media elements newly have readyState set to HAVE_ENOUGH_DATA or greater.
|
playing
| Event
| The MediaController is no longer a blocked media controller.
|
ended
| Event
| The MediaController has reached the end of all the slaved media
elements.
|
waiting
| Event
| The MediaController is now a blocked media controller.
|
ended
| Event
| All the slaved media elements have newly ended playback. |
durationchange
| Event
| The duration attribute has just been
updated.
|
timeupdate
| Event
| The media controller position changed. |
play
| Event
| The paused attribute is newly false.
|
pause
| Event
| The paused attribute is newly true.
|
ratechange
| Event
| Either the defaultPlaybackRate
attribute or the playbackRate attribute
has just been updated.
|
volumechange
| Event
| Either the volume attribute or the muted attribute has just been updated.
|
The following events fire on AudioTrackList
, VideoTrackList
, and
TextTrackList
objects:
Event name | Interface | Fired when... |
---|---|---|
change
| Event
| One or more tracks in the track list has been enabled or disabled. |
addtrack
| TrackEvent
| A track has been added to the track list. |
removetrack
| TrackEvent
| A track has been removed from the track list. |
The main security and privacy implications of the video
and audio
elements come from the ability to embed media cross-origin. There are two directions that threats
can flow: from hostile content to a victim page, and from a hostile page to victim content.
If a victim page embeds hostile content, the threat is that the content might contain scripted
code that attempts to interact with the Document
that embeds the content. To avoid
this, user agents must ensure that there is no access from the content to the embedding page. In
the case of media content that uses DOM concepts, the embedded content must be treated as if it
was in its own unrelated top-level browsing context.
For instance, if an SVG animation was embedded in a video
element,
the user agent would not give it access to the DOM of the outer page. From the perspective of
scripts in the SVG resource, the SVG file would appear to be in a lone top-level browsing context
with no parent.
If a hostile page embeds victim content, the threat is that the embedding page could obtain
information from the content that it would not otherwise have access to. The API does expose some
information: the existence of the media, its type, its duration, its size, and the performance
characteristics of its host. Such information is already potentially problematic, but in practice
the same information can more or less be obtained using the img
element, and so it
has been deemed acceptable.
However, significantly more sensitive information could be obtained if the user agent further
exposes metadata within the content such as subtitles or chapter titles. Such information is
therefore only exposed if the video resource passes a CORS resource sharing check.
The crossorigin
attribute allows authors to control
how this check is performed. [CORS]
Without this restriction, an attacker could trick a user running within a corporate network into visiting a site that attempts to load a video from a previously leaked location on the corporation's intranet. If such a video included confidential plans for a new product, then being able to read the subtitles would present a serious confidentiality breach.
This section is non-normative.
Playing audio and video resources on small devices such as set-top boxes or mobile phones is
often constrained by limited hardware resources in the device. For example, a device might only
support three simultaneous videos. For this reason, it is a good practice to release resources
held by media elements when they are done playing, either by
being very careful about removing all references to the element and allowing it to be garbage
collected, or, even better, by removing the element's src
attribute and any source
element descendants, and invoking the element's load()
method.
Similarly, when the playback rate is not exactly 1.0, hardware, software, or format limitations can cause video frames to be dropped and audio to be choppy or muted.
This section is non-normative.
How accurately various aspects of the media element API are implemented is considered a quality-of-implementation issue.
For example, when implementing the buffered
attribute,
how precise an implementation reports the ranges that have been buffered depends on how carefully
the user agent inspects the data. Since the API reports ranges as times, but the data is obtained
in byte streams, a user agent receiving a variable-bit-rate stream might only be able to determine
precise times by actually decoding all of the data. User agents aren't required to do this,
however; they can instead return estimates (e.g. based on the average bit rate seen so far) which
get revised as more information becomes available.
As a general rule, user agents are urged to be conservative rather than optimistic. For example, it would be bad to report that everything had been buffered when it had not.
Another quality-of-implementation issue would be playing a video backwards when the codec is designed only for forward playback (e.g. there aren't many key frames, and they are far apart, and the intervening frames only have deltas from the previous frame). User agents could do a poor job, e.g. only showing key frames; however, better implementations would do more work and thus do a better job, e.g. actually decoding parts of the video forwards, storing the complete frames, and then playing the frames backwards.
Similarly, while implementations are allowed to drop buffered data at any time (there is no requirement that a user agent keep all the media data obtained for the lifetime of the media element), it is again a quality of implementation issue: user agents with sufficient resources to keep all the data around are encouraged to do so, as this allows for a better user experience. For example, if the user is watching a live stream, a user agent could allow the user only to view the live video; however, a better user agent would buffer everything and allow the user to seek through the earlier material, pause it, play it forwards and backwards, etc.
When multiple tracks are synchronised with a MediaController
, it is possible for
scripts to add and remove media elements from the MediaController
's list of
slaved media elements, even while these tracks are playing. How smoothly the media
plays back in such situations is another quality-of-implementation issue.
When a media element that is paused is removed from a document and not reinserted before the next time the event loop spins, implementations that are resource constrained are encouraged to take that opportunity to release all hardware resources (like video planes, networking resources, and data buffers) used by the media element. (User agents still have to keep track of the playback position and so forth, though, in case playback is later restarted.)
map
elementname
interface HTMLMapElement : HTMLElement { attribute DOMString name; readonly attribute HTMLCollection areas; readonly attribute HTMLCollection images; };
The map
element, in conjunction with an img
element and any
area
element descendants, defines an image map. The element
represents its children.
The name
attribute gives the map a name so that
it can be referenced. The attribute must be present and must have a non-empty value with no space characters. The value of the name
attribute must not be a compatibility-caseless match for the value of the name
attribute of another map
element in the same
document. If the id
attribute is also specified, both attributes must
have the same value.
areas
Returns an HTMLCollection
of the area
elements in the
map
.
images
Returns an HTMLCollection
of the img
and object
elements that use the map
.
The areas
attribute must return an
HTMLCollection
rooted at the map
element, whose filter matches only
area
elements.
The images
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
img
and object
elements that are associated with this map
element according to the image map processing model.
The IDL attribute name
must reflect
the content attribute of the same name.
Image maps can be defined in conjunction with other content on the page, to ease maintenance. This example is of a page with an image map at the top of the page and a corresponding set of text links at the bottom.
<!DOCTYPE HTML> <TITLE>Babies™: Toys</TITLE> <HEADER> <H1>Toys</H1> <IMG SRC="/images/menu.gif" ALT="Babies™ navigation menu. Select a department to go to its page." USEMAP="#NAV"> </HEADER> ... <FOOTER> <MAP NAME="NAV"> <P> <A HREF="/clothes/">Clothes</A> <AREA ALT="Clothes" COORDS="0,0,100,50" HREF="/clothes/"> | <A HREF="/toys/">Toys</A> <AREA ALT="Toys" COORDS="0,0,100,50" HREF="/toys/"> | <A HREF="/food/">Food</A> <AREA ALT="Food" COORDS="0,0,100,50" HREF="/food/"> | <A HREF="/books/">Books</A> <AREA ALT="Books" COORDS="0,0,100,50" HREF="/books/"> </MAP> </FOOTER>
area
elementmap
element ancestor or a template
element ancestor.alt
coords
shape
href
target
download
rel
hreflang
type
interface HTMLAreaElement : HTMLElement { attribute DOMString alt; attribute DOMString coords; attribute DOMString shape; attribute DOMString target; attribute DOMString download; attribute DOMString rel; readonly attribute DOMTokenList relList; attribute DOMString hreflang; attribute DOMString type; }; HTMLAreaElement implements URLUtils;
The area
element represents either a hyperlink with some text and a
corresponding area on an image map, or a dead area on an image map.
An area
element with a parent node must have a map
element ancestor
or a template
element ancestor.
If the area
element has an href
attribute, then the area
element represents a hyperlink. In this case,
the alt
attribute must be present. It specifies the
text of the hyperlink. Its value must be text that, when presented with the texts specified for
the other hyperlinks of the image map, and with the alternative text of the image,
but without the image itself, provides the user with the same kind of choice as the hyperlink
would when used without its text but with its shape applied to the image. The alt
attribute may be left blank if there is another area
element in the same image map that points to the same resource and has a non-blank
alt
attribute.
If the area
element has no href
attribute, then the area represented by the element cannot be selected, and the alt
attribute must be omitted.
In both cases, the shape
and coords
attributes specify the area.
The shape
attribute is an enumerated
attribute. The following table lists the keywords defined for this attribute. The states
given in the first cell of the rows with keywords give the states to which those keywords map.
Some of the keywords are non-conforming, as noted in the last
column.
State | Keywords | Notes |
---|---|---|
Circle state | circle
| |
circ
| Non-conforming | |
Default state | default
| |
Polygon state | poly
| |
polygon
| Non-conforming | |
Rectangle state | rect
| |
rectangle
| Non-conforming |
The attribute may be omitted. The missing value default is the rectangle state.
The coords
attribute must, if specified,
contain a valid list of integers. This attribute gives the coordinates for the shape
described by the shape
attribute. The
processing for this attribute is described as part of the image map processing
model.
In the circle state, area
elements must
have a coords
attribute present, with three integers, the
last of which must be non-negative. The first integer must be the distance in CSS pixels from the
left edge of the image to the center of the circle, the second integer must be the distance in CSS
pixels from the top edge of the image to the center of the circle, and the third integer must be
the radius of the circle, again in CSS pixels.
In the default state state, area
elements must not have a coords
attribute. (The area is the
whole image.)
In the polygon state, area
elements must
have a coords
attribute with at least six integers, and the
number of integers must be even. Each pair of integers must represent a coordinate given as the
distances from the left and the top of the image in CSS pixels respectively, and all the
coordinates together must represent the points of the polygon, in order.
In the rectangle state, area
elements must
have a coords
attribute with exactly four integers, the
first of which must be less than the third, and the second of which must be less than the fourth.
The four points must represent, respectively, the distance from the left edge of the image to the
left side of the rectangle, the distance from the top edge to the top side, the distance from the
left edge to the right side, and the distance from the top edge to the bottom side, all in CSS
pixels.
When user agents allow users to follow hyperlinks or
download hyperlinks created using the
area
element, as described in the next section, the href
, target
,
download
, and
attributes decide how the link is followed. The rel
, hreflang
, and type
attributes may be used to indicate to the user the likely nature of the target resource before the
user follows the link.
The target
,
download
,
rel
, hreflang
, and type
attributes must be omitted if the href
attribute is not
present.
The activation behavior of area
elements is to run the following
steps:
If the area
element's Document
is not fully active,
then abort these steps.
If the area
element has a download
attribute and the algorithm is not allowed to show a popup, or the element's target
attribute is present and applying the rules
for choosing a browsing context given a browsing context name, using the value of the
target
attribute as the browsing context name, would
result in there not being a chosen browsing context, then run these substeps:
If there is an entry settings object, throw an InvalidAccessError
exception.
Abort these steps without following the hyperlink.
Otherwise, the user agent must follow the
hyperlink or download the hyperlink created by
the area
element, if any, and as determined by the download
attribute and any expressed user
preference.
The IDL attributes alt
, coords
, target
, download
,
rel
,
hreflang
, and type
, each must reflect the respective
content attributes of the same name.
The IDL attribute shape
must
reflect the shape
content attribute.
The IDL attribute relList
must
reflect the rel
content attribute.
The area
element also supports the URLUtils
interface. [URL]
When the element is created, and whenever the element's href
content attribute is set, changed, or removed, the user
agent must invoke the element's URLUtils
interface's set the input algorithm with the value of the href
content attribute, if any, or the empty string otherwise,
as the given value.
The element's URLUtils
interface's get the
base algorithm must simply return the element's base URL.
The element's URLUtils
interface's query
encoding is the document's character encoding.
When the element's URLUtils
interface invokes its update steps with a string value, the user
agent must set the element's href
content attribute to
the string value.
An image map allows geometric areas on an image to be associated with hyperlinks.
An image, in the form of an img
element or an object
element
representing an image, may be associated with an image map (in the form of a map
element) by specifying a usemap
attribute on
the img
or object
element. The usemap
attribute, if specified, must be a valid
hash-name reference to a map
element.
Consider an image that looks as follows:
If we wanted just the colored areas to be clickable, we could do it as follows:
<p> Please select a shape: <img src="shapes.png" usemap="#shapes" alt="Four shapes are available: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star."> <map name="shapes"> <area shape=rect coords="50,50,100,100"> <!-- the hole in the red box --> <area shape=rect coords="25,25,125,125" href="red.html" alt="Red box."> <area shape=circle coords="200,75,50" href="green.html" alt="Green circle."> <area shape=poly coords="325,25,262,125,388,125" href="blue.html" alt="Blue triangle."> <area shape=poly coords="450,25,435,60,400,75,435,90,450,125,465,90,500,75,465,60" href="yellow.html" alt="Yellow star."> </map> </p>
If an img
element or an object
element representing an image has a
usemap
attribute specified, user agents must process it
as follows:
First, rules for parsing a hash-name reference to a map
element
must be followed. This will return either an element (the map) or
null.
If that returned null, then abort these steps. The image is not associated with an image map after all.
Otherwise, the user agent must collect all the area
elements that are
descendants of the map. Let those be the areas.
Having obtained the list of area
elements that form the image map (the areas), interactive user agents must process the list in one of two ways.
If the user agent intends to show the text that the img
element represents, then
it must use the following steps.
In user agents that do not support images, or that have images disabled,
object
elements cannot represent images, and thus this section never applies (the
fallback content is shown instead). The following steps therefore only apply to
img
elements.
Remove all the area
elements in areas that have no href
attribute.
Remove all the area
elements in areas that have no alt
attribute, or whose alt
attribute's value is the empty string, if there is another area
element in
areas with the same value in the href
attribute and with a non-empty alt
attribute.
Each remaining area
element in areas represents a
hyperlink. Those hyperlinks should all be made available to the user in a manner
associated with the text of the img
.
In this context, user agents may represent area
and img
elements
with no specified alt
attributes, or whose alt
attributes are the empty string or some other non-visible text, in a user-agent-defined fashion
intended to indicate the lack of suitable author-provided text.
If the user agent intends to show the image and allow interaction with the image to select
hyperlinks, then the image must be associated with a set of layered shapes, taken from the
area
elements in areas, in reverse tree order (so the last
specified area
element in the map is the bottom-most shape, and
the first element in the map, in tree order, is the top-most shape).
Each area
element in areas must be processed as follows to
obtain a shape to layer onto the image:
Find the state that the element's shape
attribute
represents.
Use the rules for parsing a list of integers to parse the element's coords
attribute, if it is present, and let the result be the
coords list. If the attribute is absent, let the coords
list be the empty list.
If the number of items in the coords list is less than the minimum number
given for the area
element's current state, as per the following table, then the
shape is empty; abort these steps.
State | Minimum number of items |
---|---|
Circle state | 3 |
Default state | 0 |
Polygon state | 6 |
Rectangle state | 4 |
Check for excess items in the coords list as per the entry in the
following list corresponding to the shape
attribute's
state:
If the shape
attribute represents the rectangle state, and the first number in the list is
numerically less than the third number in the list, then swap those two numbers around.
If the shape
attribute represents the rectangle state, and the second number in the list is
numerically less than the fourth number in the list, then swap those two numbers around.
If the shape
attribute represents the circle state, and the third number in the list is less than
or equal to zero, then the shape is empty; abort these steps.
Now, the shape represented by the element is the one described for the entry in the list
below corresponding to the state of the shape
attribute:
Let x be the first number in coords, y be the second number, and r be the third number.
The shape is a circle whose center is x CSS pixels from the left edge of the image and y CSS pixels from the top edge of the image, and whose radius is r pixels.
The shape is a rectangle that exactly covers the entire image.
Let xi be the (2i)th entry in coords, and yi be the (2i+1)th entry in coords (the first entry in coords being the one with index 0).
Let the coordinates be (xi, yi), interpreted in CSS pixels measured from the top left of the image, for all integer values of i from 0 to (N/2)-1, where N is the number of items in coords.
The shape is a polygon whose vertices are given by the coordinates, and whose interior is established using the even-odd rule. [GRAPHICS]
Let x1 be the first number in coords, y1 be the second number, x2 be the third number, and y2 be the fourth number.
The shape is a rectangle whose top-left corner is given by the coordinate (x1, y1) and whose bottom right corner is given by the coordinate (x2, y2), those coordinates being interpreted as CSS pixels from the top left corner of the image.
For historical reasons, the coordinates must be interpreted relative to the
displayed image after any stretching caused by the CSS 'width' and 'height' properties
(or, for non-CSS browsers, the image element's width
and height
attributes — CSS browsers map those attributes to the
aforementioned CSS properties).
Browser zoom features and transforms applied using CSS or SVG do not affect the coordinates.
Pointing device interaction with an image associated with a set of layered shapes per the above
algorithm must result in the relevant user interaction events being first fired to the top-most
shape covering the point that the pointing device indicated, if any, or to the image element
itself, if there is no shape covering that point. User agents may also allow individual
area
elements representing hyperlinks to be selected
and activated (e.g. using a keyboard).
Because a map
element (and its area
elements) can be
associated with multiple img
and object
elements, it is possible for an
area
element to correspond to multiple focusable areas of the document.
Image maps are live; if the DOM is mutated, then the user agent must act as if it had rerun the algorithms for image maps.
The math
element from the MathML namespace falls into the
embedded content, phrasing content, and flow content
categories for the purposes of the content models in this specification.
User agents must handle text other than inter-element whitespace found in MathML
elements whose content models do not allow straight text by pretending for the purposes of MathML
content models, layout, and rendering that that text is actually wrapped in an mtext
element in the MathML namespace. (Such text is not, however,
conforming.)
User agents must act as if any MathML element whose contents does not match the element's
content model was replaced, for the purposes of MathML layout and rendering, by an merror
element in the MathML namespace containing some appropriate
error message.
To enable authors to use MathML tools that only accept MathML in its XML form, interactive HTML user agents are encouraged to provide a way to export any MathML fragment as an XML namespace-well-formed XML fragment.
The semantics of MathML elements are defined by the MathML specification and other applicable specifications. [MATHML]
Here is an example of the use of MathML in an HTML document:
<!DOCTYPE html> <html> <head> <title>The quadratic formula</title> </head> <body> <h1>The quadratic formula</h1> <p> <math> <mi>x</mi> <mo>=</mo> <mfrac> <mrow> <mo form="prefix">−</mo> <mi>b</mi> <mo>±</mo> <msqrt> <msup> <mi>b</mi> <mn>2</mn> </msup> <mo>−</mo> <mn>4</mn> <mo></mo> <mi>a</mi> <mo></mo> <mi>c</mi> </msqrt> </mrow> <mrow> <mn>2</mn> <mo></mo> <mi>a</mi> </mrow> </mfrac> </math> </p> </body> </html>
The svg
element from the SVG namespace falls into the
embedded content, phrasing content, and flow content
categories for the purposes of the content models in this specification.
To enable authors to use SVG tools that only accept SVG in its XML form, interactive HTML user agents are encouraged to provide a way to export any SVG fragment as an XML namespace-well-formed XML fragment.
When the SVG foreignObject
element contains elements from the HTML
namespace, such elements must all be flow content. [SVG]
The content model for title
elements in the SVG namespace
inside HTML documents is phrasing content. (This further constrains the
requirements given in the SVG specification.)
The semantics of SVG elements are defined by the SVG specification and other applicable specifications. [SVG]
The SVG specification includes requirements regarding the handling of elements in the DOM that
are not in the SVG namespace, that are in SVG fragments, and that are not included in a foreignObject
element. This specification does not define any processing
for elements in SVG fragments that are not in the HTML namespace; they are considered neither
conforming nor non-conforming from the perspective of this specification.
Author requirements: The width
and height
attributes on img
,
iframe
, embed
, object
, video
, and, when their
type
attribute is in the Image Button state, input
elements may be
specified to give the dimensions of the visual content of the element (the width and height
respectively, relative to the nominal direction of the output medium), in CSS pixels. The
attributes, if specified, must have values that are valid
non-negative integers.
The specified dimensions given may differ from the dimensions specified in the resource itself, since the resource may have a resolution that differs from the CSS pixel resolution. (On screens, CSS pixels have a resolution of 96ppi, but in general the CSS pixel resolution depends on the reading distance.) If both attributes are specified, then one of the following statements must be true:
The target ratio is the ratio of the intrinsic width to the intrinsic
height in the resource. The specified width and specified
height are the values of the width
and height
attributes respectively.
The two attributes must be omitted if the resource in question does not have both an intrinsic width and an intrinsic height.
If the two attributes are both zero, it indicates that the element is not intended for the user (e.g. it might be a part of a service to count page views).
The dimension attributes are not intended to be used to stretch the image.
User agent requirements: User agents are expected to use these attributes as hints for the rendering.
The width
and height
IDL attributes on the iframe
,
embed
, object
, and video
elements must reflect
the respective content attributes of the same name.
For iframe
, embed
, and object
the IDL
attributes are DOMString
; for video
the IDL attributes are
unsigned long
.
The corresponding IDL attributes for img
and
input
elements are defined in those respective elements'
sections, as they are slightly more specific to those elements' other behaviors.
Links are a conceptual construct, created by a
, area
, and
link
elements, that represent a connection between
two resources, one of which is the current Document
. There are two kinds of links in
HTML:
These are links to resources that are to be used to augment the current document, generally automatically processed by the user agent.
These are links to other resources that are generally exposed to the user by the user agent so that the user can cause the user agent to navigate to those resources, e.g. to visit them in a browser or download them.
For link
elements with an href
attribute and a
rel
attribute, links must be created for the keywords of the
rel
attribute, as defined for those keywords in the link types section.
Similarly, for a
and area
elements with an href
attribute and a rel
attribute, links must be created for the keywords of the
rel
attribute as defined for those keywords in the link types section. Unlike link
elements, however,
a
and area
element with an href
attribute that either do not have a rel
attribute, or
whose rel
attribute has no keywords that are defined as
specifying hyperlinks, must also create a hyperlink.
This implied hyperlink has no special meaning (it has no link type)
beyond linking the element's document to the resource given by the element's href
attribute.
A hyperlink can have one or more hyperlink annotations that modify the processing semantics of that hyperlink.
a
and area
elementsThe href
attribute on a
and
area
elements must have a value that is a valid URL potentially surrounded by
spaces.
The href
attribute on a
and
area
elements is not required; when those elements do not have href
attributes they do not create hyperlinks.
The target
attribute, if present, must be
a valid browsing context name or keyword. It gives the name of the browsing
context that will be used. User agents use this name when
following hyperlinks.
When an a
or area
element's activation behavior is
invoked, the user agent may allow the user to indicate a preference regarding whether the
hyperlink is to be used for navigation or whether the resource it
specifies is to be downloaded.
In the absence of a user preference, the default should be navigation if the element has no
download
attribute, and should be to download the
specified resource if it does.
Whether determined by the user's preferences or via the presence or absence of the attribute, if the decision is to use the hyperlink for navigation then the user agent must follow the hyperlink, and if the decision is to use the hyperlink to download a resource, the user agent must download the hyperlink. These terms are defined in subsequent sections below.
The download
attribute, if present,
indicates that the author intends the hyperlink to be used for downloading a resource. The
attribute may have a value; the value, if any, specifies the default file name that the author
recommends for use in labeling the resource in a local file system. There are no restrictions on
allowed values, but authors are cautioned that most file systems have limitations with regard to
what punctuation is supported in file names, and user agents are likely to adjust file names
accordingly.
The rel
attribute on a
and
area
elements controls what kinds of links the elements create. The attribute's value
must be a set of space-separated tokens. The allowed keywords
and their meanings are defined below.
The rel
attribute has no default value. If the
attribute is omitted or if none of the values in the attribute are recognized by the user agent,
then the document has no particular relationship with the destination resource other than there
being a hyperlink between the two.
The hreflang
attribute on
a
and area
elements that create hyperlinks, if present, gives the language of the linked resource. It is
purely advisory. The value must be a valid BCP 47 language tag. [BCP47]
User agents must not consider this attribute authoritative — upon
fetching the resource, user agents must use only language information associated with the resource
to determine its language, not metadata included in the link to the resource.
The type
attribute, if present, gives the
MIME type of the linked resource. It is purely advisory. The value must be a
valid MIME type. User agents must not consider the type
attribute authoritative — upon fetching the
resource, user agents must not use metadata included in the link to the resource to determine its
type.
When a user follows a hyperlink created by an element subject, the user agent must run the following steps:
Let replace be false.
Let source be the browsing context that contains the
Document
object with which subject in question is
associated.
If the user indicated a specific browsing context when following the hyperlink, or if the user agent is configured to follow hyperlinks by navigating a particular browsing context, then let target be that browsing context.
Otherwise, if subject is an a
or area
element
that has a target
attribute, then let target be the browsing context that is chosen by applying the
rules for choosing a browsing context given a browsing context name, using the value of
the target
attribute as the browsing context name. If
these rules result in the creation of a new browsing context, set replace to true.
Otherwise, if target is an a
or area
element
with no target
attribute, but the
Document
contains a base
element with a target
attribute, then let target be the
browsing context that is chosen by applying the rules for choosing a browsing
context given a browsing context name, using the value of the target
attribute of the first such base
element as
the browsing context name. If these rules result in the creation of a new browsing
context, set replace to true.
Otherwise, let target be the browsing context that subject itself is in.
Resolve the URL given by the href
attribute of that element, relative to that
element.
If that is successful, let URL be the resulting absolute URL.
Otherwise, if resolving the URL failed, the user agent may report the error to the user in a user-agent-specific manner, may queue a task to navigate the target browsing context to an error page to report the error, or may ignore the error and do nothing. In any case, the user agent must then abort these steps.
In the case of server-side image maps, append the hyperlink suffix to URL.
Queue a task to navigate the target browsing context to URL. If replace is true, the navigation must be performed with replacement enabled. The source browsing context must be source.
The task source for the tasks mentioned above is the DOM manipulation task source.
In some cases, resources are intended for later use rather than immediate viewing. To indicate
that a resource is intended to be downloaded for use later, rather than immediately used, the
download
attribute can be specified on the
a
or area
element that creates the hyperlink to that
resource.
The attribute can furthermore be given a value, to specify the file name that user agents are
to use when storing the resource in a file system. This value can be overridden by the Content-Disposition
HTTP header's filename parameters. [RFC6266]
In cross-origin situations, the download
attribute
has to be combined with the Content-Disposition
HTTP
header, specifically with the attachment
disposition type, to avoid the user
being warned of possibly nefarious activity. (This is to protect users from being made to download
sensitive personal or confidential information without their full understanding.)
When a user downloads a hyperlink created by an element, the user agent must run the following steps:
Resolve the URL given by the href
attribute of that element, relative to that
element.
If resolving the URL fails, the user agent may report the error to the user in a user-agent-specific manner, may navigate to an error page to report the error, or may ignore the error and do nothing. In either case, the user agent must abort these steps.
Otherwise, let URL be the resulting absolute URL.
In the case of server-side image maps, append the hyperlink suffix to URL.
Return to whatever algorithm invoked these steps and continue these steps asynchronously.
Fetch URL and handle the resulting resource as a download.
When a user agent is to handle a resource obtained from a fetch algorithm as a download, it should provide the user with a way to save the resource for later use, if a resource is successfully obtained; or otherwise should report any problems downloading the file to the user.
If the user agent needs a file name for a resource being handled as a download, it should select one using the following algorithm.
This algorithm is intended to mitigate security dangers involved in downloading files from untrusted sites, and user agents are strongly urged to follow it.
Let filename be the void value.
If the resource has a Content-Disposition
header, that header specifies the attachment
disposition type, and the
header includes file name information, then let filename have the value
specified by the header, and jump to the step labeled sanitize below. [RFC6266]
Let interface origin be the origin of the
Document
in which the download or
navigate action resulting in the download was initiated, if any.
Let resource origin be the origin of the URL of the
resource being downloaded, unless that URL's scheme
component is data
, in which case let resource origin be
the same as the interface origin, if any.
If there is no interface origin, then let trusted operation be true. Otherwise, let trusted operation be true if resource origin is the same origin as interface origin, and false otherwise.
If trusted operation is true and the resource has a Content-Disposition
header and that header includes file
name information, then let filename have the value specified by the header,
and jump to the step labeled sanitize below. [RFC6266]
If the download was not initiated from a hyperlink created by an
a
or area
element, or if the element of the hyperlink from
which it was initiated did not have a download
attribute when the download was initiated, or if there was such an attribute but its value when
the download was initiated was the empty string, then jump to the step labeled no proposed
file name.
Let proposed filename have the value of the download
attribute of the element of the
hyperlink that initiated the download at the time the download was
initiated.
If trusted operation is true, let filename have the value of proposed filename, and jump to the step labeled sanitize below.
If the resource has a Content-Disposition
header and that header specifies the attachment
disposition type, let filename have the value of proposed filename, and jump to the
step labeled sanitize below. [RFC6266]
No proposed file name: If trusted operation is true, or if the user indicated a preference for having the resource in question downloaded, let filename have a value derived from the URL of the resource in a user-agent-defined manner, and jump to the step labeled sanitize below.
Act in a user-agent-defined manner to safeguard the user from a potentially hostile cross-origin download. If the download is not to be aborted, then let filename be set to the user's preferred file name or to a file name selected by the user agent, and jump to the step labeled sanitize below.
If the algorithm reaches this step, then a download was begun from a different origin than
the resource being downloaded, and the origin did not mark the file as suitable for
downloading, and the download was not initiated by the user. This could be because a download
attribute was used to trigger the download, or
because the resource in question is not of a type that the user agent supports.
This could be dangerous, because, for instance, a hostile server could be trying to get a user to unknowingly download private information and then re-upload it to the hostile server, by tricking the user into thinking the data is from the hostile server.
Thus, it is in the user's interests that the user be somehow notified that the resource in question comes from quite a different source, and to prevent confusion, any suggested file name from the potentially hostile interface origin should be ignored.
Sanitize: Optionally, allow the user to influence filename. For example, a user agent could prompt the user for a file name, potentially providing the value of filename as determined above as a default value.
Adjust filename to be suitable for the local file system.
For example, this could involve removing characters that are not legal in file names, or trimming leading and trailing whitespace.
If the platform conventions do not in any way use extensions to determine the types of file on the file system, then return filename as the file name and abort these steps.
Let claimed type be the type given by the resource's Content-Type metadata, if any is known. Let named type be the type given by filename's extension, if any is known. For the purposes of this step, a type is a mapping of a MIME type to an extension.
If named type is consistent with the user's preferences (e.g. because the value of filename was determined by prompting the user), then return filename as the file name and abort these steps.
If claimed type and named type are the same type (i.e. the type given by the resource's Content-Type metadata is consistent with the type given by filename's extension), then return filename as the file name and abort these steps.
If the claimed type is known, then alter filename to add an extension corresponding to claimed type.
Otherwise, if named type is known to be potentially dangerous (e.g. it
will be treated by the platform conventions as a native executable, shell script, HTML
application, or executable-macro-capable document) then optionally alter filename to add a known-safe extension
(e.g. ".txt
").
This last step would make it impossible to download executables, which might not be desirable. As always, implementors are forced to balance security and usability in this matter.
Return filename as the file name.
For the purposes of this algorithm, a file extension
consists of any part of the file name that platform conventions dictate will be used for
identifying the type of the file. For example, many operating systems use the part of the file
name following the last dot (".
") in the file name to determine the type of
the file, and from that the manner in which the file is to be opened or executed.
User agents should ignore any directory or path information provided by the resource itself,
its URL, and any download
attribute, in
deciding where to store the resulting file in the user's file system.
The following table summarizes the link types that are defined by this specification. This table is non-normative; the actual definitions for the link types are given in the next few sections.
In this section, the term referenced document refers to the resource identified by the element representing the link, and the term current document refers to the resource within which the element representing the link finds itself.
To determine which link types apply to a link
, a
, or
area
element, the element's rel
attribute must be split on spaces. The resulting tokens are the link types
that apply to that element.
Except where otherwise specified, a keyword must not be specified more than once per rel
attribute.
Link types are always ASCII case-insensitive, and must be compared as such.
Thus, rel="next"
is the same as rel="NEXT"
.
Link type | Effect on... | Brief description | |
---|---|---|---|
link |
a and area |
||
alternate |
Hyperlink | Hyperlink | Gives alternate representations of the current document. |
author |
Hyperlink | Hyperlink | Gives a link to the author of the current document or article. |
bookmark |
not allowed | Hyperlink | Gives the permalink for the nearest ancestor section. |
help |
Hyperlink | Hyperlink | Provides a link to context-sensitive help. |
icon |
External Resource | not allowed | Imports an icon to represent the current document. |
license |
Hyperlink | Hyperlink | Indicates that the main content of the current document is covered by the copyright license described by the referenced document. |
next |
Hyperlink | Hyperlink | Indicates that the current document is a part of a series, and that the next document in the series is the referenced document. |
nofollow |
not allowed | Annotation | Indicates that the current document's original author or publisher does not endorse the referenced document. |
noreferrer |
not allowed | Annotation | Requires that the user agent not send an HTTP Referer (sic) header if the user follows the hyperlink. |
prefetch |
External Resource | External Resource | Specifies that the target resource should be preemptively cached. |
prev |
Hyperlink | Hyperlink | Indicates that the current document is a part of a series, and that the previous document in the series is the referenced document. |
search |
Hyperlink | Hyperlink | Gives a link to a resource that can be used to search through the current document and its related pages. |
stylesheet |
External Resource | not allowed | Imports a stylesheet. |
tag |
not allowed | Hyperlink | Gives a tag (identified by the given address) that applies to the current document. |
Some of the types described below list synonyms for these values. These are to be handled as specified by user agents, but must not be used in documents.
alternate
"The alternate
keyword may be used with link
,
a
, and area
elements.
The meaning of this keyword depends on the values of the other attributes.
link
element and the rel
attribute also contains the keyword stylesheet
The alternate
keyword modifies the meaning of the stylesheet
keyword in the way described for that keyword. The
alternate
keyword does not create a link of its own.
alternate
keyword is used with the type
attribute set to the value application/rss+xml
or the value application/atom+xml
The keyword creates a hyperlink referencing a syndication feed (though not necessarily syndicating exactly the same content as the current page).
The first link
, a
, or area
element in the document (in
tree order) with the alternate
keyword used with the type
attribute set to the value application/rss+xml
or the value application/atom+xml
must
be treated as the default syndication feed for the purposes of feed autodiscovery.
The following link
element gives the syndication
feed for the current page:
<link rel="alternate" type="application/atom+xml" href="data.xml">
The following extract offers various different syndication feeds:
<p>You can access the planets database using Atom feeds:</p> <ul> <li><a href="recently-visited-planets.xml" rel="alternate" type="application/atom+xml">Recently Visited Planets</a></li> <li><a href="known-bad-planets.xml" rel="alternate" type="application/atom+xml">Known Bad Planets</a></li> <li><a href="unexplored-planets.xml" rel="alternate" type="application/atom+xml">Unexplored Planets</a></li> </ul>
The keyword creates a hyperlink referencing an alternate representation of the current document.
The nature of the referenced document is given by the hreflang
, and type
attributes.
If the alternate
keyword is used with the hreflang
attribute, and that attribute's value differs
from the root element's language, it indicates that the referenced
document is a translation.
If the alternate
keyword is used with the type
attribute, it indicates that the referenced document is
a reformulation of the current document in the specified format.
The hreflang
and type
attributes can be combined when specified with the alternate
keyword.
For example, the following link is a French translation that uses the PDF format:
<link rel=alternate type=application/pdf hreflang=fr href=manual-fr>
This relationship is transitive — that is, if a document links to two other documents
with the link type "alternate
", then, in addition to implying
that those documents are alternative representations of the first document, it is also implying
that those two documents are alternative representations of each other.
author
"The author
keyword may be used with link
,
a
, and area
elements. This keyword creates a hyperlink.
For a
and area
elements, the author
keyword indicates that the referenced document provides further information about the author of
the nearest article
element ancestor of the element defining the hyperlink, if there
is one, or of the page as a whole, otherwise.
For link
elements, the author
keyword indicates
that the referenced document provides further information about the author for the page as a
whole.
The "referenced document" can be, and often is, a mailto:
URL giving the e-mail address of the author. [MAILTO]
Synonyms: For historical reasons, user agents must also treat
link
, a
, and area
elements that have a rev
attribute with the value "made
" as having the author
keyword specified as a link relationship.
bookmark
"The bookmark
keyword may be used with a
and
area
elements. This keyword creates a hyperlink.
The bookmark
keyword gives a permalink for the nearest
ancestor article
element of the linking element in question, or of the section the linking element is most closely associated with, if
there are no ancestor article
elements.
The following snippet has three permalinks. A user agent could determine which permalink applies to which part of the spec by looking at where the permalinks are given.
... <body> <h1>Example of permalinks</h1> <div id="a"> <h2>First example</h2> <p><a href="a.html" rel="bookmark">This permalink applies to only the content from the first H2 to the second H2</a>. The DIV isn't exactly that section, but it roughly corresponds to it.</p> </div> <h2>Second example</h2> <article id="b"> <p><a href="b.html" rel="bookmark">This permalink applies to the outer ARTICLE element</a> (which could be, e.g., a blog post).</p> <article id="c"> <p><a href="c.html" rel="bookmark">This permalink applies to the inner ARTICLE element</a> (which could be, e.g., a blog comment).</p> </article> </article> </body> ...
help
"The help
keyword may be used with link
,
a
, and area
elements. This keyword creates a hyperlink.
For a
and area
elements, the help
keyword indicates that the referenced document provides further help information for the parent of
the element defining the hyperlink, and its children.
In the following example, the form control has associated context-sensitive help. The user agent could use this information, for example, displaying the referenced document if the user presses the "Help" or "F1" key.
<p><label> Topic: <input name=topic> <a href="help/topic.html" rel="help">(Help)</a></label></p>
For link
elements, the help
keyword indicates that
the referenced document provides help for the page as a whole.
For a
and area
elements, on some browsers, the help
keyword causes the link to use a different cursor.
icon
"The icon
keyword may be used with link
elements.
This keyword creates an external resource link.
The specified resource is an icon representing the page or site, and should be used by the user agent when representing the page in the user interface.
Icons could be auditory icons, visual icons, or other kinds of icons. If
multiple icons are provided, the user agent must select the most appropriate icon according to the
type
, media
, and sizes
attributes. If there are multiple equally appropriate icons,
user agents must use the last one declared in tree order at the time that the user
agent collected the list of icons. If the user agent tries to use an icon but that icon is
determined, upon closer examination, to in fact be inappropriate (e.g. because it uses an
unsupported format), then the user agent must try the next-most-appropriate icon as determined by
the attributes.
User agents are not required to update icons when the list of icons changes, but are encouraged to do so.
There is no default type for resources given by the icon
keyword.
However, for the purposes of determining the type of the
resource, user agents must expect the resource to be an image.
The sizes
attribute gives the sizes of icons
for visual media. Its value, if present, is merely advisory. User agents may use the value to
decide which icon(s) to use if multiple icons are available.
If specified, the attribute must have a value that is an unordered set of unique
space-separated tokens which are ASCII case-insensitive. Each value must be
either an ASCII case-insensitive match for the string "any
", or a value that consists of two valid non-negative integers that do not have a leading "0" (U+0030) character and that are separated by a single U+0078 LATIN SMALL LETTER X or U+0058 LATIN
CAPITAL LETTER X character.
The keywords represent icon sizes in raw pixels (as opposed to CSS pixels).
An icon that is 50 CSS pixels wide intended for displays with a device pixel density of two device pixels per CSS pixel (2x, 192dpi) would have a width of 100 raw pixels. This feature does not support indicating that a different resource is to be used for small high-resolution icons vs large low-resolution icons (e.g. 50×50 2x vs 100×100 1x).
To parse and process the attribute's value, the user agent must first split the attribute's value on spaces, and must then parse each resulting keyword to determine what it represents.
The any
keyword represents that the
resource contains a scalable icon, e.g. as provided by an SVG image.
Other keywords must be further parsed as follows to determine what they represent:
If the keyword doesn't contain exactly one U+0078 LATIN SMALL LETTER X or U+0058 LATIN CAPITAL LETTER X character, then this keyword doesn't represent anything. Abort these steps for that keyword.
Let width string be the string before the "x
" or
"X
".
Let height string be the string after the "x
" or
"X
".
If either width string or height string start with a "0" (U+0030) character or contain any characters other than ASCII digits, then this keyword doesn't represent anything. Abort these steps for that keyword.
Apply the rules for parsing non-negative integers to width string to obtain width.
Apply the rules for parsing non-negative integers to height string to obtain height.
The keyword represents that the resource contains a bitmap icon with a width of width device pixels and a height of height device pixels.
The keywords specified on the sizes
attribute must not
represent icon sizes that are not actually available in the linked resource.
In the absence of a link
with the icon
keyword, for
Document
s obtained over HTTP or HTTPS, user agents may instead attempt to
fetch and use an icon with the absolute URL obtained by
resolving the URL "/favicon.ico
" against the document's
address, as if the page had declared that icon using the icon
keyword.
The following snippet shows the top part of an application with several icons.
<!DOCTYPE HTML> <html> <head> <title>lsForums — Inbox</title> <link rel=icon href=favicon.png sizes="16x16" type="image/png"> <link rel=icon href=windows.ico sizes="32x32 48x48" type="image/vnd.microsoft.icon"> <link rel=icon href=mac.icns sizes="128x128 512x512 8192x8192 32768x32768"> <link rel=icon href=iphone.png sizes="57x57" type="image/png"> <link rel=icon href=gnome.svg sizes="any" type="image/svg+xml"> <link rel=stylesheet href=lsforums.css> <script src=lsforums.js></script> <meta name=application-name content="lsForums"> </head> <body> ...
For historical reasons, the icon
keyword may be preceded by the
keyword "shortcut
". If the "shortcut
" keyword is
present, it must be come immediately before the icon
keyword and the
two keywords must be separated by only a single U+0020 SPACE character.
license
"The license
keyword may be used with link
,
a
, and area
elements. This keyword creates a hyperlink.
The license
keyword indicates that the referenced document
provides the copyright license terms under which the main content of the current document is
provided.
This specification defines the main content of a document and content that
is not deemed to be part of that main content via the main
element.
The distinction should be made clear to the user.
Consider a photo sharing site. A page on that site might describe and show a photograph, and the page might be marked up as follows:
<!DOCTYPE HTML> <html> <head> <title>Exampl Pictures: Kissat</title> <link rel="stylesheet" href="/style/default"> </head> <body> <h1>Kissat</h1> <nav> <a href="../">Return to photo index</a> </nav> <main> <figure> <img src="/pix/39627052_fd8dcd98b5.jpg"> <figcaption>Kissat</figcaption> </figure> <p>One of them has six toes!</p> <p><small>This photograph is <a rel="license" href="http://www.opensource.org/licenses/mit-license.php">MIT Licensed</a></small></p> </main> <footer> <a href="/">Home</a> | <a href="../">Photo index</a> <p><small>© copyright 2009 Exampl Pictures. All Rights Reserved.</small></p> </footer> </body> </html>
In this case the license
applies to just the photo (the main content of the document), not
the whole document. In particular not the design of the page
itself, which is covered by the copyright given at the bottom of
the document. This should be made clear in the text referencing the licensing
link and could also be made clearer in the styling
(e.g. making the license link prominently positioned near the
photograph, while having the page copyright in small text at
the foot of the page, or adding a border to the main
element.)
Synonyms: For historical reasons, user agents
must also treat the keyword "copyright
" like
the license
keyword.
nofollow
"The nofollow
keyword may be used with a
and
area
elements. This keyword does not create a hyperlink, but annotates any other hyperlinks created by the element (the
implied hyperlink, if no other keywords create one).
The nofollow
keyword indicates that the link is not endorsed
by the original author or publisher of the page, or that the link to the referenced document was
included primarily because of a commercial relationship between people affiliated with the two
pages.
noreferrer
"The noreferrer
keyword may be used with a
and
area
elements. This keyword does not create a hyperlink, but annotates any other hyperlinks created by the element (the
implied hyperlink, if no other keywords create one).
It indicates that no referrer information is to be leaked when following the link.
If a user agent follows a link defined by an a
or area
element that
has the noreferrer
keyword, the user agent must not include a
Referer
(sic) HTTP header (or equivalent for other protocols) in the
request.
This keyword also causes the opener
attribute to remain null if the hyperlink creates a new browsing context.
prefetch
"The prefetch
keyword may be used with link
,
a
, and area
elements. This keyword creates an external resource link.
The prefetch
keyword indicates that preemptively fetching and
caching the specified resource is likely to be beneficial, as it is highly likely that the user
will require this resource.
There is no default type for resources given by the prefetch
keyword.
search
"The search
keyword may be used with link
,
a
, and area
elements. This keyword creates a hyperlink.
The search
keyword indicates that the referenced document
provides an interface specifically for searching the document and its related resources.
OpenSearch description documents can be used with link
elements and
the search
link type to enable user agents to autodiscover search
interfaces. [OPENSEARCH]
stylesheet
"The stylesheet
keyword may be used with link
elements. This keyword creates an external resource
link that contributes to the styling processing model.
The specified resource is a resource that describes how to present the document. Exactly how the resource is to be processed depends on the actual type of the resource.
If the alternate
keyword is also specified on the
link
element, then the link is an alternative stylesheet; in this case,
the title
attribute must be specified on the link
element, with a non-empty value.
The default type for resources given by the stylesheet
keyword is text/css
.
The appropriate times to obtain the resource are:
When the external resource link's
link
element is inserted into a
document.
When the external resource link is created on
a link
element that is already in a Document
.
When the href
attribute of the link
element of an external resource link that is already
in a Document
is changed.
Quirk: If the document has been set to quirks mode, has the
same origin as the URL of the external resource,
and the Content-Type metadata of the external resource is not a
supported style sheet type, the user agent must instead assume it to be text/css
.
tag
"The tag
keyword may be used with a
and
area
elements. This keyword creates a hyperlink.
The tag
keyword indicates that the tag that the
referenced document represents applies to the current document.
Since it indicates that the tag applies to the current document, it would be inappropriate to use this keyword in the markup of a tag cloud, which lists the popular tags across a set of pages.
This document is about some gems, and so it is tagged with "http://en.wikipedia.org/wiki/Gemstone
" to unambiguously categorise it as applying
to the "jewel" kind of gems, and not to, say, the towns in the US, the Ruby package format, or
the Swiss locomotive class:
<!DOCTYPE HTML> <html> <head> <title>My Precious</title> </head> <body> <header><h1>My precious</h1> <p>Summer 2012</p></header> <p>Recently I managed to dispose of a red gem that had been bothering me. I now have a much nicer blue sapphire.</p> <p>The red gem had been found in a bauxite stone while I was digging out the office level, but nobody was willing to haul it away. The same red gem stayed there for literally years.</p> <footer> Tags: <a rel=tag href="http://en.wikipedia.org/wiki/Gemstone">Gemstone</a> </footer> </body> </html>
In this document, there are two articles. The "tag
"
link, however, applies to the whole page (and would do so wherever it was placed, including if it
was within the article
elements).
<!DOCTYPE HTML> <html> <head> <title>Gem 4/4</title> </head> <body> <article> <h1>801: Steinbock</h1> <p>The number 801 Gem 4/4 electro-diesel has an ibex and was rebuilt in 2002.</p> </article> <article> <h1>802: Murmeltier</h1> <figure> <img src="http://upload.wikimedia.org/wikipedia/commons/b/b0/Trains_de_la_Bernina_en_hiver_2.jpg" alt="The 802 was red with pantographs and tall vents on the side."> <figcaption>The 802 in the 1980s, above Lago Bianco.</figcaption> </figure> <p>The number 802 Gem 4/4 electro-diesel has a marmot and was rebuilt in 2003.</p> </article> <p class="topic"><a rel=tag href="http://en.wikipedia.org/wiki/Rhaetian_Railway_Gem_4/4">Gem 4/4</a></p> </body> </html>
Some documents form part of a sequence of documents.
A sequence of documents is one where each document can have a previous sibling and a next sibling. A document with no previous sibling is the start of its sequence, a document with no next sibling is the end of its sequence.
A document may be part of multiple sequences.
next
"The next
keyword may be used with link
,
a
, and area
elements. This keyword creates a hyperlink.
The next
keyword indicates that the document is part of a
sequence, and that the link is leading to the document that is the next logical document in the
sequence.
prev
"The prev
keyword may be used with link
,
a
, and area
elements. This keyword creates a hyperlink.
The prev
keyword indicates that the document is part of a
sequence, and that the link is leading to the document that is the previous logical document in
the sequence.
Synonyms: For historical reasons, user agents must also treat the keyword
"previous
" like the prev
keyword.
Extensions to the predefined set of link types may be registered in the microformats wiki existing-rel-values page. [MFREL]
Anyone is free to edit the microformats wiki existing-rel-values page at any time to add a type. Extension types must be specified with the following information:
The actual value being defined. The value should not be confusingly similar to any other defined value (e.g. differing only in case).
If the value contains a ":" (U+003A) character, it must also be an absolute URL.
link
One of the following:
link
elements.link
element; it creates a
hyperlink.link
element; it creates an external
resource link.a
and area
One of the following:
a
and area
elements.a
and area
elements; it creates a
hyperlink.a
and area
elements; it creates
an external resource link.a
and area
elements; it annotates other hyperlinks
created by the element.A short non-normative description of what the keyword's meaning is.
A link to a more detailed description of the keyword's semantics and requirements. It could be another page on the Wiki, or a link to an external page.
A list of other keyword values that have exactly the same processing requirements. Authors should not use the values defined to be synonyms, they are only intended to allow user agents to support legacy content. Anyone may remove synonyms that are not used in practice; only names that need to be processed as synonyms for compatibility with legacy content are to be registered in this way.
One of the following:
If a keyword is found to be redundant with existing values, it should be removed and listed as a synonym for the existing value.
If a keyword is registered in the "proposed" state for a period of a month or more without being used or specified, then it may be removed from the registry.
If a keyword is added with the "proposed" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. If a keyword is added with the "proposed" status and found to be harmful, then it should be changed to "discontinued" status.
Anyone can change the status at any time, but should only do so in accordance with the definitions above.
Conformance checkers may use the information given on the microformats wiki existing-rel-values page to establish if a value is allowed or not: values defined in this specification or marked as "proposed" or "ratified" must be accepted when used on the elements for which they apply as described in the "Effect on..." field, whereas values marked as "discontinued" or values not containing a U+003A COLON character but not listed in either this specification or on the aforementioned page must be reported as invalid. The remaining values must be accepted as valid if they are absolute URLs containing US-ASCII characters only and rejected otherwise. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity).
Note: Even URL-valued link types are compared ASCII-case-insensitively. Validators might choose to warn about characters U+0041 (LATIN CAPITAL LETTER A) through U+005A (LATIN CAPITAL LETTER Z) (inclusive) in the pre-case-folded form of link types that contain a colon.
When an author uses a new type not defined by either this specification or the Wiki page, conformance checkers should offer to add the value to the Wiki, with the details described above, with the "proposed" status.
Types defined as extensions in the microformats
wiki existing-rel-values page with the status "proposed" or "ratified" may be used with the
rel
attribute on link
, a
, and area
elements in accordance to the "Effect on..." field. [MFREL]
table
elementcaption
element,
followed by zero or more colgroup
elements, followed
optionally by a thead
element, followed optionally by
a tfoot
element, followed by either zero or more
tbody
elements or one or more tr
elements, followed optionally by a tfoot
element (but
there can only be one tfoot
element child in
total), optionally intermixed with one or more script-supporting elements.interface HTMLTableElement : HTMLElement { attribute HTMLTableCaptionElement? caption; HTMLElement createCaption(); void deleteCaption(); attribute HTMLTableSectionElement? tHead; HTMLElement createTHead(); void deleteTHead(); attribute HTMLTableSectionElement? tFoot; HTMLElement createTFoot(); void deleteTFoot(); readonly attribute HTMLCollection tBodies; HTMLElement createTBody(); readonly attribute HTMLCollection rows; HTMLElement insertRow(optional long index = -1); void deleteRow(long index); };
The table
element represents data with more than one dimension, in
the form of a table.
The table
element takes part in the table
model. Tables have rows, columns, and cells given by their descendants. The rows and
columns form a grid; a table's cells must completely cover that grid without overlap.
Precise rules for determining whether this conformance requirement is met are described in the description of the table model.
Authors are encouraged to provide information describing how to interpret complex tables. Guidance on how to provide such information is given below.
Tables should not be used as layout aids. Historically, many Web authors have tables in HTML as a way to control their page layout making it difficult to extract tabular data from such documents. In particular, users of accessibility tools, like screen readers, are likely to find it very difficult to navigate pages with tables used for layout. If a table is to be used for layout it must be marked with the attribute role="presentation" for a user agent to properly represent the table to an assistive technology and to properly convey the intent of the author to tools that wish to extract tabular data from the document.
There are a variety of alternatives to using HTML tables for layout, primarily using CSS positioning and the CSS table model. [CSS]
The border
attribute may be specified on a table
element to
explicitly indicate that the table
element is not being
used for layout purposes. If specified, the attribute's value must
either be the empty string or the value "1
".
The attribute is used by certain user agents as an indication that
borders should be drawn around cells of the table.
Tables can be complicated to understand and navigate. To help users with this, user agents should clearly delineate cells in a table from each other, unless the user agent has classified the table as a layout table.
Authors and implementors are encouraged to consider using some of the table design techniques described below to make tables easier to navigate for users.
User agents, especially those that do table analysis on arbitrary content, are encouraged to find heuristics to determine which tables actually contain data and which are merely being used for layout. This specification does not define a precise heuristic, but the following are suggested as possible indicators:
Feature | Indication |
---|---|
The use of the role attribute with the value presentation
| Probably a layout table |
The use of the border attribute with the non-conforming value 0
| Probably a layout table |
The use of the non-conforming cellspacing and cellpadding attributes with the value 0
| Probably a layout table |
The use of caption , thead , or th elements
| Probably a non-layout table |
The use of the headers and scope attributes
| Probably a non-layout table |
The use of the border attribute with a value other than 0
| Probably a non-layout table |
Explicit visible borders set using CSS | Probably a non-layout table |
The use of the summary attribute
| Not a good indicator (both layout and non-layout tables have historically been given this attribute) |
It is quite possible that the above suggestions are wrong. Implementors are urged to provide feedback elaborating on their experiences with trying to create a layout table detection heuristic.
caption
[ = value ]Returns the table's caption
element.
Can be set, to replace the caption
element. If the new value is not a
caption
element, throws a HierarchyRequestError
exception.
createCaption
()Ensures the table has a caption
element, and returns it.
deleteCaption
()Ensures the table does not have a caption
element.
tHead
[ = value ]Returns the table's thead
element.
Can be set, to replace the thead
element. If the new value is not a
thead
element, throws a HierarchyRequestError
exception.
createTHead
()Ensures the table has a thead
element, and returns it.
deleteTHead
()Ensures the table does not have a thead
element.
tFoot
[ = value ]Returns the table's tfoot
element.
Can be set, to replace the tfoot
element. If the new value is not a
tfoot
element, throws a HierarchyRequestError
exception.
createTFoot
()Ensures the table has a tfoot
element, and returns it.
deleteTFoot
()Ensures the table does not have a tfoot
element.
tBodies
Returns an HTMLCollection
of the tbody
elements of the table.
createTBody
()Creates a tbody
element, inserts it into the table, and returns it.
rows
Returns an HTMLCollection
of the tr
elements of the table.
insertRow
( [ index ] )Creates a tr
element, along with a tbody
if required, inserts them
into the table at the position given by the argument, and returns the tr
.
The position is relative to the rows in the table. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the table.
If the given position is less than −1 or greater than the number of rows, throws an
IndexSizeError
exception.
deleteRow
(index)Removes the tr
element with the given position in the table.
The position is relative to the rows in the table. The index −1 is equivalent to deleting the last row of the table.
If the given position is less than −1 or greater than the index of the last row, or if
there are no rows, throws an IndexSizeError
exception.
The caption
IDL attribute must return, on
getting, the first caption
element child of the table
element, if any,
or null otherwise. On setting, if the new value is a caption
element, the first
caption
element child of the table
element, if any, must be removed, and
the new value must be inserted as the first node of the table
element. If the new
value is not a caption
element, then a HierarchyRequestError
DOM
exception must be thrown instead.
The createCaption()
method must return
the first caption
element child of the table
element, if any; otherwise
a new caption
element must be created, inserted as the first node of the
table
element, and then returned.
The deleteCaption()
method must remove
the first caption
element child of the table
element, if any.
The tHead
IDL attribute must return, on
getting, the first thead
element child of the table
element, if any, or
null otherwise. On setting, if the new value is a thead
element, the first
thead
element child of the table
element, if any, must be removed, and
the new value must be inserted immediately before the first element in the table
element that is neither a caption
element nor a colgroup
element, if
any, or at the end of the table if there are no such elements. If the new value is not a
thead
element, then a HierarchyRequestError
DOM exception must be thrown
instead.
The createTHead()
method must return the
first thead
element child of the table
element, if any; otherwise a new
thead
element must be created and inserted immediately before the first element in
the table
element that is neither a caption
element nor a
colgroup
element, if any, or at the end of the table if there are no such elements,
and then that new element must be returned.
The deleteTHead()
method must remove the
first thead
element child of the table
element, if any.
The tFoot
IDL attribute must return, on
getting, the first tfoot
element child of the table
element, if any, or
null otherwise. On setting, if the new value is a tfoot
element, the first
tfoot
element child of the table
element, if any, must be removed, and
the new value must be inserted immediately before the first element in the table
element that is neither a caption
element, a colgroup
element, nor a
thead
element, if any, or at the end of the table if there are no such elements. If
the new value is not a tfoot
element, then a HierarchyRequestError
DOM
exception must be thrown instead.
The createTFoot()
method must return the
first tfoot
element child of the table
element, if any; otherwise a new
tfoot
element must be created and inserted immediately before the first element in
the table
element that is neither a caption
element, a
colgroup
element, nor a thead
element, if any, or at the end of the
table if there are no such elements, and then that new element must be returned.
The deleteTFoot()
method must remove the
first tfoot
element child of the table
element, if any.
The tBodies
attribute must return an
HTMLCollection
rooted at the table
node, whose filter matches only
tbody
elements that are children of the table
element.
The createTBody()
method must create a
new tbody
element, insert it immediately after the last tbody
element
child in the table
element, if any, or at the end of the table
element
if the table
element has no tbody
element children, and then must return
the new tbody
element.
The rows
attribute must return an
HTMLCollection
rooted at the table
node, whose filter matches only
tr
elements that are either children of the table
element, or children
of thead
, tbody
, or tfoot
elements that are themselves
children of the table
element. The elements in the collection must be ordered such
that those elements whose parent is a thead
are included first, in tree order,
followed by those elements whose parent is either a table
or tbody
element, again in tree order, followed finally by those elements whose parent is a
tfoot
element, still in tree order.
The behavior of the insertRow(index)
method depends on the state of the table. When it is called,
the method must act as required by the first item in the following list of conditions that
describes the state of the table and the index argument:
rows
collection:IndexSizeError
exception.rows
collection has zero elements in it, and the
table
has no tbody
elements in it:tbody
element, then create a tr
element,
then append the tr
element to the tbody
element, then append the
tbody
element to the table
element, and finally return the
tr
element.rows
collection has zero elements in it:tr
element, append it to the last tbody
element in the table, and return the tr
element.rows
collection:tr
element, and append it to the parent of the last
tr
element in the rows
collection. Then, the
newly created tr
element must be returned.tr
element, insert it immediately before the indexth tr
element in the rows
collection, in the same parent, and finally must return the newly created tr
element.When the deleteRow(index)
method is called, the user agent must run the following
steps:
If index is equal to −1, then index must be
set to the number of items in the rows
collection, minus
one.
Now, if index is less than zero, or greater than or equal to the
number of elements in the rows
collection, the method must
instead throw an IndexSizeError
exception, and these steps must be aborted.
Otherwise, the method must remove the indexth element in the rows
collection from its parent.
The border
IDL
attribute must reflect the content attribute of the
same name.
Here is an example of a table being used to mark up a Sudoku puzzle. Observe the lack of headers, which are not necessary in such a table.
<section> <style scoped> table { border-collapse: collapse; border: solid thick; } colgroup, tbody { border: solid medium; } td { border: solid thin; height: 1.4em; width: 1.4em; text-align: center; padding: 0; } </style> <h1>Today's Sudoku</h1> <table> <colgroup><col><col><col> <colgroup><col><col><col> <colgroup><col><col><col> <tbody> <tr> <td> 1 <td> <td> 3 <td> 6 <td> <td> 4 <td> 7 <td> <td> 9 <tr> <td> <td> 2 <td> <td> <td> 9 <td> <td> <td> 1 <td> <tr> <td> 7 <td> <td> <td> <td> <td> <td> <td> <td> 6 <tbody> <tr> <td> 2 <td> <td> 4 <td> <td> 3 <td> <td> 9 <td> <td> 8 <tr> <td> <td> <td> <td> <td> <td> <td> <td> <td> <tr> <td> 5 <td> <td> <td> 9 <td> <td> 7 <td> <td> <td> 1 <tbody> <tr> <td> 6 <td> <td> <td> <td> 5 <td> <td> <td> <td> 2 <tr> <td> <td> <td> <td> <td> 7 <td> <td> <td> <td> <tr> <td> 9 <td> <td> <td> 8 <td> <td> 2 <td> <td> <td> 5 </table> </section>
For tables that consist of more than just a grid of cells with headers in the first row and headers in the first column, and for any table in general where the reader might have difficulty understanding the content, authors should include explanatory information introducing the table. This information is useful for all users, but is especially useful for users who cannot see the table, e.g. users of screen readers.
Such explanatory information should introduce the purpose of the table, outline its basic cell structure, highlight any trends or patterns, and generally teach the user how to use the table.
For instance, the following table:
Negative | Characteristic | Positive |
---|---|---|
Sad | Mood | Happy |
Failing | Grade | Passing |
...might benefit from a description explaining the way the table is laid out, something like "Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column".
There are a variety of ways to include this information, such as:
<p id="summary">In the following table, characteristics are given in the second column, with the negative side in the left column and the positive side in the right column.</p> <table aria-describedby="summary"> <caption>Characteristics with positive and negative sides</caption> <thead> <tr> <th id="n"> Negative <th> Characteristic <th> Positive <tbody> <tr> <td headers="n r1"> Sad <th id="r1"> Mood <td> Happy <tr> <td headers="n r2"> Failing <th id="r2"> Grade <td> Passing </table>
In the example above the
aria-describedby
attribute is used to explicitly associate the information
with the table for assistive technology users.
caption
<table> <caption> <strong>Characteristics with positive and negative sides.</strong> <p>Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column.</p> </caption> <thead> <tr> <th id="n"> Negative <th> Characteristic <th> Positive <tbody> <tr> <td headers="n r1"> Sad <th id="r1"> Mood <td> Happy <tr> <td headers="n r2"> Failing <th id="r2"> Grade <td> Passing </table>
caption
, in a details
element<table> <caption> <strong>Characteristics with positive and negative sides.</strong> <details> <summary>Help</summary> <p>Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column.</p> </details> </caption> <thead> <tr> <th id="n"> Negative <th> Characteristic <th> Positive <tbody> <tr> <td headers="n r1"> Sad <th id="r1"> Mood <td> Happy <tr> <td headers="n r2"> Failing <th id="r2"> Grade <td> Passing </table>
figure
<figure> <figcaption>Characteristics with positive and negative sides</figcaption> <p>Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column.</p> <table> <thead> <tr> <th id="n"> Negative <th> Characteristic <th> Positive <tbody> <tr> <td headers="n r1"> Sad <th id="r1"> Mood <td> Happy <tr> <td headers="n r2"> Failing <th id="r2"> Grade <td> Passing </table> </figure>
figure
's figcaption
<figure> <figcaption> <strong>Characteristics with positive and negative sides</strong> <p>Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column.</p> </figcaption> <table> <thead> <tr> <th id="n"> Negative <th> Characteristic <th> Positive <tbody> <tr> <td headers="n r1"> Sad <th id="r1"> Mood <td> Happy <tr> <td headers="n r2"> Failing <th id="r2"> Grade <td> Passing </table> </figure>
Authors may also use other techniques, or combinations of the above techniques, as appropriate.
The best option, of course, rather than writing a description explaining the way the table is laid out, is to adjust the table such that no explanation is needed.
In the case of the table used in the examples above, a simple
rearrangement of the table so that the headers are on the top and
left sides removes the need for an explanation as well as removing
the need for the use of headers
attributes:
<table> <caption>Characteristics with positive and negative sides</caption> <thead> <tr> <th> Characteristic <th> Negative <th> Positive <tbody> <tr> <th> Mood <td> Sad <td> Happy <tr> <th> Grade <td> Failing <td> Passing </table>
Good table design is key to making tables more readable and usable.
In visual media, providing column and row borders and alternating row backgrounds can be very effective to make complicated tables more readable.
For tables with large volumes of numeric content, using monospaced fonts can help users see patterns, especially in situations where a user agent does not render the borders. (Unfortunately, for historical reasons, not rendering borders on tables is a common default.)
In speech media, table cells can be distinguished by reporting the corresponding headers before reading the cell's contents, and by allowing users to navigate the table in a grid fashion, rather than serializing the entire contents of the table in source order.
Authors are encouraged to use CSS to achieve these effects.
User agents are encouraged to render tables using these techniques whenever the page does not use CSS and the table is not classified as a layout table.
caption
elementtable
element.table
elements.interface HTMLTableCaptionElement : HTMLElement {};
The caption
element represents the title of the table
that is its parent, if it has a parent and that is a table
element.
The caption
element takes part in the table model.
When a table
element is the only content in a figure
element other
than the figcaption
, the caption
element should be omitted in favor of
the figcaption
.
A caption can introduce context for a table, making it significantly easier to understand.
Consider, for instance, the following table:
1 | 2 | 3 | 4 | 5 | 6 | |
---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | 7 |
2 | 3 | 4 | 5 | 6 | 7 | 8 |
3 | 4 | 5 | 6 | 7 | 8 | 9 |
4 | 5 | 6 | 7 | 8 | 9 | 10 |
5 | 6 | 7 | 8 | 9 | 10 | 11 |
6 | 7 | 8 | 9 | 10 | 11 | 12 |
In the abstract, this table is not clear. However, with a caption giving the table's number (for reference in the main prose) and explaining its use, it makes more sense:
<caption> <p>Table 1. <p>This table shows the total score obtained from rolling two six-sided dice. The first row represents the value of the first die, the first column the value of the second die. The total is given in the cell that corresponds to the values of the two dice. </caption>
This provides the user with more context:
1 | 2 | 3 | 4 | 5 | 6 | |
---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | 7 |
2 | 3 | 4 | 5 | 6 | 7 | 8 |
3 | 4 | 5 | 6 | 7 | 8 | 9 |
4 | 5 | 6 | 7 | 8 | 9 | 10 |
5 | 6 | 7 | 8 | 9 | 10 | 11 |
6 | 7 | 8 | 9 | 10 | 11 | 12 |
colgroup
elementtable
element, after any
caption
elements and before any thead
,
tbody
, tfoot
, and tr
elements.span
attribute is present: Empty.span
attribute is absent: Zero or more col
and template
elements.span
interface HTMLTableColElement : HTMLElement { attribute unsigned long span; };
The colgroup
element represents a group of one or more columns in the table
that is its parent, if it has a
parent and that is a table
element.
If the colgroup
element contains no col
elements, then the element
may have a span
content attribute specified,
whose value must be a valid non-negative integer greater than zero.
The colgroup
element and its span
attribute take part in the table model.
The span
IDL attribute must
reflect the content attribute of the same name. The value must be limited to
only non-negative numbers greater than zero.
col
elementcolgroup
element that doesn't have
a span
attribute.span
HTMLTableColElement
, same as for
colgroup
elements. This interface defines one member,
span
.
If a col
element has a parent and that is a colgroup
element that
itself has a parent that is a table
element, then the col
element
represents one or more columns in the column group represented by that colgroup
.
The element may have a span
content attribute
specified, whose value must be a valid non-negative integer greater than zero.
The col
element and its span
attribute take
part in the table model.
The span
IDL attribute must reflect
the content attribute of the same name. The value must be limited to only non-negative
numbers greater than zero.
tbody
elementtable
element, after any
caption
, colgroup
, and
thead
elements, but only if there are no
tr
elements that are children of the
table
element.tr
and script-supporting elementsinterface HTMLTableSectionElement : HTMLElement { readonly attribute HTMLCollection rows; HTMLElement insertRow(optional long index = -1); void deleteRow(long index); };
The HTMLTableSectionElement
interface is also
used for thead
and tfoot
elements.
The tbody
element represents a block of rows that consist of a
body of data for the parent table
element, if the tbody
element has a
parent and it is a table
.
The tbody
element takes part in the table model.
rows
Returns an HTMLCollection
of the tr
elements of the table
section.
insertRow
( [ index ] )Creates a tr
element, inserts it into the table section at the position given by
the argument, and returns the tr
.
The position is relative to the rows in the table section. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the table section.
If the given position is less than −1 or greater than the number of rows, throws an
IndexSizeError
exception.
deleteRow
(index)Removes the tr
element with the given position in the table section.
The position is relative to the rows in the table section. The index −1 is equivalent to deleting the last row of the table section.
If the given position is less than −1 or greater than the index of the last row, or if
there are no rows, throws an IndexSizeError
exception.
The rows
attribute must return an
HTMLCollection
rooted at the element, whose filter matches only tr
elements that are children of the element.
The insertRow(index)
method must, when invoked on an element table section, act as follows:
If index is less than −1 or greater than the number of elements in
the rows
collection, the method must throw an
IndexSizeError
exception.
If index is −1 or equal to the number of items in the rows
collection, the method must create a tr
element,
append it to the element table section, and return the newly created
tr
element.
Otherwise, the method must create a tr
element, insert it as a child of the table section element, immediately before the indexth
tr
element in the rows
collection, and finally
must return the newly created tr
element.
The deleteRow(index)
method must remove the indexth element in the rows
collection from its parent. If index is
less than zero or greater than or equal to the number of elements in the rows
collection, the method must instead throw an
IndexSizeError
exception.
thead
elementtable
element, after any
caption
, and colgroup
elements and before any tbody
, tfoot
, and
tr
elements, but only if there are no other
thead
elements that are children of the
table
element.tr
and script-supporting elementsHTMLTableSectionElement
, as defined for
tbody
elements.The thead
element represents the block of rows that consist of
the column labels (headers) for the parent table
element, if the thead
element has a parent and it is a table
.
The thead
element takes part in the table model.
This example shows a thead
element being used. Notice the use of both
th
and td
elements in the thead
element: the first row is
the headers, and the second row is an explanation of how to fill in the table.
<table> <caption> School auction sign-up sheet </caption> <thead> <tr> <th><label for=e1>Name</label> <th><label for=e2>Product</label> <th><label for=e3>Picture</label> <th><label for=e4>Price</label> <tr> <td>Your name here <td>What are you selling? <td>Link to a picture <td>Your reserve price <tbody> <tr> <td>Ms Danus <td>Doughnuts <td><img src="http://example.com/mydoughnuts.png" title="Doughnuts from Ms Danus"> <td>$45 <tr> <td><input id=e1 type=text name=who required form=f> <td><input id=e2 type=text name=what required form=f> <td><input id=e3 type=url name=pic form=f> <td><input id=e4 type=number step=0.01 min=0 value=0 required form=f> </table> <form id=f action="/auction.cgi"> <input type=button name=add value="Submit"> </form>
tfoot
elementtable
element, after any
caption
, colgroup
, and thead
elements and before any tbody
and tr
elements, but only if there are no other tfoot
elements that are children of the table
element.table
element, after any
caption
, colgroup
, thead
,
tbody
, and tr
elements, but only if there
are no other tfoot
elements that are children of the
table
element.tr
and script-supporting elementsHTMLTableSectionElement
, as defined for
tbody
elements.The tfoot
element represents the block of rows that consist of
the column summaries (footers) for the parent table
element, if the
tfoot
element has a parent and it is a table
.
The tfoot
element takes part in the table
model.
tr
elementthead
element.tbody
element.tfoot
element.table
element, after any
caption
, colgroup
, and thead
elements, but only if there are no tbody
elements that
are children of the table
element.td
, th
, and script-supporting elementsinterface HTMLTableRowElement : HTMLElement { readonly attribute long rowIndex; readonly attribute long sectionRowIndex; readonly attribute HTMLCollection cells; HTMLElement insertCell(optional long index = -1); void deleteCell(long index); };
The tr
element represents a row of
cells in a table.
The tr
element takes part in the table model.
rowIndex
Returns the position of the row in the table's rows
list.
Returns −1 if the element isn't in a table.
sectionRowIndex
Returns the position of the row in the table section's rows
list.
Returns −1 if the element isn't in a table section.
cells
Returns an HTMLCollection
of the td
and th
elements of
the row.
insertCell
( [ index ] )Creates a td
element, inserts it into the table row at the position given by the
argument, and returns the td
.
The position is relative to the cells in the row. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the row.
If the given position is less than −1 or greater than the number of cells, throws an
IndexSizeError
exception.
deleteCell
(index)Removes the td
or th
element with the given position in the
row.
The position is relative to the cells in the row. The index −1 is equivalent to deleting the last cell of the row.
If the given position is less than −1 or greater than the index of the last cell, or
if there are no cells, throws an IndexSizeError
exception.
The rowIndex
attribute must, if the element has
a parent table
element, or a parent tbody
, thead
, or
tfoot
element and a grandparent table
element, return the index
of the tr
element in that table
element's rows
collection. If there is no such table
element,
then the attribute must return −1.
The sectionRowIndex
attribute must, if
the element has a parent table
, tbody
, thead
, or
tfoot
element, return the index of the tr
element in the parent
element's rows
collection (for tables, that's the HTMLTableElement.rows
collection; for table sections, that's the
HTMLTableRowElement.rows
collection). If there is no such
parent element, then the attribute must return −1.
The cells
attribute must return an
HTMLCollection
rooted at the tr
element, whose filter matches only
td
and th
elements that are children of the tr
element.
The insertCell(index)
method must act as follows:
If index is less than −1 or greater than the number of elements in
the cells
collection, the method must throw an
IndexSizeError
exception.
If index is equal to −1 or equal to the number of items in cells
collection, the method must create a td
element,
append it to the tr
element, and return the newly created td
element.
Otherwise, the method must create a td
element, insert it as a child of the
tr
element, immediately before the indexth td
or
th
element in the cells
collection, and finally
must return the newly created td
element.
The deleteCell(index)
method must remove the indexth element in the cells
collection from its parent. If index is less
than zero or greater than or equal to the number of elements in the cells
collection, the method must instead throw an
IndexSizeError
exception.
td
elementtr
element.colspan
rowspan
headers
interface HTMLTableDataCellElement : HTMLTableCellElement {};
The td
element represents a data cell in a table.
The td
element and its colspan
, rowspan
, and headers
attributes take part in the table model.
User agents, especially in non-visual environments or where displaying the table as a 2D grid
is impractical, may give the user context for the cell when rendering the contents of a cell; for
instance, giving its position in the table model, or listing the cell's header cells
(as determined by the algorithm for assigning header cells). When a cell's header
cells are being listed, user agents may use the value of abbr
attributes on those header cells, if any, instead of the contents of the header cells
themselves.
th
elementtr
element.header
, footer
, sectioning content, or heading content descendants.colspan
rowspan
headers
scope
abbr
interface HTMLTableHeaderCellElement : HTMLTableCellElement {
attribute DOMString scope;
attribute DOMString abbr;
};
The th
element represents a header cell in a table.
The th
element may have a scope
content attribute specified. The scope
attribute is an
enumerated attribute with five states, four of which have explicit keywords:
row
keyword, which maps to the
row statecol
keyword, which maps to the
column staterowgroup
keyword, which maps to
the row group stateth
element's scope
attribute must
not be in the row group state if the element is not
anchored in a row group.colgroup
keyword, which maps to
the column group stateth
element's scope
attribute must
not be in the column group state if the element is
not anchored in a column group.The scope
attribute's missing value default is the
auto state.
The th
element may have an abbr
content attribute specified. Its value must be an alternative label for the header cell, to be
used when referencing the cell in other contexts (e.g. when describing the header cells that apply
to a data cell). It is typically an abbreviated form of the full header cell, but can also be an
expansion, or merely a different phrasing.
The th
element and its colspan
, rowspan
, headers
, and
scope
attributes take part in the table model.
The scope
IDL attribute must reflect
the content attribute of the same name, limited to only known values.
The following example shows how the scope
attribute's rowgroup
value affects which data cells a header cell
applies to.
Here is a markup fragment showing a table:
The tbody
elements in this example identify the range of the row groups.
<table> <caption>Measurement of legs and tails in Cats and English speakers</caption> <thead> <tr> <th> ID <th> Measurement <th> Average <th> Maximum <tbody> <tr> <td> <th scope=rowgroup> Cats <td> <td> <tr> <td> 93 <th scope=row> Legs <td> 3.5 <td> 4 <tr> <td> 10 <th scope=row> Tails <td> 1 <td> 1 </tbody> <tbody> <tr> <td> <th scope=rowgroup> English speakers <td> <td> <tr> <td> 32 <th scope=row> Legs <td> 2.67 <td> 4 <tr> <td> 35 <th scope=row> Tails <td> 0.33 <td> 1 </tbody> </table>
This would result in the following table:
ID | Measurement | Average | Maximum |
---|---|---|---|
Cats | |||
93 | Legs | 3.5 | 4 |
10 | Tails | 1 | 1 |
English speakers | |||
32 | Legs | 2.67 | 4 |
35 | Tails | 0.33 | 1 |
The header cells in row 1 ('ID', 'Measurement', 'Average' and 'Maximum') each apply only to the cells in their column.
The header cells with a scope=rowgroup
('Cats' and 'English speakers') apply to all the cells in their row group other
than the cells (to their left) in column 1:
The header 'Cats' (row 2, column 2) applies to the headers 'Legs' (row 3, column 2) and 'Tails' (row 4, column 2) and to the data cells in rows 2, 3 and 4 of the 'Average' and 'Maximum' columns.
The header 'English speakers' (row 5, column 2) applies to the headers 'Legs' (row 6, column 2) and 'Tails' (row 7, column 2) and to the data cells in rows 5, 6 and 7 of the 'Average' and 'Maximum' columns.
Each of the 'Legs' and 'Tails' header cells has a scope=row
and therefore apply to the data cells (to the right)
in their row, from the 'Average' and 'Maximum' columns.
td
and th
elementsThe td
and th
elements may have a colspan
content attribute specified, whose value must
be a valid non-negative integer greater than zero.
The td
and th
elements may also have a rowspan
content attribute specified, whose value must
be a valid non-negative integer. For this attribute, the value zero means that the
cell is to span all the remaining rows in the row group.
These attributes give the number of columns and rows respectively that the cell is to span. These attributes must not be used to overlap cells, as described in the description of the table model.
The td
and th
element may have a headers
content attribute specified. The headers
attribute, if specified, must contain a string consisting
of an unordered set of unique space-separated tokens that are
case-sensitive, each of which must have the value of an ID of a th
element taking part in the same table as the td
or th
element (as defined by the table model).
A th
element with ID id is
said to be directly targeted by all td
and th
elements in the
same table that have headers
attributes whose values include as one of their tokens
the ID id. A th
element A is said to be targeted by a th
or td
element
B if either A is directly targeted by B or if there exists an element C that is itself
targeted by the element B and A is directly
targeted by C.
A th
element must not be targeted by itself.
The colspan
, rowspan
, and headers
attributes take part in the table model.
The td
and th
elements implement interfaces that inherit from the
HTMLTableCellElement
interface:
interface HTMLTableCellElement : HTMLElement {
attribute unsigned long colSpan;
attribute unsigned long rowSpan;
[PutForwards=value] readonly attribute DOMSettableTokenList headers;
readonly attribute long cellIndex;
};
cellIndex
Returns the position of the cell in the row's cells
list.
This does not necessarily correspond to the x-position of the cell in the
table, since earlier cells might cover multiple rows or columns.
Returns −1 if the element isn't in a row.
The colSpan
IDL attribute must
reflect the colspan
content attribute. Its
default value is 1.
The rowSpan
IDL attribute must
reflect the rowspan
content attribute. Its
default value is 1.
The headers
IDL attribute must
reflect the content attribute of the same name.
The cellIndex
IDL attribute must, if the
element has a parent tr
element, return the index of the cell's element in the parent
element's cells
collection. If there is no such parent element,
then the attribute must return −1.
The various table elements and their content attributes together define the table model.
A table consists of cells aligned on a two-dimensional grid of
slots with coordinates (x, y). The grid is finite, and is either empty or has one or more slots. If the grid
has one or more slots, then the x coordinates are always in the range 0 ≤ x < xwidth, and the y coordinates are always in the
range 0 ≤ y < yheight. If one or both of xwidth and yheight are zero, then the
table is empty (has no slots). Tables correspond to table
elements.
A cell is a set of slots anchored at a slot (cellx, celly), and with
a particular width and height such that the cell covers
all the slots with coordinates (x, y) where cellx ≤ x < cellx+width and celly ≤ y < celly+height. Cells can either be data cells
or header cells. Data cells correspond to td
elements, and header cells
correspond to th
elements. Cells of both types can have zero or more associated
header cells.
It is possible, in certain error cases, for two cells to occupy the same slot.
A row is a complete set of slots from x=0 to x=xwidth-1, for a particular value of y. Rows usually
correspond to tr
elements, though a row group
can have some implied rows at the end in some cases involving
cells spanning multiple rows.
A column is a complete set of slots from y=0 to y=yheight-1, for a particular value of x. Columns can
correspond to col
elements. In the absence of col
elements, columns are
implied.
A row group is a set of rows anchored at a slot (0, groupy) with a particular height such that the row group
covers all the slots with coordinates (x, y) where 0 ≤ x < xwidth and groupy ≤ y < groupy+height. Row groups correspond to
tbody
, thead
, and tfoot
elements. Not every row is
necessarily in a row group.
A column group is a set of columns anchored at a slot (groupx, 0) with a particular width such that the column group
covers all the slots with coordinates (x, y) where groupx ≤ x < groupx+width and 0 ≤ y < yheight. Column
groups correspond to colgroup
elements. Not every column is necessarily in a column
group.
Row groups cannot overlap each other. Similarly, column groups cannot overlap each other.
A cell cannot cover slots that are from two or more row groups. It is, however, possible for a cell to be in multiple column groups. All the slots that form part of one cell are part of zero or one row groups and zero or more column groups.
In addition to cells, columns, rows, row groups, and column
groups, tables can have a caption
element
associated with them. This gives the table a heading, or legend.
A table model error is an error with the data represented by table
elements and their descendants. Documents must not have table model errors.
To determine which elements correspond to which slots in a table associated with a table
element, to determine the
dimensions of the table (xwidth and yheight), and to determine if there are any table model errors, user agents must use the following algorithm:
Let xwidth be zero.
Let yheight be zero.
Let pending tfoot
elements be a list of tfoot
elements, initially empty.
Let the table be the table represented
by the table
element. The xwidth and yheight variables give the table's
dimensions. The table is initially empty.
If the table
element has no children elements, then return the
table (which will be empty), and abort these steps.
Associate the first caption
element child of the table
element with
the table. If there are no such children, then it has no associated
caption
element.
Let the current element be the first element child of the
table
element.
If a step in this algorithm ever requires the current element to be advanced to the next child of the table
when
there is no such next child, then the user agent must jump to the step labeled end, near
the end of this algorithm.
While the current element is not one of the following elements, advance the current element to the next
child of the table
:
If the current element is a colgroup
, follow these
substeps:
Column groups: Process the current element according to the appropriate case below:
col
element childrenFollow these steps:
Let xstart have the value of xwidth.
Let the current column be the first col
element child
of the colgroup
element.
Columns: If the current column col
element has
a span
attribute, then parse its value using the
rules for parsing non-negative integers.
If the result of parsing the value is not an error or zero, then let span be that value.
Otherwise, if the col
element has no span
attribute, or if trying to parse the attribute's value
resulted in an error or zero, then let span be 1.
Increase xwidth by span.
Let the last span columns in
the table correspond to the current column
col
element.
If current column is not the last col
element child of
the colgroup
element, then let the current column be the
next col
element child of the colgroup
element, and return to
the step labeled columns.
Let all the last columns in the
table from x=xstart to
x=xwidth-1 form a new column group, anchored at the slot (xstart, 0), with width xwidth-xstart, corresponding to the colgroup
element.
col
element childrenIf the colgroup
element has a span
attribute, then parse its value using the rules for parsing non-negative
integers.
If the result of parsing the value is not an error or zero, then let span be that value.
Otherwise, if the colgroup
element has no span
attribute, or if trying to parse the attribute's
value resulted in an error or zero, then let span be 1.
Increase xwidth by span.
Let the last span columns in
the table form a new column
group, anchored at the slot (xwidth-span, 0), with width span, corresponding to the colgroup
element.
While the current element is not one of the following elements, advance the current element to the
next child of the table
:
If the current element is a colgroup
element, jump to the
step labeled column groups above.
Let ycurrent be zero.
Let the list of downward-growing cells be an empty list.
Rows: While the current element is not one of the following
elements, advance the current
element to the next child of the table
:
If the current element is a tr
, then run the algorithm
for processing rows, advance the current element to the next child of the table
, and return to the
step labeled rows.
Run the algorithm for ending a row group.
If the current element is a tfoot
, then add that element to
the list of pending tfoot
elements, advance the current element to the next
child of the table
, and return to the step labeled rows.
The current element is either a thead
or a
tbody
.
Run the algorithm for processing row groups.
Return to the step labeled rows.
End: For each tfoot
element in the list of pending
tfoot
elements, in tree order, run the algorithm for processing row
groups.
If there exists a row or column in the table containing only slots that do not have a cell anchored to them, then this is a table model error.
Return the table.
The algorithm for processing row groups, which is invoked by the set of steps above
for processing thead
, tbody
, and tfoot
elements, is:
Let ystart have the value of yheight.
For each tr
element that is a child of the element being processed, in tree
order, run the algorithm for processing rows.
If yheight > ystart, then let all the last rows in the table from y=ystart to y=yheight-1 form a new row group, anchored at the slot with coordinate (0, ystart), with height yheight-ystart, corresponding to the element being processed.
Run the algorithm for ending a row group.
The algorithm for ending a row group, which is invoked by the set of steps above when starting and ending a block of rows, is:
While ycurrent is less than yheight, follow these steps:
Increase ycurrent by 1.
Empty the list of downward-growing cells.
The algorithm for processing rows, which is invoked by the set of steps above for
processing tr
elements, is:
If yheight is equal to ycurrent, then increase yheight by 1. (ycurrent is never greater than yheight.)
Let xcurrent be 0.
If the tr
element being processed has no td
or th
element children, then increase ycurrent by 1, abort
this set of steps, and return to the algorithm above.
Let current cell be the first td
or th
element child
in the tr
element being processed.
Cells: While xcurrent is less than xwidth and the slot with coordinate (xcurrent, ycurrent) already has a cell assigned to it, increase xcurrent by 1.
If xcurrent is equal to xwidth, increase xwidth by 1. (xcurrent is never greater than xwidth.)
If the current cell has a colspan
attribute, then parse that attribute's
value, and let colspan be the result.
If parsing that value failed, or returned zero, or if the attribute is absent, then let colspan be 1, instead.
If the current cell has a rowspan
attribute, then parse that attribute's
value, and let rowspan be the result.
If parsing that value failed or if the attribute is absent, then let rowspan be 1, instead.
If rowspan is zero and the table
element's
Document
is not set to quirks mode, then let cell grows
downward be true, and set rowspan to 1. Otherwise, let cell grows downward be false.
If xwidth < xcurrent+colspan, then let xwidth be xcurrent+colspan.
If yheight < ycurrent+rowspan, then let yheight be ycurrent+rowspan.
Let the slots with coordinates (x, y) such that xcurrent ≤ x < xcurrent+colspan and ycurrent ≤ y < ycurrent+rowspan be covered by a new cell c, anchored at (xcurrent, ycurrent), which has width colspan and height rowspan, corresponding to the current cell element.
If the current cell element is a th
element, let this new
cell c be a header cell; otherwise, let it be a data cell.
To establish which header cells apply to the current cell element, use the algorithm for assigning header cells described in the next section.
If any of the slots involved already had a cell covering them, then this is a table model error. Those slots now have two cells overlapping.
If cell grows downward is true, then add the tuple {c, xcurrent, colspan} to the list of downward-growing cells.
Increase xcurrent by colspan.
If current cell is the last td
or th
element child in
the tr
element being processed, then increase ycurrent by 1, abort this set of steps, and return to the algorithm
above.
Let current cell be the next td
or th
element child
in the tr
element being processed.
Return to the step labeled cells.
When the algorithms above require the user agent to run the algorithm for growing downward-growing cells, the user agent must, for each {cell, cellx, width} tuple in the list of downward-growing cells, if any, extend the cell cell so that it also covers the slots with coordinates (x, ycurrent), where cellx ≤ x < cellx+width.
Each cell can be assigned zero or more header cells. The algorithm for assigning header cells to a cell principal cell is as follows.
Let header list be an empty list of cells.
Let (principalx, principaly) be the coordinate of the slot to which the principal cell is anchored.
headers
attribute specifiedTake the value of the principal cell's headers
attribute and split it on spaces, letting id list be the list of tokens
obtained.
For each token in the id list, if the
first element in the Document
with an ID equal to
the token is a cell in the same table, and that cell is not the
principal cell, then add that cell to header list.
headers
attribute specifiedLet principalwidth be the width of the principal cell.
Let principalheight be the height of the principal cell.
For each value of y from principaly to principaly+principalheight-1, run the internal algorithm for scanning and assigning header cells, with the principal cell, the header list, the initial coordinate (principalx,y), and the increments Δx=−1 and Δy=0.
For each value of x from principalx to principalx+principalwidth-1, run the internal algorithm for scanning and assigning header cells, with the principal cell, the header list, the initial coordinate (x,principaly), and the increments Δx=0 and Δy=−1.
If the principal cell is anchored in a row group, then add all header cells that are row group headers and are anchored in the same row group with an x-coordinate less than or equal to principalx+principalwidth-1 and a y-coordinate less than or equal to principaly+principalheight-1 to header list.
If the principal cell is anchored in a column group, then add all header cells that are column group headers and are anchored in the same column group with an x-coordinate less than or equal to principalx+principalwidth-1 and a y-coordinate less than or equal to principaly+principalheight-1 to header list.
Remove all the empty cells from the header list.
Remove any duplicates from the header list.
Remove principal cell from the header list if it is there.
Assign the headers in the header list to the principal cell.
The internal algorithm for scanning and assigning header cells, given a principal cell, a header list, an initial coordinate (initialx, initialy), and Δx and Δy increments, is as follows:
Let x equal initialx.
Let y equal initialy.
Let opaque headers be an empty list of cells.
Let in header block be true, and let headers from current header block be a list of cells containing just the principal cell.
Let in header block be false and let headers from current header block be an empty list of cells.
Loop: Increment x by Δx; increment y by Δy.
For each invocation of this algorithm, one of Δx and Δy will be −1, and the other will be 0.
If either x or y is less than 0, then abort this internal algorithm.
If there is no cell covering slot (x, y), or if there is more than one cell covering slot (x, y), return to the substep labeled loop.
Let current cell be the cell covering slot (x, y).
Set in header block to true.
Add current cell to headers from current header block.
Let blocked be false.
If there are any cells in the opaque headers list anchored with the same x-coordinate as the current cell, and with the same width as current cell, then let blocked be true.
If the current cell is not a column header, then let blocked be true.
If there are any cells in the opaque headers list anchored with the same y-coordinate as the current cell, and with the same height as current cell, then let blocked be true.
If the current cell is not a row header, then let blocked be true.
If blocked is false, then add the current cell to the headers list.
Set in header block to false. Add all the cells in headers from current header block to the opaque headers list, and empty the headers from current header block list.
Return to the step labeled loop.
A header cell anchored at the slot with coordinate (x, y) with width width and height height is said to be a column header if any of the following conditions are true:
scope
attribute is in the column state, orscope
attribute is in the auto state, and there are no data cells in any of the cells
covering slots with y-coordinates y .. y+height-1.A header cell anchored at the slot with coordinate (x, y) with width width and height height is said to be a row header if any of the following conditions are true:
scope
attribute is in the row state, orscope
attribute is in the auto state, the cell is not a column header, and
there are no data cells in any of the cells covering slots with x-coordinates
x .. x+width-1.A header cell is said to be a column group header if its scope
attribute is in the column
group state.
A header cell is said to be a row group header if its scope
attribute is in the row
group state.
A cell is said to be an empty cell if it contains no elements and its text content, if any, consists only of White_Space characters.
This section is non-normative.
A form is a component of a Web page that has form controls, such as text fields, buttons, checkboxes, range controls, or color pickers. A user can interact with such a form, providing data that can then be sent to the server for further processing (e.g. returning the results of a search or calculation). No client-side scripting is needed in many cases, though an API is available so that scripts can augment the user experience or use forms for purposes other than submitting data to a server.
Writing a form consists of several steps, which can be performed in any order: writing the user interface, implementing the server-side processing, and configuring the user interface to communicate with the server.
This section is non-normative.
For the purposes of this brief introduction, we will create a pizza ordering form.
Any form starts with a form
element, inside which are placed the controls. Most
controls are represented by the input
element, which by default provides a one-line
text field. To label a control, the label
element is used; the label text and the
control itself go inside the label
element. Each part of a form is considered a
paragraph, and is typically separated from other parts using p
elements.
Putting this together, here is how one might ask for the customer's name:
<form> <p><label>Customer name: <input></label></p> </form>
To let the user select the size of the pizza, we can use a set of radio buttons. Radio buttons
also use the input
element, this time with a type
attribute with the value radio
. To make the radio buttons work as a group, they are
given a common name using the name
attribute. To group a batch
of controls together, such as, in this case, the radio buttons, one can use the
fieldset
element. The title of such a group of controls is given by the first element
in the fieldset
, which has to be a legend
element.
<form> <p><label>Customer name: <input></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size> Small </label></p> <p><label> <input type=radio name=size> Medium </label></p> <p><label> <input type=radio name=size> Large </label></p> </fieldset> </form>
Changes from the previous step are highlighted.
To pick toppings, we can use checkboxes. These use the input
element with a type
attribute with the value checkbox
:
<form> <p><label>Customer name: <input></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size> Small </label></p> <p><label> <input type=radio name=size> Medium </label></p> <p><label> <input type=radio name=size> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox> Bacon </label></p> <p><label> <input type=checkbox> Extra Cheese </label></p> <p><label> <input type=checkbox> Onion </label></p> <p><label> <input type=checkbox> Mushroom </label></p> </fieldset> </form>
The pizzeria for which this form is being written is always making mistakes, so it needs a way
to contact the customer. For this purpose, we can use form controls specifically for telephone
numbers (input
elements with their type
attribute set to tel
) and e-mail addresses
(input
elements with their type
attribute set to
email
):
<form> <p><label>Customer name: <input></label></p> <p><label>Telephone: <input type=tel></label></p> <p><label>E-mail address: <input type=email></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size> Small </label></p> <p><label> <input type=radio name=size> Medium </label></p> <p><label> <input type=radio name=size> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox> Bacon </label></p> <p><label> <input type=checkbox> Extra Cheese </label></p> <p><label> <input type=checkbox> Onion </label></p> <p><label> <input type=checkbox> Mushroom </label></p> </fieldset> </form>
We can use an input
element with its type
attribute set to time
to ask for a delivery time. Many
of these form controls have attributes to control exactly what values can be specified; in this
case, three attributes of particular interest are min
, max
, and step
. These set the
minimum time, the maximum time, and the interval between allowed values (in seconds). This
pizzeria only delivers between 11am and 9pm, and doesn't promise anything better than 15 minute
increments, which we can mark up as follows:
<form> <p><label>Customer name: <input></label></p> <p><label>Telephone: <input type=tel></label></p> <p><label>E-mail address: <input type=email></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size> Small </label></p> <p><label> <input type=radio name=size> Medium </label></p> <p><label> <input type=radio name=size> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox> Bacon </label></p> <p><label> <input type=checkbox> Extra Cheese </label></p> <p><label> <input type=checkbox> Onion </label></p> <p><label> <input type=checkbox> Mushroom </label></p> </fieldset> <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p> </form>
The textarea
element can be used to provide a free-form text field. In this
instance, we are going to use it to provide a space for the customer to give delivery
instructions:
<form> <p><label>Customer name: <input></label></p> <p><label>Telephone: <input type=tel></label></p> <p><label>E-mail address: <input type=email></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size> Small </label></p> <p><label> <input type=radio name=size> Medium </label></p> <p><label> <input type=radio name=size> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox> Bacon </label></p> <p><label> <input type=checkbox> Extra Cheese </label></p> <p><label> <input type=checkbox> Onion </label></p> <p><label> <input type=checkbox> Mushroom </label></p> </fieldset> <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p> <p><label>Delivery instructions: <textarea></textarea></label></p> </form>
Finally, to make the form submittable we use the button
element:
<form> <p><label>Customer name: <input></label></p> <p><label>Telephone: <input type=tel></label></p> <p><label>E-mail address: <input type=email></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size> Small </label></p> <p><label> <input type=radio name=size> Medium </label></p> <p><label> <input type=radio name=size> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox> Bacon </label></p> <p><label> <input type=checkbox> Extra Cheese </label></p> <p><label> <input type=checkbox> Onion </label></p> <p><label> <input type=checkbox> Mushroom </label></p> </fieldset> <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p> <p><label>Delivery instructions: <textarea></textarea></label></p> <p><button>Submit order</button></p> </form>
This section is non-normative.
The exact details for writing a server-side processor are out of scope for this specification.
For the purposes of this introduction, we will assume that the script at https://pizza.example.com/order.cgi
is configured to accept submissions using the
application/x-www-form-urlencoded
format,
expecting the following parameters sent in an HTTP POST body:
custname
custtel
custemail
size
small
, medium
, or large
topping
bacon
, cheese
, onion
, and mushroom
delivery
comments
This section is non-normative.
Form submissions are exposed to servers in a variety of ways, most commonly as HTTP GET or POST
requests. To specify the exact method used, the method
attribute is specified on the form
element. This doesn't specify how the form data is
encoded, though; to specify that, you use the enctype
attribute. You also have to specify the URL of the service that will handle the
submitted data, using the action
attribute.
For each form control you want submitted, you then have to give a name that will be used to
refer to the data in the submission. We already specified the name for the group of radio buttons;
the same attribute (name
) also specifies the submission name.
Radio buttons can be distinguished from each other in the submission by giving them different
values, using the value
attribute.
Multiple controls can have the same name; for example, here we give all the checkboxes the same
name, and the server distinguishes which checkbox was checked by seeing which values are submitted
with that name — like the radio buttons, they are also given unique values with the value
attribute.
Given the settings in the previous section, this all becomes:
<form method="post" enctype="application/x-www-form-urlencoded" action="https://pizza.example.com/order.cgi"> <p><label>Customer name: <input name="custname"></label></p> <p><label>Telephone: <input type=tel name="custtel"></label></p> <p><label>E-mail address: <input type=email name="custemail"></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size value="small"> Small </label></p> <p><label> <input type=radio name=size value="medium"> Medium </label></p> <p><label> <input type=radio name=size value="large"> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p> <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p> <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p> <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p> </fieldset> <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery"></label></p> <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p> <p><button>Submit order</button></p> </form>
There is no particular significance to the way some of the attributes have their values quoted and others don't. The HTML syntax allows a variety of equally valid ways to specify attributes, as discussed in the syntax section.
For example, if the customer entered "Denise Lawrence" as their name, "555-321-8642" as their telephone number, did not specify an e-mail address, asked for a medium-sized pizza, selected the Extra Cheese and Mushroom toppings, entered a delivery time of 7pm, and left the delivery instructions text field blank, the user agent would submit the following to the online Web service:
custname=Denise+Lawrence&custtel=555-321-8624&custemail=&size=medium&topping=cheese&topping=mushroom&delivery=19%3A00&comments=
This section is non-normative.
Forms can be annotated in such a way that the user agent will check the user's input before the form is submitted. The server still has to verify the input is valid (since hostile users can easily bypass the form validation), but it allows the user to avoid the wait incurred by having the server be the sole checker of the user's input.
The simplest annotation is the required
attribute,
which can be specified on input
elements to indicate that the form is not to be
submitted until a value is given. By adding this attribute to the customer name, pizza size, and
delivery time fields, we allow the user agent to notify the user when the user submits the form
without filling in those fields:
<form method="post" enctype="application/x-www-form-urlencoded" action="https://pizza.example.com/order.cgi"> <p><label>Customer name: <input name="custname" required></label></p> <p><label>Telephone: <input type=tel name="custtel"></label></p> <p><label>E-mail address: <input type=email name="custemail"></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size required value="small"> Small </label></p> <p><label> <input type=radio name=size required value="medium"> Medium </label></p> <p><label> <input type=radio name=size required value="large"> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p> <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p> <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p> <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p> </fieldset> <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p> <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p> <p><button>Submit order</button></p> </form>
It is also possible to limit the length of the input, using the maxlength
attribute. By adding this to the textarea
element, we can limit users to 1000 characters, preventing them from writing huge essays to the
busy delivery drivers instead of staying focused and to the point:
<form method="post" enctype="application/x-www-form-urlencoded" action="https://pizza.example.com/order.cgi"> <p><label>Customer name: <input name="custname" required></label></p> <p><label>Telephone: <input type=tel name="custtel"></label></p> <p><label>E-mail address: <input type=email name="custemail"></label></p> <fieldset> <legend> Pizza Size </legend> <p><label> <input type=radio name=size required value="small"> Small </label></p> <p><label> <input type=radio name=size required value="medium"> Medium </label></p> <p><label> <input type=radio name=size required value="large"> Large </label></p> </fieldset> <fieldset> <legend> Pizza Toppings </legend> <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p> <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p> <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p> <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p> </fieldset> <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p> <p><label>Delivery instructions: <textarea name="comments" maxlength=1000></textarea></label></p> <p><button>Submit order</button></p> </form>
When a form is submitted, invalid
events are
fired at each form control that is invalid, and then at the form
element itself. This
can be useful for displaying a summary of the problems with the form, since typically the browser
itself will only report one problem at a time.
This section is non-normative.
In this pizza delivery example, the times are specified in the format "HH:MM": two digits for the hour, in 24-hour format, and two digits for the time. (Seconds could also be specified, though they are not necessary in this example.)
In some locales, however, times are often expressed differently when presented to users. For example, in the United States, it is still common to use the 12-hour clock with an am/pm indicator, as in "2pm". In France, it is common to separate the hours from the minutes using an "h" character, as in "14h00".
Similar issues exist with dates, with the added complication that even the order of the components is not always consistent — for example, in Cyprus the first of February 2003 would typically be written "1/2/03", while that same date in Japan would typically be written as "2003年02月01日" — and even with numbers, where locales differ, for example, in what punctuation is used as the decimal separator and the thousands separator.
It is therefore important to distinguish the time, date, and number formats used in HTML and in form submissions, which are always the formats defined in this specification (and based on the well-established ISO 8601 standard for computer-readable date and time formats), from the time, date, and number formats presented to the user by the browser and accepted as input from the user by the browser.
The format used "on the wire", i.e. in HTML markup and in form submissions, is intended to be computer-readable and consistent irrespective of the user's locale. Dates, for instance, are always written in the format "YYYY-MM-DD", as in "2003-02-01". Users are not expected to ever see this format.
The time, date, or number given by the page in the wire format is then translated to the user's preferred presentation (based on user preferences or on the locale of the page itself), before being displayed to the user. Similarly, after the user inputs a time, date, or number using their preferred format, the user agent converts it back to the wire format before putting it in the DOM or submitting it.
This allows scripts in pages and on servers to process times, dates, and numbers in a consistent manner without needing to support dozens of different formats, while still supporting the users' needs.
See also the implementation notes regarding localization of form controls.
Mostly for historical reasons, elements in this section fall into several overlapping (but subtly different) categories in addition to the usual ones like flow content, phrasing content, and interactive content.
A number of the elements are form-associated elements, which means they can have a form owner.
The form-associated elements fall into several subcategories:
Denotes elements that are listed in the form.elements
and fieldset.elements
APIs.
Denotes elements that can be used for constructing the
form data set when a form
element is submitted.
Some submittable elements can be, depending on their attributes, buttons. The prose below defines when an element is a button. Some buttons are specifically submit buttons.
Denotes elements that can be affected when a form
element is reset.
Denotes elements that have a form
content attribute, and a
matching form
IDL attribute, that allow authors to specify an
explicit form owner.
Some elements, not all of them form-associated,
are categorized as labelable elements. These are elements that
can be associated with a label
element.
button
input
(if the type
attribute is not in the Hidden state)keygen
meter
output
progress
select
textarea
form
elementform
element descendants.accept-charset
action
autocomplete
enctype
method
name
novalidate
target
[OverrideBuiltins] interface HTMLFormElement : HTMLElement { attribute DOMString acceptCharset; attribute DOMString action; attribute DOMString autocomplete; attribute DOMString enctype; attribute DOMString encoding; attribute DOMString method; attribute DOMString name; attribute boolean noValidate; attribute DOMString target; readonly attribute HTMLFormControlsCollection elements; readonly attribute long length; getter Element (unsigned long index); getter (RadioNodeList or Element) (DOMString name); void submit(); void reset(); boolean checkValidity(); boolean reportValidity(); };
The form
element represents a collection of form-associated elements, some of which can represent
editable values that can be submitted to a server for processing.
The accept-charset
attribute gives the
character encodings that are to be used for the submission. If specified, the value must be an
ordered set of unique space-separated tokens that are ASCII
case-insensitive, and each token must be an ASCII case-insensitive match for
one of the labels of an ASCII-compatible character
encoding. [ENCODING]
The name
attribute represents the
form
's name within the forms
collection. The
value must not be the empty string, and the value must be unique amongst the form
elements in the forms
collection that it is in, if
any.
The autocomplete
attribute is an
enumerated attribute. The attribute has two states. The on
keyword maps to the on state, and the off
keyword maps to the off state. The attribute may also be omitted. The
missing value default is the on state.
The off state indicates that by default,
form controls in the form will have their autofill field name set to "off
"; the on state indicates that by default, form controls
in the form will have their autofill field name set to "on
".
The action
, enctype
,
method
, novalidate
,
and target
attributes are attributes for form
submission.
elements
Returns an HTMLCollection
of the form controls in the form (excluding image
buttons for historical reasons).
length
Returns the number of form controls in the form (excluding image buttons for historical reasons).
Returns the indexth element in the form (excluding image buttons for historical reasons).
Returns the form control (or, if there are several, a RadioNodeList
of the form
controls) in the form with the given ID or name
(excluding image buttons for historical reasons); or, if there
are none, returns the img
element with the given ID.
Once an element has been referenced using a particular name, that name will continue being
available as a way to reference that element in this method, even if the element's actual ID or name
changes, for as long as
the element remains in the Document
.
If there are multiple matching items, then a RadioNodeList
object containing all
those elements is returned.
submit
()Submits the form.
reset
()Resets the form.
checkValidity
()Returns true if the form's controls are all valid; otherwise, returns false.
reportValidity
()Returns true if the form's controls are all valid; otherwise, returns false and informs the user.
The autocomplete
IDL attribute must
reflect the content attribute of the same name, limited to only known
values.
The name
IDL attribute must reflect
the content attribute of the same name.
The acceptCharset
IDL attribute must
reflect the accept-charset
content
attribute.
The elements
IDL attribute must return an
HTMLFormControlsCollection
rooted at the Document
node while the
form
element is in a Document
and rooted at the
form
element itself when it is not, whose filter matches listed elements whose form owner is the
form
element, with the exception of input
elements whose type
attribute is in the Image
Button state, which must, for historical reasons, be excluded from this particular
collection.
The length
IDL attribute must return the number
of nodes represented by the elements
collection.
The supported property indices at any instant are the indices supported by the
object returned by the elements
attribute at that
instant.
When a form
element is indexed for indexed property
retrieval, the user agent must return the value returned by the item
method on the elements
collection, when invoked with the given index as its
argument.
Each form
element has a mapping of names to elements called the past names
map. It is used to persist names of controls even when they change names.
The supported property names consist of the names obtained from the following algorithm, in the order obtained from this algorithm:
Let sourced names be an initially empty ordered list of tuples consisting of a string, an element, a source, where the source is either id, name, or past, and, if the source is past, an age.
For each listed element candidate
whose form owner is the form
element, with the exception of any
input
elements whose type
attribute is in the
Image Button state, run these substeps:
If candidate has an id
attribute, add
an entry to sourced names with that id
attribute's value as the string, candidate as the element, and id as
the source.
If candidate has a name
attribute,
add an entry to sourced names with that name
attribute's value as the string, candidate
as the element, and name as the source.
For each img
element candidate whose form owner
is the form
element, run these substeps:
If candidate has an id
attribute, add
an entry to sourced names with that id
attribute's value as the string, candidate as the element, and id as
the source.
If candidate has a name
attribute,
add an entry to sourced names with that name
attribute's value as the string, candidate
as the element, and name as the source.
For each entry past entry in the past names map add an entry to sourced names with the past entry's name as the string, past entry's element as the element, past as the source, and the length of time past entry has been in the past names map as the age.
Sort sourced names by tree order of the element entry of each tuple, sorting entries with the same element by putting entries whose source is id first, then entries whose source is name, and finally entries whose source is past, and sorting entries with the same element and source by their age, oldest first.
Remove any entries in sourced names that have the empty string as their name.
Remove any entries in sourced names that have the same name as an earlier entry in the map.
Return the list of names from sourced names, maintaining their relative order.
The properties exposed in this way must not be enumerable.
When a form
element is indexed for named property
retrieval, the user agent must run the following steps:
Let candidates be a live RadioNodeList
object containing all the listed elements whose form
owner is the form
element that have either an id
attribute or a name
attribute equal to name, with the exception of input
elements whose type
attribute is in the Image
Button state, in tree order.
If candidates is empty, let candidates be a
live RadioNodeList
object containing all the img
elements
that are descendants of the form
element and that have either an id
attribute or a name
attribute equal
to name, in tree order.
If candidates is empty, name is the name of one of
the entries in the form
element's past names map: return the object
associated with name in that map.
If candidates contains more than one node, return candidates and abort these steps.
Otherwise, candidates contains exactly one node. Add a mapping from
name to the node in candidates in the form
element's past names map, replacing the previous entry with the same name, if
any.
Return the node in candidates.
If an element listed in a form
element's past names map changes
form owner, then its entries must be removed from that map.
The submit()
method, when invoked, must submit the form
element from the form
element itself, with the submitted from submit()
method flag set.
The reset()
method, when invoked, must run the
following steps:
If the form
element is marked as locked for reset, then abort these
steps.
Mark the form
element as locked for reset.
Unmark the form
element as locked for reset.
If the checkValidity()
method is
invoked, the user agent must statically validate the constraints of the
form
element, and return true if the constraint validation return a positive
result, and false if it returned a negative result.
If the reportValidity()
method is
invoked, the user agent must interactively validate the constraints of the
form
element, and return true if the constraint validation return a positive
result, and false if it returned a negative result.
This example shows two search forms:
<form action="http://www.google.com/search" method="get"> <label>Google: <input type="search" name="q"></label> <input type="submit" value="Search..."> </form> <form action="http://www.bing.com/search" method="get"> <label>Bing: <input type="search" name="q"></label> <input type="submit" value="Search..."> </form>
label
elementlabel
elements.form
for
interface HTMLLabelElement : HTMLElement { readonly attribute HTMLFormElement? form; attribute DOMString htmlFor; readonly attribute HTMLElement? control; };
The label
element represents a caption in a user interface. The
caption can be associated with a specific form control, known as the
label
element's labeled control, either using the for
attribute, or by putting the form control inside the
label
element itself.
Except where otherwise specified by the following rules, a label
element has no
labeled control.
The for
attribute may be specified to indicate a
form control with which the caption is to be associated. If the attribute is specified, the
attribute's value must be the ID of a labelable element in the same Document
as the
label
element. If the attribute is specified and there is an
element in the Document
whose ID is equal to the
value of the for
attribute, and the first such element is a
labelable element, then that element is the label
element's labeled control.
If the for
attribute is not specified, but the
label
element has a labelable element descendant,
then the first such descendant in tree order is the label
element's
labeled control.
The label
element's exact default presentation and behavior, in particular what
its activation behavior might be, if anything, should match the platform's label
behavior. The activation behavior of a label
element for events targeted
at interactive content descendants of a label
element, and any
descendants of those interactive content descendants, must be to do nothing.
For example, on platforms where clicking a checkbox label checks the checkbox, clicking the
label
in the following snippet could trigger the user agent to run synthetic
click activation steps on the input
element, as if the element itself had
been triggered by the user:
<label><input type=checkbox name=lost> Lost</label>
On other platforms, the behavior might be just to focus the control, or do nothing.
The form
attribute is used to explicitly associate the
label
element with its form owner.
The following example shows three form controls each with a label, two of which have small text showing the right format for users to use.
<p><label>Full name: <input name=fn> <small>Format: First Last</small></label></p> <p><label>Age: <input name=age type=number min=0></label></p> <p><label>Post code: <input name=pc> <small>Format: AB12 3CD</small></label></p>
control
Returns the form control that is associated with this element.
The htmlFor
IDL attribute must
reflect the for
content attribute.
The control
IDL attribute must return the
label
element's labeled control, if any, or null if there isn't one.
The form
IDL attribute is part of the element's forms
API.
labels
Returns a NodeList
of all the label
elements that the form control
is associated with.
Labelable elements have a NodeList
object
associated with them that represents the list of label
elements, in tree
order, whose labeled control is the element in question. The labels
IDL attribute of labelable elements, on getting, must return that
NodeList
object.
input
elementtype
attribute is not in the Hidden state: Interactive content.type
attribute is not in the Hidden state: Listed, labelable, submittable, resettable, and reassociateable form-associated element.type
attribute is in the Hidden state: Listed, submittable, resettable, and reassociateable form-associated element.type
attribute is not in the Hidden state: Palpable content.accept
alt
autocomplete
autofocus
checked
dirname
disabled
form
formaction
formenctype
formmethod
formnovalidate
formtarget
height
list
max
maxlength
min
minlength
multiple
name
pattern
placeholder
readonly
required
size
src
step
type
value
width
title
attribute has special semantics on this element.interface HTMLInputElement : HTMLElement {
attribute DOMString accept;
attribute DOMString alt;
attribute DOMString autocomplete;
attribute boolean autofocus;
attribute boolean defaultChecked;
attribute boolean checked;
attribute DOMString dirName;
attribute boolean disabled;
readonly attribute HTMLFormElement? form;
readonly attribute FileList? files;
attribute DOMString formAction;
attribute DOMString formEnctype;
attribute DOMString formMethod;
attribute boolean formNoValidate;
attribute DOMString formTarget;
attribute unsigned long height;
attribute boolean indeterminate;
readonly attribute HTMLElement? list;
attribute DOMString max;
attribute long maxLength;
attribute DOMString min;
attribute long minLength;
attribute boolean multiple;
attribute DOMString name;
attribute DOMString pattern;
attribute DOMString placeholder;
attribute boolean readOnly;
attribute boolean required;
attribute unsigned long size;
attribute DOMString src;
attribute DOMString step;
attribute DOMString type;
attribute DOMString defaultValue;
[TreatNullAs=EmptyString] attribute DOMString value;
attribute Date? valueAsDate;
attribute unrestricted double valueAsNumber;
attribute unsigned long width;
void stepUp(optional long n = 1);
void stepDown(optional long n = 1);
readonly attribute boolean willValidate;
readonly attribute ValidityState validity;
readonly attribute DOMString validationMessage;
boolean checkValidity();
boolean reportValidity();
void setCustomValidity(DOMString error);
readonly attribute NodeList labels;
void select();
attribute unsigned long selectionStart;
attribute unsigned long selectionEnd;
attribute DOMString selectionDirection;
void setRangeText(DOMString replacement);
void setRangeText(DOMString replacement, unsigned long start, unsigned long end, optional SelectionMode selectionMode = "preserve");
void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction);
};
The input
element represents a typed data field, usually with a form
control to allow the user to edit the data.
The type
attribute controls the data type (and
associated control) of the element. It is an enumerated attribute. The following
table lists the keywords and states for the attribute — the keywords in the left column map
to the states in the cell in the second column on the same row as the keyword.
Keyword | State | Data type | Control type |
---|---|---|---|
hidden
| Hidden | An arbitrary string | n/a |
text
| Text | Text with no line breaks | A text field |
search
| Search | Text with no line breaks | Search field |
tel
| Telephone | Text with no line breaks | A text field |
url
| URL | An absolute URL | A text field |
email
| An e-mail address or list of e-mail addresses | A text field | |
password
| Password | Text with no line breaks (sensitive information) | A text field that obscures data entry |
datetime
| Date and Time | A date and time (year, month, day, hour, minute, second, fraction of a second) with the time zone set to UTC | A date and time control |
date
| Date | A date (year, month, day) with no time zone | A date control |
month
| Month | A date consisting of a year and a month with no time zone | A month control |
week
| Week | A date consisting of a week-year number and a week number with no time zone | A week control |
time
| Time | A time (hour, minute, seconds, fractional seconds) with no time zone | A time control |
datetime-local
| Local Date and Time | A date and time (year, month, day, hour, minute, second, fraction of a second) with no time zone | A date and time control |
number
| Number | A numerical value | A text field or spinner control |
range
| Range | A numerical value, with the extra semantic that the exact value is not important | A slider control or similar |
color
| Color | An sRGB color with 8-bit red, green, and blue components | A color well |
checkbox
| Checkbox | A set of zero or more values from a predefined list | A checkbox |
radio
| Radio Button | An enumerated value | A radio button |
file
| File Upload | Zero or more files each with a MIME type and optionally a file name | A label and a button |
submit
| Submit Button | An enumerated value, with the extra semantic that it must be the last value selected and initiates form submission | A button |
image
| Image Button | A coordinate, relative to a particular image's size, with the extra semantic that it must be the last value selected and initiates form submission | Either a clickable image, or a button |
reset
| Reset Button | n/a | A button |
button
| Button | n/a | A button |
The missing value default is the Text state.
Which of the accept
, alt
, autocomplete
, checked
, dirname
, formaction
, formenctype
, formmethod
, formnovalidate
, formtarget
, height
,
list
, max
, maxlength
, min
, minlength
, multiple
, pattern
, placeholder
, readonly
, required
,
size
, src
, step
, and width
content
attributes, the checked
, files
, valueAsDate
,
valueAsNumber
, and list
IDL attributes, the select()
method, the selectionStart
, selectionEnd
, and selectionDirection
, IDL attributes, the setRangeText()
and setSelectionRange()
methods, the stepUp()
and stepDown()
methods, and the input
and change
events apply to an input
element depends on
the state of its type
attribute. The subsections that define
each type also clearly define in normative "bookkeeping" sections which of these feature apply,
and which do not apply, to each type. The behavior of these features depends on whether
they apply or not, as defined in their various sections (q.v. for content attributes, for APIs, for events).
The following table is non-normative and summarizes which of those content attributes, IDL attributes, methods, and events apply to each state:
Hidden | Text, Search | URL, Telephone | Password | Date and Time, Date, Month, Week, Time | Local Date and Time | Number | Range | Color | Checkbox, Radio Button | File Upload | Submit Button | Image Button | Reset Button, Button | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Content attributes | |||||||||||||||
accept
| · | · | · | · | · | · | · | · | · | · | · | Yes | · | · | · |
alt
| · | · | · | · | · | · | · | · | · | · | · | · | · | Yes | · |
autocomplete
| · | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | · | · | · | · | · |
checked
| · | · | · | · | · | · | · | · | · | · | Yes | · | · | · | · |
dirname
| · | Yes | · | · | · | · | · | · | · | · | · | · | · | · | · |
formaction
| · | · | · | · | · | · | · | · | · | · | · | · | Yes | Yes | · |
formenctype
| · | · | · | · | · | · | · | · | · | · | · | · | Yes | Yes | · |
formmethod
| · | · | · | · | · | · | · | · | · | · | · | · | Yes | Yes | · |
formnovalidate
| · | · | · | · | · | · | · | · | · | · | · | · | Yes | Yes | · |
formtarget
| · | · | · | · | · | · | · | · | · | · | · | · | Yes | Yes | · |
height
| · | · | · | · | · | · | · | · | · | · | · | · | · | Yes | · |
list
| · | Yes | Yes | Yes | · | Yes | Yes | Yes | Yes | Yes | · | · | · | · | · |
max
| · | · | · | · | · | Yes | Yes | Yes | Yes | · | · | · | · | · | · |
maxlength
| · | Yes | Yes | Yes | Yes | · | · | · | · | · | · | · | · | · | · |
min
| · | · | · | · | · | Yes | Yes | Yes | Yes | · | · | · | · | · | · |
minlength
| · | Yes | Yes | Yes | Yes | · | · | · | · | · | · | · | · | · | · |
multiple
| · | · | · | Yes | · | · | · | · | · | · | · | Yes | · | · | · |
pattern
| · | Yes | Yes | Yes | Yes | · | · | · | · | · | · | · | · | · | · |
placeholder
| · | Yes | Yes | Yes | Yes | · | · | Yes | · | · | · | · | · | · | · |
readonly
| · | Yes | Yes | Yes | Yes | Yes | Yes | Yes | · | · | · | · | · | · | · |
required
| · | Yes | Yes | Yes | Yes | Yes | Yes | Yes | · | · | Yes | Yes | · | · | · |
size
| · | Yes | Yes | Yes | Yes | · | · | · | · | · | · | · | · | · | · |
src
| · | · | · | · | · | · | · | · | · | · | · | · | · | Yes | · |
step
| · | · | · | · | · | Yes | Yes | Yes | Yes | · | · | · | · | · | · |
width
| · | · | · | · | · | · | · | · | · | · | · | · | · | Yes | · |
IDL attributes and methods | |||||||||||||||
checked
| · | · | · | · | · | · | · | · | · | · | Yes | · | · | · | · |
files
| · | · | · | · | · | · | · | · | · | · | · | Yes | · | · | · |
value
| default | value | value | value | value | value | value | value | value | value | default/on | filename | default | default | default |
valueAsDate
| · | · | · | · | · | Yes | · | · | · | · | · | · | · | · | · |
valueAsNumber
| · | · | · | · | · | Yes | Yes | Yes | Yes | · | · | · | · | · | · |
list
| · | Yes | Yes | Yes | · | Yes | Yes | Yes | Yes | Yes | · | · | · | · | · |
select()
| · | Yes | Yes | · | Yes | · | · | · | · | · | · | · | · | · | · |
selectionStart
| · | Yes | Yes | · | Yes | · | · | · | · | · | · | · | · | · | · |
selectionEnd
| · | Yes | Yes | · | Yes | · | · | · | · | · | · | · | · | · | · |
selectionDirection
| · | Yes | Yes | · | Yes | · | · | · | · | · | · | · | · | · | · |
setRangeText()
| · | Yes | Yes | · | Yes | · | · | · | · | · | · | · | · | · | · |
setSelectionRange()
| · | Yes | Yes | · | Yes | · | · | · | · | · | · | · | · | · | · |
stepDown()
| · | · | · | · | · | Yes | Yes | Yes | Yes | · | · | · | · | · | · |
stepUp()
| · | · | · | · | · | Yes | Yes | Yes | Yes | · | · | · | · | · | · |
Events | |||||||||||||||
input event
| · | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | · | · | · |
change event
| · | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | · | · | · |
Some states of the type
attribute define a value
sanitization algorithm.
Each input
element has a value, which is
exposed by the value
IDL attribute. Some states define an
algorithm to convert a string to a number, an
algorithm to convert a number to a string, an
algorithm to convert a string to a Date
object, and an algorithm to convert a
Date
object to a string, which are used by max
, min
, step
, valueAsDate
, valueAsNumber
, stepDown()
, and stepUp()
.
Each input
element has a boolean dirty
value flag. The dirty value flag must be
initially set to false when the element is created, and must be set to true whenever the user
interacts with the control in a way that changes the value.
(It is also set to true when the value is programmatically changed, as described in the definition
of the value
IDL attribute.)
The value
content attribute gives the default
value of the input
element. When the value
content attribute is added, set,
or removed, if the control's dirty value flag
is false, the user agent must set the value of the element
to the value of the value
content attribute, if there is
one, or the empty string otherwise, and then run the current value sanitization
algorithm, if one is defined.
Each input
element has a checkedness,
which is exposed by the checked
IDL attribute.
Each input
element has a boolean dirty checkedness flag. When it is true, the
element is said to have a dirty checkedness.
The dirty checkedness flag must be initially
set to false when the element is created, and must be set to true whenever the user interacts with
the control in a way that changes the checkedness.
The checked
content attribute is a
boolean attribute that gives the default checkedness of the input
element. When the checked
content attribute is added,
if the control does not have dirty checkedness, the
user agent must set the checkedness of the element to
true; when the checked
content attribute is removed, if
the control does not have dirty checkedness, the user
agent must set the checkedness of the element to
false.
The reset algorithm for input
elements is to set the dirty value flag and
dirty checkedness flag back to false, set
the value of the element to the value of the value
content attribute, if there is one, or the empty string
otherwise, set the checkedness of the element to true if
the element has a checked
content attribute and false if
it does not, empty the list of selected
files, and then invoke the value sanitization algorithm, if the type
attribute's current state defines one.
Each input
element can be mutable. Except where
otherwise specified, an input
element is always mutable. Similarly, except where otherwise specified, the user
agent should not allow the user to modify the element's value or checkedness.
When an input
element is disabled, it is not mutable.
The readonly
attribute can also in some
cases (e.g. for the Date state, but not the Checkbox state) stop an input
element from
being mutable.
The cloning steps for input
elements
must propagate the value, dirty value flag, checkedness, and dirty checkedness flag from the node being cloned
to the copy.
When an input
element is first created, the element's rendering and behavior must
be set to the rendering and behavior defined for the type
attribute's state, and the value sanitization algorithm, if one is defined for the
type
attribute's state, must be invoked.
When an input
element's type
attribute
changes state, the user agent must run the following steps:
If the previous state of the element's type
attribute
put the value
IDL attribute in the value mode, and the element's value is not the empty string, and the new state of the element's
type
attribute puts the value
IDL attribute in either the default mode or the default/on mode, then set the element's value
content attribute to the element's value.
Otherwise, if the previous state of the element's type
attribute put the value
IDL attribute in any mode other than the value mode, and the
new state of the element's type
attribute puts the value
IDL attribute in the value mode, then set the value of the element to the value of the value
content attribute, if there is one, or the empty string
otherwise, and then set the control's dirty value
flag to false.
Update the element's rendering and behavior to the new state's.
Invoke the value sanitization algorithm, if one is defined for the type
attribute's new state.
The name
attribute represents the element's name.
The dirname
attribute controls how the element's directionality is submitted.
The disabled
attribute is used to make the control non-interactive and to prevent its value from being submitted.
The form
attribute is used to explicitly associate the input
element with its form owner.
The autofocus
attribute controls focus.
The autocomplete
attribute controls how the user agent provides autofill behavior.
The indeterminate
IDL attribute must
initially be set to false. On getting, it must return the last value it was set to. On setting, it
must be set to the new value. It has no effect except for changing the appearance of checkbox controls.
The accept
, alt
, max
,
min
, multiple
, pattern
, placeholder
, required
, size
, src
,
and step
IDL attributes must reflect
the respective content attributes of the same name. The dirName
IDL attribute must reflect the
dirname
content attribute. The readOnly
IDL attribute must reflect the
readonly
content attribute. The defaultChecked
IDL attribute must
reflect the checked
content attribute. The
defaultValue
IDL attribute must
reflect the value
content attribute.
The type
IDL attribute must reflect
the respective content attribute of the same name, limited to only known values.
The maxLength
IDL attribute must reflect
the maxlength
content attribute, limited to only
non-negative numbers. The minLength
IDL attribute must reflect
the minlength
content attribute, limited to only
non-negative numbers.
The IDL attributes width
and height
must return the rendered width and height of
the image, in CSS pixels, if an image is being rendered, and is being rendered to a
visual medium; or else the intrinsic width and height of the image, in CSS pixels, if an image is
available but not being rendered to a visual medium; or else 0,
if no image is available. When the input
element's
type
attribute is not in the Image Button state, then no image is available. [CSS]
On setting, they must act as if they reflected the respective content attributes of the same name.
The willValidate
, validity
, and validationMessage
IDL attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The labels
IDL
attribute provides a list of the element's label
s. The select()
, selectionStart
, selectionEnd
, selectionDirection
, setRangeText()
, and setSelectionRange()
methods and IDL attributes
expose the element's text selection. The autofocus
, disabled
, form
, and name
IDL attributes are part of the element's forms API.
type
attributetype=hidden
)The input
element represents a value that is not intended to be
examined or manipulated by the user.
Constraint validation: If an input
element's type
attribute is in the Hidden state, it is barred from constraint
validation.
If the name
attribute is present and has a value that is a
case-sensitive match for the string "_charset_
", then the element's value
attribute must be omitted.
The
value
IDL attribute applies to this element and is
in mode default.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
autocomplete
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
The input
and change
events do not apply.
type=text
) state and Search state (type=search
)When an input
element's type
attribute is in
the Text state or the Search state, the rules in this section apply.
The input
element represents a one line plain text edit control for
the element's value.
The difference between the Text state and the Search state is primarily stylistic: on platforms where search fields are distinguished from regular text fields, the Search state might result in an appearance consistent with the platform's search fields rather than appearing like a regular text field.
If the element is mutable, its value should be editable by the user. User agents must not allow users to insert "LF" (U+000A) or "CR" (U+000D) characters into the element's value.
If the element is mutable, the user agent should allow the user to change the writing direction of the element, setting it either to a left-to-right writing direction or a right-to-left writing direction. If the user does so, the user agent must then run the following steps:
Set the element's dir
attribute to "ltr
" if the user selected a left-to-right writing direction, and
"rtl
" if the user selected a right-to-left writing
direction.
Queue a task to fire a simple event that bubbles named input
at the input
element.
The value
attribute, if specified, must have a value that
contains no "LF" (U+000A) or "CR" (U+000D) characters.
The value sanitization algorithm is as follows: Strip line breaks from the value.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
dirname
,
list
,
maxlength
,
minlength
,
pattern
,
placeholder
,
readonly
,
required
, and
size
content attributes;
list
,
selectionStart
,
selectionEnd
,
selectionDirection
, and
value
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
max
,
min
,
multiple
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
type=tel
)The input
element represents a control for editing a telephone number
given in the element's value.
If the element is mutable, its value should be editable by the user. User agents may change the spacing and, with care, the punctuation of values that the user enters. User agents must not allow users to insert "LF" (U+000A) or "CR" (U+000D) characters into the element's value.
The value
attribute, if specified, must have a value that
contains no "LF" (U+000A) or "CR" (U+000D) characters.
The value sanitization algorithm is as follows: Strip line breaks from the value.
Unlike the URL and E-mail types, the Telephone type does not enforce a particular syntax. This is
intentional; in practice, telephone number fields tend to be free-form fields, because there are a
wide variety of valid phone numbers. Systems that need to enforce a particular format are
encouraged to use the pattern
attribute or the setCustomValidity()
method to hook into the client-side
validation mechanism.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
maxlength
,
minlength
,
pattern
,
placeholder
,
readonly
,
required
, and
size
content attributes;
list
,
selectionStart
,
selectionEnd
,
selectionDirection
, and
value
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
max
,
min
,
multiple
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
type=url
)The input
element represents a control for editing a single
absolute URL given in the element's value.
If the element is mutable, the user agent should allow the user to change the URL represented by its value. User agents may allow the user to set the value to a string that is not a valid absolute URL, but may also or instead automatically escape characters entered by the user so that the value is always a valid absolute URL (even if that isn't the actual value seen and edited by the user in the interface). User agents should allow the user to set the value to the empty string. User agents must not allow users to insert "LF" (U+000A) or "CR" (U+000D) characters into the value.
The value
attribute, if specified and not empty, must
have a value that is a valid URL potentially surrounded by spaces that is also an
absolute URL.
The value sanitization algorithm is as follows: Strip line breaks from the value, then strip leading and trailing whitespace from the value.
Constraint validation: While the value of the element is neither the empty string nor a valid absolute URL, the element is suffering from a type mismatch.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
maxlength
,
minlength
,
pattern
,
placeholder
,
readonly
,
required
, and
size
content attributes;
list
,
selectionStart
,
selectionEnd
,
selectionDirection
, and
value
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
max
,
min
,
multiple
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
If a document contained the following markup:
<input type="url" name="location" list="urls"> <datalist id="urls"> <option label="MIME: Format of Internet Message Bodies" value="http://tools.ietf.org/html/rfc2045"> <option label="HTML 4.01 Specification" value="http://www.w3.org/TR/html4/"> <option label="Form Controls" value="http://www.w3.org/TR/xforms/slice8.html#ui-commonelems-hint"> <option label="Scalable Vector Graphics (SVG) 1.1 Specification" value="http://www.w3.org/TR/SVG/"> <option label="Feature Sets - SVG 1.1 - 20030114" value="http://www.w3.org/TR/SVG/feature.html"> <option label="The Single UNIX Specification, Version 3" value="http://www.unix-systems.org/version3/"> </datalist>
...and the user had typed "www.w3", and the user agent had also found that the user
had visited http://www.w3.org/Consortium/#membership
and
http://www.w3.org/TR/XForms/
in the recent past, then the rendering might look like
this:
The first four URLs in this sample consist of the four URLs in the author-specified list that match the text the user has entered, sorted in some UA-defined manner (maybe by how frequently the user refers to those URLs). Note how the UA is using the knowledge that the values are URLs to allow the user to omit the scheme part and perform intelligent matching on the domain name.
The last two URLs (and probably many more, given the scrollbar's indications of more values being available) are the matches from the user agent's session history data. This data is not made available to the page DOM. In this particular case, the UA has no titles to provide for those values.
type=email
)How the E-mail state operates depends on whether the
multiple
attribute is specified or not.
multiple
attribute is not specified on the
elementThe input
element represents a control for editing an e-mail
address given in the element's value.
If the element is mutable, the user agent should allow the user to change the e-mail address represented by its value. User agents may allow the user to set the value to a string that is not a valid e-mail address. The user agent should act in a manner consistent with expecting the user to provide a single e-mail address. User agents should allow the user to set the value to the empty string. User agents must not allow users to insert "LF" (U+000A) or "CR" (U+000D) characters into the value. User agents may transform the value for display and editing; in particular, user agents should convert punycode in the value to IDN in the display and vice versa.
Constraint validation: While the user interface is representing input that the user agent cannot convert to punycode, the control is suffering from bad input.
The value
attribute, if specified and not empty, must
have a value that is a single valid e-mail address.
The value sanitization algorithm is as follows: Strip line breaks from the value, then strip leading and trailing whitespace from the value.
When the multiple
attribute is removed, the user
agent must run the value sanitization algorithm.
Constraint validation: While the value of the element is neither the empty string nor a single valid e-mail address, the element is suffering from a type mismatch.
multiple
attribute is specified on
the elementThe element's values are the result of splitting on commas the element's value.
The input
element represents a control for adding, removing, and
editing the e-mail addresses given in the element's values.
If the element is mutable, the user agent should allow the user to add, remove, and edit the e-mail addresses represented by its values. User agents may allow the user to set any individual value in the list of values to a string that is not a valid e-mail address, but must not allow users to set any individual value to a string containing "," (U+002C), "LF" (U+000A), or "CR" (U+000D) characters. User agents should allow the user to remove all the addresses in the element's values. User agents may transform the values for display and editing; in particular, user agents should convert punycode in the value to IDN in the display and vice versa.
Constraint validation: While the user interface describes a situation where an individual value contains a "," (U+002C) or is representing input that the user agent cannot convert to punycode, the control is suffering from bad input.
Whenever the user changes the element's values, the user agent must run the following steps:
Let latest values be a copy of the element's values.
Strip leading and trailing whitespace from each value in latest values.
Let the element's value be the result of concatenating all the values in latest values, separating each value from the next by a single "," (U+002C) character, maintaining the list's order.
The value
attribute, if specified, must have a value
that is a valid e-mail address list.
The value sanitization algorithm is as follows:
Split on commas the element's value, strip leading and trailing whitespace from each resulting token, if any, and let the element's values be the (possibly empty) resulting list of (possibly empty) tokens, maintaining the original order.
Let the element's value be the result of concatenating the element's values, separating each value from the next by a single "," (U+002C) character, maintaining the list's order.
When the multiple
attribute is set, the user agent
must run the value sanitization algorithm.
Constraint validation: While the value of the element is not a valid e-mail address list, the element is suffering from a type mismatch.
A valid e-mail address is a string that matches the email
production of the following ABNF, the character set for which is Unicode. This ABNF implements the
extensions described in RFC 1123. [ABNF] [RFC5322] [RFC1034] [RFC1123]
email = 1*( atext / "." ) "@" label *( "." label ) label = let-dig [ [ ldh-str ] let-dig ] ; limited to a length of 63 characters by RFC 1034 section 3.5 atext = < as defined in RFC 5322 section 3.2.3 > let-dig = < as defined in RFC 1034 section 3.5 > ldh-str = < as defined in RFC 1034 section 3.5 >
This requirement is a willful violation of RFC 5322, which defines a syntax for e-mail addresses that is simultaneously too strict (before the "@" character), too vague (after the "@" character), and too lax (allowing comments, whitespace characters, and quoted strings in manners unfamiliar to most users) to be of practical use here.
The following JavaScript- and Perl-compatible regular expression is an implementation of the above definition.
/^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/
A valid e-mail address list is a set of comma-separated tokens, where each token is itself a valid e-mail address. To obtain the list of tokens from a valid e-mail address list, and implementation must split the string on commas.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
, and
size
content attributes;
list
and
value
IDL attributes.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
max
,
min
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
and
stepUp()
methods.
type=password
)The input
element represents a one line plain text edit control for
the element's value. The user agent should obscure the value
so that people other than the user cannot see it.
If the element is mutable, its value should be editable by the user. User agents must not allow users to insert "LF" (U+000A) or "CR" (U+000D) characters into the value.
The value
attribute, if specified, must have a value that
contains no "LF" (U+000A) or "CR" (U+000D) characters.
The value sanitization algorithm is as follows: Strip line breaks from the value.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
maxlength
,
minlength
,
pattern
,
placeholder
,
readonly
,
required
, and
size
content attributes;
selectionStart
,
selectionEnd
,
selectionDirection
, and
value
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
min
,
multiple
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
list
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
type=datetime
)When an input
element's type
attribute is in
the Date and Time state, the rules in this section
apply.
The input
element represents a control for setting the element's
value to a string representing a specific global date and time. User agents may display
the date and time in whatever time zone is appropriate for the user.
If the element is mutable, the user agent should allow the user to change the global date and time represented by its value, as obtained by parsing a global date and time from it. User agents must not allow the user to set the value to a non-empty string that is not a valid normalized forced-UTC global date and time string, though user agents may allow the user to set and view the time in another time zone and silently translate the time to and from the UTC time zone in the value. If the user agent provides a user interface for selecting a global date and time, then the value must be set to a valid normalized forced-UTC global date and time string representing the user's selection. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid normalized forced-UTC global date and time string, the control is suffering from bad input.
See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.
The value
attribute, if specified and not empty, must
have a value that is a valid global date and time string.
The value sanitization algorithm is as follows: If the value of the element is a valid global date and time string, then adjust the time so that the value represents the same point in time but expressed in the UTC time zone as a valid normalized forced-UTC global date and time string, otherwise, set it to the empty string instead.
The min
attribute, if specified, must have a value that is
a valid global date and time string. The max
attribute, if specified, must have a value that is a valid global date and time
string.
The step
attribute is expressed in seconds. The step scale factor is 1000 (which
converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest global date and time for which the element would not suffer from a step mismatch.
The algorithm to convert a string to a
number, given a string input, is as follows: If parsing a global date and time from input results in an error, then return an error; otherwise, return the number of
milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the
value "1970-01-01T00:00:00.0Z
") to the parsed global date and time, ignoring leap seconds.
The algorithm to convert a number to a
string, given a number input, is as follows: Return a
valid normalized forced-UTC global date and time string that represents the global date and time that is input
milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value
"1970-01-01T00:00:00.0Z
").
The algorithm to convert a string to a
Date
object, given a string input, is as follows:
If parsing a global date and time from
input results in an error, then return an error; otherwise, return a new Date
object representing the parsed global date and time, expressed in UTC.
The algorithm to convert a
Date
object to a string, given a Date
object input, is as follows: Return a valid normalized forced-UTC global
date and time string that represents the global date and
time that is represented by input.
The Date and Time state (and other date- and time-related states described in subsequent sections) is not intended for the entry of values for which a precise date and time relative to the contemporary calendar cannot be established. For example, it would be inappropriate for the entry of times like "one millisecond after the big bang", "the early part of the Jurassic period", or "a winter around 250 BCE".
For the input of dates before the introduction of the Gregorian calendar, authors are
encouraged to not use the Date and Time state (and
the other date- and time-related states described in subsequent sections), as user agents are not
required to support converting dates and times from earlier periods to the Gregorian calendar,
and asking users to do so manually puts an undue burden on users. (This is complicated by the
manner in which the Gregorian calendar was phased in, which occurred at different times in
different countries, ranging from partway through the 16th century all the way to early in the
20th.) Instead, authors are encouraged to provide fine-grained input controls using the
select
element and input
elements with the Number state.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
max
,
min
,
readonly
,
required
, and
step
content attributes;
list
,
value
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
selectionStart
,
selectionEnd
, and
selectionDirection
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
The following fragment shows part of a calendar application. A user can specify a date and time for a meeting (in his local time zone, probably, though the user agent can allow the user to change that), and since the submitted data includes the time-zone offset, the application can ensure that the meeting is shown at the correct time regardless of the time zones used by all the participants.
<fieldset> <legend>Add Meeting</legend> <p><label>Meeting name: <input type=text name="meeting.label"></label> <p><label>Meeting time: <input type=datetime name="meeting.start"></label> </fieldset>
Had the application used the datetime-local
type instead, the calendar
application would have also had to explicitly determine which time zone the user intended.
For events where the precise time is to vary as the user travels (e.g. "celebrate the new
year!"), and for recurring events that are to stay at the same time for a specific geographic
location even though that location may go in and out of daylight savings time (e.g. "bring the
kid to school"), the datetime-local
type
combined with a select
element (or other similar control) to pick the specific
geographic location to which to anchor the time would be more appropriate.
type=date
)The input
element represents a control for setting the element's
value to a string representing a specific date.
If the element is mutable, the user agent should allow the user to change the date represented by its value, as obtained by parsing a date from it. User agents must not allow the user to set the value to a non-empty string that is not a valid date string. If the user agent provides a user interface for selecting a date, then the value must be set to a valid date string representing the user's selection. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid date string, the control is suffering from bad input.
See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.
The value
attribute, if specified and not empty, must
have a value that is a valid date string.
The value sanitization algorithm is as follows: If the value of the element is not a valid date string, then set it to the empty string instead.
The min
attribute, if specified, must have a value that is
a valid date string. The max
attribute, if
specified, must have a value that is a valid date string.
The step
attribute is expressed in days. The step scale factor is 86,400,000
(which converts the days to milliseconds, as used in the other algorithms). The default step is 1 day.
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest date for which the element would not suffer from a step mismatch.
The algorithm to convert a string to a
number, given a string input, is as follows: If parsing a date from input results in an
error, then return an error; otherwise, return the number of milliseconds elapsed from midnight
UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z
") to midnight UTC on the morning of the parsed date, ignoring leap seconds.
The algorithm to convert a number to a
string, given a number input, is as follows: Return a
valid date string that represents the date that, in
UTC, is current input milliseconds after midnight UTC on the morning of
1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z
").
The algorithm to convert a string to a
Date
object, given a string input, is as follows:
If parsing a date from input results
in an error, then return an error; otherwise, return a new
Date
object representing midnight UTC on the morning of the parsed date.
The algorithm to convert a
Date
object to a string, given a Date
object input, is as follows: Return a valid date string that
represents the date current at the time represented by input in the UTC time zone.
See the note on historical dates in the Date and Time state section.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
max
,
min
,
readonly
,
required
, and
step
content attributes;
list
,
value
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
selectionStart
,
selectionEnd
, and
selectionDirection
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
type=month
)The input
element represents a control for setting the element's
value to a string representing a specific month.
If the element is mutable, the user agent should allow the user to change the month represented by its value, as obtained by parsing a month from it. User agents must not allow the user to set the value to a non-empty string that is not a valid month string. If the user agent provides a user interface for selecting a month, then the value must be set to a valid month string representing the user's selection. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid month string, the control is suffering from bad input.
See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.
The value
attribute, if specified and not empty, must
have a value that is a valid month string.
The value sanitization algorithm is as follows: If the value of the element is not a valid month string, then set it to the empty string instead.
The min
attribute, if specified, must have a value that is
a valid month string. The max
attribute, if
specified, must have a value that is a valid month string.
The step
attribute is expressed in months. The step scale factor is 1 (there is no
conversion needed as the algorithms use months). The default step is 1 month.
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest month for which the element would not suffer from a step mismatch.
The algorithm to convert a string to a number, given a string input, is as follows: If parsing a month from input results in an error, then return an error; otherwise, return the number of months between January 1970 and the parsed month.
The algorithm to convert a number to a string, given a number input, is as follows: Return a valid month string that represents the month that has input months between it and January 1970.
The algorithm to convert a string to a
Date
object, given a string input, is as follows:
If parsing a month from input
results in an error, then return an error; otherwise, return a
new Date
object representing midnight UTC on the morning of the first day of
the parsed month.
The algorithm to convert a
Date
object to a string, given a Date
object input, is as follows: Return a valid month string that
represents the month current at the time represented by input in the UTC time zone.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
max
,
min
,
readonly
,
required
, and
step
content attributes;
list
,
value
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
selectionStart
,
selectionEnd
, and
selectionDirection
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
type=week
)The input
element represents a control for setting the element's
value to a string representing a specific week.
If the element is mutable, the user agent should allow the user to change the week represented by its value, as obtained by parsing a week from it. User agents must not allow the user to set the value to a non-empty string that is not a valid week string. If the user agent provides a user interface for selecting a week, then the value must be set to a valid week string representing the user's selection. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid week string, the control is suffering from bad input.
See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.
The value
attribute, if specified and not empty, must
have a value that is a valid week string.
The value sanitization algorithm is as follows: If the value of the element is not a valid week string, then set it to the empty string instead.
The min
attribute, if specified, must have a value that is
a valid week string. The max
attribute, if
specified, must have a value that is a valid week string.
The step
attribute is expressed in weeks. The step scale factor is 604,800,000
(which converts the weeks to milliseconds, as used in the other algorithms). The default step is 1 week. The default step base is −259,200,000 (the start
of week 1970-W01).
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest week for which the element would not suffer from a step mismatch.
The algorithm to convert a string to a
number, given a string input, is as follows: If parsing a week string from input results in
an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight
UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z
") to midnight UTC on the morning of the Monday of the
parsed week, ignoring leap seconds.
The algorithm to convert a number to a
string, given a number input, is as follows: Return a
valid week string that represents the week that, in
UTC, is current input milliseconds after midnight UTC on the morning of
1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z
").
The algorithm to convert a string to a
Date
object, given a string input, is as follows:
If parsing a week from input results
in an error, then return an error; otherwise, return a new
Date
object representing midnight UTC on the morning of the Monday of the
parsed week.
The algorithm to convert a
Date
object to a string, given a Date
object input, is as follows: Return a valid week string that
represents the week current at the time represented by input in the UTC time zone.
The following common input
element content attributes, IDL attributes, and
methods apply to the element:
autocomplete
,
list
,
max
,
min
,
readonly
,
required
, and
step
content attributes;
list
,
value
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
selectionStart
,
selectionEnd
, and
selectionDirection
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
type=time
)The input
element represents a control for setting the element's
value to a string representing a specific time.
If the element is mutable, the user agent should allow the user to change the time represented by its value, as obtained by parsing a time from it. User agents must not allow the user to set the value to a non-empty string that is not a valid time string. If the user agent provides a user interface for selecting a time, then the value must be set to a valid time string representing the user's selection. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid time string, the control is suffering from bad input.
See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.
The value
attribute, if specified and not empty, must
have a value that is a valid time string.
The value sanitization algorithm is as follows: If the value of the element is not a valid time string, then set it to the empty string instead.
The form control has a periodic domain.
The min
attribute, if specified, must have a value that is
a valid time string. The max
attribute, if
specified, must have a value that is a valid time string.
The step
attribute is expressed in seconds. The step scale factor is 1000 (which
converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest time for which the element would not suffer from a step mismatch.
The algorithm to convert a string to a number, given a string input, is as follows: If parsing a time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight to the parsed time on a day with no time changes.
The algorithm to convert a number to a string, given a number input, is as follows: Return a valid time string that represents the time that is input milliseconds after midnight on a day with no time changes.
The algorithm to convert a string to a
Date
object, given a string input, is as follows:
If parsing a time from input results
in an error, then return an error; otherwise, return a new
Date
object representing the parsed time in
UTC on 1970-01-01.
The algorithm to convert a
Date
object to a string, given a Date
object input, is as follows: Return a valid time string that
represents the UTC time component that is represented by input.
The following common input
element content attributes, IDL attributes, and
methods apply to the element:
autocomplete
,
list
,
max
,
min
,
readonly
,
required
, and
step
content attributes;
list
,
value
,
valueAsDate
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
selectionStart
,
selectionEnd
, and
selectionDirection
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
type=datetime-local
)When an input
element's type
attribute is in
the Local Date and Time state, the rules in
this section apply.
The input
element represents a control for setting the element's
value to a string representing a local date and time, with no time-zone offset
information.
If the element is mutable, the user agent should allow the user to change the date and time represented by its value, as obtained by parsing a date and time from it. User agents must not allow the user to set the value to a non-empty string that is not a valid normalized local date and time string. If the user agent provides a user interface for selecting a local date and time, then the value must be set to a valid normalized local date and time string representing the user's selection. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid normalized local date and time string, the control is suffering from bad input.
See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.
The value
attribute, if specified and not empty, must
have a value that is a valid local date and time string.
The value sanitization algorithm is as follows: If the value of the element is a valid local date and time string, then set it to a valid normalized local date and time string representing the same date and time; otherwise, set it to the empty string instead.
The min
attribute, if specified, must have a value that is
a valid local date and time string. The max
attribute, if specified, must have a value that is a valid local date and time
string.
The step
attribute is expressed in seconds. The step scale factor is 1000 (which
converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest local date and time for which the element would not suffer from a step mismatch.
The algorithm to convert a string to a
number, given a string input, is as follows: If parsing a date and time from input results in an error, then return an error; otherwise, return the number of
milliseconds elapsed from midnight on the morning of 1970-01-01 (the time represented by the value
"1970-01-01T00:00:00.0
") to the parsed local date and time, ignoring leap seconds.
The algorithm to convert a number to a
string, given a number input, is as follows: Return a
valid normalized local date and time string that represents the date and time that is
input milliseconds after midnight on the morning of 1970-01-01 (the time
represented by the value "1970-01-01T00:00:00.0
").
See the note on historical dates in the Date and Time state section.
The following common input
element content
attributes, IDL attributes, and methods apply to the element:
autocomplete
,
list
,
max
,
min
,
readonly
,
required
, and
step
content attributes;
list
,
value
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is
in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not
apply to the element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the
element:
checked
,
files
,
selectionStart
,
selectionEnd
,
selectionDirection
, and
valueAsDate
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
The following example shows part of a flight booking application. The application uses an
input
element with its type
attribute set to
datetime-local
, and it then interprets the
given date and time in the time zone of the selected airport.
<fieldset> <legend>Destination</legend> <p><label>Airport: <input type=text name=to list=airports></label></p> <p><label>Departure time: <input type=datetime-local name=totime step=3600></label></p> </fieldset> <datalist id=airports> <option value=ATL label="Atlanta"> <option value=MEM label="Memphis"> <option value=LHR label="London Heathrow"> <option value=LAX label="Los Angeles"> <option value=FRA label="Frankfurt"> </datalist>
If the application instead used the datetime
type, then the user would have to work out the time-zone conversions himself, which is clearly
not a good user experience!
type=number
)The input
element represents a control for setting the element's
value to a string representing a number.
If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating-point number values to it. User agents must not allow the user to set the value to a non-empty string that is not a valid floating-point number. If the user agent provides a user interface for selecting a number, then the value must be set to the best representation of the number representing the user's selection as a floating-point number. User agents should allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid floating-point number, the control is suffering from bad input.
This specification does not define what user interface user agents are to use; user agent vendors are encouraged to consider what would best serve their users' needs. For example, a user agent in Persian or Arabic markets might support Persian and Arabic numeric input (converting it to the format required for submission as described above). Similarly, a user agent designed for Romans might display the value in Roman numerals rather than in decimal; or (more realistically) a user agent designed for the French market might display the value with apostrophes between thousands and commas before the decimals, and allow the user to enter a value in that manner, internally converting it to the submission format described above.
The value
attribute, if specified and not empty, must
have a value that is a valid floating-point number.
The value sanitization algorithm is as follows: If the value of the element is not a valid floating-point number, then set it to the empty string instead.
The min
attribute, if specified, must have a value that is
a valid floating-point number. The max
attribute,
if specified, must have a value that is a valid floating-point number.
The step scale factor is 1. The default step is 1 (allowing only integers to be selected by the user, unless the step base has a non-integer value).
When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest number for which the element would not suffer from a step mismatch. If there are two such numbers, user agents are encouraged to pick the one nearest positive infinity.
The algorithm to convert a string to a number, given a string input, is as follows: If applying the rules for parsing floating-point number values to input results in an error, then return an error; otherwise, return the resulting number.
The algorithm to convert a number to a string, given a number input, is as follows: Return a valid floating-point number that represents input.
The following common input
element content attributes, IDL attributes, and
methods apply to the element:
autocomplete
,
list
,
max
,
min
,
placeholder
,
readonly
,
required
, and
step
content attributes;
list
,
value
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
selectionStart
,
selectionEnd
,
selectionDirection
, and
valueAsDate
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
Here is an example of using a numeric input control:
<label>How much do you want to charge? $<input type=number min=0 step=0.01 name=price></label>
As described above, a user agent might support numeric input in the user's local format, converting it to the format required for submission as described above. This might include handling grouping separators (as in "872,000,000,000") and various decimal separators (such as "3,99" vs "3.99") or using local digits (such as those in Arabic, Devanagari, Persian, and Thai).
The type=number
state is not appropriate for input that
happens to only consist of numbers but isn't strictly speaking a number. For example, it would be
inappropriate for credit card numbers or US postal codes. A simple way of determining whether to
use type=number
is to consider whether it would make sense for the input
control to have a spinbox interface (e.g. with "up" and "down" arrows). Getting a credit card
number wrong by 1 in the last digit isn't a minor mistake, it's as wrong as getting every digit
incorrect. So it would not make sense for the user to select a credit card number using "up" and
"down" buttons. When a spinbox interface is not appropriate, type=text
is
probably the right choice (possibly with a pattern
attribute).
type=range
)The input
element represents a control for setting the element's
value to a string representing a number, but with the caveat
that the exact value is not important, letting UAs provide a simpler interface than they do for
the Number state.
In this state, the range and step constraints are enforced even during user input, and there is no way to set the value to the empty string.
If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating-point number values to it. User agents must not allow the user to set the value to a string that is not a valid floating-point number. If the user agent provides a user interface for selecting a number, then the value must be set to a best representation of the number representing the user's selection as a floating-point number. User agents must not allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid floating-point number, the control is suffering from bad input.
The value
attribute, if specified, must have a value that
is a valid floating-point number.
The value sanitization algorithm is as follows: If the value of the element is not a valid floating-point number, then set it to a valid floating-point number that represents the default value.
The min
attribute, if specified, must have a value that is
a valid floating-point number. The default
minimum is 0. The max
attribute, if specified, must
have a value that is a valid floating-point number. The default maximum is 100.
The default value is the minimum plus half the difference between the minimum and the maximum, unless the maximum is less than the minimum, in which case the default value is the minimum.
When the element is suffering from an underflow, the user agent must set the element's value to a valid floating-point number that represents the minimum.
When the element is suffering from an overflow, if the maximum is not less than the minimum, the user agent must set the element's value to a valid floating-point number that represents the maximum.
The step scale factor is
1. The default step is 1 (allowing only
integers, unless the min
attribute has a non-integer
value).
When the element is suffering from a step mismatch, the user agent must round the element's value to the nearest number for which the element would not suffer from a step mismatch, and which is greater than or equal to the minimum, and, if the maximum is not less than the minimum, which is less than or equal to the maximum, if there is a number that matches these constraints. If two numbers match these constraints, then user agents must use the one nearest to positive infinity.
For example, the markup
<input type="range" min=0 max=100 step=20 value=50>
results in a range control whose initial value is 60.
The algorithm to convert a string to a number, given a string input, is as follows: If applying the rules for parsing floating-point number values to input results in an error, then return an error; otherwise, return the resulting number.
The algorithm to convert a number to a string, given a number input, is as follows: Return a valid floating-point number that represents input.
The following common input
element content attributes, IDL attributes, and
methods apply to the element:
autocomplete
,
list
,
max
,
min
, and
step
content attributes;
list
,
value
, and
valueAsNumber
IDL attributes;
stepDown()
and
stepUp()
methods.
The value
IDL attribute is in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
maxlength
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
,
src
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
selectionStart
,
selectionEnd
,
selectionDirection
, and
valueAsDate
IDL attributes;
select()
,
setRangeText()
, and
setSelectionRange()
methods.
Here is an example of a range control using an autocomplete list with the list
attribute. This could be useful if there are values along the
full range of the control that are especially important, such as preconfigured light levels or
typical speed limits in a range control used as a speed control. The following markup
fragment:
<input type="range" min="-100" max="100" value="0" step="10" name="power" list="powers">
<datalist id="powers">
<option value="0">
<option value="-30">
<option value="30">
<option value="++50">
</datalist>
...with the following style sheet applied:
input { height: 75px; width: 49px; background: #D5CCBB; color: black; }
...might render as:
Note how the UA determined the orientation of the control from the ratio of the
style-sheet-specified height and width properties. The colors were similarly derived from the
style sheet. The tick marks, however, were derived from the markup. In particular, the step
attribute has not affected the placement of tick marks, the
UA deciding to only use the author-specified completion values and then adding longer tick marks
at the extremes.
Note also how the invalid value ++50
was completely ignored.
For another example, consider the following markup fragment:
<input name=x type=range min=100 max=700 step=9.09090909 value=509.090909>
A user agent could display in a variety of ways, for instance:
Or, alternatively, for instance:
The user agent could pick which one to display based on the dimensions given in the style sheet. This would allow it to maintain the same resolution for the tick marks, despite the differences in width.
Finally, here is an example of a range control with two labeled values:
<input type="range" name="a" list="a-values"> <datalist id="a-values"> <option value="10" label="Low"> <option value="90" label="High"> </datalist>
With styles that make the control draw vertically, it might look as follows:
type=color
)The input
element represents a color well control, for setting the
element's value to a string representing a simple
color.
In this state, there is always a color picked, and there is no way to set the value to the empty string.
If the element is mutable, the user agent should allow the user to change the color represented by its value, as obtained from applying the rules for parsing simple color values to it. User agents must not allow the user to set the value to a string that is not a valid lowercase simple color. If the user agent provides a user interface for selecting a color, then the value must be set to the result of using the rules for serializing simple color values to the user's selection. User agents must not allow the user to set the value to the empty string.
Constraint validation: While the user interface describes input that the user agent cannot convert to a valid lowercase simple color, the control is suffering from bad input.
The value
attribute, if specified and not empty, must
have a value that is a valid simple color.
The value sanitization algorithm is as follows: If the value of the element is a valid simple color, then
set it to the value of the element converted to ASCII
lowercase; otherwise, set it to the string "#000000
".
The following common input
element content attributes and IDL attributes apply to the element:
autocomplete
and
list
content attributes;
list
and
value
IDL attributes.
The value
IDL attribute is in mode value.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
type=checkbox
)The input
element represents a two-state control that represents the
element's checkedness state. If the element's checkedness state is true, the control represents a positive
selection, and if it is false, a negative selection. If the element's indeterminate
IDL attribute is set to true, then the
control's selection should be obscured as if the control was in a third, indeterminate, state.
The control is never a true tri-state control, even if the element's indeterminate
IDL attribute is set to true. The indeterminate
IDL attribute only gives the appearance of a
third state.
If the element is mutable, then: The pre-click
activation steps consist of setting the element's checkedness to its opposite value (i.e. true if it is false,
false if it is true), and of setting the element's indeterminate
IDL attribute to false. The canceled
activation steps consist of setting the checkedness
and the element's indeterminate
IDL attribute back to
the values they had before the pre-click activation steps were run. The
activation behavior is to fire a simple event that bubbles named input
at the element and then fire a simple event that bubbles named change
at the element.
If the element is not mutable, it has no activation behavior.
Constraint validation: If the element is required and its checkedness is false, then the element is suffering from being missing.
indeterminate
[ = value ]When set, overrides the rendering of checkbox controls so that the current value is not visible.
The following common input
element content attributes and IDL attributes apply to the element:
checked
, and
required
content attributes;
checked
and
value
IDL attributes.
The value
IDL attribute is in mode default/on.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
autocomplete
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the element:
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
type=radio
)When an input
element's type
attribute is in
the Radio Button state, the rules in this section
apply.
The input
element represents a control that, when used in conjunction
with other input
elements, forms a radio button group in which only one
control can have its checkedness state set to true. If the
element's checkedness state is true, the control
represents the selected control in the group, and if it is false, it indicates a control in the
group that is not selected.
The radio button group that contains an input
element a also contains all the other input
elements b
that fulfill all of the following conditions:
input
element b's type
attribute is in the Radio
Button state.name
attribute, their name
attributes are not empty, and the value of a's name
attribute is a compatibility
caseless match for the value of b's name
attribute.A document must not contain an input
element whose radio button group
contains only that element.
When any of the following phenomena occur, if the element's checkedness state is true after the occurrence, the checkedness state of all the other elements in the same radio button group must be set to false:
name
attribute is set, changed, or
removed.If the element is mutable, then: The pre-click
activation steps consist of setting the element's checkedness to true. The canceled activation steps
consist of setting the element's checkedness to false. The
activation behavior is to fire a simple event that bubbles named input
at the element and then fire a simple event that bubbles named change
at the element. .
If the element is not mutable, it has no activation behavior.
Constraint validation: If an element in the radio button group is required, and all of the input
elements in the
radio button group have a checkedness that is
false, then the element is suffering from being missing.
If none of the radio buttons in a radio button group are checked when they are inserted into the document, then they will all be initially unchecked in the interface, until such time as one of them is checked (either by the user or by script).
The following common input
element content attributes and IDL attributes apply to the element:
checked
and
required
content attributes;
checked
and
value
IDL attributes.
The value
IDL attribute is in mode default/on.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
autocomplete
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the element:
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
type=file
)When an input
element's type
attribute is in
the File Upload state, the rules in this section
apply.
The input
element represents a list of selected files, each file consisting of a file
name, a file type, and a file body (the contents of the file).
File names must not contain path components, even in the case that a user has selected an entire directory hierarchy or multiple files with the same name from different directories. Path components are those separated by "\" (U+005C) character characters.
Unless the multiple
attribute is set, there must be
no more than one file in the list of selected
files.
If the element is mutable, then the element's activation behavior is to run the following steps:
If the algorithm is not allowed to show a popup, then abort these steps without doing anything else.
Return, but continue running these steps asynchronously.
Optionally, wait until any prior execution of this algorithm has terminated.
Display a prompt to the user requesting that the user specify some files. If the multiple
attribute is not set, there must be no more than one
file selected; otherwise, any number may be selected. Files can be from the filesystem or created
on the fly, e.g. a picture taken from a camera connected to the user's device.
Wait for the user to have made their selection.
Queue a task to first update the element's selected files so that it represents the user's
selection, then fire a simple event that bubbles named input
at the input
element, and finally fire a
simple event that bubbles named change
at the
input
element.
If the element is mutable, the user agent should allow the
user to change the files on the list in other ways also, e.g. adding or removing files by
drag-and-drop. When the user does so, the user agent must queue a task to first
update the element's selected files so that
it represents the user's new selection, then fire a simple event that bubbles named
input
at the input
element, and finally fire
a simple event that bubbles named change
at the
input
element.
If the element is not mutable, it has no activation behavior and the user agent must not allow the user to change the element's selection.
Constraint validation: If the element is required and the list of selected files is empty, then the element is suffering from being missing.
The accept
attribute may be specified to
provide user agents with a hint of what file types will be accepted.
If specified, the attribute must consist of a set of comma-separated tokens, each of which must be an ASCII case-insensitive match for one of the following:
audio/*
video/*
image/*
The tokens must not be ASCII case-insensitive matches for any of the other tokens (i.e. duplicates are not allowed). To obtain the list of tokens from the attribute, the user agent must split the attribute value on commas.
User agents may use the value of this attribute to display a more appropriate user interface
than a generic file picker. For instance, given the value image/*
, a user
agent could offer the user the option of using a local camera or selecting a photograph from their
photo collection; given the value audio/*
, a user agent could offer the user
the option of recording a clip using a headset microphone.
User agents should prevent the user from selecting files that are not accepted by one (or more) of these tokens.
Authors are encouraged to specify both any MIME types and any corresponding extensions when looking for data in a specific format.
For example, consider an application that converts Microsoft Word documents to Open Document Format files. Since Microsoft Word documents are described with a wide variety of MIME types and extensions, the site can list several, as follows:
<input type="file" accept=".doc,.docx,.xml,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document">
On platforms that only use file extensions to describe file types, the extensions listed here can be used to filter the allowed documents, while the MIME types can be used with the system's type registration table (mapping MIME types to extensions used by the system), if any, to determine any other extensions to allow. Similarly, on a system that does not have file names or extensions but labels documents with MIME types internally, the MIME types can be used to pick the allowed files, while the extensions can be used if the system has an extension registration table that maps known extensions to MIME types used by the system.
Extensions tend to be ambiguous (e.g. there are an untold number of formats
that use the ".dat
" extension, and users can typically quite easily rename
their files to have a ".doc
" extension even if they are not Microsoft Word
documents), and MIME types tend to be unreliable (e.g. many formats have no formally registered
types, and many formats are in practice labeled using a number of different MIME types). Authors
are reminded that, as usual, data received from a client should be treated with caution, as it may
not be in an expected format even if the user is not hostile and the user agent fully obeyed the
accept
attribute's requirements.
For historical reasons, the value
IDL attribute prefixes
the file name with the string "C:\fakepath\
". Some legacy user agents
actually included the full path (which was a security vulnerability). As a result of this,
obtaining the file name from the value
IDL attribute in a
backwards-compatible way is non-trivial. The following function extracts the file name in a
suitably compatible manner:
function extractFilename(path) { if (path.substr(0, 12) == "C:\\fakepath\\") return path.substr(12); // modern browser var x; x = path.lastIndexOf('/'); if (x >= 0) // Unix-based path return path.substr(x+1); x = path.lastIndexOf('\\'); if (x >= 0) // Windows-based path return path.substr(x+1); return path; // just the file name }
This can be used as follows:
<p><input type=file name=image onchange="updateFilename(this.value)"></p> <p>The name of the file you picked is: <span id="filename">(none)</span></p> <script> function updateFilename(path) { var name = extractFilename(path); document.getElementById('filename').textContent = name; } </script>
The following common input
element content attributes and IDL attributes apply to the element:
accept
,
multiple
, and
required
content attributes;
files
and
value
IDL attributes.
The value
IDL attribute is in mode filename.
The input
and change
events apply.
The following content attributes must not be specified and do not apply to the
element:
alt
,
autocomplete
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
pattern
,
placeholder
,
readonly
,
size
,
src
,
step
, and
width
.
The element's value
attribute must be omitted.
The following IDL attributes and methods do not apply to the element:
checked
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
type=submit
)When an input
element's type
attribute is in
the Submit Button state, the rules in this section
apply.
The input
element represents a button that, when activated, submits
the form. If the element has a value
attribute, the button's label must be the value of that attribute; otherwise, it must be an
implementation-defined string that means "Submit" or some such. The element is a button, specifically a submit
button.
If the element is mutable, then the element's
activation behavior is as follows: if the element has a form owner,
and the element's Document
is fully active,
submit the form owner from the
input
element; otherwise, do nothing.
If the element is not mutable, it has no activation behavior.
The formaction
, formenctype
, formmethod
, formnovalidate
, and formtarget
attributes are attributes for form
submission.
The formnovalidate
attribute can be
used to make submit buttons that do not trigger the constraint validation.
The following common input
element content attributes and IDL attributes apply to the element:
formaction
,
formenctype
,
formmethod
,
formnovalidate
, and
formtarget
content attributes;
value
IDL attribute.
The value
IDL attribute is in mode default.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
autocomplete
,
checked
,
dirname
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
The input
and change
events do not apply.
type=image
)When an input
element's type
attribute is in
the Image Button state, the rules in this section
apply.
The input
element represents either an image from which a user can
select a coordinate and submit the form, or alternatively a button from which the user can submit
the form. The element is a button, specifically a submit button.
The coordinate is sent to the server during form submission by sending two entries for the element, derived from the name
of the control but with ".x
" and ".y
" appended to the
name with the x and y components of the coordinate
respectively.
The image is given by the src
attribute. The
src
attribute must be present, and must contain a valid
non-empty URL potentially surrounded by spaces referencing a non-interactive, optionally
animated, image resource that is neither paged nor scripted.
When any of the following events occur, unless the user agent cannot support images, or its
support for images has been disabled, or the user agent only fetches elements on demand, or the
src
attribute's value is the empty string, the user agent must
resolve the value of the src
attribute, relative to the element, and if that is successful,
must fetch the resulting absolute URL:
input
element's type
attribute is first
set to the Image Button state (possibly when the
element is first created), and the src
attribute is
present.input
element's type
attribute is
changed back to the Image Button state, and the src
attribute is present, and its value has changed since the last
time the type
attribute was in the Image Button state.input
element's type
attribute is in
the Image Button state, and the src
attribute is set or changed.Fetching the image must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run.
If the image was successfully obtained, with no network errors, and the image's type is a supported image type, and the image is a valid image of that type, then the image is said to be available. If this is true before the image is completely downloaded, each task that is queued by the networking task source while the image is being fetched must update the presentation of the image appropriately.
The user agent should apply the image sniffing rules to determine the type of the image, with the image's associated Content-Type headers giving the official type. If these rules are not applied, then the type of the image must be the type given by the image's associated Content-Type headers.
User agents must not support non-image resources with the input
element. User
agents must not run executable code embedded in the image resource. User agents must only display
the first page of a multipage resource. User agents must not allow the resource to act in an
interactive fashion, but should honor any animation in the resource.
The task that is queued by
the networking task source once the resource has been fetched, must, if the download was successful and the image is available, queue a task to fire a simple
event named load
at the input
element; and
otherwise, if the fetching process fails without a response from the remote server, or completes
but the image is not a valid or supported image, queue a task to fire a simple
event named error
on the input
element.
The alt
attribute provides the textual label for
the button for users and user agents who cannot use the image. The alt
attribute must be present, and must contain a non-empty string
giving the label that would be appropriate for an equivalent button if the image was
unavailable.
The input
element supports dimension attributes.
If the src
attribute is set, and the image is available and the user agent is configured to display that image,
then: The element represents a control for selecting a coordinate from the image specified by the
src
attribute; if the element is mutable, the user agent should allow the user to select this coordinate, and the element's activation
behavior is as follows: if the element has a form owner, and the element's
Document
is fully active, take the user's selected coordinate, and submit the input
element's form owner
from the input
element. If the user activates the control without explicitly
selecting a coordinate, then the coordinate (0,0) must be assumed.
Otherwise, the element represents a submit button whose label is given by the
value of the alt
attribute; if the element is mutable, then the element's activation behavior is as
follows: if the element has a form owner, and the element's Document
is
fully active, set the selected
coordinate to (0,0), and submit the
input
element's form owner from the input
element.
In either case, if the element is mutable but has no
form owner or the element's Document
is not fully active,
then its activation behavior must be to do nothing. If the element is not mutable, it has no activation behavior.
The selected coordinate must consist of an x-component and a y-component. The coordinates represent the position relative to the edge of the image, with the coordinate space having the positive x direction to the right, and the positive y direction downwards.
The x-component must be a valid integer representing a number x in the range −(borderleft+paddingleft) ≤ x ≤ width+borderright+paddingright, where width is the rendered width of the image, borderleft is the width of the border on the left of the image, paddingleft is the width of the padding on the left of the image, borderright is the width of the border on the right of the image, and paddingright is the width of the padding on the right of the image, with all dimensions given in CSS pixels.
The y-component must be a valid integer representing a number y in the range −(bordertop+paddingtop) ≤ y ≤ height+borderbottom+paddingbottom, where height is the rendered height of the image, bordertop is the width of the border above the image, paddingtop is the width of the padding above the image, borderbottom is the width of the border below the image, and paddingbottom is the width of the padding below the image, with all dimensions given in CSS pixels.
Where a border or padding is missing, its width is zero CSS pixels.
The formaction
, formenctype
, formmethod
, formnovalidate
, and formtarget
attributes are attributes for form
submission.
width
[ = value ]height
[ = value ]These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known.
They can be set, to change the corresponding content attributes.
The following common input
element content attributes and IDL attributes apply to the element:
alt
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
src
, and
width
content attributes;
value
IDL attribute.
The value
IDL attribute is in mode default.
The following content attributes must not be specified and do not apply to the
element:
accept
,
autocomplete
,
checked
,
dirname
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
, and
step
.
The element's value
attribute must be omitted.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
The input
and change
events do not apply.
Many aspects of this state's behavior are similar to the behavior of the
img
element. Readers are encouraged to read that section, where many of the same
requirements are described in more detail.
Take the following form:
<form action="process.cgi"> <input type=image src=map.png name=where alt="Show location list"> </form>
If the user clicked on the image at coordinate (127,40) then the URL used to submit the form
would be "process.cgi?where.x=127&where.y=40
".
(In this example, it's assumed that for users who don't see the map, and who instead just see a button labeled "Show location list", clicking the button will cause the server to show a list of locations to pick from instead of the map.)
type=reset
)When an input
element's type
attribute is in
the Reset Button state, the rules in this section
apply.
The input
element represents a button that, when activated, resets
the form. If the element has a value
attribute, the button's label must be the value of that attribute; otherwise, it must be an
implementation-defined string that means "Reset" or some such. The element is a button.
If the element is mutable, then the element's
activation behavior, if the element has a form owner and the element's
Document
is fully active, is to reset the form owner; otherwise, it is to do
nothing.
If the element is not mutable, it has no activation behavior.
Constraint validation: The element is barred from constraint validation.
The value
IDL attribute applies to this element and is in mode default.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
autocomplete
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
The input
and change
events do not apply.
type=button
)The input
element represents a button with no default behavior. A
label for the button must be provided in the value
attribute, though it may be the empty string. If the element has a value
attribute, the button's label must be the value of that
attribute; otherwise, it must be the empty string. The element is a button.
If the element is mutable, the element's activation behavior is to do nothing.
If the element is not mutable, it has no activation behavior.
Constraint validation: The element is barred from constraint validation.
The value
IDL attribute applies to this element and is in mode default.
The following content attributes must not be specified and do not apply to the
element:
accept
,
alt
,
autocomplete
,
checked
,
dirname
,
formaction
,
formenctype
,
formmethod
,
formnovalidate
,
formtarget
,
height
,
list
,
max
,
maxlength
,
min
,
minlength
,
multiple
,
pattern
,
placeholder
,
readonly
,
required
,
size
,
src
,
step
, and
width
.
The following IDL attributes and methods do not apply to the element:
checked
,
files
,
list
,
selectionStart
,
selectionEnd
,
selectionDirection
,
valueAsDate
, and
valueAsNumber
IDL attributes;
select()
,
setRangeText()
,
setSelectionRange()
,
stepDown()
, and
stepUp()
methods.
The input
and change
events do not apply.
This section is non-normative.
The formats shown to the user in date, time, and number controls is independent of the format used for form submission.
Browsers are encouraged to use user interfaces that present dates, times, and numbers according
to the conventions of either the locale implied by the input
element's
language or the user's preferred locale. Using the page's locale will ensure
consistency with page-provided data.
For example, it would be confusing to users if an American English page claimed that a Cirque De Soleil show was going to be showing on 02/03, but their browser, configured to use the British English locale, only showed the date 03/02 in the ticket purchase date picker. Using the page's locale would at least ensure that the date was presented in the same format everywhere. (There's still a risk that the user would end up arriving a month late, of course, but there's only so much that can be done about such cultural differences...)
input
element attributesThese attributes only apply to an input
element if its type
attribute is in a state whose definition
declares that the attribute applies. When an attribute
doesn't apply to an input
element, user agents must
ignore the attribute, regardless of the requirements and definitions below.
maxlength
and minlength
attributesThe maxlength
attribute, when it applies, is a form control maxlength
attribute controlled by the input
element's dirty value flag.
The minlength
attribute, when it applies, is a form control minlength
attribute controlled by the input
element's dirty value flag.
If the input
element has a maximum allowed value length, then the
code-unit length of the value of the element's value
attribute must be equal to or less than the element's
maximum allowed value length.
The following extract shows how a messaging client's text entry could be arbitrarily restricted to a fixed number of characters, thus forcing any conversation through this medium to be terse and discouraging intelligent discourse.
<label>What are you doing? <input name=status maxlength=140></label>
Here, a password is given a minimum length:
<p><label>Username: <input name=u required></label> <p><label>Password: <input name=p required minlength=12></label>
size
attributeThe size
attribute gives the number of
characters that, in a visual rendering, the user agent is to allow the user to see while editing
the element's value.
The size
attribute, if specified, must have a value that
is a valid non-negative integer greater than zero.
If the attribute is present, then its value must be parsed using the rules for parsing non-negative integers, and if the result is a number greater than zero, then the user agent should ensure that at least that many characters are visible.
The size
IDL attribute is limited to only
non-negative numbers greater than zero and has a default value of 20.
readonly
attributeThe readonly
attribute is a boolean
attribute that controls whether or not the user can edit the form control. When specified, the element is not mutable.
Constraint validation: If the readonly
attribute is specified on an input
element, the element is barred from constraint validation.
The difference between disabled
and readonly
is that read-only controls are still focusable, so the
user can still select the text and interact with it, whereas disabled controls are entirely
non-interactive. (For this reason, only text controls can be made read-only: it wouldn't make
sense for checkboxes or buttons, for instances.)
In the following example, the existing product identifiers cannot be modified, but they are still displayed as part of the form, for consistency with the row representing a new product (where the identifier is not yet filled in).
<form action="products.cgi" method="post" enctype="multipart/form-data"> <table> <tr> <th> Product ID <th> Product name <th> Price <th> Action <tr> <td> <input readonly="readonly" name="1.pid" value="H412"> <td> <input required="required" name="1.pname" value="Floor lamp Ulke"> <td> $<input required="required" type="number" min="0" step="0.01" name="1.pprice" value="49.99"> <td> <button formnovalidate="formnovalidate" name="action" value="delete:1">Delete</button> <tr> <td> <input readonly="readonly" name="2.pid" value="FG28"> <td> <input required="required" name="2.pname" value="Table lamp Ulke"> <td> $<input required="required" type="number" min="0" step="0.01" name="2.pprice" value="24.99"> <td> <button formnovalidate="formnovalidate" name="action" value="delete:2">Delete</button> <tr> <td> <input required="required" name="3.pid" value="" pattern="[A-Z0-9]+"> <td> <input required="required" name="3.pname" value=""> <td> $<input required="required" type="number" min="0" step="0.01" name="3.pprice" value=""> <td> <button formnovalidate="formnovalidate" name="action" value="delete:3">Delete</button> </table> <p> <button formnovalidate="formnovalidate" name="action" value="add">Add</button> </p> <p> <button name="action" value="update">Save</button> </p> </form>
required
attributeThe required
attribute is a boolean
attribute. When specified, the element is required.
Constraint validation: If the element is required, and its value
IDL attribute applies and is in the mode value, and the element is mutable, and the element's value is the empty string, then the element is suffering
from being missing.
The following form has two required fields, one for an e-mail address and one for a password. It also has a third field that is only considered valid if the user types the same password in the password field and this third field.
<h1>Create new account</h1> <form action="/newaccount" method=post oninput="up2.setCustomValidity(up2.value != up.value ? 'Passwords do not match.' : '')"> <p> <label for="username">E-mail address:</label> <input id="username" type=email required name=un> <p> <label for="password1">Password:</label> <input id="password1" type=password required name=up> <p> <label for="password2">Confirm password:</label> <input id="password2" type=password name=up2> <p> <input type=submit value="Create account"> </form>
For radio buttons, the required
attribute is
satisfied if any of the radio buttons in the group is
selected. Thus, in the following example, any of the radio buttons can be checked, not just the
one marked as required:
<fieldset> <legend>Did the movie pass the Bechdel test?</legend> <p><label><input type="radio" name="bechdel" value="no-characters"> No, there are not even two female characters in the movie. </label> <p><label><input type="radio" name="bechdel" value="no-names"> No, the female characters never talk to each other. </label> <p><label><input type="radio" name="bechdel" value="no-topic"> No, when female characters talk to each other it's always about a male character. </label> <p><label><input type="radio" name="bechdel" value="yes" required> Yes. </label> <p><label><input type="radio" name="bechdel" value="unknown"> I don't know. </label> </fieldset>
To avoid confusion as to whether a radio button group is required or not, authors are encouraged to specify the attribute on all the radio buttons in a group. Indeed, in general, authors are encouraged to avoid having radio button groups that do not have any initially checked controls in the first place, as this is a state that the user cannot return to, and is therefore generally considered a poor user interface.
multiple
attributeThe multiple
attribute is a boolean
attribute that indicates whether the user is to be allowed to specify more than one
value.
The following extract shows how an e-mail client's "Cc" field could accept multiple e-mail addresses.
<label>Cc: <input type=email multiple name=cc></label>
If the user had, amongst many friends in his user contacts database, two friends "Arthur Dent" (with address "art@example.net") and "Adam Josh" (with address "adamjosh@example.net"), then, after the user has typed "a", the user agent might suggest these two e-mail addresses to the user.
The page could also link in the user's contacts database from the site:
<label>Cc: <input type=email multiple name=cc list=contacts></label> ... <datalist id="contacts"> <option value="hedral@damowmow.com"> <option value="pillar@example.com"> <option value="astrophy@cute.example"> <option value="astronomy@science.example.org"> </datalist>
Suppose the user had entered "bob@example.net" into this text field, and then started typing a
second e-mail address starting with "a". The user agent might show both the two friends mentioned
earlier, as well as the "astrophy" and "astronomy" values given in the datalist
element.
The following extract shows how an e-mail client's "Attachments" field could accept multiple files for upload.
<label>Attachments: <input type=file multiple name=att></label>
pattern
attributeThe pattern
attribute specifies a regular
expression against which the control's value, or, when the
multiple
attribute applies and is set, the control's values, are to be checked.
If specified, the attribute's value must match the JavaScript Pattern production. [ECMA262]
If an input
element has a pattern
attribute specified, and the attribute's value, when compiled as a JavaScript regular expression
with the global
, ignoreCase
, and multiline
flags disabled (see ECMA262 Edition 5, sections 15.10.7.2
through 15.10.7.4), compiles successfully, then the resulting regular expression is the element's
compiled pattern regular expression. If the element has no such attribute, or if the
value doesn't compile successfully, then the element has no compiled pattern regular
expression. [ECMA262]
Constraint validation: If the element's value is not the empty string, and either the element's multiple
attribute is not specified or it does not apply to the input
element given its type
attribute's current state, and the element has a
compiled pattern regular expression but that regular expression does not match the
entirety of the element's value, then the element is
suffering from a pattern mismatch.
Constraint validation: If the element's value is not the empty string, and the element's multiple
attribute is specified and applies to the input
element, and the element has
a compiled pattern regular expression but that regular expression does not match the
entirety of each of the element's values, then the
element is suffering from a pattern mismatch.
The compiled pattern regular expression, when matched against a string, must have its start anchored to the start of the string and its end anchored to the end of the string.
This implies that the regular expression language used for this attribute is the
same as that used in JavaScript, except that the pattern
attribute is matched against the entire value, not just any subset (somewhat as if it implied a
^(?:
at the start of the pattern and a )$
at the
end).
When an input
element has a pattern
attribute specified, authors should provide a description of the pattern in text near the
control. Authors may also include a title
attribute to give a description of the pattern. User agents may use
the contents of this attribute, if it is present, when informing the
user that the pattern is not matched, or at any other suitable time,
such as in a tooltip or read out by assistive technology when the
control gains focus.
Relying on the title
attribute alone is currently discouraged as many user agents do not expose the attribute in an
accessible manner as required by this specification (e.g. requiring a pointing device such as a
mouse to cause a tooltip to appear, which excludes keyboard-only users and touch-only users,
such as anyone with a modern phone or tablet).
For example, the following snippet includes the pattern description in text below the input
,
the pattern description is also included in the title
attribute:
<label> Part number: <input pattern="[0-9][A-Z]{3}" name="part" data-x="A part number is a digit followed by three uppercase letters."/> </label> <p>A part number is a digit followed by three uppercase letters.</p>
The presence of the pattern description in text makes the advice available to any user regardless of device.
The presence of the pattern description in the title attribute, results in the description being announced by assistive technology such as screen readers when the input receives focus.
If the user has attempted to submit the form with incorrect information, the presence of the title attribute text could also cause the UA to display an alert such as:
A part number is a digit followed by three uppercase letters. You cannot submit this form when the field is incorrect.
In this example, the pattern description is in text below the input
,
but not in the title
attribute. The
aria-describedby
attribute
is used to explicitly associate the text description with the control, the description is announced by
assistive technology such as screen readers when the input
receives focus:
<label> Part number: <input pattern="[0-9][A-Z]{3}" name="part" aria-describedby="description"> </label> <p id="description">A part number is a digit followed by three uppercase letters.</p>
When a control has a pattern
attribute, the title
attribute, if used, must describe the pattern. Additional
information could also be included, so long as it assists the user in filling in the control.
Otherwise, assistive technology would be impaired.
For instance, if the title attribute contained the caption of the control, assistive technology could end up saying something like The text you have entered does not match the required pattern. Birthday, which is not useful.
UAs may still show the title
in non-error situations (for
example, as a tooltip when hovering over the control), so authors should be careful not to word
title
s as if an error has necessarily occurred.
min
and max
attributesSome form controls can have explicit constraints applied limiting the allowed range of values that the user can provide. Normally, such a range would be linear and continuous. A form control can have a periodic domain, however, in which case the form control's broadest possible range is finite, and authors can specify explicit ranges within it that span the boundaries.
Specifically, the broadest range of a type=time
control is midnight to midnight (24 hours), and
authors can set both continuous linear ranges (such as 9pm to 11pm) and discontinuous ranges
spanning midnight (such as 11pm to 1am).
The min
and max
attributes indicate the allowed range of values for
the element.
Their syntax is defined by the section that defines the type
attribute's current state.
If the element has a min
attribute, and the result of
applying the algorithm to convert a string to a
number to the value of the min
attribute is a number,
then that number is the element's minimum; otherwise, if the
type
attribute's current state defines a default minimum, then that is the minimum; otherwise, the element has no minimum.
The min
attribute also defines the step base.
If the element has a max
attribute, and the result of
applying the algorithm to convert a string to a
number to the value of the max
attribute is a number,
then that number is the element's maximum; otherwise, if the
type
attribute's current state defines a default maximum, then that is the maximum; otherwise, the element has no maximum.
If the element does not have a periodic domain, the
max
attribute's value (the maximum) must not be less than the min
attribute's value (its minimum).
If an element that does not have a periodic domain has a maximum that is less than its minimum, then so long as the element has a value, it will either be suffering from an underflow or suffering from an overflow.
An element has a reversed range if it has a periodic domain and its maximum is less than its minimum.
An element has range limitations if it has a defined minimum or a defined maximum.
Constraint validation: When the element has a minimum and does not have a reversed range, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is less than the minimum, the element is suffering from an underflow.
Constraint validation: When the element has a maximum and does not have a reversed range, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is more than the maximum, the element is suffering from an overflow.
Constraint validation: When an element has a reversed range, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is more than the maximum and less than the minimum, the element is simultaneously suffering from an underflow and suffering from an overflow.
The following date control limits input to dates that are before the 1980s:
<input name=bday type=date max="1979-12-31">
The following number control limits input to whole numbers greater than zero:
<input name=quantity required="" type="number" min="1" value="1">
The following time control limits input to those minutes that occur between 9pm and 6am, defaulting to midnight:
<input name="sleepStart" type=time min="21:00" max="06:00" step="60" value="00:00">
step
attributeThe step
attribute indicates the granularity
that is expected (and required) of the value, by limiting
the allowed values. The section that defines the type
attribute's current state also defines the default step, the step scale factor, and in some cases the default step base, which are used in processing the
attribute as described below.
The step
attribute, if specified, must either have a value
that is a valid floating-point number that parses to a number that is greater than zero, or must have a
value that is an ASCII case-insensitive match for the string "any
".
The attribute provides the allowed value step for the element, as follows:
any
", then there is no allowed
value step.The step base is the value returned by the following algorithm:
If the element has a min
content attribute, and the
result of applying the algorithm to convert a
string to a number to the value of the min
content
attribute is not an error, then return that result and abort these steps.
If the element has a value
content attribute, and
the result of applying the algorithm to convert a
string to a number to the value of the value
content
attribute is not an error, then return that result and abort these steps.
If a default step base is defined for
this element given its type
attribute's state, then return
it and abort these steps.
Return zero.
Constraint validation: When the element has an allowed value step, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and that number subtracted from the step base is not an integral multiple of the allowed value step, the element is suffering from a step mismatch.
The following range control only accepts values in the range 0..1, and allows 256 steps in that range:
<input name=opacity type=range min=0 max=1 step=0.00392156863>
The following control allows any time in the day to be selected, with any accuracy (e.g. thousandth-of-a-second accuracy or more):
<input name=favtime type=time step=any>
Normally, time controls are limited to an accuracy of one minute.
list
attributeThe list
attribute is used to identify an
element that lists predefined options suggested to the user.
If present, its value must be the ID of a datalist
element in the same document.
The suggestions source element is the first element in
the document in tree order to have an ID equal to the
value of the list
attribute, if that element is a
datalist
element. If there is no list
attribute,
or if there is no element with that ID, or if the first element
with that ID is not a datalist
element, then there is
no suggestions source element.
If there is a suggestions source element, then, when
the user agent is allowing the user to edit the input
element's value, the user agent should offer the suggestions represented by
the suggestions source element to the user in a manner
suitable for the type of control used. The user agent may use the suggestion's label to identify the suggestion if appropriate.
How user selections of suggestions are handled depends on whether the element is a control accepting a single value only, or whether it accepts multiple values:
multiple
attribute
specified or if the multiple
attribute does not
applyWhen the user selects a suggestion, the input
element's value must be set to the selected suggestion's value, as if the user had written that value himself.
multiple
attribute specified, and the multiple
attribute does
applyWhen the user selects a suggestion, the user agent must either add a new entry to the
input
element's values, whose value
is the selected suggestion's value, or change an
existing entry in the input
element's values to have the value given by the selected
suggestion's value, as if the user had himself added
an entry with that value, or edited an existing entry to be that value. Which behavior is to be
applied depends on the user interface in a user-agent-defined manner.
If the list
attribute does not
apply, there is no suggestions source element.
This URL field offers some suggestions.
<label>Homepage: <input name=hp type=url list=hpurls></label> <datalist id=hpurls> <option value="http://www.google.com/" label="Google"> <option value="http://www.reddit.com/" label="Reddit"> </datalist>
Other URLs from the user's history might show also; this is up to the user agent.
This example demonstrates how to design a form that uses the autocompletion list feature while still degrading usefully in legacy user agents.
If the autocompletion list is merely an aid, and is not important to the content, then simply
using a datalist
element with children option
elements is enough. To
prevent the values from being rendered in legacy user agents, they need to be placed inside the
value
attribute instead of inline.
<p> <label> Enter a breed: <input type="text" name="breed" list="breeds"> <datalist id="breeds"> <option value="Abyssinian"> <option value="Alpaca"> <!-- ... --> </datalist> </label> </p>
However, if the values need to be shown in legacy UAs, then fallback content can be placed
inside the datalist
element, as follows:
<p> <label> Enter a breed: <input type="text" name="breed" list="breeds"> </label> <datalist id="breeds"> <label> or select one from the list: <select name="breed"> <option value=""> (none selected) <option>Abyssinian <option>Alpaca <!-- ... --> </select> </label> </datalist> </p>
The fallback content will only be shown in UAs that don't support datalist
. The
options, on the other hand, will be detected by all UAs, even though they are not children of the
datalist
element.
Note that if an option
element used in a datalist
is selected
, it will be selected by default by legacy UAs
(because it affects the select
), but it will not have any effect on the
input
element in UAs that support datalist
.
placeholder
attributeThe placeholder
attribute represents a
short hint (a word or short phrase) intended to aid the user with data entry when the
control has no value. A hint could be a sample value or a brief description of the expected
format. The attribute, if specified, must have a value that contains no "LF" (U+000A) or
"CR" (U+000D) characters.
The placeholder
attribute should not be used as a
replacement for a label
. For a longer hint or other advisory text, place the text
next to the control.
Use of the placeholder
attribute as a replacement for a label
can reduce the
accessibility and usability of the control for a range of users including older
users and users with cognitive, mobility, fine motor skill or vision impairments.
While the hint given by the control's label
is shown at all times, the short
hint given in the placeholder
attribute is only shown before the user enters a value. Furthermore,
placeholder
text may be mistaken for
a pre-filled value, and as commonly implemented the default color of the placeholder text
provides insufficient contrast and the lack of a separate visible label
reduces the size of the hit region available for setting focus on the control.
User agents should present this hint to the user, after having stripped line breaks from it, when the element's value is the empty string and the control is not focused (i.e., by displaying it inside a blank unfocused control).
Here is an example of a mail configuration user interface that uses the placeholder
attribute:
<fieldset> <legend>Mail Account</legend> <p><label>Name: <input type="text" name="fullname" placeholder="John Ratzenberger"></label></p> <p><label>Address: <input type="email" name="address" placeholder="john@example.net"></label></p> <p><label>Password: <input type="password" name="password"></label></p> <p><label>Description: <input type="text" name="desc" placeholder="My Email Account"></label></p> </fieldset>
In situations where the control's content has one directionality but the placeholder needs to have a different directionality, Unicode's bidirectional-algorithm formatting characters can be used in the attribute value:
<input name=t1 type=tel placeholder="‫ رقم الهاتف 1 ‮"> <input name=t2 type=tel placeholder="‫ رقم الهاتف 2 ‮">
For slightly more clarity, here's the same example using numeric character references instead of inline Arabic:
<input name=t1 type=tel placeholder="‫رقم الهاتف 1‮"> <input name=t2 type=tel placeholder="‫رقم الهاتف 2‮">
input
element APIsvalue
[ = value ]Returns the current value of the form control.
Can be set, to change the value.
Throws an InvalidStateError
exception if it is set to any value other than the
empty string when the control is a file upload control.
checked
[ = value ]Returns the current checkedness of the form control.
Can be set, to change the checkedness.
files
Returns a FileList
object listing the selected files of the form control.
Returns null if the control isn't a file control.
valueAsDate
[ = value ]Returns a Date
object representing the form control's value, if applicable; otherwise, returns null.
Can be set, to change the value.
Throws an InvalidStateError
exception if the control isn't date- or
time-based.
valueAsNumber
[ = value ]Returns a number representing the form control's value, if applicable; otherwise, returns NaN.
Can be set, to change the value. Setting this to NaN will set the underlying value to the empty string.
Throws an InvalidStateError
exception if the control is neither date- or
time-based nor numeric.
stepUp
( [ n ] )stepDown
( [ n ] )Changes the form control's value by the value given in
the step
attribute, multiplied by n.
The default value for n is 1.
Throws InvalidStateError
exception if the control is neither date- or time-based
nor numeric, or if the step
attribute's value is "any
".
list
Returns the datalist
element indicated by the list
attribute.
The value
IDL attribute allows scripts to
manipulate the value of an input
element. The
attribute is in one of the following modes, which define its behavior:
On getting, it must return the current value of the
element. On setting, it must set the element's value to
the new value, set the element's dirty value
flag to true, invoke the value sanitization algorithm, if the element's
type
attribute's current state defines one, and then, if
the element has a text entry cursor position, should move the text entry cursor position to the
end of the text field, unselecting any selected text and resetting the selection direction to
none.
On getting, if the element has a value
attribute, it
must return that attribute's value; otherwise, it must return the empty string. On setting, it
must set the element's value
attribute to the new
value.
On getting, if the element has a value
attribute, it
must return that attribute's value; otherwise, it must return the string "on
". On setting, it must set the element's value
attribute to the new value.
On getting, it must return the string "C:\fakepath\
" followed by the
name of the first file in the list of selected
files, if any, or the empty string if the list is empty. On setting, if the new value is
the empty string, it must empty the list of selected files; otherwise, it must throw an
InvalidStateError
exception.
This "fakepath" requirement is a sad accident of history. See the example in the File Upload state section for more information.
The checked
IDL attribute allows scripts to
manipulate the checkedness of an input
element. On getting, it must return the current checkedness of the element; and on setting, it must set the
element's checkedness to the new value and set the
element's dirty checkedness flag to
true.
The files
IDL attribute allows scripts to
access the element's selected files. On
getting, if the IDL attribute applies, it must return a
FileList
object that represents the current selected files. The same object must be returned
until the list of selected files changes. If
the IDL attribute does not apply, then it must instead return
null. [FILEAPI]
The valueAsDate
IDL attribute represents
the value of the element, interpreted as a date.
On getting, if the valueAsDate
attribute does not apply, as defined for the input
element's type
attribute's current state, then return null. Otherwise, run
the algorithm to convert a string to a
Date
object defined for that state; if the algorithm returned a
Date
object, then return it, otherwise, return null.
On setting, if the valueAsDate
attribute does not apply, as defined for the input
element's type
attribute's current state, then throw an
InvalidStateError
exception; otherwise, if the new value is null or a
Date
object representing the NaN time value, then set the value of the element to the empty string; otherwise, run the algorithm to convert a Date
object to a
string, as defined for that state, on the new value, and set the value of the element to the resulting string.
The valueAsNumber
IDL attribute
represents the value of the element, interpreted as a
number.
On getting, if the valueAsNumber
attribute does not apply, as defined for the input
element's type
attribute's current state, then return a Not-a-Number (NaN)
value. Otherwise, if the valueAsDate
attribute
applies, run the algorithm to convert a string to a Date
object defined for that state; if the algorithm returned a Date
object, then
return the time value of the object (the number of milliseconds from midnight UTC the
morning of 1970-01-01 to the time represented by the Date
object), otherwise, return
a Not-a-Number (NaN) value. Otherwise, run the algorithm to convert a string to a number defined
for that state; if the algorithm returned a number, then return it, otherwise, return a
Not-a-Number (NaN) value.
On setting, if the new value is infinite, then throw a TypeError
exception.
Otherwise, if the valueAsNumber
attribute does not apply, as defined for the input
element's type
attribute's current state, then throw an
InvalidStateError
exception. Otherwise, if the new value is a Not-a-Number (NaN)
value, then set the value of the element to the empty
string. Otherwise, if the valueAsDate
attribute applies, run the algorithm to convert a Date
object to a
string defined for that state, passing it a Date
object whose time
value is the new value, and set the value of the element
to the resulting string. Otherwise, run the algorithm to convert a number to a string, as
defined for that state, on the new value, and set the value
of the element to the resulting string.
The stepDown(n)
and stepUp(n)
methods, when invoked,
must run the following algorithm:
If the stepDown()
and stepUp()
methods do not apply, as defined for the
input
element's type
attribute's current state,
then throw an InvalidStateError
exception, and abort these steps.
If the element has no allowed value step, then
throw an InvalidStateError
exception, and abort these steps.
If the element has a minimum and a maximum and the minimum is greater than the maximum, then abort these steps.
If the element has a minimum and a maximum and there is no value greater than or equal to the element's minimum and less than or equal to the element's maximum that, when subtracted from the step base, is an integral multiple of the allowed value step, then abort these steps.
If applying the algorithm to convert a string to a number to the string given by the element's value does not result in an error, then let value be the result of that algorithm. Otherwise, let value be zero.
If value subtracted from the step
base is not an integral multiple of the allowed value
step, then set value to the nearest value that, when subtracted from
the step base, is an integral multiple of the allowed value step, and that is less than value if the method invoked was the stepDown()
and more than value
otherwise.
Otherwise (value subtracted from the step base is an integral multiple of the allowed value step), run the following substeps:
Let n be the argument.
Let delta be the allowed value step multiplied by n.
If the method invoked was the stepDown()
method,
negate delta.
Let value be the result of adding delta to value.
If the element has a minimum, and value is less than that minimum, then set value to the smallest value that, when subtracted from the step base, is an integral multiple of the allowed value step, and that is more than or equal to minimum.
If the element has a maximum, and value is greater than that maximum, then set value to the largest value that, when subtracted from the step base, is an integral multiple of the allowed value step, and that is less than or equal to maximum.
Let value as string be the result of running the algorithm to convert a number to a string, as
defined for the input
element's type
attribute's current state, on value.
Set the value of the element to value as string.
The list
IDL attribute must return the current
suggestions source element, if any, or null otherwise.
When the input
and change
events apply (which is the case for all
input
controls other than buttons and those with
the type
attribute in the Hidden state), the events are fired to indicate that the
user has interacted with the control. The input
event fires whenever the user has modified the data of the control. The change
event fires when the value is committed, if
that makes sense for the control, or else when the control loses focus. In all cases, the input
event comes before the corresponding change
event (if any).
When an input
element has a defined activation behavior, the rules
for dispatching these events, if they apply, are given
in the section above that defines the type
attribute's
state. (This is the case for all input
controls with the type
attribute in the Checkbox state, the Radio Button state, or the File Upload state.)
For input
elements without a defined activation behavior, but to
which these events apply, and for which the user
interface involves both interactive manipulation and an explicit commit action, then when the user
changes the element's value, the user agent must
queue a task to fire a simple event that bubbles named input
at the input
element, and any time the user commits
the change, the user agent must queue a task to fire a simple event that
bubbles named change
at the input
element.
An example of a user interface involving both interactive manipulation and a
commit action would be a Range controls that use a
slider, when manipulated using a pointing device. While the user is dragging the control's knob,
input
events would fire whenever the position changed, whereas
the change
event would only fire when the user let go of the
knob, committing to a specific value.
For input
elements without a defined activation behavior, but to
which these events apply, and for which the user
interface involves an explicit commit action but no intermediate manipulation, then any time the
user commits a change to the element's value, the user
agent must queue a task to first fire a simple event that bubbles named
input
at the input
element, and then fire a
simple event that bubbles named change
at the
input
element.
An example of a user interface with a commit action would be a Color control that consists of a single button that brings up a color wheel: if the value only changes when the dialog is closed, then that would be the explicit commit action. On the other hand, if the control can be focused and manipulating the control changes the color interactively, then there might be no commit action.
Another example of a user interface with a commit action would be a Date control that allows both text-based user input and user selection from a drop-down calendar: while text input might not have an explicit commit step, selecting a date from the drop down calendar and then dismissing the drop down would be a commit action.
For input
elements without a defined activation behavior, but to
which these events apply, any time the user causes the
element's value to change without an explicit commit
action, the user agent must queue a task to fire a simple event that
bubbles named input
at the input
element. The
corresponding change
event, if any, will be fired when the
control loses focus.
Examples of a user changing the element's value would include the user typing into a text field, pasting a new value into the field, or undoing an edit in that field. Some user interactions do not cause changes to the value, e.g. hitting the "delete" key in an empty text field, or replacing some text in the field with text from the clipboard that happens to be exactly the same text.
A Range control in the form of a slider that the user has focused and is interacting with using a keyboard would be another example of the user changing the element's value without a commit step.
In the case of tasks that just fire an input
event, user agents may wait for a suitable break in the user's
interaction before queuing the tasks; for example, a user agent
could wait for the user to have not hit a key for 100ms, so as to only fire the event when the
user pauses, instead of continuously for each keystroke.
When the user agent is to change an input
element's value on behalf of the user (e.g. as part of a form prefilling
feature), the user agent must queue a task to first update the value accordingly, then fire a simple event that
bubbles named input
at the input
element, then
fire a simple event that bubbles named change
at
the input
element.
These events are not fired in response to changes made to the values of form controls by scripts. (This is to make it easier to update the values of form controls in response to the user manipulating the controls, without having to then filter out the script's own changes to avoid an infinite loop.)
The task source for these tasks is the user interaction task source.
button
elementautofocus
disabled
form
formaction
formenctype
formmethod
formnovalidate
formtarget
name
type
value
interface HTMLButtonElement : HTMLElement {
attribute boolean autofocus;
attribute boolean disabled;
readonly attribute HTMLFormElement? form;
attribute DOMString formAction;
attribute DOMString formEnctype;
attribute DOMString formMethod;
attribute boolean formNoValidate;
attribute DOMString formTarget;
attribute DOMString name;
attribute DOMString type;
attribute DOMString value;
readonly attribute boolean willValidate;
readonly attribute ValidityState validity;
readonly attribute DOMString validationMessage;
boolean checkValidity();
boolean reportValidity();
void setCustomValidity(DOMString error);
readonly attribute NodeList labels;
};
The button
element represents a button labeled by its contents.
The element is a button.
The type
attribute controls the behavior of
the button when it is activated. It is an enumerated attribute. The following table
lists the keywords and states for the attribute — the keywords in the left column map to the
states in the cell in the second column on the same row as the keyword.
Keyword | State | Brief description |
---|---|---|
submit
| Submit Button | Submits the form. |
reset
| Reset Button | Resets the form. |
button
| Button | Does nothing. |
The missing value default is the Submit Button state.
If the type
attribute is in the Submit Button state, the element is specifically a
submit button.
Constraint validation: If the type
attribute is in the Reset Button state, or the
Button state, the element is barred from constraint
validation.
When a button
element is not disabled,
its activation behavior element is to run the steps defined in the following list for
the current state of the element's type
attribute:
If the element has a form owner and the element's Document
is
fully active, the element must submit the
form owner from the button
element.
If the element has a form owner and the element's Document
is
fully active, the element must reset the
form owner.
Do nothing.
The form
attribute is used to explicitly associate the
button
element with its form owner. The name
attribute represents the element's name. The disabled
attribute is used to make the control non-interactive and
to prevent its value from being submitted. The autofocus
attribute controls focus. The formaction
, formenctype
, formmethod
, formnovalidate
, and formtarget
attributes are attributes for form
submission.
The formnovalidate
attribute can be
used to make submit buttons that do not trigger the constraint validation.
The formaction
, formenctype
, formmethod
, formnovalidate
, and formtarget
must not be specified if the element's type
attribute is not in the Submit Button state.
The value
attribute gives the element's value
for the purposes of form submission. The element's value is
the value of the element's value
attribute, if there is
one, or the empty string otherwise.
A button (and its value) is only included in the form submission if the button itself was used to initiate the form submission.
The type
IDL attribute must
reflect the content attribute of the same name, limited to only known
values.
The willValidate
, validity
, and validationMessage
IDL attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The labels
IDL
attribute provides a list of the element's label
s. The autofocus
, disabled
, form
, and name
IDL attributes are
part of the element's forms API.
The following button is labeled "Show hint" and pops up a dialog box when activated:
<button type=button onclick="alert('This 15-20 minute piece was composed by George Gershwin.')"> Show hint </button>
select
elementoption
, optgroup
, and script-supporting elements.autofocus
disabled
form
multiple
name
required
size
interface HTMLSelectElement : HTMLElement { attribute boolean autofocus; attribute boolean disabled; readonly attribute HTMLFormElement? form; attribute boolean multiple; attribute DOMString name; attribute boolean required; attribute unsigned long size; readonly attribute DOMString type; readonly attribute HTMLOptionsCollection options; attribute unsigned long length; getter Element? item(unsigned long index); HTMLOptionElement? namedItem(DOMString name); void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null); void remove(); // ChildNode overload void remove(long index); setter creator void (unsigned long index, HTMLOptionElement? option); readonly attribute HTMLCollection selectedOptions; attribute long selectedIndex; attribute DOMString value; readonly attribute boolean willValidate; readonly attribute ValidityState validity; readonly attribute DOMString validationMessage; boolean checkValidity(); boolean reportValidity(); void setCustomValidity(DOMString error); readonly attribute NodeList labels; };
The select
element represents a control for selecting amongst a set of
options.
The multiple
attribute is a boolean
attribute. If the attribute is present, then the select
element
represents a control for selecting zero or more options from the list of options. If the attribute is absent, then the
select
element represents a control for selecting a single option from
the list of options.
The size
attribute gives the number of options
to show to the user. The size
attribute, if specified, must
have a value that is a valid non-negative integer greater than zero.
The display size of a select
element is the
result of applying the rules for parsing non-negative integers to the value of
element's size
attribute, if it has one and parsing it is
successful. If applying those rules to the attribute's value is not successful, or if the size
attribute is absent, then the element's display size is 4 if the element's multiple
content attribute is present, and 1 otherwise.
The list of options for a select
element consists of all the option
element children of the select
element, and all the option
element children of all the optgroup
element
children of the select
element, in tree order.
The required
attribute is a boolean
attribute. When specified, the user will be required to select a value before submitting
the form.
If a select
element has a required
attribute specified, does not have a multiple
attribute
specified, and has a display size of 1; and if the value of the first option
element in the
select
element's list of options (if
any) is the empty string, and that option
element's parent node is the
select
element (and not an optgroup
element), then that
option
is the select
element's placeholder label option.
If a select
element has a required
attribute specified, does not have a multiple
attribute
specified, and has a display size of 1, then the
select
element must have a placeholder label option.
Constraint validation: If the element has its required
attribute specified, and either none of the
option
elements in the select
element's list of options have their selectedness set to true, or the only
option
element in the select
element's list of options with its selectedness set to true is the placeholder label
option, then the element is suffering from being missing.
If the multiple
attribute is absent, and the element
is not disabled, then the user agent should allow the
user to pick an option
element in its list
of options that is itself not disabled. Upon
this option
element being picked (either
through a click, or through unfocusing the element after changing its value,
or through any other mechanism), and before the
relevant user interaction event is queued (e.g. before the
click
event), the user agent must set the selectedness of the picked option
element
to true, set its dirtiness to true, and then
send select
update notifications.
If the multiple
attribute is absent, whenever an
option
element in the select
element's list of options has its selectedness set to true, and whenever an
option
element with its selectedness
set to true is added to the select
element's list of options, the user agent must set the selectedness of all the other option
elements in its list of options to false.
If the multiple
attribute is absent and the element's
display size is greater than 1, then the user agent
should also allow the user to request that the option
whose selectedness is true, if any, be unselected. Upon this
request being conveyed to the user agent, and before the relevant user interaction event is queued (e.g. before the click
event), the user agent must set the selectedness
of that option
element to false, set its dirtiness to true, and then send
select
update notifications.
If nodes are inserted or nodes are removed causing the list of options to gain or lose one or more
option
elements, or if an option
element in the list of options asks for a
reset, then, if the select
element's multiple
attribute is absent, the select
element's display size is 1, and no option
elements in the select
element's list of
options have their selectedness set to
true, the user agent must set the selectedness of
the first option
element in the list of
options in tree order that is not disabled, if any, to true.
If the multiple
attribute is present, and the element
is not disabled, then the user agent should allow the
user to toggle the selectedness of the option
elements in its
list of options that are themselves not disabled. Upon such an element being toggled (either through a click,
or any other mechanism), and before the relevant user interaction event is queued (e.g. before a related click
event), the selectedness of the option
element must be changed (from true to false or false to true), the dirtiness of the element must be set to true, and the
user agent must send select
update notifications.
When the user agent is to send select
update notifications, queue
a task to first fire a simple event that bubbles named input
at the select
element, and then fire a simple
event that bubbles named change
at the
select
element, using the user interaction task source as the task
source.
The reset algorithm for select
elements is to go through all the option
elements in the element's list of options, set their selectedness to true if the option
element
has a selected
attribute, and false otherwise, set their dirtiness to false, and then
have the option
elements ask for a reset.
The form
attribute is used to explicitly associate the
select
element with its form owner. The name
attribute represents the element's name. The disabled
attribute is used to make the control non-interactive and
to prevent its value from being submitted. The autofocus
attribute controls focus.
A select
element that is not disabled is
mutable.
type
Returns "select-multiple
" if the element has a multiple
attribute, and "select-one
"
otherwise.
options
Returns an HTMLOptionsCollection
of the list of options.
length
[ = value ]Returns the number of elements in the list of options.
When set to a smaller number, truncates the number of option
elements in the
select
.
When set to a greater number, adds new blank option
elements to the
select
.
item
(index)Returns the item with index index from the list of options. The items are sorted in tree order.
namedItem
(name)Returns the first item with ID or name
name from the list of options.
Returns null if no element with that ID could be found.
add
(element [, before ])Inserts element before the node given by before.
The before argument can be a number, in which case element is inserted before the item with that number, or an element from the list of options, in which case element is inserted before that element.
If before is omitted, null, or a number out of range, then element will be added at the end of the list.
This method will throw a HierarchyRequestError
exception if element is an ancestor of the element into which it is to be inserted.
selectedOptions
Returns an HTMLCollection
of the list
of options that are selected.
selectedIndex
[ = value ]Returns the index of the first selected item, if any, or −1 if there is no selected item.
Can be set, to change the selection.
value
[ = value ]Returns the value of the first selected item, if any, or the empty string if there is no selected item.
Can be set, to change the selection.
The type
IDL attribute, on getting, must return
the string "select-one
" if the multiple
attribute is absent, and the string "select-multiple
" if the multiple
attribute is present.
The options
IDL attribute must return an
HTMLOptionsCollection
rooted at the select
node, whose filter matches
the elements in the list of options.
The options
collection is also mirrored on the
HTMLSelectElement
object. The supported property indices at any instant
are the indices supported by the object returned by the options
attribute at that instant.
The length
IDL attribute must return the
number of nodes represented by the options
collection. On setting, it must act like the attribute
of the same name on the options
collection.
The item(index)
method must
return the value returned by the method of the same
name on the options
collection, when invoked with
the same argument.
The namedItem(name)
method must return the value returned by the
method of the same name on the options
collection,
when invoked with the same argument.
When the user agent is to set the value of a new
indexed property for a given property index index to a new value value, it must instead set the value
of a new indexed property with the given property index index to the
new value value on the options
collection.
Similarly, the add()
method must act like its
namesake method on that same options
collection.
The remove()
method must act like its
namesake method on that same options
collection when it
has arguments, and like its namesake method on the ChildNode
interface implemented by
the HTMLSelectElement
ancestor interface Element
when it has no
arguments.
The selectedOptions
IDL attribute
must return an HTMLCollection
rooted at the select
node, whose filter
matches the elements in the list of options that
have their selectedness set to true.
The selectedIndex
IDL attribute, on
getting, must return the index of the first
option
element in the list of options
in tree order that has its selectedness set to true, if any. If there isn't one,
then it must return −1.
On setting, the selectedIndex
attribute must set
the selectedness of all the option
elements in the list of options to false, and then
the option
element in the list of
options whose index is the given new value, if
any, must have its selectedness set to true and its dirtiness set to true.
This can result in no element having a selectedness set to true even in the case of the
select
element having no multiple
attribute
and a display size of 1.
The value
IDL attribute, on getting, must
return the value of the first option
element in the list of options in tree
order that has its selectedness set to
true, if any. If there isn't one, then it must return the empty string.
On setting, the value
attribute must set the selectedness of all the option
elements in
the list of options to false, and then the first
option
element in the list of
options, in tree order, whose value
is equal to the given new value, if any, must have its selectedness set to true and its dirtiness set to true.
This can result in no element having a selectedness set to true even in the case of the
select
element having no multiple
attribute
and a display size of 1.
The multiple
, required
, and size
IDL attributes must reflect the
respective content attributes of the same name. The size
IDL
attribute has a default value of zero.
For historical reasons, the default value of the size
IDL attribute does not return the actual size used, which, in
the absence of the size
content attribute, is either 1 or 4
depending on the presence of the multiple
attribute.
The willValidate
, validity
, and validationMessage
IDL attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The labels
IDL
attribute provides a list of the element's label
s. The autofocus
, disabled
, form
, and name
IDL attributes are
part of the element's forms API.
The following example shows how a select
element can be used to offer the user
with a set of options from which the user can select a single option. The default option is
preselected.
<p> <label for="unittype">Select unit type:</label> <select id="unittype" name="unittype"> <option value="1"> Miner </option> <option value="2"> Puffer </option> <option value="3" selected> Snipey </option> <option value="4"> Max </option> <option value="5"> Firebot </option> </select> </p>
When there is no default option, a placeholder can be used instead:
<select name="unittype" required> <option value=""> Select unit type </option> <option value="1"> Miner </option> <option value="2"> Puffer </option> <option value="3"> Snipey </option> <option value="4"> Max </option> <option value="5"> Firebot </option> </select>
Here, the user is offered a set of options from which he can select any number. By default, all five options are selected.
<p> <label for="allowedunits">Select unit types to enable on this map:</label> <select id="allowedunits" name="allowedunits" multiple> <option value="1" selected> Miner </option> <option value="2" selected> Puffer </option> <option value="3" selected> Snipey </option> <option value="4" selected> Max </option> <option value="5" selected> Firebot </option> </select> </p>
Sometimes, a user has to select one or more items. This example shows such an interface.
<p>Select the songs from that you would like on your Act II Mix Tape:</p> <select multiple required name="act2"> <option value="s1">It Sucks to Be Me (Reprise) <option value="s2">There is Life Outside Your Apartment <option value="s3">The More You Ruv Someone <option value="s4">Schadenfreude <option value="s5">I Wish I Could Go Back to College <option value="s6">The Money Song <option value="s7">School for Monsters <option value="s8">The Money Song (Reprise) <option value="s9">There's a Fine, Fine Line (Reprise) <option value="s10">What Do You Do With a B.A. in English? (Reprise) <option value="s11">For Now </select>
datalist
elementoption
elements.interface HTMLDataListElement : HTMLElement { readonly attribute HTMLCollection options; };
The datalist
element represents a set of option
elements that
represent predefined options for other controls. In the rendering, the datalist
element represents nothing and it, along with its children, should
be hidden.
The datalist
element can be used in two ways. In the simplest case, the
datalist
element has just option
element children.
<label> Sex: <input name=sex list=sexes> <datalist id=sexes> <option value="Female"> <option value="Male"> </datalist> </label>
In the more elaborate case, the datalist
element can be given contents that are to
be displayed for down-level clients that don't support datalist
. In this case, the
option
elements are provided inside a select
element inside the
datalist
element.
<label> Sex: <input name=sex list=sexes> </label> <datalist id=sexes> <label> or select from the list: <select name=sex> <option value=""> <option>Female <option>Male </select> </label> </datalist>
The datalist
element is hooked up to an input
element using the list
attribute on the input
element.
Each option
element that is a descendant of the datalist
element,
that is not disabled, and whose value is a string that isn't the empty string, represents a
suggestion. Each suggestion has a value and a label.
options
Returns an HTMLCollection
of the options
elements of the
datalist
element.
The options
IDL attribute must return an
HTMLCollection
rooted at the datalist
node, whose filter matches
option
elements.
Constraint validation: If an element has a datalist
element
ancestor, it is barred from constraint validation.
optgroup
elementselect
element.option
and script-supporting elements.disabled
label
interface HTMLOptGroupElement : HTMLElement { attribute boolean disabled; attribute DOMString label; };
The optgroup
element represents a group of option
elements with a common label.
The element's group of option
elements consists of the option
elements that are children of the optgroup
element.
When showing option
elements in select
elements, user agents should
show the option
elements of such groups as being related to each other and separate
from other option
elements.
The disabled
attribute is a
boolean attribute and can be used to disable a group of option
elements
together.
The label
attribute must be specified. Its
value gives the name of the group, for the purposes of the user interface. User
agents should use this attribute's value when labeling the group of option
elements
in a select
element.
The disabled
and label
attributes must reflect the
respective content attributes of the same name.
The following snippet shows how a set of lessons from three courses could be offered in a
select
drop-down widget:
<form action="courseselector.dll" method="get"> <p>Which course would you like to watch today? <p><label>Course: <select name="c"> <optgroup label="8.01 Physics I: Classical Mechanics"> <option value="8.01.1">Lecture 01: Powers of Ten <option value="8.01.2">Lecture 02: 1D Kinematics <option value="8.01.3">Lecture 03: Vectors <optgroup label="8.02 Electricity and Magnestism"> <option value="8.02.1">Lecture 01: What holds our world together? <option value="8.02.2">Lecture 02: Electric Field <option value="8.02.3">Lecture 03: Electric Flux <optgroup label="8.03 Physics III: Vibrations and Waves"> <option value="8.03.1">Lecture 01: Periodic Phenomenon <option value="8.03.2">Lecture 02: Beats <option value="8.03.3">Lecture 03: Forced Oscillations with Damping </select> </label> <p><input type=submit value="▶ Play"> </form>
option
elementselect
element.datalist
element.optgroup
element.label
attribute and a value
attribute: Empty.label
attribute but no value
attribute: Text.label
attribute: Text that is not inter-element whitespace.disabled
label
selected
value
[NamedConstructor=Option(optional DOMString text = "", optional DOMString value, optional boolean defaultSelected = false, optional boolean selected = false)] interface HTMLOptionElement : HTMLElement { attribute boolean disabled; readonly attribute HTMLFormElement? form; attribute DOMString label; attribute boolean defaultSelected; attribute boolean selected; attribute DOMString value; attribute DOMString text; readonly attribute long index; };
The option
element represents an option in a select
element or as part of a list of suggestions in a datalist
element.
In certain circumstances described in the definition of the select
element, an
option
element can be a select
element's placeholder label
option. A placeholder label option does not represent an actual option, but
instead represents a label for the select
control.
The disabled
attribute is a boolean
attribute. An option
element is disabled if its disabled
attribute is present or if it is a child of an
optgroup
element whose disabled
attribute
is present.
An option
element that is disabled must
prevent any click
events that are queued on the user interaction task source from being dispatched on the
element.
The label
attribute provides a label for
element. The label of an option
element is
the value of the label
content attribute, if there is one,
or, if there is not, the value of the element's text
IDL
attribute.
The label
content attribute, if specified, must not be
empty.
The value
attribute provides a value for
element. The value of an option
element is
the value of the value
content attribute, if there is one,
or, if there is not, the value of the element's text
IDL
attribute.
The selected
attribute is a boolean
attribute. It represents the default selectedness of the element.
The dirtiness of an option
element is
a boolean state, initially false. It controls whether adding or removing the selected
content attribute has any effect.
The selectedness of an option
element is a boolean state, initially false. Except where otherwise specified, when the element is
created, its selectedness must be set to true if
the element has a selected
attribute. Whenever an
option
element's selected
attribute is
added, if its dirtiness is false, its selectedness must be set to true.
Whenever an
option
element's selected
attribute is
removed, if its dirtiness is false, its selectedness must be set to false.
The Option()
constructor, when called with three
or fewer arguments, overrides the initial state of the selectedness state to always be false even if the third
argument is true (implying that a selected
attribute is
to be set). The fourth argument can be used to explicitly set the initial selectedness state when using the constructor.
A select
element whose multiple
attribute is not specified must not have more than one descendant option
element with
its selected
attribute set.
An option
element's index is the number of
option
elements that are in the same list of
options but that come before it in tree order. If the option
element is not in a list of options, then the
option
element's index is zero.
selected
Returns true if the element is selected, and false otherwise.
Can be set, to override the current state of the element.
index
Returns the index of the element in its select
element's options
list.
form
Returns the element's form
element, if any, or null otherwise.
text
Same as textContent
, except that spaces are collapsed and script
elements are skipped.
Option
( [ text [, value [, defaultSelected [, selected ] ] ] ] )Returns a new option
element.
The text argument sets the contents of the element.
The value argument sets the value
attribute.
The defaultSelected argument sets the selected
attribute.
The selected argument sets whether or not the element is selected. If it is omitted, even if the defaultSelected argument is true, the element is not selected.
The disabled
IDL attribute must
reflect the content attribute of the same name. The defaultSelected
IDL attribute must
reflect the selected
content attribute.
The label
IDL attribute, on getting, must
return the element's label. On setting, the element's
label
content attribute must be set to the new value.
The value
IDL attribute, on getting, must
return the element's value. On setting, the element's
value
content attribute must be set to the new value.
The selected
IDL attribute, on getting,
must return true if the element's selectedness is
true, and false otherwise. On setting, it must set the element's selectedness to the new value, set its dirtiness to true, and then cause the
element to ask for a reset.
The index
IDL attribute must return the
element's index.
The text
IDL attribute, on getting, must return
the result of stripping and collapsing
whitespace from the concatenation of data of all the
Text
node descendants of the option
element, in tree order,
excluding any that are descendants of descendants of the option
element that are
themselves script
elements in the HTML namespace or script
elements in the SVG namespace.
On setting, the text
attribute must act as if the
textContent
IDL attribute on the element had been set to the new value.
The form
IDL attribute's behavior depends on
whether the option
element is in a select
element or not. If the
option
has a select
element as its parent, or has an
optgroup
element as its parent and that optgroup
element has a
select
element as its parent, then the form
IDL
attribute must return the same value as the form
IDL attribute
on that select
element. Otherwise, it must return null.
A constructor is provided for creating HTMLOptionElement
objects (in addition to
the factory methods from DOM such as createElement()
): Option(text, value, defaultSelected, selected)
. When invoked as a
constructor, it must return a new HTMLOptionElement
object (a new option
element). If the first argument is not the empty string, the new object must have as its only
child a Text
node whose data is the value of that argument. Otherwise, it must have
no children. If the value argument is present, the new object must have a
value
attribute set with the value of the argument as its
value. If the defaultSelected argument is true, the new object must have a
selected
attribute set with no value. If the selected argument is true, the new object must have its selectedness set to true; otherwise the selectedness must be set to false, even if the defaultSelected argument is true. The element's document must be the active
document of the browsing context of the Window
object on which
the interface object of the invoked constructor is found.
textarea
elementautocomplete
autofocus
cols
dirname
disabled
form
maxlength
minlength
name
placeholder
readonly
required
rows
wrap
interface HTMLTextAreaElement : HTMLElement { attribute DOMString autocomplete; attribute boolean autofocus; attribute unsigned long cols; attribute DOMString dirName; attribute boolean disabled; readonly attribute HTMLFormElement? form; attribute long maxLength; attribute long minLength; attribute DOMString name; attribute DOMString placeholder; attribute boolean readOnly; attribute boolean required; attribute unsigned long rows; attribute DOMString wrap; readonly attribute DOMString type; attribute DOMString defaultValue; [TreatNullAs=EmptyString] attribute DOMString value; readonly attribute unsigned long textLength; readonly attribute boolean willValidate; readonly attribute ValidityState validity; readonly attribute DOMString validationMessage; boolean checkValidity(); boolean reportValidity(); void setCustomValidity(DOMString error); readonly attribute NodeList labels; void select(); attribute unsigned long selectionStart; attribute unsigned long selectionEnd; attribute DOMString selectionDirection; void setRangeText(DOMString replacement); void setRangeText(DOMString replacement, unsigned long start, unsigned long end, optional SelectionMode selectionMode = "preserve"); void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction); };
The textarea
element represents a multiline plain text edit
control for the element's raw
value. The contents of the control represent the control's default value.
The raw value of a textarea
control must be initially the empty string.
This element has rendering requirements involving the bidirectional algorithm.
The readonly
attribute is a
boolean attribute used to control whether the text can be edited by the user or
not.
In this example, a text field is marked read-only because it represents a read-only file:
Filename: <code>/etc/bash.bashrc</code> <textarea name="buffer" readonly> # System-wide .bashrc file for interactive bash(1) shells. # To enable the settings / commands in this file for login shells as well, # this file has to be sourced in /etc/profile. # If not running interactively, don't do anything [ -z "$PS1" ] && return ...</textarea>
Constraint validation: If the readonly
attribute is specified on a textarea
element, the element is barred from constraint validation.
A textarea
element is mutable if it is
neither disabled nor has a readonly
attribute specified.
When a textarea
is mutable, its raw value should be editable by the user: the user agent
should allow the user to edit, insert, and remove text, and to insert and remove line breaks in
the form of "LF" (U+000A) characters. Any time the user causes the element's raw value to change, the user agent must queue a
task to fire a simple event that bubbles named input
at the textarea
element. User agents may wait for a
suitable break in the user's interaction before queuing the task; for example, a user agent could
wait for the user to have not hit a key for 100ms, so as to only fire the event when the user
pauses, instead of continuously for each keystroke.
A textarea
element has a dirty value
flag, which must be initially set to false, and must be set to true whenever the user
interacts with the control in a way that changes the raw
value.
When the textarea
element's textContent
IDL attribute changes value,
if the element's dirty value flag is false, then the
element's raw value must be set to the value of
the element's textContent
IDL attribute.
The reset algorithm for textarea
elements is to set the element's value to the
value of the element's textContent
IDL attribute.
If the element is mutable, the user agent should allow the user to change the writing direction of the element, setting it either to a left-to-right writing direction or a right-to-left writing direction. If the user does so, the user agent must then run the following steps:
Set the element's dir
attribute to "ltr
" if the user selected a left-to-right writing direction, and
"rtl
" if the user selected a right-to-left writing
direction.
Queue a task to fire a simple event that bubbles named input
at the textarea
element.
The cols
attribute specifies the expected
maximum number of characters per line. If the cols
attribute is specified, its value must be a valid non-negative integer greater than
zero. If applying the rules for parsing non-negative integers to
the attribute's value results in a number greater than zero, then the element's character width is that value; otherwise, it is
20.
The user agent may use the textarea
element's character width as a hint to the user as to how many
characters the server prefers per line (e.g. for visual user agents by making the width of the
control be that many characters). In visual renderings, the user agent should wrap the user's
input in the rendering so that each line is no wider than this number of characters.
The rows
attribute specifies the number of
lines to show. If the rows
attribute is specified, its
value must be a valid non-negative integer greater than zero. If
applying the rules for parsing non-negative integers to the attribute's value results
in a number greater than zero, then the element's character
height is that value; otherwise, it is 2.
Visual user agents should set the height of the control to the number of lines given by character height.
The wrap
attribute is an enumerated
attribute with two keywords and states: the soft
keyword which maps to the Soft state, and the hard
keyword which maps to the Hard state. The missing value default is the
Soft state.
The Soft state indicates that the text in the
textarea
is not to be wrapped when it is submitted (though it can still be wrapped in
the rendering).
The Hard state indicates that the text in the
textarea
is to have newlines added by the user agent so that the text is wrapped when
it is submitted.
If the element's wrap
attribute is in the Hard state, the cols
attribute must be specified.
For historical reasons, the element's value is normalised in three different ways for three
different purposes. The raw value is the value as
it was originally set. It is not normalized. The API
value is the value used in the value
IDL attribute.
It is normalized so that line breaks use "LF" (U+000A) characters. Finally, there is the
form submission value. It is normalized so that line breaks
use U+000D CARRIAGE RETURN "CRLF" (U+000A) character pairs, and in addition, if necessary
given the element's wrap
attribute, additional line breaks
are inserted to wrap the text at the given width.
The element's API value is defined to be the element's raw value with the following transformation applied:
Replace every U+000D CARRIAGE RETURN "CRLF" (U+000A) character pair from the raw value with a single "LF" (U+000A) character.
Replace every remaining U+000D CARRIAGE RETURN character from the raw value with a single "LF" (U+000A) character.
The element's value is defined to be the element's raw value with the following transformation applied:
Replace every occurrence of a "CR" (U+000D) character not followed by a "LF" (U+000A) character, and every occurrence of a "LF" (U+000A) character not preceded by a "CR" (U+000D) character, by a two-character string consisting of a U+000D CARRIAGE RETURN "CRLF" (U+000A) character pair.
If the element's wrap
attribute is in the Hard state, insert U+000D CARRIAGE RETURN "CRLF" (U+000A) character pairs into the string using a UA-defined algorithm so that each line
has no more than character width characters. For
the purposes of this requirement, lines are delimited by the start of the string, the end of the
string, and U+000D CARRIAGE RETURN "CRLF" (U+000A) character pairs.
The maxlength
attribute is a form control maxlength
attribute controlled
by the textarea
element's dirty value
flag.
If the textarea
element has a maximum allowed value length, then the
element's children must be such that the code-unit length of the value of the
element's textContent
IDL attribute is equal to or less than the element's
maximum allowed value length.
The minlength
attribute is a form control minlength
attribute controlled
by the textarea
element's dirty value
flag.
The required
attribute is a
boolean attribute. When specified, the user will be required to enter a value before
submitting the form.
Constraint validation: If the element has its required
attribute specified, and the element is mutable, and the element's value is the empty string, then the element is suffering
from being missing.
The placeholder
attribute represents
a short hint (a word or short phrase) intended to aid the user with data entry when the
control has no value. A hint could be a sample value or a brief description of the expected
format.
The placeholder
attribute
should not be used as a replacement for a label
. For a
longer hint or other advisory text, place the text next to the control.
Use of the placeholder
attribute as a replacement for a label
can reduce the
accessibility and usability of the control for a range of users including older
users and users with cognitive, mobility, fine motor skill or vision impairments.
While the hint given by the control's label
is shown at all times, the short
hint given in the placeholder
attribute is only shown before the user enters a value. Furthermore,
placeholder
text may be mistaken for
a pre-filled value, and as commonly implemented the default color of the placeholder text
provides insufficient contrast and the lack of a separate visible label
reduces the size of the hit region available for setting focus on the control.
User agents should present this hint to the user when the element's value is the empty string and the control is not focused (e.g. by displaying it inside a blank unfocused control). All U+000D CARRIAGE RETURN U+000A LINE FEED character pairs (CRLF) in the hint, as well as all other "CR" (U+000D) and "LF" (U+000A) characters in the hint, must be treated as line breaks when rendering the hint.
The name
attribute represents the element's name.
The dirname
attribute controls how the element's directionality is submitted.
The disabled
attribute is used to make the control
non-interactive and to prevent its value from being submitted.
The form
attribute is used to explicitly associate the
textarea
element with its form owner.
The autofocus
attribute controls focus.
The autocomplete
attribute controls how the user agent
provides autofill behavior.
type
Returns the string "textarea
".
value
Returns the current value of the element.
Can be set, to change the value.
The cols
, placeholder
, required
, rows
, and wrap
attributes must reflect the
respective content attributes of the same name. The cols
and rows
attributes are limited to only non-negative
numbers greater than zero. The cols
attribute's
default value is 20. The rows
attribute's default value is
2. The dirName
IDL attribute must
reflect the dirname
content attribute. The maxLength
IDL attribute must
reflect the maxlength
content attribute,
limited to only non-negative numbers. The minLength
IDL attribute must
reflect the minlength
content attribute,
limited to only non-negative numbers. The readOnly
IDL attribute must reflect
the readonly
content attribute.
The type
IDL attribute must return the value
"textarea
".
The defaultValue
IDL attribute must
act like the element's textContent
IDL attribute.
The value
attribute must, on getting, return
the element's API value; on setting, it must set
the element's raw value to the new value, set the
element's dirty value flag to true, and should then
move the text entry cursor position to the end of the text field, unselecting any selected text
and resetting the selection direction to none.
The textLength
IDL attribute must
return the code-unit length of the element's API value.
The willValidate
, validity
, and validationMessage
IDL attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The labels
IDL
attribute provides a list of the element's label
s. The select()
, selectionStart
, selectionEnd
, selectionDirection
, setRangeText()
, and setSelectionRange()
methods and IDL attributes
expose the element's text selection. The autofocus
, disabled
, form
, and name
IDL attributes are part of the element's forms API.
Here is an example of a textarea
being used for unrestricted free-form text input
in a form:
<p>If you have any comments, please let us know: <textarea cols=80 name=comments></textarea></p>
To specify a maximum length for the comments, one can use the maxlength
attribute:
<p>If you have any short comments, please let us know: <textarea cols=80 name=comments maxlength=200></textarea></p>
To give a default value, text can be included inside the element:
<p>If you have any comments, please let us know: <textarea cols=80 name=comments>You rock!</textarea></p>
You can also give a minimum length. Here, a letter needs to be filled out by the user; a template (which is shorter than the minimum length) is provided, but is insufficient to submit the form:
<textarea required minlength="500">Dear Madam Speaker, Regarding your letter dated ... ... Yours Sincerely, ...</textarea>
A placeholder can be given as well, to suggest the basic form to the user, without providing an explicit template:
<textarea placeholder="Dear Francine, They closed the parks this week, so we won't be able to meet your there. Should we just have dinner? Love, Daddy"></textarea>
To have the browser submit the directionality of
the element along with the value, the dirname
attribute can be
specified:
<p>If you have any comments, please let us know (you may use either English or Hebrew for your comments): <textarea cols=80 name=comments dirname=comments.dir></textarea></p>
keygen
elementautofocus
challenge
disabled
form
keytype
name
interface HTMLKeygenElement : HTMLElement { attribute boolean autofocus; attribute DOMString challenge; attribute boolean disabled; readonly attribute HTMLFormElement? form; attribute DOMString keytype; attribute DOMString name; readonly attribute DOMString type; readonly attribute boolean willValidate; readonly attribute ValidityState validity; readonly attribute DOMString validationMessage; boolean checkValidity(); boolean reportValidity(); void setCustomValidity(DOMString error); readonly attribute NodeList labels; };
The keygen
element represents a key pair generator control. When the
control's form is submitted, the private key is stored in the local keystore, and the public key
is packaged and sent to the server.
The challenge
attribute may be specified.
Its value will be packaged with the submitted key.
The keytype
attribute is an
enumerated attribute. The following table lists the keywords and states for the
attribute — the keywords in the left column map to the states listed in the cell in the
second column on the same row as the keyword. User agents are not required to support these
values, and must only recognize values whose corresponding algorithms they support.
Keyword | State |
---|---|
rsa
| RSA |
The invalid value default state is the unknown state. The missing value default state is the RSA state, if it is supported, or the unknown state otherwise.
This specification does not specify what key types user agents are to support — it is possible for a user agent to not support any key types at all.
The user agent may expose a user interface for each keygen
element to allow the
user to configure settings of the element's key pair generator, e.g. the key length.
The reset algorithm for keygen
elements is to set these various configuration settings back to their defaults.
The element's value is the string returned from the following algorithm:
Use the appropriate step from the following list:
keytype
attribute is in the RSA stateGenerate an RSA key pair using the settings given by the user, if appropriate, using the
md5WithRSAEncryption
RSA signature algorithm (the signature algorithm
with MD5 and the RSA encryption algorithm) referenced in section 2.2.1 ("RSA Signature
Algorithm") of RFC 3279, and defined in RFC 2313. [RFC3279] [RFC2313]
keytype
attribute is in the unknown stateThe given key type is not supported. Return the empty string and abort this algorithm.
Let private key be the generated private key.
Let public key be the generated public key.
Let signature algorithm be the selected signature algorithm.
If the element has a challenge
attribute, then let
challenge be that attribute's value. Otherwise, let challenge be the empty string.
Let algorithm be an ASN.1 AlgorithmIdentifier
structure as defined by RFC 5280, with the algorithm
field giving the
ASN.1 OID used to identify signature algorithm, using the OIDs defined in
section 2.2 ("Signature Algorithms") of RFC 3279, and the parameters
field
set up as required by RFC 3279 for AlgorithmIdentifier
structures for that
algorithm. [X690] [RFC5280] [RFC3279]
Let spki be an ASN.1 SubjectPublicKeyInfo
structure
as defined by RFC 5280, with the algorithm
field set to the algorithm structure from the previous step, and the subjectPublicKey
field set to the BIT STRING value resulting from ASN.1 DER
encoding the public key. [X690] [RFC5280]
Let publicKeyAndChallenge be an ASN.1 PublicKeyAndChallenge
structure as defined below, with the spki
field set to the spki structure from the previous step, and the challenge
field set to the string challenge obtained earlier. [X690]
Let signature be the BIT STRING value resulting from ASN.1 DER encoding the signature generated by applying the signature algorithm to the byte string obtained by ASN.1 DER encoding the publicKeyAndChallenge structure, using private key as the signing key. [X690]
Let signedPublicKeyAndChallenge be an ASN.1
SignedPublicKeyAndChallenge
structure as defined below, with the publicKeyAndChallenge
field set to the publicKeyAndChallenge
structure, the signatureAlgorithm
field set to the algorithm structure, and the signature
field set to the BIT
STRING signature from the previous step. [X690]
Return the result of base64 encoding the result of ASN.1 DER encoding the signedPublicKeyAndChallenge structure. [RFC4648] [X690]
The data objects used by the above algorithm are defined as follows. These definitions use the same "ASN.1-like" syntax defined by RFC 5280. [RFC5280]
PublicKeyAndChallenge ::= SEQUENCE { spki SubjectPublicKeyInfo, challenge IA5STRING } SignedPublicKeyAndChallenge ::= SEQUENCE { publicKeyAndChallenge PublicKeyAndChallenge, signatureAlgorithm AlgorithmIdentifier, signature BIT STRING }
Constraint validation: The keygen
element is barred from
constraint validation.
The form
attribute is used to explicitly associate the
keygen
element with its form owner. The name
attribute represents the element's name. The disabled
attribute is used to make the control non-interactive and
to prevent its value from being submitted. The autofocus
attribute controls focus.
type
Returns the string "keygen
".
The challenge
IDL attribute must
reflect the content attribute of the same name.
The keytype
IDL attribute must
reflect the content attribute of the same name, limited to only known
values.
The type
IDL attribute must return the value
"keygen
".
The willValidate
, validity
, and validationMessage
IDL attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The labels
IDL
attribute provides a list of the element's label
s. The autofocus
, disabled
, form
, and name
IDL attributes are
part of the element's forms API.
This specification does not specify how the private key generated is to be used.
It is expected that after receiving the SignedPublicKeyAndChallenge
(SPKAC)
structure, the server will generate a client certificate and offer it back to the user for
download; this certificate, once downloaded and stored in the key store along with the private
key, can then be used to authenticate to services that use TLS and certificate authentication.
To generate a key pair, add the private key to the user's key store, and submit the public key to the server, markup such as the following can be used:
<form action="processkey.cgi" method="post" enctype="multipart/form-data"> <p><keygen name="key"></p> <p><input type=submit value="Submit key..."></p> </form>
The server will then receive a form submission with a packaged RSA public key as the value of
"key
". This can then be used for various purposes, such as generating a
client certificate, as mentioned above.
output
elementfor
form
name
interface HTMLOutputElement : HTMLElement {
[PutForwards=value] readonly attribute DOMSettableTokenList htmlFor;
readonly attribute HTMLFormElement? form;
attribute DOMString name;
readonly attribute DOMString type;
attribute DOMString defaultValue;
attribute DOMString value;
readonly attribute boolean willValidate;
readonly attribute ValidityState validity;
readonly attribute DOMString validationMessage;
boolean checkValidity();
boolean reportValidity();
void setCustomValidity(DOMString error);
readonly attribute NodeList labels;
};
The output
element represents the result of a calculation or user
action.
The for
content attribute allows an explicit
relationship to be made between the result of a calculation and the elements that represent the
values that went into the calculation or that otherwise influenced the calculation. The for
attribute, if specified, must contain a string consisting of an
unordered set of unique space-separated tokens that are case-sensitive,
each of which must have the value of an ID of an element in the
same Document
.
The form
attribute is used to explicitly associate the
output
element with its form owner. The name
attribute represents the element's name.
The element has a value mode flag which is either value or default. Initially, the value mode flag must be set to default.
The element also has a default value. Initially, the default value must be the empty string.
When the value mode flag is in mode default, the contents of the element represent both the
value of the element and its default value. When
the value mode flag is in mode value, the contents of the element represent the value of
the element only, and the default value is only
accessible using the defaultValue
IDL attribute.
Whenever the element's descendants are changed in any way, if the value mode flag is in mode default, the element's default value must be set to the value of the element's
textContent
IDL attribute.
The reset algorithm for output
elements is to set the element's value mode flag to default and then to set the element's
textContent
IDL attribute to the value of the element's default value (thus replacing the element's child
nodes).
value
[ = value ]Returns the element's current value.
Can be set, to change the value.
defaultValue
[ = value ]Returns the element's current default value.
Can be set, to change the default value.
type
Returns the string "output
".
The value
IDL attribute must act like the
element's textContent
IDL attribute, except that on setting, in addition, before the
child nodes are changed, the element's value mode flag
must be set to value.
The defaultValue
IDL attribute, on
getting, must return the element's default value.
On setting, the attribute must set the element's default
value, and, if the element's value mode flag is in
the mode default, set the element's
textContent
IDL attribute as well.
The type
attribute must return the string
"output
".
The htmlFor
IDL attribute must
reflect the for
content attribute.
The willValidate
, validity
, and validationMessage
IDL attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The labels
IDL
attribute provides a list of the element's label
s. The form
and name
IDL attributes are part
of the element's forms API.
A simple calculator could use output
for its display of calculated results:
<form onsubmit="return false" oninput="o.value = a.valueAsNumber + b.valueAsNumber"> <input name=a type=number step=any> + <input name=b type=number step=any> = <output name=o for="a b"></output> </form>
In this example, an output
element is used to report the results from a remote
server, as they come in:
<output id="result"></output> <script> var primeSource = new WebSocket('ws://primes.example.net/'); primeSource.onmessage = function (event) { document.getElementById('result').value = event.data; } </script>
progress
elementprogress
element descendants.value
max
interface HTMLProgressElement : HTMLElement { attribute double value; attribute double max; readonly attribute double position; readonly attribute NodeList labels; };
The progress
element represents the completion progress of a task.
The progress is either indeterminate, indicating that progress is being made but that it is not
clear how much more work remains to be done before the task is complete (e.g. because the task is
waiting for a remote host to respond), or the progress is a number in the range zero to a maximum,
giving the fraction of work that has so far been completed.
There are two attributes that determine the current task completion represented by the element.
The value
attribute specifies how much of the
task has been completed, and the max
attribute
specifies how much work the task requires in total. The units are arbitrary and not specified.
To make a determinate progress bar, add a value
attribute with the current progress (either a number from
0.0 to 1.0, or, if the max
attribute is specified, a number
from 0 to the value of the max
attribute). To make an
indeterminate progress bar, remove the value
attribute.
Authors are encouraged to also include the current value and the maximum value inline as text inside the element, so that the progress is made available to users of legacy user agents.
Here is a snippet of a Web application that shows the progress of some automated task:
<section> <h2>Task Progress</h2> <p>Progress: <progress id="p" max=100><span>0</span>%</progress></p> <script> var progressBar = document.getElementById('p'); function updateProgress(newValue) { progressBar.value = newValue; progressBar.getElementsByTagName('span')[0].textContent = newValue; } </script> </section>
(The updateProgress()
method in this example would be called by some other code
on the page to update the actual progress bar as the task progressed.)
The value
and max
attributes, when present, must have values that are valid floating-point numbers. The value
attribute, if present, must have a value equal to or
greater than zero, and less than or equal to the value of the max
attribute, if present, or 1.0, otherwise. The max
attribute, if present, must have a value greater than
zero.
The progress
element is the wrong element to use for something that
is just a gauge, as opposed to task progress. For instance, indicating disk space usage using
progress
would be inappropriate. Instead, the meter
element is available
for such use cases.
User agent requirements: If the value
attribute is omitted, then the progress bar is an indeterminate progress bar. Otherwise, it is a
determinate progress bar.
If the progress bar is a determinate progress bar and the element has a max
attribute, the user agent must parse the max
attribute's value according to the rules for parsing
floating-point number values. If this does not result in an error, and if the parsed value
is greater than zero, then the maximum value of the
progress bar is that value. Otherwise, if the element has no max
attribute, or if it has one but parsing it resulted in an
error, or if the parsed value was less than or equal to zero, then the maximum value of the progress bar is 1.0.
If the progress bar is a determinate progress bar, user agents must parse the value
attribute's value according to the rules for
parsing floating-point number values. If this does not result in an error, and if the
parsed value is less than the maximum value and
greater than zero, then the current value of the
progress bar is that parsed value. Otherwise, if the parsed value was greater than or equal to the
maximum value, then the current value of the progress bar is the maximum value of the progress bar. Otherwise, if parsing
the value
attribute's value resulted in an error, or a
number less than or equal to zero, then the current
value of the progress bar is zero.
UA requirements for showing the progress bar: When representing a
progress
element to the user, the UA should indicate whether it is a determinate or
indeterminate progress bar, and in the former case, should indicate the relative position of the
current value relative to the maximum value.
position
For a determinate progress bar (one with known current and maximum values), returns the result of dividing the current value by the maximum value.
For an indeterminate progress bar, returns −1.
If the progress bar is an indeterminate progress bar, then the position
IDL attribute must return −1.
Otherwise, it must return the result of dividing the current
value by the maximum value.
If the progress bar is an indeterminate progress bar, then the value
IDL attribute, on getting, must return 0.
Otherwise, it must return the current value. On
setting, the given value must be converted to the best representation of the number as a
floating-point number and then the value
content
attribute must be set to that string.
Setting the value
IDL attribute to itself
when the corresponding content attribute is absent would change the progress bar from an
indeterminate progress bar to a determinate progress bar with no progress.
The max
IDL attribute must
reflect the content attribute of the same name, limited to numbers greater than
zero. The default value for max
is 1.0.
The labels
IDL attribute provides a list of the element's
label
s.
meter
elementmeter
element descendants.value
min
max
low
high
optimum
interface HTMLMeterElement : HTMLElement { attribute double value; attribute double min; attribute double max; attribute double low; attribute double high; attribute double optimum; readonly attribute NodeList labels; };
The meter
element represents a scalar measurement within a known
range, or a fractional value; for example disk usage, the relevance of a query result, or the
fraction of a voting population to have selected a particular candidate.
This is also known as a gauge.
The meter
element should not be used to indicate progress (as in a
progress bar). For that role, HTML provides a separate progress
element.
The meter
element also does not represent a scalar value of arbitrary
range — for example, it would be wrong to use this to report a weight, or height, unless
there is a known maximum value.
There are six attributes that determine the semantics of the gauge represented by the element.
The min
attribute specifies the lower bound of
the range, and the max
attribute specifies the
upper bound. The value
attribute specifies the
value to have the gauge indicate as the "measured" value.
The other three attributes can be used to segment the gauge's range into "low", "medium", and
"high" parts, and to indicate which part of the gauge is the "optimum" part. The low
attribute specifies the range that is considered to
be the "low" part, and the high
attribute
specifies the range that is considered to be the "high" part. The optimum
attribute gives the position that is
"optimum"; if that is higher than the "high" value then this indicates that the higher the value,
the better; if it's lower than the "low" mark then it indicates that lower values are better, and
naturally if it is in between then it indicates that neither high nor low values are good.
Authoring requirements: The value
attribute must be specified. The value
, min
, low
, high
, max
, and optimum
attributes,
when present, must have values that are valid
floating-point numbers.
In addition, the attributes' values are further constrained:
Let value be the value
attribute's
number.
If the min
attribute is specified, then let minimum be that attribute's value; otherwise, let it be zero.
If the max
attribute is specified, then let maximum be that attribute's value; otherwise, let it be 1.0.
The following inequalities must hold, as applicable:
low
≤ maximum (if low
is specified)high
≤ maximum (if high
is specified)optimum
≤ maximum (if optimum
is specified)low
≤ high
(if
both low
and high
are
specified)If no minimum or maximum is specified, then the range is assumed to be 0..1, and the value thus has to be within that range.
Authors are encouraged to include a textual representation of the gauge's state in the
element's contents, for users of user agents that do not support the meter
element.
The following examples show three gauges that would all be three-quarters full:
Storage space usage: <meter value=6 max=8>6 blocks used (out of 8 total)</meter> Voter turnout: <meter value=0.75><img alt="75%" src="graph75.png"></meter> Tickets sold: <meter min="0" max="100" value="75"></meter>
The following example is incorrect use of the element, because it doesn't give a range (and since the default maximum is 1, both of the gauges would end up looking maxed out):
<p>The grapefruit pie had a radius of <meter value=12>12cm</meter> and a height of <meter value=2>2cm</meter>.</p> <!-- BAD! -->
Instead, one would either not include the meter element, or use the meter element with a defined range to give the dimensions in context compared to other pies:
<p>The grapefruit pie had a radius of 12cm and a height of 2cm.</p> <dl> <dt>Radius: <dd> <meter min=0 max=20 value=12>12cm</meter> <dt>Height: <dd> <meter min=0 max=10 value=2>2cm</meter> </dl>
There is no explicit way to specify units in the meter
element, but the units may
be specified in the title
attribute in free-form text.
The example above could be extended to mention the units:
<dl> <dt>Radius: <dd> <meter min=0 max=20 value=12 title="centimeters">12cm</meter> <dt>Height: <dd> <meter min=0 max=10 value=2 title="centimeters">2cm</meter> </dl>
User agent requirements: User agents must parse the min
, max
, value
, low
, high
, and optimum
attributes using the rules for parsing floating-point number values.
User agents must then use all these numbers to obtain values for six points on the gauge, as follows. (The order in which these are evaluated is important, as some of the values refer to earlier ones.)
If the min
attribute is specified and a value could be
parsed out of it, then the minimum value is that value. Otherwise, the minimum value is
zero.
If the max
attribute is specified and a value could be
parsed out of it, then the candidate maximum value is that value. Otherwise, the candidate
maximum value is 1.0.
If the candidate maximum value is greater than or equal to the minimum value, then the maximum value is the candidate maximum value. Otherwise, the maximum value is the same as the minimum value.
If the value
attribute is specified and a value could
be parsed out of it, then that value is the candidate actual value. Otherwise, the candidate
actual value is zero.
If the candidate actual value is less than the minimum value, then the actual value is the minimum value.
Otherwise, if the candidate actual value is greater than the maximum value, then the actual value is the maximum value.
Otherwise, the actual value is the candidate actual value.
If the low
attribute is specified and a value could be
parsed out of it, then the candidate low boundary is that value. Otherwise, the candidate low
boundary is the same as the minimum value.
If the candidate low boundary is less than the minimum value, then the low boundary is the minimum value.
Otherwise, if the candidate low boundary is greater than the maximum value, then the low boundary is the maximum value.
Otherwise, the low boundary is the candidate low boundary.
If the high
attribute is specified and a value could be
parsed out of it, then the candidate high boundary is that value. Otherwise, the candidate high
boundary is the same as the maximum value.
If the candidate high boundary is less than the low boundary, then the high boundary is the low boundary.
Otherwise, if the candidate high boundary is greater than the maximum value, then the high boundary is the maximum value.
Otherwise, the high boundary is the candidate high boundary.
If the optimum
attribute is specified and a value
could be parsed out of it, then the candidate optimum point is that value. Otherwise, the
candidate optimum point is the midpoint between the minimum value and the maximum value.
If the candidate optimum point is less than the minimum value, then the optimum point is the minimum value.
Otherwise, if the candidate optimum point is greater than the maximum value, then the optimum point is the maximum value.
Otherwise, the optimum point is the candidate optimum point.
All of which will result in the following inequalities all being true:
UA requirements for regions of the gauge: If the optimum point is equal to the low boundary or the high boundary, or anywhere in between them, then the region between the low and high boundaries of the gauge must be treated as the optimum region, and the low and high parts, if any, must be treated as suboptimal. Otherwise, if the optimum point is less than the low boundary, then the region between the minimum value and the low boundary must be treated as the optimum region, the region from the low boundary up to the high boundary must be treated as a suboptimal region, and the remaining region must be treated as an even less good region. Finally, if the optimum point is higher than the high boundary, then the situation is reversed; the region between the high boundary and the maximum value must be treated as the optimum region, the region from the high boundary down to the low boundary must be treated as a suboptimal region, and the remaining region must be treated as an even less good region.
UA requirements for showing the gauge: When representing a meter
element to the user, the UA should indicate the relative position of the actual value to the
minimum and maximum values, and the relationship between the actual value and the three regions of
the gauge.
The following markup:
<h3>Suggested groups</h3> <ul> <li> <p><a href="/group/comp.infosystems.www.authoring.stylesheets/view">comp.infosystems.www.authoring.stylesheets</a> - <a href="/group/comp.infosystems.www.authoring.stylesheets/subscribe">join</a></p> <p>Group description: <strong>Layout/presentation on the WWW.</strong></p> <p><meter value="0.5">Moderate activity,</meter> Usenet, 618 subscribers</p> </li> <li> <p><a href="/group/netscape.public.mozilla.xpinstall/view">netscape.public.mozilla.xpinstall</a> - <a href="/group/netscape.public.mozilla.xpinstall/subscribe">join</a></p> <p>Group description: <strong>Mozilla XPInstall discussion.</strong></p> <p><meter value="0.25">Low activity,</meter> Usenet, 22 subscribers</p> </li> <li> <p><a href="/group/mozilla.dev.general/view">mozilla.dev.general</a> - <a href="/group/mozilla.dev.general/subscribe">join</a></p> <p><meter value="0.25">Low activity,</meter> Usenet, 66 subscribers</p> </li> </ul>
Might be rendered as follows:
User agents may combine the value of the title
attribute and the other attributes to provide context-sensitive
help or inline text detailing the actual values.
For example, the following snippet:
<meter min=0 max=60 value=23.2 title=seconds></meter>
...might cause the user agent to display a gauge with a tooltip saying "Value: 23.2 out of 60." on one line and "seconds" on a second line.
The value
IDL attribute, on getting, must
return the actual value. On setting, the given value
must be converted to the best representation of the number as a floating-point number
and then the value
content attribute must be set to that
string.
The min
IDL attribute, on getting, must return
the minimum value. On setting, the given value must be
converted to the best representation of the number as a floating-point number and
then the min
content attribute must be set to that string.
The max
IDL attribute, on getting, must return
the maximum value. On setting, the given value must be
converted to the best representation of the number as a floating-point number and
then the max
content attribute must be set to that string.
The low
IDL attribute, on getting, must return
the low boundary. On setting, the given value must be
converted to the best representation of the number as a floating-point number and
then the low
content attribute must be set to that string.
The high
IDL attribute, on getting, must return
the high boundary. On setting, the given value must be
converted to the best representation of the number as a floating-point number and
then the high
content attribute must be set to that
string.
The optimum
IDL attribute, on getting, must
return the optimum value. On setting, the given value
must be converted to the best representation of the number as a floating-point number
and then the optimum
content attribute must be set to that
string.
The labels
IDL attribute provides a list of the element's
label
s.
The following example shows how a gauge could fall back to localized or pretty-printed text.
<p>Disk usage: <meter min=0 value=170261928 max=233257824>170 261 928 bytes used out of 233 257 824 bytes available</meter></p>
fieldset
elementlegend
element, followed by flow content.disabled
form
name
interface HTMLFieldSetElement : HTMLElement { attribute boolean disabled; readonly attribute HTMLFormElement? form; attribute DOMString name; readonly attribute DOMString type; readonly attribute HTMLFormControlsCollection elements; readonly attribute boolean willValidate; readonly attribute ValidityState validity; readonly attribute DOMString validationMessage; boolean checkValidity(); boolean reportValidity(); void setCustomValidity(DOMString error); };
The fieldset
element represents a set of form controls optionally
grouped under a common name.
The name of the group is given by the first legend
element that is a child of the
fieldset
element, if any. The remainder of the descendants form the group.
The disabled
attribute, when specified,
causes all the form control descendants of the fieldset
element, excluding those that
are descendants of the fieldset
element's first legend
element child, if
any, to be disabled.
The form
attribute is used to explicitly associate the
fieldset
element with its form owner. The name
attribute represents the element's name.
type
Returns the string "fieldset".
elements
Returns an HTMLFormControlsCollection
of the form controls in the element.
The disabled
IDL attribute must
reflect the content attribute of the same name.
The type
IDL attribute must return the string
"fieldset
".
The elements
IDL attribute must return an
HTMLFormControlsCollection
rooted at the fieldset
element, whose filter
matches listed elements.
The willValidate
, validity
, and validationMessage
attributes, and the checkValidity()
, reportValidity()
, and setCustomValidity()
methods, are part of the
constraint validation API. The form
and name
IDL attributes are part of the element's forms API.
This example shows a fieldset
element being used to group a set of related
controls:
<fieldset> <legend>Display</legend> <div><label><input type=radio name=c value=0 checked> Black on White</label></div> <div><label><input type=radio name=c value=1> White on Black</label></div> <div><label><input type=checkbox name=g> Use grayscale</label></div> <div><label>Enhance contrast <input type=range name=e list=contrast min=0 max=100 value=0 step=1></label></div> <datalist id=contrast> <option label=Normal value=0> <option label=Maximum value=100> </datalist> </fieldset>
The div elements used in the code samples above and below are not intended to convey any semantic meaning and are used only to create a non-inline rendering of the grouped fieldset controls.
The following snippet shows a fieldset with a checkbox in the legend that controls whether or not the fieldset is enabled. The contents of the fieldset consist of two required text fields and an optional year/month control.
<fieldset name="clubfields" disabled> <legend> <label> <input type=checkbox name=club onchange="form.clubfields.disabled = !checked"> Use Club Card </label> </legend> <div><label>Name on card: <input name=clubname required></label></div> <div><label>Card number: <input name=clubnum required pattern="[-0-9]+"></label></div> <div><label>Expiry date: <input name=clubexp type=month></label></div> </fieldset>
You can also nest fieldset
elements. Here is an example expanding on the previous
one that does so:
<fieldset name="clubfields" disabled> <legend> <label> <input type=checkbox name=club onchange="form.clubfields.disabled = !checked"> Use Club Card </label> </legend> <div><label>Name on card: <input name=clubname required></label></div> <fieldset name="numfields"> <legend> <label> <input type=radio checked name=clubtype onchange="form.numfields.disabled = !checked"> My card has numbers on it </label> </legend> <div><label>Card number: <input name=clubnum required pattern="[-0-9]+"></label></div> </fieldset> <fieldset name="letfields" disabled> <legend> <label> <input type=radio name=clubtype onchange="form.letfields.disabled = !checked"> My card has letters on it </label> </legend> <div><label>Card code: <input name=clublet required pattern="[A-Za-z]+"></label></> </fieldset> </fieldset>
In this example, if the outer "Use Club Card" checkbox is not checked, everything inside the
outer fieldset
, including the two radio buttons in the legends of the two nested
fieldset
s, will be disabled. However, if the checkbox is checked, then the radio
buttons will both be enabled and will let you select which of the two inner
fieldset
s is to be enabled.
legend
elementfieldset
element.interface HTMLLegendElement : HTMLElement { readonly attribute HTMLFormElement? form; };
The legend
element represents a caption for the rest of the contents
of the legend
element's parent fieldset
element, if
any.
form
Returns the element's form
element, if any, or null otherwise.
The form
IDL attribute's behavior depends on
whether the legend
element is in a fieldset
element or not. If the
legend
has a fieldset
element as its parent, then the form
IDL attribute must return the same value as the form
IDL attribute on that fieldset
element. Otherwise,
it must return null.
Form controls have a value and a checkedness. (The latter is only used by input
elements.) These are used to describe how the user interacts with the control.
To define the behaviour of constraint validation in the face of the input
element's multiple
attribute, input
elements
can also have separately defined values.
A form control can be designated as mutable.
This determines (by means of definitions and requirements in this specification that rely on whether an element is so designated) whether or not the user can modify the value or checkedness of a form control, or whether or not a control can be automatically prefilled.
A form-associated element can have a relationship with a form
element, which is called the element's form owner. If a form-associated
element is not associated with a form
element, its form owner is
said to be null.
A form-associated element is, by default, associated with its nearest ancestor form
element (as described
below), but, if it is reassociateable, may have a
form
attribute specified to override this.
This feature allows authors to work around the lack of support for nested
form
elements.
If a reassociateable form-associated
element has a form
attribute specified, then that
attribute's value must be the ID of a form
element in
the element's owner Document
.
The rules in this section are complicated by the fact that although conforming
documents will never contain nested form
elements, it is quite possible (e.g. using a
script that performs DOM manipulation) to generate documents that have such nested elements. They
are also complicated by rules in the HTML parser that, for historical reasons, can result in a
form-associated element being associated with a form
element that is not
its ancestor.
When a form-associated element is created, its form owner must be initialized to null (no owner).
When a form-associated element is to be associated with a form, its form owner must be set to that form.
When a form-associated element or one of its ancestors is inserted into a Document
, then the user agent must
reset the form owner of that form-associated element. The HTML parser overrides this requirement when inserting form
controls.
When an element is removed from a
Document
resulting in a form-associated element and its
form owner (if any) no longer being in the same home subtree, then the
user agent must reset the form owner of that form-associated
element.
When a reassociateable form-associated
element's form
attribute is set, changed, or removed,
then the user agent must reset the form owner of that element.
When a reassociateable form-associated
element has a form
attribute and the ID of any of the elements in the Document
changes, then the
user agent must reset the form owner of that form-associated
element.
When a reassociateable form-associated
element has a form
attribute and an element with an
ID is inserted
into or removed from the
Document
, then the user agent must reset the form owner of that
form-associated element.
When the user agent is to reset the form owner of a form-associated element, it must run the following steps:
If the element's form owner is not null, and either the element is not reassociateable or its form
content attribute is not present, and the element's form owner is its nearest
form
element ancestor after the change to the ancestor chain, then do nothing, and
abort these steps.
Let the element's form owner be null.
If the element is reassociateable, has a form
content attribute, and is itself in a Document
, then run these substeps:
If the first element in the Document
to
have an ID that is case-sensitively equal to the element's form
content attribute's value is a form
element,
then associate the form-associated
element with that form
element.
Abort the "reset the form owner" steps.
Otherwise, if the form-associated element in question has an ancestor
form
element, then associate the
form-associated element with the nearest such ancestor form
element.
Otherwise, the element is left unassociated.
In the following non-conforming snippet:
... <form id="a"> <div id="b"></div> </form> <script> document.getElementById('b').innerHTML = '<table><tr><td><form id="c"><input id="d"></table>' + '<input id="e">'; </script> ...
The form owner of "d" would be the inner nested form "c", while the form owner of "e" would be the outer form "a".
This happens as follows: First, the "e" node gets associated with "c" in the HTML
parser. Then, the innerHTML
algorithm moves the nodes
from the temporary document to the "b" element. At this point, the nodes see their ancestor chain
change, and thus all the "magic" associations done by the parser are reset to normal ancestor
associations.
This example is a non-conforming document, though, as it is a violation of the content models
to nest form
elements.
form
Returns the element's form owner.
Returns null if there isn't one.
Reassociateable form-associated elements have a form
IDL attribute, which, on getting, must return the element's form owner, or null if
there isn't one.
name
attributeThe name
content attribute gives the name of the
form control, as used in form submission and in the form
element's elements
object. If the attribute is specified, its value must
not be the empty string.
Any non-empty value for name
is allowed, but the names
"_charset_
" and "isindex
" are special:
isindex
This value, if used as the name of a Text control
that is the first control in a form that is submitted using the application/x-www-form-urlencoded
mechanism, causes
the submission to only include the value of this control, with no name.
_charset_
This value, if used as the name of a Hidden
control with no value
attribute, is automatically given a
value during submission consisting of the submission character encoding.
dirname
attributeThe dirname
attribute on a form control element
enables the submission of the directionality of the element, and gives the name of
the field that contains this value during form submission. If such an attribute is
specified, its value must not be the empty string.
In this example, a form contains a text field and a submission button:
<form action="addcomment.cgi" method=post> <p><label>Comment: <input type=text name="comment" dirname="comment.dir" required></label></p> <p><button name="mode" type=submit value="add">Post Comment</button></p> </form>
When the user submits the form, the user agent includes three fields, one called "comment", one called "comment.dir", and one called "mode"; so if the user types "Hello", the submission body might be something like:
comment=Hello&comment.dir=ltr&mode=add
If the user manually switches to a right-to-left writing direction and enters "مرحبا", the submission body might be something like:
comment=%D9%85%D8%B1%D8%AD%D8%A8%D8%A7&comment.dir=rtl&mode=add
maxlength
attributeA form control maxlength
attribute,
controlled by a dirty value flag, declares a limit on the number of characters
a user can input.
If an element has its form control maxlength
attribute specified, the attribute's value must be a valid
non-negative integer. If the attribute is specified and applying the rules for
parsing non-negative integers to its value results in a number, then that number is the
element's maximum allowed value length. If the attribute is omitted or parsing its
value results in an error, then there is no maximum allowed value length.
Constraint validation: If an element has a maximum allowed value length, its dirty value flag is true, its value was last changed by a user edit (as opposed to a change made by a script), and the code-unit length of the element's value is greater than the element's maximum allowed value length, then the element is suffering from being too long.
User agents may prevent the user from causing the element's value to be set to a value whose code-unit length is greater than the element's maximum allowed value length.
minlength
attributeA form control minlength
attribute,
controlled by a dirty value flag, declares a lower bound on the number of
characters a user can input.
The minlength
attribute does not imply the
required
attribute. If the form control has no minlength
attribute, then the value can still be omitted; the
minlength
attribute only kicks in once the user has entered
a value at all. If the empty string is not allowed, then the required
attribute also needs to be set.
If an element has its form control minlength
attribute specified, the attribute's value must be a valid
non-negative integer. If the attribute is specified and applying the rules for
parsing non-negative integers to its value results in a number, then that number is the
element's minimum allowed value length. If the attribute is omitted or parsing its
value results in an error, then there is no minimum allowed value length.
If an element has both a maximum allowed value length and a minimum allowed value length, the minimum allowed value length must be smaller than or equal to the maximum allowed value length.
Constraint validation: If an element has a minimum allowed value length, its value is not the empty string, and the code-unit length of the element's value is less than the element's minimum allowed value length, then the element is suffering from being too short.
In this example, there are four text fields. The first is required, and has to be at least 5 characters long. The other three are optional, but if the user fills one in, the user has to enter at least 10 characters.
<form action="/events/menu.cgi" method="post"> <p><label>Name of Event: <input required minlength=5 maxlength=50 name=event></label></p> <p><label>Describe what you would like for breakfast, if anything: <textarea name="breakfast" minlength="10"></textarea></label></p> <p><label>Describe what you would like for lunch, if anything: <textarea name="lunch" minlength="10"></textarea></label></p> <p><label>Describe what you would like for dinner, if anything: <textarea name="dinner" minlength="10"></textarea></label></p> <p><input type=submit value="Submit Request"></p> </form>
disabled
attributeThe disabled
content attribute is a
boolean attribute.
A form control is disabled if its disabled
attribute is set, or if it is a descendant of a
fieldset
element whose disabled
attribute
is set and is not a descendant of that fieldset
element's first
legend
element child, if any.
A form control that is disabled must prevent any click
events that are queued on the
user interaction task source from being dispatched on the element.
Constraint validation: If an element is disabled, it is barred from constraint validation.
The disabled
IDL attribute must
reflect the disabled
content attribute.
Attributes for form submission can be specified both on form
elements
and on submit buttons (elements that represent buttons
that submit forms, e.g. an input
element whose type
attribute is in the Submit Button state).
The attributes for form submission that may be specified on form
elements are action
, enctype
, method
, novalidate
, and target
.
The corresponding attributes for form submission that may be specified on submit buttons are formaction
, formenctype
, formmethod
, formnovalidate
, and formtarget
. When omitted, they default to the values given on
the corresponding attributes on the form
element.
The action
and formaction
content attributes, if specified, must
have a value that is a valid non-empty URL potentially surrounded by spaces.
The action of an element is the value of the element's
formaction
attribute, if the element is a submit button and has such an attribute, or the value of its
form owner's action
attribute, if it has
one, or else the empty string.
The method
and formmethod
content attributes are enumerated attributes with the following keywords and
states:
get
, mapping to the
state GET, indicating the HTTP GET method.post
, mapping to the
state POST, indicating the HTTP POST method.The invalid value default for these attributes is the GET state. The missing value default for the method
attribute is also the GET state. (There is no missing value default for the
formmethod
attribute.)
The method of an element is one of those states. If the
element is a submit button and has a formmethod
attribute, then the element's method is that attribute's state; otherwise, it is the form
owner's method
attribute's state.
Here the method
attribute is used to explicitly specify
the default value, "get
", so that the search
query is submitted in the URL:
<form method="get" action="/search.cgi"> <p><label>Search terms: <input type=search name=q></label></p> <p><input type=submit></p> </form>
On the other hand, here the method
attribute is used to
specify the value "post
", so that the user's
message is submitted in the HTTP request's body:
<form method="post" action="/post-message.cgi"> <p><label>Message: <input type=text name=m></label></p> <p><input type=submit value="Submit message"></p> </form>
In this example, a form
is used with a dialog
. The method
attribute's "dialog
" keyword is used to have the dialog
automatically close when the form is submitted.
<dialog id="ship">
<form method=dialog>
<p>A ship has arrived in the harbour.</p>
<button type=submit value="board">Board the ship</button>
<button type=submit value="call">Call to the captain</button>
</form>
</dialog>
<script>
var ship = document.getElementById('ship');
ship.showModal();
ship.onclose = function (event) {
if (ship.returnValue == 'board') {
// ...
} else {
// ...
}
};
</script>
The enctype
and formenctype
content attributes are enumerated attributes with the following keywords and
states:
application/x-www-form-urlencoded
" keyword and corresponding state.multipart/form-data
" keyword and corresponding state.text/plain
" keyword and corresponding state.The invalid value default for these attributes is the application/x-www-form-urlencoded
state. The missing
value default for the enctype
attribute is also the application/x-www-form-urlencoded
state. (There is no
missing value default for the formenctype
attribute.)
The enctype of an element is one of those three states.
If the element is a submit button and has a formenctype
attribute, then the element's enctype is that attribute's state; otherwise, it is the
form owner's enctype
attribute's state.
The target
and formtarget
content attributes, if specified, must
have values that are valid browsing context
names or keywords.
The target of an element is the value of the element's
formtarget
attribute, if the element is a submit button and has such an attribute; or the value of its
form owner's target
attribute, if it has
such an attribute; or, if the Document
contains a base
element with a
target
attribute, then the value of the target
attribute of the first such base
element; or,
if there is no such element, the empty string.
The novalidate
and formnovalidate
content attributes are boolean attributes. If present, they indicate that the form is
not to be validated during submission.
The no-validate state of an element is true if the
element is a submit button and the element's formnovalidate
attribute is present, or if the element's
form owner's novalidate
attribute is present,
and false otherwise.
This attribute is useful to include "save" buttons on forms that have validation constraints, to allow users to save their progress even though they haven't fully entered the data in the form. The following example shows a simple form that has two required fields. There are three buttons: one to submit the form, which requires both fields to be filled in; one to save the form so that the user can come back and fill it in later; and one to cancel the form altogether.
<form action="editor.cgi" method="post"> <p><label>Name: <input required name=fn></label></p> <p><label>Essay: <textarea required name=essay></textarea></label></p> <p><input type=submit name=submit value="Submit essay"></p> <p><input type=submit formnovalidate name=save value="Save essay"></p> <p><input type=submit formnovalidate name=cancel value="Cancel"></p> </form>
The action
IDL attribute must
reflect the content attribute of the same name, except that on getting, when the
content attribute is missing or its value is the empty string, the document's address
must be returned instead. The target
IDL attribute
must reflect the content attribute of the same name. The method
and enctype
IDL attributes must reflect the
respective content attributes of the same name, limited to only known values. The
encoding
IDL attribute must reflect
the enctype
content attribute, limited to only known
values. The noValidate
IDL attribute must
reflect the novalidate
content attribute. The
formAction
IDL attribute must
reflect the formaction
content attribute,
except that on getting, when the content attribute is missing or its value is the empty string,
the document's address must be returned instead. The formEnctype
IDL attribute must reflect
the formenctype
content attribute, limited to only
known values. The formMethod
IDL
attribute must reflect the formmethod
content
attribute, limited to only known values. The formNoValidate
IDL attribute must
reflect the formnovalidate
content
attribute. The formTarget
IDL attribute must
reflect the formtarget
content attribute.
autofocus
attributeThe autofocus
content attribute allows the
author to indicate that a control is to be focused as soon as the page is loaded or as soon as the
dialog
within which it finds itself is shown, allowing the user to just start typing
without having to manually focus the main control.
The autofocus
attribute is a boolean
attribute.
An element's nearest ancestor autofocus scoping root element is the element itself
if the element is a dialog
element, or else is the element's nearest ancestor
dialog
element, if any, or else is the element's root element.
There must not be two elements with the same nearest ancestor autofocus scoping root
element that both have the autofocus
attribute
specified.
When an element with the autofocus
attribute specified
is inserted into a document, user agents
should run the following steps:
Let target be the element's Document
.
If target has no browsing context, abort these steps.
If target's browsing context has no top-level browsing context (e.g. it is a nested browsing context with no parent browsing context), abort these steps.
If target's active sandboxing flag set has the sandboxed automatic features browsing context flag, abort these steps.
If target's origin is not the same as the origin of the Document
of the currently
focused element in target's top-level browsing context, abort
these steps.
If target's origin is not the same as the origin of the active document of target's top-level browsing context, abort these steps.
If the user agent has already reached the last step of this list of steps in response to
an element being inserted into a
Document
whose top-level browsing context's active
document is the same as target's top-level browsing
context's active document, abort these steps.
If the user has indicated (for example, by starting to type in a form control) that he does not wish focus to be changed, then optionally abort these steps.
Queue a task that checks to see if the element is focusable, and if so, runs the focusing steps for that element. User agents may also change the scrolling position of the document, or perform some other action that brings the element to the user's attention. The task source for this task is the user interaction task source.
This handles the automatic focusing during document load. The showModal()
method of dialog
elements also
processes the autofocus
attribute.
Focusing the control does not imply that the user agent must focus the browser window if it has lost focus.
The autofocus
IDL attribute must
reflect the content attribute of the same name.
In the following snippet, the text control would be focused when the document was loaded.
<input maxlength="256" name="q" value="" autofocus> <input type="submit" value="Search">
autocomplete
attributeUser agents sometimes have features for helping users fill forms in, for example prefilling the
user's address based on earlier user input. The autocomplete
content attribute can be used to hint
to the user agent how to, or indeed whether to, provide such a feature.
The attribute, if present, must have a value that is an ASCII case-insensitive
match for the string "off
", or a single token that
is an ASCII case-insensitive match for the string "on
"
The "off
" keyword indicates either
that the control's input data is particularly sensitive (for example the activation code for a
nuclear weapon); or that it is a value that will never be reused (for example a one-time-key for a
bank login) and the user will therefore have to explicitly enter the data each time, instead of
being able to rely on the UA to prefill the value for him; or that the document provides its own
autocomplete mechanism and does not want the user agent to provide autocompletion values.
The "on
" keyword indicates that the
user agent is allowed to provide the user with autocompletion values, but does not provide any
further information about what kind of data the user might be expected to enter. User agents would
have to use heuristics to decide what autocompletion values to suggest.
If the autocomplete
attribute is omitted, the default
value corresponding to the state of the element's form owner's autocomplete
attribute is used instead (either "on
" or "off
"). If there is no form owner, then the
value "on
" is used.
When an element's autofill field name is "off
", the user agent should not remember the control's
value, and should not offer past values to the user.
In addition, when an element's autofill field name is "off
", values are reset
when traversing the history.
Banks frequently do not want UAs to prefill login information:
<p><label>Account: <input type="text" name="ac" autocomplete="off"></label></p> <p><label>PIN: <input type="password" name="pin" autocomplete="off"></label></p>
When an element's autofill field name is not "off
", the user agent may store the control's value, and may offer previously stored values to the user.
When the autofill field name is "on
",
the user agent should attempt to use heuristics to determine the most appropriate values to offer
the user, e.g. based on the element's name
value, the position
of the element in the document's DOM, what other fields exist in the form, and so forth.
The autocompletion mechanism must be implemented by the user agent acting as if the user had modified the element's value, and must be done at a time where the element is mutable (e.g. just after the element has been inserted into the document, or when the user agent stops parsing). User agents must only prefill controls using values that the user could have entered.
A user agent prefilling a form control's value must not cause that control to suffer from a type mismatch, suffer from a pattern mismatch, suffer from being too long, suffer from being too short, suffer from an underflow, suffer from an overflow, or suffer from a step mismatch. Where possible given the control's constraints, user agents must use the format given as canonical in the aforementioned table. Where it's not possible for the canonical format to be used, user agents should use heuristics to attempt to convert values so that they can be used.
A user agent may allow the user to override an element's autofill field name, e.g.
to change it from "off
" to "on
" to allow values to be remembered and prefilled despite
the page author's objections, or to always "off
",
never remembering values. However, user agents should not allow users to trivially override the
autofill field name from "off
" to
"on
" or other values, as there are significant
security implications for the user if all values are always remembered, regardless of the site's
preferences.
The autocomplete
IDL attribute, on getting,
must return the element's IDL-exposed autofill value, and on setting, must
reflect the content attribute of the same name.
The input
and textarea
elements define the following members in their
DOM interfaces for handling their selection:
void select(); attribute unsigned long selectionStart; attribute unsigned long selectionEnd; attribute DOMString selectionDirection; void setRangeText(DOMString replacement); void setRangeText(DOMString replacement, unsigned long start, unsigned long end, optional SelectionMode selectionMode = "preserve"); void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction = "preserve");
The setRangeText
method uses the following
enumeration:
enum SelectionMode { "select", "start", "end", "preserve", // default };
These methods and attributes expose and control the selection of input
and
textarea
text fields.
select
()Selects everything in the text field.
selectionStart
[ = value ]Returns the offset to the start of the selection.
Can be set, to change the start of the selection.
selectionEnd
[ = value ]Returns the offset to the end of the selection.
Can be set, to change the end of the selection.
selectionDirection
[ = value ]Returns the current direction of the selection.
Can be set, to change the direction of the selection.
The possible values are "forward
", "backward
", and "none
".
setSelectionRange
(start, end [, direction] )Changes the selection to cover the given substring in the given direction. If the direction is omitted, it will be reset to be the platform default (none or forward).
setRangeText
(replacement [, start, end [, selectionMode ] ] )Replaces a range of text with the new text. If the start and end arguments are not provided, the range is assumed to be the selection.
The final argument determines how the selection should be set after the text has been replaced. The possible values are:
select
"start
"end
"preserve
"For input
elements, calling these methods while they don't apply, and getting or setting these attributes while they don't apply, must throw an InvalidStateError
exception. Otherwise, they
must act as described below.
For input
elements, these methods and attributes must operate on the element's
value. For textarea
elements, these methods and
attributes must operate on the element's raw
value.
Where possible, user interface features for changing the text selection in input
and textarea
elements must be implemented in terms of the DOM API described in this
section, so that, e.g., all the same events fire.
The selections of input
and textarea
elements have a
direction, which is either forward, backward, or none. This direction
is set when the user manipulates the selection. The exact meaning of the selection direction
depends on the platform.
On Windows, the direction indicates the position of the caret relative to the selection: a forward selection has the caret at the end of the selection and a backward selection has the caret at the start of the selection. Windows has no none direction. On Mac, the direction indicates which end of the selection is affected when the user adjusts the size of the selection using the arrow keys with the Shift modifier: the forward direction means the end of the selection is modified, and the backwards direction means the start of the selection is modified. The none direction is the default on Mac, it indicates that no particular direction has yet been selected. The user sets the direction implicitly when first adjusting the selection, based on which directional arrow key was used.
The select()
method must cause the
contents of the text field to be fully selected, with the selection direction being none, if the
platform support selections with the direction none, or otherwise forward. The user
agent must then queue a task to fire a simple event that bubbles named
select
at the element, using the user interaction task
source as the task source.
The selectionStart
attribute
must, on getting, return the offset (in logical order) to the character that immediately follows
the start of the selection. If there is no selection, then it must return the offset (in logical
order) to the character that immediately follows the text entry cursor.
On setting, it must act as if the setSelectionRange()
method had been called,
with the new value as the first argument; the current value of the selectionEnd
attribute as the second argument,
unless the current value of the selectionEnd
is less than the new value, in which case the second argument must also be the new value; and the
current value of the selectionDirection
as the third argument.
The selectionEnd
attribute
must, on getting, return the offset (in logical order) to the character that immediately follows
the end of the selection. If there is no selection, then it must return the offset (in logical
order) to the character that immediately follows the text entry cursor.
On setting, it must act as if the setSelectionRange()
method had been called,
with the current value of the selectionStart
attribute as the first argument,
the new value as the second argument, and the current value of the selectionDirection
as the third argument.
The selectionDirection
attribute must, on getting, return the string corresponding to the current selection direction: if
the direction is forward, "forward
"; if the direction is
backward, "backward
"; and otherwise, "none
".
On setting, it must act as if the setSelectionRange()
method had been called,
with the current value of the selectionStart
attribute as the first argument,
the current value of the selectionEnd
attribute as the second argument, and the new value as the third argument.
The setSelectionRange(start, end, direction)
method
must set the selection of the text field to the sequence of characters starting with the character
at the startth position (in logical order) and ending with the character at
the (end-1)th position. Arguments greater than the
length of the value of the text field must be treated as pointing at the end of the text field. If
end is less than or equal to start then the start of the
selection and the end of the selection must both be placed immediately before the character with
offset end. In UAs where there is no concept of an empty selection, this must
set the cursor to be just before the character with offset end. The direction
of the selection must be set to backward if direction is a
case-sensitive match for the string "backward
", forward
if direction is a case-sensitive match for the string "forward
" or if the platform does not support selections with the direction
none, and none otherwise (including if the argument is omitted). The user agent must
then queue a task to fire a simple event that bubbles named select
at the element, using the user interaction task
source as the task source.
The setRangeText(replacement, start, end, selectMode)
method must run the following steps:
If the method has only one argument, then let start and end have the values of the selectionStart
attribute and the selectionEnd
attribute respectively.
Otherwise, let start, end have the values of the second and third arguments respectively.
If start is greater than end, then throw an
IndexSizeError
exception and abort these steps.
If start is greater than the length of the value of the text field, then set it to the length of the value of the text field.
If end is greater than the length of the value of the text field, then set it to the length of the value of the text field.
Let selection start be the current value of the selectionStart
attribute.
Let selection end be the current value of the selectionEnd
attribute.
If start is less than end, delete the sequence of characters starting with the character at the startth position (in logical order) and ending with the character at the (end-1)th position.
Insert the value of the first argument into the text of the value of the text field, immediately before the startth character.
Let new length be the length of the value of the first argument.
Let new end be the sum of start and new length.
Run the appropriate set of substeps from the following list:
select
"Let selection start be start.
Let selection end be new end.
start
"Let selection start and selection end be start.
end
"Let selection start and selection end be new end.
preserve
" (the default)Let old length be end minus start.
Let delta be new length minus old length.
If selection start is greater than end, then increment it by delta. (If delta is negative, i.e. the new text is shorter than the old text, then this will decrease the value of selection start.)
Otherwise: if selection start is greater than start, then set it to start. (This snaps the start of the selection to the start of the new text if it was in the middle of the text that it replaced.)
If selection end is greater than end, then increment it by delta in the same way.
Otherwise: if selection end is greater than start, then set it to new end. (This snaps the end of the selection to the end of the new text if it was in the middle of the text that it replaced.)
Set the selection of the text field to the sequence of characters starting with the character at the selection startth position (in logical order) and ending with the character at the (selection end-1)th position. In UAs where there is no concept of an empty selection, this must set the cursor to be just before the character with offset end. The direction of the selection must be set to forward if the platform does not support selections with the direction none, and none otherwise.
Queue a task to fire a simple event that bubbles named select
at the element, using the user interaction task
source as the task source.
All elements to which this API applies have either a selection or a text entry cursor position at all times (even for elements that are not being rendered). User agents should follow platform conventions to determine their initial state.
Characters with no visible rendering, such as U+200D ZERO WIDTH JOINER, still count as characters. Thus, for instance, the selection can include just an invisible character, and the text insertion cursor can be placed to one side or another of such a character.
To obtain the currently selected text, the following JavaScript suffices:
var selectionText = control.value.substring(control.selectionStart, control.selectionEnd);
To add some text at the start of a text control, while maintaining the text selection, the three attributes must be preserved:
var oldStart = control.selectionStart; var oldEnd = control.selectionEnd; var oldDirection = control.selectionDirection; var prefix = "http://"; control.value = prefix + control.value; control.setSelectionRange(oldStart + prefix.length, oldEnd + prefix.length, oldDirection);
A submittable element is a candidate for constraint
validation except when a condition has barred
the element from constraint validation. (For example, an element is barred from
constraint validation if it is an object
element.)
An element can have a custom validity error message defined. Initially, an element
must have its custom validity error message set to the empty string. When its value
is not the empty string, the element is suffering from a custom error. It can be set
using the setCustomValidity()
method. The user
agent should use the custom validity error message when alerting the user to the
problem with the control.
An element can be constrained in various ways. The following is the list of validity states that a form control can be in, making the control invalid for the purposes of constraint validation. (The definitions below are non-normative; other parts of this specification define more precisely when each state applies or does not.)
When a control has no value but has a required
attribute (input
required
, select
required
, textarea
required
), or, in the case of an element in a radio
button group, any of the other elements in the group has a required
attribute.
When a control that allows arbitrary user input has a value that is not in the correct syntax (E-mail, URL).
When a control has a value that doesn't satisfy the
pattern
attribute.
When a control has a value that is too long for the
form control maxlength
attribute
(input
maxlength
, textarea
maxlength
).
When a control has a value that is too short for the
form control minlength
attribute
(input
minlength
, textarea
minlength
).
When a control has a value that is too low for the
min
attribute.
When a control has a value that is too high for the
max
attribute.
When a control has a value that doesn't fit the
rules given by the step
attribute.
When a control has incomplete input and the user agent does not think the user ought to be able to submit the form in its current state.
When a control's custom validity error message (as set by the element's
setCustomValidity()
method) is not the empty
string.
An element can still suffer from these states even when the element is disabled; thus these states can be represented in the DOM even if validating the form during submission wouldn't indicate a problem to the user.
An element satisfies its constraints if it is not suffering from any of the above validity states.
When the user agent is required to statically validate the constraints of
form
element form, it must run the following steps, which return
either a positive result (all the controls in the form are valid) or a negative
result (there are invalid controls) along with a (possibly empty) list of elements that are
invalid and for which no script has claimed responsibility:
Let controls be a list of all the submittable elements whose form owner is form, in tree order.
Let invalid controls be an initially empty list of elements.
For each element field in controls, in tree order, run the following substeps:
If field is not a candidate for constraint validation, then move on to the next element.
Otherwise, if field satisfies its constraints, then move on to the next element.
Otherwise, add field to invalid controls.
If invalid controls is empty, then return a positive result and abort these steps.
Let unhandled invalid controls be an initially empty list of elements.
For each element field in invalid controls, if any, in tree order, run the following substeps:
Fire a simple event named invalid
that
is cancelable at field.
If the event was not canceled, then add field to unhandled invalid controls.
Return a negative result with the list of elements in the unhandled invalid controls list.
If a user agent is to interactively validate the constraints of form
element form, then the user agent must run the following steps:
Statically validate the constraints of form, and let unhandled invalid controls be the list of elements returned if the result was negative.
If the result was positive, then return that result and abort these steps.
Report the problems with the constraints of at least one of the elements given in unhandled invalid controls to the user. User agents may focus one of those
elements in the process, by running the focusing steps for that element, and may
change the scrolling position of the document, or perform some other action that brings the
element to the user's attention. User agents may report more than one constraint violation. User
agents may coalesce related constraint violation reports if appropriate (e.g. if multiple radio
buttons in a group are marked as required, only one error
need be reported). If one of the controls is not being rendered (e.g. it has the
hidden
attribute set) then user agents may report a script
error.
Return a negative result.
willValidate
Returns true if the element will be validated when the form is submitted; false otherwise.
setCustomValidity
(message)Sets a custom error, so that the element would fail to validate. The given message is the message to be shown to the user when reporting the problem to the user.
If the argument is the empty string, clears the custom error.
validity
. valueMissing
Returns true if the element has no value but is a required field; false otherwise.
validity
. typeMismatch
Returns true if the element's value is not in the correct syntax; false otherwise.
validity
. patternMismatch
Returns true if the element's value doesn't match the provided pattern; false otherwise.
validity
. tooLong
Returns true if the element's value is longer than the provided maximum length; false otherwise.
validity
. tooShort
Returns true if the element's value, if it is not the empty string, is shorter than the provided minimum length; false otherwise.
validity
. rangeUnderflow
Returns true if the element's value is lower than the provided minimum; false otherwise.
validity
. rangeOverflow
Returns true if the element's value is higher than the provided maximum; false otherwise.
validity
. stepMismatch
Returns true if the element's value doesn't fit the rules given by the step
attribute; false otherwise.
validity
. badInput
Returns true if the user has provided input in the user interface that the user agent is unable to convert to a value; false otherwise.
validity
. customError
Returns true if the element has a custom error; false otherwise.
validity
. valid
Returns true if the element's value has no validity problems; false otherwise.
checkValidity
()Returns true if the element's value has no validity problems; false otherwise. Fires an invalid
event at the element in the latter case.
reportValidity
()Returns true if the element's value has no validity problems; otherwise, returns false, fires
an invalid
event at the element, and (if the event isn't
canceled) reports the problem to the user.
validationMessage
Returns the error message that would be shown to the user if the element was to be checked for validity.
The willValidate
attribute must return
true if an element is a candidate for constraint validation, and false otherwise
(i.e. false if any conditions are barring it from
constraint validation).
The setCustomValidity(message)
, when invoked, must set the custom validity error
message to the value of the given message argument.
In the following example, a script checks the value of a form control each time it is edited,
and whenever it is not a valid value, uses the setCustomValidity()
method to set an appropriate
message.
<label>Feeling: <input name=f type="text" oninput="check(this)"></label> <script> function check(input) { if (input.value == "good" || input.value == "fine" || input.value == "tired") { input.setCustomValidity('"' + input.value + '" is not a feeling.'); } else { // input is fine -- reset the error message input.setCustomValidity(''); } } </script>
The validity
attribute must return a
ValidityState
object that represents the validity states of the element.
This object is live, and the same object must be returned each time the element's
validity
attribute is retrieved.
interface ValidityState { readonly attribute boolean valueMissing; readonly attribute boolean typeMismatch; readonly attribute boolean patternMismatch; readonly attribute boolean tooLong; readonly attribute boolean tooShort; readonly attribute boolean rangeUnderflow; readonly attribute boolean rangeOverflow; readonly attribute boolean stepMismatch; readonly attribute boolean badInput; readonly attribute boolean customError; readonly attribute boolean valid; };
A ValidityState
object has the following attributes. On getting, they must return
true if the corresponding condition given in the following list is true, and false otherwise.
valueMissing
The control is suffering from being missing.
typeMismatch
The control is suffering from a type mismatch.
patternMismatch
The control is suffering from a pattern mismatch.
tooLong
The control is suffering from being too long.
tooShort
The control is suffering from being too short.
rangeUnderflow
The control is suffering from an underflow.
rangeOverflow
The control is suffering from an overflow.
stepMismatch
The control is suffering from a step mismatch.
badInput
The control is suffering from bad input.
customError
The control is suffering from a custom error.
valid
None of the other conditions are true.
When the checkValidity()
method is
invoked, if the element is a candidate for constraint validation and does not satisfy its constraints, the user agent must fire a simple
event named invalid
that is cancelable (but in this case
has no default action) at the element and return false. Otherwise, it must only return true
without doing anything else.
When the reportValidity()
method is
invoked, if the element is a candidate for constraint validation and does not satisfy its constraints, the user agent must: fire a simple
event named invalid
that is cancelable at the element,
and if that event is not canceled, report the problems with the constraints of that element to the
user; then, return false. Otherwise, it must only return true without doing anything else. When
reporting the problem with the constraints to the user, the user agent may run the focusing
steps for that element, and may change the scrolling position of the document, or perform
some other action that brings the element to the user's attention. User agents may report more
than one constraint violation, if the element suffers from multiple problems at once. If the
element is not being rendered, then the user agent may, instead of notifying the
user, report a script error.
The validationMessage
attribute must
return the empty string if the element is not a candidate for constraint validation
or if it is one but it satisfies its constraints; otherwise,
it must return a suitably localized message that the user agent would show the user if this were
the only form control with a validity constraint problem. If the user agent would not actually
show a textual message in such a situation (e.g. it would show a graphical cue instead), then the
attribute must return a suitably localized message that expresses (one or more of) the validity
constraint(s) that the control does not satisfy. If the element is a candidate for
constraint validation and is suffering from a custom error, then the
custom validity error message should be present in the return value.
Servers should not rely on client-side validation. Client-side validation can be intentionally bypassed by hostile users, and unintentionally bypassed by users of older user agents or automated tools that do not implement these features. The constraint validation features are only intended to improve the user experience, not to provide any kind of security mechanism.
This section is non-normative.
When a form is submitted, the data in the form is converted into the structure specified by the enctype, and then sent to the destination specified by the action using the given method.
For example, take the following form:
<form action="/find.cgi" method=get> <input type=text name=t> <input type=search name=q> <input type=submit> </form>
If the user types in "cats" in the first field and "fur" in the second, and then hits the
submit button, then the user agent will load /find.cgi?t=cats&q=fur
.
On the other hand, consider this form:
<form action="/find.cgi" method=post enctype="multipart/form-data"> <input type=text name=t> <input type=search name=q> <input type=submit> </form>
Given the same user input, the result on submission is quite different: the user agent instead does an HTTP POST to the given URL, with as the entity body something like the following text:
------kYFrd4jNJEgCervE Content-Disposition: form-data; name="t" cats ------kYFrd4jNJEgCervE Content-Disposition: form-data; name="q" fur ------kYFrd4jNJEgCervE--
A form
element's default button is the first submit button in tree order whose form
owner is that form
element.
If the user agent supports letting the user submit a form implicitly (for example, on some platforms hitting the "enter" key while a text field is focused implicitly submits the form), then doing so for a form whose default button has a defined activation behavior must cause the user agent to run synthetic click activation steps on that default button.
Consequently, if the default button is disabled, the form is not submitted when such an implicit submission mechanism is used. (A button has no activation behavior when disabled.)
There are pages on the Web that are only usable if there is a way to implicitly submit forms, so user agents are strongly encouraged to support this.
If the form has
no submit button, then the implicit submission
mechanism must do nothing if the form has more than one field that blocks implicit
submission, and must submit the form
element from the form
element itself otherwise.
For the purpose of the previous paragraph, an element is a field that blocks implicit
submission of a form
element if it is an input
element whose
form owner is that form
element and whose type
attribute is in one of the following states:
Text,
Search,
URL,
Telephone,
E-mail,
Password,
Date and Time,
Date,
Month,
Week,
Time,
Local Date and Time,
Number
When a form
element form is submitted from an element submitter
(typically a button), optionally with a submitted from submit()
method flag set, the user agent must run the
following steps:
Let form document be the form's
Document
.
If form document has no associated browsing context or its active sandboxing flag set has its sandboxed forms browsing context flag set, then abort these steps without doing anything.
Let form browsing context be the browsing context of form document.
If the submitted from submit()
method flag is not set, and the submitter element's no-validate state is false, then interactively
validate the constraints of form and examine the result: if the result
is negative (the constraint validation concluded that there were invalid fields and probably
informed the user of this) then fire a simple event named invalid
at the form element and then abort these
steps.
If the submitted from submit()
method flag is not set, then fire a simple event that bubbles and is
cancelable named submit
, at form. If the
event's default action is prevented (i.e. if the event is canceled) then abort these steps.
Otherwise, continue (effectively the default action is to perform the submission).
Let form data set be the result of constructing the form data set for form in the context of submitter.
Let action be the submitter element's action.
If action is the empty string, let action be the document's address of the form document.
Resolve the URL action, relative to the submitter element. If this fails, abort these steps.
Let action be the resulting absolute URL.
Let action components be the resulting parsed URL.
Let scheme be the scheme of the resulting parsed URL.
Let enctype be the submitter element's enctype.
Let method be the submitter element's method.
Let target be the submitter element's target.
If the user indicated a specific browsing context to use when submitting the form, then let target browsing context be that browsing context. Otherwise, apply the rules for choosing a browsing context given a browsing context name using target as the name and form browsing context as the context in which the algorithm is executed, and let target browsing context be the resulting browsing context.
If target browsing context was created in the previous step, or,
alternatively, if the form document has not yet completely
loaded and the submitted from submit()
method flag is set, then let replace be true. Otherwise, let it be
false.
Otherwise, select the appropriate row in the table below based on the value of scheme as given by the first cell of each row. Then, select the appropriate cell on that row based on the value of method as given in the first cell of each column. Then, jump to the steps named in that cell and defined below the table.
GET | POST | |
---|---|---|
http
| Mutate action URL | Submit as entity body |
https
| Mutate action URL | Submit as entity body |
ftp
| Get action URL | Get action URL |
javascript
| Get action URL | Get action URL |
data
| Get action URL | Post to data: |
mailto
| Mail with headers | Mail as body |
If scheme is not one of those listed in this table, then the behavior is not defined by this specification. User agents should, in the absence of another specification defining this, act in a manner analogous to that defined in this specification for similar schemes.
Each form
element has a planned navigation, which is either null or a
task; when the form
is first created, its
planned navigation must be set to null. In the behaviours described below, when the
user agent is required to plan to navigate to a particular resource destination, it must run the following steps:
If the form
has a non-null planned navigation, remove it from
its task queue.
Let the form
's planned navigation be a new task that consists of running the following steps:
Let the form
's planned navigation be null.
Navigate target browsing context to the particular resource destination. If replace is true, then target browsing context must be navigated with replacement enabled.
For the purposes of this task, target browsing context and replace are the variables that were set up when the overall form submission algorithm was run, with their values as they stood when this planned navigation was queued.
Queue the task that is the form
's new
planned navigation.
The task source for this task is the DOM manipulation task source.
The behaviors are as follows:
Let query be the result of encoding the form data
set using the application/x-www-form-urlencoded
encoding
algorithm, interpreted as a US-ASCII string.
Set parsed action's query component to query.
Let destination be a new URL formed by applying the URL serializer algorithm to parsed action.
Plan to navigate to destination.
Let entity body be the result of encoding the form data set using the appropriate form encoding algorithm.
Let MIME type be determined as follows:
application/x-www-form-urlencoded
application/x-www-form-urlencoded
".multipart/form-data
multipart/form-data;
", a U+0020 SPACE character, the string "boundary=
", and the multipart/form-data
boundary
string generated by the multipart/form-data
encoding
algorithm.text/plain
text/plain
".Otherwise, plan to navigate to action using the HTTP method given by method and with entity body as the entity body, of type MIME type.
Plan to navigate to action.
The form data set is discarded.
Let data be the result of encoding the form data set using the appropriate form encoding algorithm.
If action contains the string "%%%%
" (four U+0025
PERCENT SIGN characters), then percent encode all bytes in data that, if interpreted as US-ASCII, are not characters in the URL
default encode set, and then, treating the result as a US-ASCII string,
UTF-8 percent encode all the U+0025 PERCENT SIGN characters in the resulting
string and replace the first occurrence of "%%%%
" in action with the resulting doubly-escaped string. [URL]
Otherwise, if action contains the string "%%
"
(two U+0025 PERCENT SIGN characters in a row, but not four), then UTF-8 percent
encode all characters in data that, if interpreted as US-ASCII, are
not characters in the URL default encode set, and then, treating the result as a
US-ASCII string, replace the first occurrence of "%%
" in action with the resulting escaped string. [URL]
Plan to navigate to the potentially modified action (which
will be a data:
URL).
Let headers be the resulting encoding the form data
set using the application/x-www-form-urlencoded
encoding
algorithm, interpreted as a US-ASCII string.
Replace occurrences of "+" (U+002B) characters in headers with
the string "%20
".
Let destination consist of all the characters from the first character in action to the character immediately before the first "?" (U+003F) character, if any, or the end of the string if there are none.
Append a single "?" (U+003F) character to destination.
Append headers to destination.
Plan to navigate to destination.
Let body be the resulting of encoding the form data set using the appropriate form encoding algorithm and then percent encoding all the bytes in the resulting byte string that, when interpreted as US-ASCII, are not characters in the URL default encode set. [URL]
Let destination have the same value as action.
If destination does not contain a "?" (U+003F) character, append a single "?" (U+003F) character to destination. Otherwise, append a single U+0026 AMPERSAND character (&).
Append the string "body=
" to destination.
Append body, interpreted as a US-ASCII string, to destination.
Plan to navigate to destination.
The appropriate form encoding algorithm is determined as follows:
application/x-www-form-urlencoded
application/x-www-form-urlencoded
encoding
algorithm.multipart/form-data
multipart/form-data
encoding algorithm.text/plain
text/plain
encoding algorithm.The algorithm to construct the form data set for a form form optionally in the context of a submitter submitter is as follows. If not specified otherwise, submitter is null.
Let controls be a list of all the submittable elements whose form owner is form, in tree order.
Let the form data set be a list of name-value-type tuples, initially empty.
Loop: For each element field in controls, in tree order, run the following substeps:
If any of the following conditions are met, then skip these substeps for this element:
datalist
element ancestor.input
element whose type
attribute is in the Checkbox state and whose checkedness is false.input
element whose type
attribute is in the Radio Button state and whose checkedness is false.input
element whose type
attribute is in the Image Button state, and either the field element does not have a name
attribute
specified, or its name
attribute's value is the empty
string.object
element that is not using
a plugin.Otherwise, process field as follows:
Let type be the value of the type
IDL
attribute of field.
If the field element is an input
element whose type
attribute is in the Image Button state, then run these further nested
substeps:
If the field element has a name
attribute specified and its value is not the empty string, let name be
that value followed by a single "." (U+002E) character. Otherwise, let name be the empty string.
Let namex be the string consisting of the concatenation of name and a single U+0078 LATIN SMALL LETTER X character (x).
Let namey be the string consisting of the concatenation of name and a single U+0079 LATIN SMALL LETTER Y character (y).
The field element is submitter, and before this algorithm was invoked the user indicated a coordinate. Let x be the x-component of the coordinate selected by the user, and let y be the y-component of the coordinate selected by the user.
Append an entry to the form data set with the name namex, the value x, and the type type.
Append an entry to the form data set with the name namey and the value y, and the type type.
Skip the remaining substeps for this element: if there are any more elements in controls, return to the top of the loop step, otherwise, jump to the end step below.
Let name be the value of the field element's
name
attribute.
If the field element is a select
element, then for each
option
element in the select
element's list of options whose selectedness is true and that is not disabled, append an entry to the form data
set with the name as the name, the value of the option
element as the value, and
type as the type.
Otherwise, if the field element is an input
element whose
type
attribute is in the Checkbox state or the Radio Button state, then run these further nested
substeps:
If the field element has a value
attribute specified, then let value
be the value of that attribute; otherwise, let value be the string "on
".
Append an entry to the form data set with name as the name, value as the value, and type as the type.
Otherwise, if the field element is an input
element
whose type
attribute is in the File Upload state, then for each file selected in the input
element,
append an entry to the form data set with the name as
the name, the file (consisting of the name, the type, and the body) as the value, and type as the type. If there are no selected files, then append an entry to the
form data set with the name as the name, the empty
string as the value, and application/octet-stream
as the type.
Otherwise, if the field element is an object
element:
try to obtain a form submission value from the plugin, and if that is successful,
append an entry to the form data set with name as the
name, the returned form submission value as the value, and the string "object
" as the type.
Otherwise, append an entry to the form data set with name as the name, the value of the field element as the value, and type as the type.
If the element has a dirname
attribute, and that
attribute's value is not the empty string, then run these substeps:
Let dirname be the value of the element's dirname
attribute.
Let dir be the string "ltr
" if the
directionality of the element is 'ltr', and "rtl
" otherwise (i.e. when the directionality of the element is
'rtl').
Append an entry to the form data set with dirname as the name, dir as the value, and the string
"direction
" as the type.
An element can only have a dirname
attribute if it is a textarea
element or an input
element whose
type
attribute is in either the Text state or the Search state.
End: For the name of each entry in the form data set, and for the
value of each entry in the form data set whose type is not "file
" or "textarea
", replace every occurrence of a "CR" (U+000D) character not followed by a "LF" (U+000A) character, and every
occurrence of a "LF" (U+000A) character not preceded by a "CR" (U+000D)
character, by a two-character string consisting of a U+000D CARRIAGE RETURN "CRLF" (U+000A) character pair.
In the case of the value of
textarea
elements, this newline normalization is already performed during the
conversion of the control's raw value into the
control's value (which also performs any necessary line
wrapping). In the case of input
elements type
attributes in the File Upload state, the value is not
normalized.
Return the form data set.
If the user agent is to pick an encoding for a form, optionally with an allow non-ASCII-compatible encodings flag set, it must run the following substeps:
Let input be the value of the form
element's accept-charset
attribute.
Let candidate encoding labels be the result of splitting input on spaces.
Let candidate encodings be an empty list of character encodings.
For each token in candidate encoding labels in turn (in the order in which they were found in input), get an encoding for the token and, if this does not result in failure, append the encoding to candidate encodings.
If the allow non-ASCII-compatible encodings flag is not set, remove any encodings that are not ASCII-compatible character encodings from candidate encodings.
If candidate encodings is empty, return UTF-8 and abort these steps.
Each character encoding in candidate encodings can represent a finite number of characters. (For example, UTF-8 can represent all 1.1 million or so Unicode code points, while Windows-1252 can only represent 256.)
For each encoding in candidate encodings, determine how many of the characters in the names and values of the entries in the form data set the encoding can represent (without ignoring duplicates). Let max be the highest such count. (For UTF-8, max would equal the number of characters in the names and values of the entries in the form data set.)
Return the first encoding in candidate encodings that can encode max characters in the names and values of the entries in the form data set.
This form data set encoding is in many ways an aberrant monstrosity, the result of many years of implementation accidents and compromises leading to a set of requirements necessary for interoperability, but in no way representing good design practices. In particular, readers are cautioned to pay close attention to the twisted details involving repeated (and in some cases nested) conversions between character encodings and byte sequences.
The application/x-www-form-urlencoded
encoding algorithm is as
follows:
Let result be the empty string.
If the form
element has an accept-charset
attribute, let the selected character
encoding be the result of picking an encoding for the form.
Otherwise, if the form
element has no accept-charset
attribute, but the document's
character encoding is an ASCII-compatible character encoding, then that is
the selected character encoding.
Otherwise, let the selected character encoding be UTF-8.
Let charset be the name of the selected character encoding.
For each entry in the form data set, perform these substeps:
If the entry's name is "_charset_
" and its
type is "hidden
", replace its value with charset.
If the entry's type is "file
", replace its value with the file's
name only.
For each character in the entry's name and value that cannot be expressed using the selected character encoding, replace the character by a string consisting of a U+0026 AMPERSAND character (&), a "#" (U+0023) character, one or more ASCII digits representing the Unicode code point of the character in base ten, and finally a ";" (U+003B) character.
Encode the entry's name and value using the encoder for the selected character encoding. The entry's name and value are now byte strings.
For each byte in the entry's name and value, apply the appropriate subsubsteps from the following list:
Leave the byte as is.
Let s be a string consisting of a U+0025 PERCENT SIGN character (%) followed by uppercase ASCII hex digits representing the hexadecimal value of the byte in question (zero-padded if necessary).
Encode the string s as US-ASCII, so that it is now a byte string.
Replace the byte in question in the name or value being processed by the bytes in s, preserving their relative order.
Interpret the entry's name and value as Unicode strings encoded in US-ASCII. (All of the bytes in the string will be in the range 0x00 to 0x7F; the high bit will be zero throughout.) The entry's name and value are now Unicode strings again.
If the entry's name is "isindex
", its type is
"text
", and this is the first entry in the form data
set, then append the value to result and skip the rest of the
substeps for this entry, moving on to the next entry, if any, or the next step in the overall
algorithm otherwise.
If this is not the first entry, append a single U+0026 AMPERSAND character (&) to result.
Append the entry's name to result.
Append a single "=" (U+003D) character to result.
Append the entry's value to result.
Encode result as US-ASCII and return the resulting byte stream.
To decode
application/x-www-form-urlencoded
payloads, the following algorithm should be
used. This algorithm uses as inputs the payload itself, payload, consisting of
a Unicode string using only characters in the range U+0000 to U+007F; a default character encoding
encoding; and optionally an isindex flag indicating that
the payload is to be processed as if it had been generated for a form containing an isindex
control. The output of this algorithm is a sorted list
of name-value pairs. If the isindex flag is set and the first control really
was an isindex
control, then the first name-value pair
will have as its name the empty string.
Which default character encoding to use can only be determined on a case-by-case basis, but generally the best character encoding to use as a default is the one that was used to encode the page on which the form used to create the payload was itself found. In the absence of a better default, UTF-8 is suggested.
The isindex flag is for legacy use only. Forms in conforming HTML documents will not generate payloads that need to be decoded with this flag set.
Let strings be the result of strictly splitting the string payload on U+0026 AMPERSAND characters (&).
If the isindex flag is set and the first string in strings does not contain a "=" (U+003D) character, insert a "=" (U+003D) character at the start of the first string in strings.
Let pairs be an empty list of name-value pairs.
For each string string in strings, run these substeps:
If string contains a "=" (U+003D) character, then let name be the substring of string from the start of string up to but excluding its first "=" (U+003D) character, and let value be the substring from the first character, if any, after the first "=" (U+003D) character up to the end of string. If the first "=" (U+003D) character is the first character, then name will be the empty string. If it is the last character, then value will be the empty string.
Otherwise, string contains no "=" (U+003D) characters. Let name have the value of string and let value be the empty string.
Replace any "+" (U+002B) characters in name and value with U+0020 SPACE characters.
Replace any escape in name and value with the character represented by the escape. This replacement must not be recursive.
An escape is a "%" (U+0025) character followed by two ASCII hex digits.
The character represented by an escape is the Unicode character whose code point is equal to the value of the two characters after the "%" (U+0025) character, interpreted as a hexadecimal number (in the range 0..255).
So for instance the string "A%2BC
" would become
"A+C
". Similarly, the string "100%25AA%21
" becomes
the string "100%AA!
".
Convert the name and value strings to their byte representation in ISO-8859-1 (i.e. convert the Unicode string to a byte string, mapping code points to byte values directly).
Add a pair consisting of name and value to pairs.
If any of the name-value pairs in pairs have a name component
consisting of the string "_charset_
" encoded in US-ASCII, and the value
component of the first such pair, when decoded as US-ASCII, is the name of a supported character
encoding, then let encoding be that character encoding (replacing the default
passed to the algorithm).
Convert the name and value components of each name-value pair in pairs to Unicode by interpreting the bytes according to the encoding encoding.
Return pairs.
Parameters on the application/x-www-form-urlencoded
MIME type are
ignored. In particular, this MIME type does not support the charset
parameter.
The multipart/form-data
encoding algorithm is as follows:
Let result be the empty string.
If the algorithm was invoked with an explicit character encoding, let the selected character
encoding be that encoding. (This algorithm is used by other specifications, which provide an
explicit character encoding to avoid the dependency on the form
element described
in the next paragraph.)
Otherwise, if the form
element has an accept-charset
attribute, let the selected character
encoding be the result of picking an encoding for the form.
Otherwise, if the form
element has no accept-charset
attribute, but the document's
character encoding is an ASCII-compatible character encoding, then that is
the selected character encoding.
Otherwise, let the selected character encoding be UTF-8.
Let charset be the name of the selected character encoding.
For each entry in the form data set, perform these substeps:
If the entry's name is "_charset_
" and its
type is "hidden
", replace its value with charset.
For each character in the entry's name and value that cannot be expressed using the selected character encoding, replace the character by a string consisting of a U+0026 AMPERSAND character (&), a "#" (U+0023) character, one or more ASCII digits representing the Unicode code point of the character in base ten, and finally a ";" (U+003B) character.
Encode the (now mutated) form data set using the rules described by RFC
2388, Returning Values from Forms: multipart/form-data
, and
return the resulting byte stream. [RFC2388]
Each entry in the form data set is a field, the name of the entry is the field name and the value of the entry is the field value.
The order of parts must be the same as the order of fields in the form data set. Multiple entries with the same name must be treated as distinct fields.
In particular, this means that multiple files submitted as part of a single
<input type=file multiple>
element will result in each file
having its own field; the "sets of files" feature ("multipart/mixed
") of
RFC 2388 is not used.
The parts of the generated multipart/form-data
resource that correspond
to non-file fields must not have a Content-Type
header specified. Their names and
values must be encoded using the character encoding selected above (field names in particular do
not get converted to a 7-bit safe encoding as suggested in RFC 2388).
File names included in the generated multipart/form-data
resource (as
part of file fields) must use the character encoding selected above, though the precise name may
be approximated if necessary (e.g. newlines could be removed from file names, quotes could be
changed to "%22", and characters not expressible in the selected character encoding could be
replaced by other characters). User agents must not use the RFC 2231 encoding suggested by RFC
2388.
The boundary used by the user agent in generating the return value of this algorithm is the
multipart/form-data
boundary string. (This value is used to
generate the MIME type of the form submission payload generated by this algorithm.)
For details on how to interpret multipart/form-data
payloads, see RFC 2388. [RFC2388]
The text/plain
encoding algorithm is as follows:
Let result be the empty string.
If the form
element has an accept-charset
attribute, let the selected character
encoding be the result of picking an encoding for the form, with the allow
non-ASCII-compatible encodings flag unset.
Otherwise, if the form
element has no accept-charset
attribute, then that is the selected
character encoding.
Let charset be the name of the selected character encoding.
If the entry's name is "_charset_
" and its type
is "hidden
", replace its value with charset.
If the entry's type is "file
", replace its value with the file's
name only.
For each entry in the form data set, perform these substeps:
Append the entry's name to result.
Append a single "=" (U+003D) character to result.
Append the entry's value to result.
Append a "CR" (U+000D) "LF" (U+000A) character pair to result.
Encode result using the encoder for the selected character encoding and return the resulting byte stream.
Payloads using the text/plain
format are intended to be human readable. They are
not reliably interpretable by computer, as the format is ambiguous (for example, there is no way
to distinguish a literal newline in a value from the newline at the end of the value).
When a form
element form is reset, the user agent must fire a simple event named
reset
, that bubbles and is cancelable, at form, and then, if that event is not canceled, must invoke the reset algorithm of each resettable element whose form owner is form.
Each resettable element defines its own reset algorithm. Changes made to form controls as part of
these algorithms do not count as changes caused by the user (and thus, e.g., do not cause input
events to fire).
details
elementsummary
element followed by flow content.open
interface HTMLDetailsElement : HTMLElement { attribute boolean open; };
The details
element represents a disclosure widget from which the
user can obtain additional information or controls.
The details
element is not appropriate for footnotes. Please see the section on footnotes for details on how to mark up footnotes.
The first summary
element child of the element, if any,
represents the summary or legend of the details. If there is no
child summary
element, the user agent should provide its own legend (e.g.
"Details").
The rest of the element's contents represents the additional information or controls.
The open
content attribute is a boolean
attribute. If present, it indicates that both the summary and the additional information is
to be shown to the user. If the attribute is absent, only the summary is to be shown.
When the element is created, if the attribute is absent, the additional information should be hidden; if the attribute is present, that information should be shown. Subsequently, if the attribute is removed, then the information should be hidden; if the attribute is added, the information should be shown.
The user agent should allow the user to request that the additional information be shown or
hidden. To honor a request for the details to be shown, the user agent must set the open
attribute on the element to the value open
. To honor a request for the information to be hidden, the user agent must
remove the open
attribute from the element.
Whenever the open
attribute is added to or removed from
a details
element, the user agent must queue a task that runs the
following steps, which are known as the details notification task steps, for this
details
element:
If another task has been queued to run the details notification task steps for this
details
element, then abort these steps.
When the open
attribute is toggled
several times in succession, these steps essentially get coalesced so that only one event is
fired.
Fire a simple event named toggle
at the
details
element.
The task source for this task must be the DOM manipulation task source.
The open
IDL attribute must
reflect the open
content attribute.
The following example shows the details
element being used to hide technical
details in a progress report.
<section class="progress window"> <h1>Copying "Really Achieving Your Childhood Dreams"</h1> <details> <summary>Copying... <progress max="375505392" value="97543282"></progress> 25%</summary> <dl> <dt>Transfer rate:</dt> <dd>452KB/s</dd> <dt>Local filename:</dt> <dd>/home/rpausch/raycd.m4v</dd> <dt>Remote filename:</dt> <dd>/var/www/lectures/raycd.m4v</dd> <dt>Duration:</dt> <dd>01:16:27</dd> <dt>Color profile:</dt> <dd>SD (6-1-6)</dd> <dt>Dimensions:</dt> <dd>320×240</dd> </dl> </details> </section>
The following shows how a details
element can be used to hide some controls by
default:
<details> <summary><label for=fn>Name & Extension:</label></summary> <p><input type=text id=fn name=fn value="Pillar Magazine.pdf"> <p><label><input type=checkbox name=ext checked> Hide extension</label> </details>
One could use this in conjunction with other details
in a list to allow the user
to collapse a set of fields down to a small set of headings, with the ability to open each
one.
In these examples, the summary really just summarises what the controls can change, and not the actual values, which is less than ideal.
Because the open
attribute is added and removed
automatically as the user interacts with the control, it can be used in CSS to style the element
differently based on its state. Here, a stylesheet is used to animate the color of the summary
when the element is opened or closed:
<style> details > summary { transition: color 1s; color: black; } details[open] > summary { color: red; } </style> <details> <summary>Automated Status: Operational</summary> <p>Velocity: 12m/s</p> <p>Direction: North</p> </details>
summary
elementdetails
element.HTMLElement
.The summary
element represents a summary, caption, or legend for the
rest of the contents of the summary
element's parent details
element, if any.
dialog
elementopen
interface HTMLDialogElement : HTMLElement { attribute boolean open; attribute DOMString returnValue; void show(optional (MouseEvent or Element) anchor); void showModal(optional (MouseEvent or Element) anchor); void close(optional DOMString returnValue); };
The dialog
element represents a part of an application that a user interacts with
to perform a task, for example a dialog box, inspector, or window.
The open
attribute is a boolean
attribute. When specified, it indicates that the dialog
element is active and
that the user can interact with it.
A dialog
element without an open
attribute
specified should not be shown to the user. This requirement may be implemented indirectly through
the style layer. For example, user agents that support the suggested
default rendering implement this requirement using the CSS rules described in the rendering section.
show
( [ anchor ] )Displays the dialog
element.
The argument, if provided, provides an anchor point to which the element will be fixed.
showModal
( [ anchor ] )Displays the dialog
element and makes it the top-most modal dialog.
The argument, if provided, provides an anchor point to which the element will be fixed.
This method honors the autofocus
attribute.
close
( [ result ] )Closes the dialog
element.
The argument, if provided, provides a return value.
returnValue
[ = result ]Returns the dialog
's return value.
Can be set, to update the return value.
When the show()
method is invoked, the user
agent must run the following steps:
If the element already has an open
attribute, then
abort these steps.
Add an open
attribute to the dialog
element, whose value is the empty string.
If the show()
method was invoked with an argument,
set up the position of the dialog
element, using that argument as the
anchor. Otherwise, set up the default static position of the dialog
element.
Each Document
has a stack of dialog
elements known as the
pending dialog stack. When a Document
is created, this stack must be
initialized to be empty.
When an element is added to the pending dialog stack, it must also be added to the top layer layer. When an element is removed from the pending dialog stack, it must be removed from the top layer. [FULLSCREEN]
When the showModal()
method is invoked,
the user agent must run the following steps:
Let subject be the dialog
element on which the method was
invoked.
If subject already has an open
attribute, then throw an InvalidStateError
exception and abort these steps.
If subject is not in a Document
, then throw
an InvalidStateError
exception and abort these steps.
Add an open
attribute to subject, whose value is the empty string.
If the showModal()
method was invoked with an
argument, set up the position of subject, using that argument as
the anchor. Otherwise, set up the default static position of the dialog
element.
Let subject's Document
be blocked by the modal dialog subject.
Push subject onto subject's
Document
's pending dialog stack.
Let control be the first element in tree order that has an autofocus
attribute specified and whose nearest ancestor
dialog
element is subject, if any.
If there isn't one, then let control be the first element in tree order
that is focusable and whose nearest ancestor dialog
element is subject, if any.
If there isn't one of those either but subject itself is focusable, then let control be subject. (This is unusual.)
If there is no control, then abort these steps.
Run the focusing steps for control.
If at any time a dialog
element is removed from a Document
, then if that dialog
is in that
Document
's pending dialog stack, the following steps must be run:
Let subject be that dialog
element and document be the Document
from which it is being removed.
Remove subject from document's pending dialog stack.
If document's pending dialog stack is not empty, then let document be blocked by the modal dialog that is at the top of document's pending dialog stack. Otherwise, let document be no longer blocked by a modal dialog at all.
When the close()
method is invoked, the user
agent must close the dialog that the method was invoked on. If the method was invoked
with an argument, that argument must be used as the return value; otherwise, there is no return
value.
When a dialog
element subject is to be closed, optionally with a return value result, the user agent
must run the following steps:
If subject does not have an open
attribute, then throw an InvalidStateError
exception and abort these steps.
Remove subject's open
attribute.
If the argument result was provided, then set the returnValue
attribute to the value of result.
If subject is in its Document
's pending dialog
stack, then run these substeps:
Remove subject from that pending dialog stack.
If that pending dialog stack is not empty, then let subject's Document
be blocked by the modal dialog that is at the top of the pending dialog
stack. Otherwise, let document be no longer blocked by a modal
dialog at all.
Queue a task to fire a simple event named close
at subject.
The returnValue
IDL attribute, on
getting, must return the last value to which it was set. On setting, it must be set to the new
value. When the element is created, it must be set to the empty string.
Canceling dialogs: When a Document
's pending dialog
stack is not empty, user agents may provide a user interface that, upon activation, queues a task to fire a simple event named cancel
that is cancelable at the top dialog
element on the Document
's pending dialog stack. The default action of
this event must be to check if that element has an open
attribute, and if it does, close the dialog with no return value.
An example of such a UI mechanism would be the user pressing the "Escape" key.
The containing block of all dialog
elements that are absolutely positioned
must be the initial containing block.
All dialog
elements are always in one of two modes: mundanely aligned,
or magically aligned. When a dialog
element is created, it must be placed
in the mundanely aligned mode and the user agent must set up the default static
position for that element, without an anchor.
When a user agent is to set up the default static position of an element subject without an anchor, if that element is being rendered, it must set up the element such that its top static position, for the purposes of calculating the used value of the 'top' property, is the value that would place the element's top margin edge as far from the top of the viewport as the element's bottom margin edge from the bottom of the viewport, if the element's height is less than the height of the viewport, and otherwise is the value that would place the element's top margin edge at the top of the viewport.
If there is a dialog
element that is mundanely aligned and that is
being rendered when its browsing context changes viewport width (as
measured in CSS pixels), then the user agent must set up the default static position
of all such elements in that browsing context again, still without anchors.
When a dialog
element that is mundanely aligned starts being
rendered, the user agent must set up the default static position of that
element, without an anchor.
This top static position of a mundanely aligned dialog
element must
remain the element's top static position until the set up the default static position
algorithm is once again invoked for that element. (The element's static position is only used in
calculating the used value of the 'top' property in certain situations; it's not used, for
instance, to position the element if its 'position' property is set to 'static'.)
When a user agent is to set up the position of an element subject using an anchor anchor, it must run the following steps:
If anchor is a MouseEvent
object, then run these
substeps:
If anchor's target element does not have a rendered box, or is in a different document than subject, then let subject be mundanely aligned, set up the default static position of subject without an anchor, and abort the set up the position steps.
Let anchor element be an anonymous element rendered as a box with zero height and width (so its margin and border boxes both just form a point), positioned so that its top and left are at the coordinate identified by the event, and whose properties all compute to their initial values.
Otherwise, let anchor element be anchor.
Let subject be magically aligned to anchor element.
While an element A is magically aligned to an element B, the following requirements apply:
If at any time either A or B cease having rendered
boxes, A and B cease being in the same
Document
, or B ceases being earlier than A
in tree order, let subject be mundanely aligned,
and set up the default static position of subject without an
anchor.
A's 'position' property must compute to the keyword 'absolute-anchored' rather than whatever it would otherwise compute to (i.e. the 'position' property's specified value is ignored).
The 'absolute-anchored' keyword's requirements are described below.
The anchor points for A and B are defined as per the appropriate entry in the following list:
The anchor points of A and B are the center points of their respective first boxes' border boxes.
The anchor point of B is the point given by its 'anchor-point' property.
If the anchor point of B is the center point of B's first box's border box, then A's anchor point is the center point of its first box's margin box.
Otherwise, A's anchor point is on one of its margin edges. Consider four hypothetical half-infinite lines L1, L2, L3, and L4 that each start in the center of B's first box's border box, and that extend respectively through the top left corner, top right corner, bottom right corner, and bottom left corner of B's first box's border box. A's anchor point is determined by the location of B's anchor point relative to these four hypothetical lines, as follows:
If the anchor point of B lies on L1 or L2, or inside the area bounded by L1 and L2 that also contains the points above B's first box's border box, then let A's anchor point be the horizontal center of A's bottom margin edge.
Otherwise, if the anchor point of B lies on L3 or L4, or inside the area bounded by L4 and L4 that also contains the points below B's first box's border box, then let A's anchor point be the horizontal center of A's top margin edge.
Otherwise, if the anchor point of B lies inside the area bounded by L4 and L1 that also contains the points to the left of B's first box's border box, then let A's anchor point be the vertical center of A's right margin edge.
Otherwise, the anchor point of B lies inside the area bounded by L2 and L3 that also contains the points to the right of B's first box's border box; let A's anchor point be the vertical center of A's left margin edge.
The anchor point of A is the point given by its 'anchor-point' property.
If the anchor point of A is the center point of A's first box's margin box, then B's anchor point is the center point of its first box's border box.
Otherwise, B's anchor point is on one of its border edges. Consider four hypothetical half-infinite lines L1, L2, L3, and L4 that each start in the center of A's first box's margin box, and that extend respectively through the top left corner, top right corner, bottom right corner, and bottom left corner of A's first box's margin box. B's anchor point is determined by the location of A's anchor point relative to these four hypothetical lines, as follows:
If the anchor point of A lies on L1 or L2, or inside the area bounded by L1 and L2 that also contains the points above A's first box's margin box, then let B's anchor point be the horizontal center of B's bottom border edge.
Otherwise, if the anchor point of A lies on L3 or L4, or inside the area bounded by L4 and L4 that also contains the points below A's first box's margin box, then let B's anchor point be the horizontal center of B's top border edge.
Otherwise, if the anchor point of A lies inside the area bounded by L4 and L1 that also contains the points to the left of A's first box's margin box, then let B's anchor point be the vertical center of B's right border edge.
Otherwise, the anchor point of A lies inside the area bounded by L2 and L3 that also contains the points to the right of A's first box's margin box; let B's anchor point be the vertical center of B's left border edge.
The anchor points of A and B are the points given by their respective 'anchor-point' properties.
The rules above generally use A's margin box, but B's border box. This is because while A always has a margin box, and using the margin box allows for the dialog to be positioned offset from the box it is annotating, B sometimes does not have a margin box (e.g. if it is a table-cell), or has a margin box whose position may be not entirely clear (e.g. in the face of margin collapsing and 'clear' handling of in-flow blocks).
In cases where B does not have a border box but its border box is used by the algorithm above, user agents must use its first box's content area instead. (This is in particular an issue with boxes in tables that have 'border-collapse' set to 'collapse'.)
When an element's 'position' property computes to 'absolute-anchored', the 'float' property does not apply and must compute to 'none', the 'display' property must compute to a value as described by the table in the section of CSS 2.1 describing the relationships between 'display', 'position', and 'float', and the element's box must be positioned using the rules for absolute positioning but with its static position set such that if the box is positioned in its static position, its anchor point is exactly aligned over the anchor point of the element to which it is magically aligned. Elements aligned in this way are absolutely positioned. For the purposes of determining the containing block of other elements, the 'absolute-anchored' keyword must be treated like the 'absolute' keyword.
The trivial example of an element that does not have a rendered box is one whose 'display' property computes to 'none'. However, there are many other cases; e.g. table columns do not have boxes (their properties merely affect other boxes).
If an element to which another element is anchored changes rendering, the anchored element will be be repositioned accordingly. (In other words, the requirements above are live, they are not just calculated once per anchored element.)
The 'absolute-anchored'
keyword is not a keyword that can be specified in CSS; the 'position' property can only compute to
this value if the dialog
element is positioned via the APIs described above.
Elements positioned in this way are not clipped by the 'overflow' property of ancestors (nor moved by the resulting scrolling mechanisms), since the containing block is the initial containing block. Anchoring to an element that is so clipped (and shifted) can therefore result in unexpected effects (where the anchored element moves along with the clipped element, but isn't itself clipped).
User agents in visual interactive media should allow the user to pan the viewport to access all
parts of a dialog
element's border box, even if the element is larger than the
viewport and the viewport would otherwise not have a scroll mechanism (e.g. because the viewport's
'overflow' property is set to 'hidden').
The open
IDL attribute must
reflect the open
content attribute.
This section will eventually be moved to a CSS specification; it is specified here only on an interim basis until an editor can be found to own this.
Value: | none | <position> |
---|---|
Initial: | none |
Applies to: | all elements |
Inherited: | no |
Percentages: | refer to width or height of box; see prose |
Media: | visual |
Computed value: | The specified value, but with any lengths replaced by their corresponding absolute length |
Animatable: | no |
Canonical order: | per grammar |
The 'anchor-point' property specifies a point to which dialog boxes are to be aligned.
If the value is a <position>, the anchor point is the point given by the value, which must be interpreted relative to the element's first rendered box's margin box. Percentages must be calculated relative to the element's first rendered box's margin box (specifically, its width for the horizontal position and its height for the vertical position). [CSSVALUES] [CSS]
If the value is the keyword 'none', then no explicit anchor point is defined. The user agent
will pick an anchor point automatically if necessary (as described in the definition of the
open()
method above).
Scripts allow authors to add interactivity to their documents.
Authors are encouraged to use declarative alternatives to scripting where possible, as declarative mechanisms are often more maintainable, and many users disable scripting.
For example, instead of using script to show or hide a section to show more details, the
details
element could be used.
Authors are also encouraged to make their applications degrade gracefully in the absence of scripting support.
script
elementsrc
attribute, depends on the value of the type
attribute, but must match
script content restrictions.src
attribute, the element must be either empty or contain only
script documentation that also matches script
content restrictions.src
type
charset
async
defer
crossorigin
interface HTMLScriptElement : HTMLElement { attribute DOMString src; attribute DOMString type; attribute DOMString charset; attribute boolean async; attribute boolean defer; attribute DOMString crossOrigin; attribute DOMString text; };
The script
element allows authors to include dynamic script and data blocks in
their documents. The element does not represent content for the
user.
When used to include dynamic scripts, the scripts may either be embedded inline or may be
imported from an external file using the src
attribute. If
the language is not that described by "text/javascript
", then the type
attribute must be present, as described below. Whatever
language is used, the contents of the script
element must conform with the
requirements of that language's specification.
When used to include data blocks (as opposed to scripts), the data must be embedded inline, the
format of the data must be given using the type
attribute,
the src
attribute must not be specified, and the contents of
the script
element must conform to the requirements defined for the format used.
The type
attribute gives the language of the
script or format of the data. If the attribute is present, its value must be a valid MIME
type. The charset
parameter must not be specified. The default, which
is used if the attribute is absent, is "text/javascript
".
The src
attribute, if specified, gives the
address of the external script resource to use. The value of the attribute must be a valid
non-empty URL potentially surrounded by spaces identifying a script resource of the type
given by the type
attribute, if the attribute is present, or
of the type "text/javascript
", if the attribute is absent. A resource is a
script resource of a given type if that type identifies a scripting language and the resource
conforms with the requirements of that language's specification.
The charset
attribute gives the character
encoding of the external script resource. The attribute must not be specified if the src
attribute is not present. If the attribute is set, its value
must be an ASCII case-insensitive match for one of the labels of an encoding, and must specify the same encoding as
the charset
parameter of the Content-Type
metadata of the external file, if any. [ENCODING]
The async
and defer
attributes are boolean attributes that indicate how the script should be executed. The defer
and async
attributes
must not be specified if the src
attribute is not
present.
There are three possible modes that can be selected using these attributes. If the async
attribute is present, then the script will be executed
asynchronously, as soon as it is available. If the async
attribute is not present but the defer
attribute is
present, then the script is executed when the page has finished parsing. If neither attribute is
present, then the script is fetched and executed immediately, before the user agent continues
parsing the page.
The exact processing details for these attributes are, for mostly historical
reasons, somewhat non-trivial, involving a number of aspects of HTML. The implementation
requirements are therefore by necessity scattered throughout the specification. The algorithms
below (in this section) describe the core of this processing, but these algorithms reference and
are referenced by the parsing rules for script
start and end tags in HTML, in foreign content,
and in XML, the rules for the document.write()
method, the handling of scripting, etc.
The defer
attribute may be specified even if the async
attribute is specified, to cause legacy Web browsers that
only support defer
(and not async
) to fall back to the defer
behavior instead of the synchronous blocking behavior that
is the default.
The crossorigin
attribute is a
CORS settings attribute. It controls, for scripts that are obtained from other origins, whether error information will be exposed.
Changing the src
, type
, charset
, async
, defer
, and crossorigin
attributes dynamically has no direct effect;
these attribute are only used at specific times described below.
A script
element has several associated pieces of state.
The first is a flag indicating whether or not the script block has been "already
started". Initially, script
elements must have this flag unset (script blocks,
when created, are not "already started"). The cloning
steps for script
elements must set the "already started" flag on the copy if
it is set on the element being cloned.
The second is a flag indicating whether the element was "parser-inserted".
Initially, script
elements must have this flag unset. It is set by the HTML
parser and the XML parser on script
elements they insert and
affects the processing of those elements.
The third is a flag indicating whether the element will "force-async". Initially,
script
elements must have this flag set. It is unset by the HTML parser
and the XML parser on script
elements they insert. In addition, whenever
a script
element whose "force-async" flag is set has a async
content attribute added, the element's
"force-async" flag must be unset.
The fourth is a flag indicating whether or not the script block is "ready to be
parser-executed". Initially, script
elements must have this flag unset (script
blocks, when created, are not "ready to be parser-executed"). This flag is used only for elements
that are also "parser-inserted", to let the parser know when to execute the
script.
The last few pieces of state are the script block's type, the
script block's character encoding, and the script block's fallback character
encoding. They are determined when the script is prepared, based on the attributes on
the element at that time, and the Document
of the script
element.
When a script
element that is not marked as being "parser-inserted"
experiences one of the events listed in the following list, the user agent must synchronously
prepare the script
element:
script
element gets inserted
into a document, at the time the node is inserted
according to the DOM, after any other script
elements inserted at the same time that
are earlier in the Document
in tree order.script
element is in a Document
and a node or
document fragment is inserted into the
script
element, after any script
elements inserted at that time.script
element is in a Document
and has a src
attribute set where previously the element had no such
attribute.To prepare a script, the user agent must act as follows:
If the script
element is marked as having "already started", then
the user agent must abort these steps at this point. The script is not executed.
If the element has its "parser-inserted" flag set, then set was-parser-inserted to true and unset the element's "parser-inserted" flag. Otherwise, set was-parser-inserted to false.
This is done so that if parser-inserted script
elements fail to run
when the parser tries to run them, e.g. because they are empty or specify an unsupported
scripting language, another script can later mutate them and cause them to run again.
If was-parser-inserted is true and the element does not have an async
attribute, then set the element's
"force-async" flag to true.
This is done so that if a parser-inserted script
element fails to
run when the parser tries to run it, but it is later executed after a script dynamically updates
it, it will execute asynchronously even if the async
attribute isn't set.
If the element has no src
attribute, and its child
nodes, if any, consist only of comment nodes and empty Text
nodes, then the user
agent must abort these steps at this point. The script is not executed.
If the element is not in a Document
, then the user agent must abort
these steps at this point. The script is not executed.
If either:
script
element has a type
attribute
and its value is the empty string, orscript
element has no type
attribute
but it has a language
attribute and that
attribute's value is the empty string, orscript
element has neither a type
attribute nor a language
attribute, then...let the script block's type for this script
element be "text/javascript
".
Otherwise, if the script
element has a type
attribute, let the script block's type for this
script
element be the value of that attribute with any leading or trailing
sequences of space characters removed.
Otherwise, the element has a non-empty language
attribute; let the script block's type for this script
element be the
concatenation of the string "text/
" followed by the value of the language
attribute.
The language
attribute is never
conforming, and is always ignored if there is a type
attribute present.
If the user agent does not support the scripting language given by the
script block's type for this script
element, then the user agent must abort
these steps at this point. The script is not executed.
If was-parser-inserted is true, then flag the element as "parser-inserted" again, and set the element's "force-async" flag to false.
The user agent must set the element's "already started" flag.
The state of the element at this moment is later used to determine the script source.
If the element is flagged as "parser-inserted", but the element's
Document
is not the Document
of the parser that created the element,
then abort these steps.
If scripting is disabled for the script
element, then the user agent must abort these steps at this point. The script is not
executed.
The definition of scripting is disabled
means that, amongst others, the following scripts will not execute: scripts in
XMLHttpRequest
's responseXML
documents, scripts in DOMParser
-created documents, scripts in documents created by
XSLTProcessor
's transformToDocument
feature, and scripts
that are first inserted by a script into a Document
that was created using the
createDocument()
API. [XHR] [DOMPARSING] [DOM]
If the script
element has an event
attribute and a for
attribute, then run these substeps:
Let for be the value of the for
attribute.
Let event be the value of the event
attribute.
Strip leading and trailing whitespace from event and for.
If for is not an ASCII case-insensitive match for the
string "window
", then the user agent must abort these steps at this
point. The script is not executed.
If event is not an ASCII case-insensitive match for
either the string "onload
" or the string "onload()
", then the user agent must abort these steps at this point. The script
is not executed.
If the script
element has a charset
attribute, then let the script block's character encoding for this
script
element be the result of getting an encoding from the value of
the charset
attribute.
Otherwise, let the script block's fallback character encoding for this
script
element be the same as the
encoding of the document itself.
Only one of these two pieces of state is set.
If the element has a src
content attribute, run these
substeps:
Let src be the value of the element's src
attribute.
If src is the empty string, queue a task to fire
a simple event named error
at the element, and abort
these steps.
Resolve src relative to the element.
If the previous step failed, queue a task to fire a simple
event named error
at the element, and abort these
steps.
Do a potentially CORS-enabled fetch of the resulting
absolute URL, with the mode being the current state of the element's crossorigin
content attribute, the origin being the origin of the script
element's
Document
, and the default origin behaviour set to taint.
The resource obtained in this fashion can be either CORS-same-origin or CORS-cross-origin. This only affects how error reporting happens.
For performance reasons, user agents may start fetching the script (as defined above) as
soon as the src
attribute is set, instead, in the hope
that the element will be inserted into the document (and that the crossorigin
attribute won't change value in the
meantime). Either way, once the element is inserted into the document, the load must have started as described in this
step. If the UA performs such prefetching, but the element is never inserted in the document,
or the src
attribute is dynamically changed, or the crossorigin
attribute is dynamically changed, then the
user agent will not execute the script so obtained, and the fetching process will have been
effectively wasted.
Then, the first of the following options that describes the situation must be followed:
src
attribute, and the element has a defer
attribute, and
the element has been flagged as "parser-inserted", and the element does not have
an async
attributeThe element must be added to the end of the list of scripts that will execute when the
document has finished parsing associated with the Document
of the parser
that created the element.
The task that the networking task source places on the task queue once the fetching algorithm has completed must set the element's "ready to be parser-executed" flag. The parser will handle executing the script.
src
attribute, and the element has been flagged as
"parser-inserted", and the element does not have an async
attributeThe element is the pending parsing-blocking script of the
Document
of the parser that created the element. (There can only be one such
script per Document
at a time.)
The task that the networking task source places on the task queue once the fetching algorithm has completed must set the element's "ready to be parser-executed" flag. The parser will handle executing the script.
src
attribute, and the element has been flagged as
"parser-inserted", and either the parser that created the script
is
an XML parser or it's an HTML parser whose script nesting
level is not greater than one, and the Document
of the HTML
parser or XML parser that created the script
element has
a style sheet that is blocking scriptsThe element is the pending parsing-blocking script of the
Document
of the parser that created the element. (There can only be one such
script per Document
at a time.)
Set the element's "ready to be parser-executed" flag. The parser will handle executing the script.
src
attribute, does not have an async
attribute, and does not have the
"force-async" flag setThe element must be added to the end of the list of scripts that will execute in order
as soon as possible associated with the Document
of the script
element at the time the prepare a script algorithm started.
The task that the networking task source places on the task queue once the fetching algorithm has completed must run the following steps:
If the element is not now the first element in the list of scripts that will execute in order as soon as possible to which it was added above, then mark the element as ready but abort these steps without executing the script yet.
Execution: Execute the script block corresponding to the first script element in this list of scripts that will execute in order as soon as possible.
Remove the first element from this list of scripts that will execute in order as soon as possible.
If this list of scripts that will execute in order as soon as possible is still not empty and the first entry has already been marked as ready, then jump back to the step labeled execution.
src
attributeThe element must be added to the set of scripts that will execute as soon as
possible of the Document
of the script
element at the time the
prepare a script algorithm started.
The task that the networking task source places on the task queue once the fetching algorithm has completed must execute the script block and then remove the element from the set of scripts that will execute as soon as possible.
Fetching an external script must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined above) has been run.
The pending parsing-blocking script of a Document
is used by the
Document
's parser(s).
If a script
element that blocks a parser gets moved to another
Document
before it would normally have stopped blocking that parser, it nonetheless
continues blocking that parser until the condition that causes it to be blocking the parser no
longer applies (e.g. if the script is a pending parsing-blocking script because there
was a style sheet that is blocking scripts when it was parsed, but then the script is
moved to another Document
before the style sheet loads, the script still blocks the
parser until the style sheets are all loaded, at which time the script executes and the parser is
unblocked).
When the user agent is required to execute a script block, it must run the following steps:
If the element is flagged as "parser-inserted", but the element's
Document
is not the Document
of the parser that created the element,
then abort these steps.
Jump to the appropriate set of steps from the list below:
Executing the script block must just consist of firing
a simple event named error
at the element.
Executing the script block must consist of running the following steps. For the purposes of
these steps, the script is considered to be from an external file if, while the
prepare a script algorithm above was running for this script, the
script
element had a src
attribute
specified.
Initialize the script block's source as follows:
The contents of that file, interpreted as a Unicode string, are the script source.
To obtain the Unicode string, the user agent run the following steps:
If the resource's Content Type metadata, if any, specifies a character encoding, and the user agent supports that encoding, then let character encoding be that encoding, and jump to the bottom step in this series of steps.
If the algorithm above set the script block's character encoding, then let character encoding be that encoding, and jump to the bottom step in this series of steps.
Let character encoding be the script block's fallback character encoding.
If the specification for the script block's type gives specific rules for decoding files in that format to Unicode, follow them, using character encoding as the character encoding specified by higher-level protocols, if necessary.
Otherwise, decode the file to Unicode, using character encoding as the fallback encoding.
The decode algorithm overrides character encoding if the file contains a BOM.
The external file is the script source. When it is later executed, it must be interpreted in a manner consistent with the specification defining the language given by the script block's type.
The value of the text
IDL attribute at the time
the element's "already started" flag was last set is the script source.
The child nodes of the script
element at the time the element's
"already started" flag was last set are the script source.
Fire a simple event named beforescriptexecute
that bubbles and is cancelable
at the script
element.
If the event is canceled, then abort these steps.
If the script is from an external file, then increment the
ignore-destructive-writes counter of the script
element's
Document
. Let neutralized doc be that
Document
.
Create a script, using the script block's source, the
URL from which the script was obtained, the script block's
type as the scripting language, and the script settings object of the script
element's
Document
's Window
object.
If the script came from a resource that was fetched in the steps above, and the resource was CORS-cross-origin, then pass the muted errors flag to the create a script algorithm as well.
This is where the script is compiled and actually executed.
Decrement the ignore-destructive-writes counter of neutralized doc, if it was incremented in the earlier step.
Fire a simple event named afterscriptexecute
that bubbles (but is not
cancelable) at the script
element.
If the script is from an external file, fire a simple event named load
at the script
element.
Otherwise, the script is internal; queue a task to fire a simple
event named load
at the script
element.
The IDL attributes src
, type
, charset
, defer
, each must reflect the respective
content attributes of the same name.
The crossOrigin
IDL attribute must
reflect the crossorigin
content
attribute, limited to only known values.
The async
IDL attribute controls whether the
element will execute asynchronously or not. If the element's "force-async" flag is
set, then, on getting, the async
IDL attribute must return
true, and on setting, the "force-async" flag must first be unset, and then the
content attribute must be removed if the IDL attribute's new value is false, and must be set to
the empty string if the IDL attribute's new value is true. If the element's
"force-async" flag is not set, the IDL attribute must reflect
the async
content attribute.
text
[ = value ]Returns the contents of the element, ignoring child nodes that aren't Text
nodes.
Can be set, to replace the element's children with the given value.
The IDL attribute text
must return a
concatenation of the contents of all the Text
nodes that are children of the
script
element (ignoring any other nodes such as comments or elements), in tree
order. On setting, it must act the same way as the textContent
IDL attribute.
When inserted using the document.write()
method, script
elements execute (typically synchronously), but when inserted using
innerHTML
and outerHTML
attributes, they do not execute at all.
In this example, two script
elements are used. One embeds an external script, and
the other includes some data.
<script src="game-engine.js"></script> <script type="text/x-game-map"> ........U.........e o............A....e .....A.....AAA....e .A..AAA...AAAAA...e </script>
The data in this case might be used by the script to generate the map of a video game. The data doesn't have to be used that way, though; maybe the map data is actually embedded in other parts of the page's markup, and the data block here is just used by the site's search engine to help users who are looking for particular features in their game maps.
The following sample shows how a script element can be used to define a function that is then
used by other parts of the document. It also shows how a script
element can be used
to invoke script while the document is being parsed, in this case to initialize the form's
output.
<script> function calculate(form) { var price = 52000; if (form.elements.brakes.checked) price += 1000; if (form.elements.radio.checked) price += 2500; if (form.elements.turbo.checked) price += 5000; if (form.elements.sticker.checked) price += 250; form.elements.result.value = price; } </script> <form name="pricecalc" onsubmit="return false" onchange="calculate(this)"> <fieldset> <legend>Work out the price of your car</legend> <p>Base cost: £52000.</p> <p>Select additional options:</p> <ul> <li><label><input type=checkbox name=brakes> Ceramic brakes (£1000)</label></li> <li><label><input type=checkbox name=radio> Satellite radio (£2500)</label></li> <li><label><input type=checkbox name=turbo> Turbo charger (£5000)</label></li> <li><label><input type=checkbox name=sticker> "XZ" sticker (£250)</label></li> </ul> <p>Total: £<output name=result></output></p> </fieldset> <script> calculate(document.forms.pricecalc); </script> </form>
A user agent is said to support the scripting language if each component of the script block's type is an ASCII case-insensitive match for the corresponding component in the MIME type string of a scripting language that the user agent implements.
The following lists the MIME type strings that user agents must recognize, and the languages to which they refer:
application/ecmascript
"application/javascript
"application/x-ecmascript
"application/x-javascript
"text/ecmascript
"text/javascript
"text/javascript1.0
"text/javascript1.1
"text/javascript1.2
"text/javascript1.3
"text/javascript1.4
"text/javascript1.5
"text/jscript
"text/livescript
"text/x-ecmascript
"text/x-javascript
"User agents may support other MIME types for other languages, but must not support other MIME types for the languages in the list above. User agents are not required to support the languages listed above.
The following MIME types (with or without parameters) must not be interpreted as scripting languages:
text/plain
"
text/xml
"
application/octet-stream
"
application/xml
"
These types are explicitly listed here because they are poorly-defined types that are nonetheless likely to be used as formats for data blocks, and it would be problematic if they were suddenly to be interpreted as script by a user agent.
When examining types to determine if they represent supported languages, user agents must not ignore MIME parameters. Types are to be compared including all parameters.
For example, types that include the charset
parameter will
not be recognized as referencing any of the scripting languages listed above.
script
elementsThe easiest and safest way to avoid the rather strange restrictions described in
this section is to always escape "<!--
" as "<\!--
", "<script
" as "<\script
", and "</script
" as "<\/script
" when these sequences appear in literals in scripts (e.g. in strings, regular expressions, or
comments), and to avoid writing code that uses such constructs in expressions. Doing so avoids the pitfalls that the restrictions in this section are prone to
triggering: namely, that, for historical reasons, parsing of script
blocks in HTML is
a strange and exotic practice that acts unintuitively in the face of these sequences.
The textContent
of a script
element must match the script
production in the following ABNF, the character set for which is Unicode.
[ABNF]
script = outer *( comment-open inner comment-close outer ) outer = < any string that doesn't contain a substring that matches not-in-outer > not-in-outer = comment-open inner = < any string that doesn't contain a substring that matches not-in-inner > not-in-inner = comment-close / script-open comment-open = "<!--" comment-close = "-->" script-open = "<" s c r i p t tag-end s = %x0053 ; U+0053 LATIN CAPITAL LETTER S s =/ %x0073 ; U+0073 LATIN SMALL LETTER S c = %x0043 ; U+0043 LATIN CAPITAL LETTER C c =/ %x0063 ; U+0063 LATIN SMALL LETTER C r = %x0052 ; U+0052 LATIN CAPITAL LETTER R r =/ %x0072 ; U+0072 LATIN SMALL LETTER R i = %x0049 ; U+0049 LATIN CAPITAL LETTER I i =/ %x0069 ; U+0069 LATIN SMALL LETTER I p = %x0050 ; U+0050 LATIN CAPITAL LETTER P p =/ %x0070 ; U+0070 LATIN SMALL LETTER P t = %x0054 ; U+0054 LATIN CAPITAL LETTER T t =/ %x0074 ; U+0074 LATIN SMALL LETTER T tag-end = %x0009 ; "tab" (U+0009) tag-end =/ %x000A ; "LF" (U+000A) tag-end =/ %x000C ; "FF" (U+000C) tag-end =/ %x0020 ; U+0020 SPACE tag-end =/ %x002F ; "/" (U+002F) tag-end =/ %x003E ; ">" (U+003E)
When a script
element contains script documentation, there are
further restrictions on the contents of the element, as described in the section below.
The following script illustrates this issue. Suppose you have a script that contains a string, as in:
var example = 'Consider this string: <!-- <script>'; console.log(example);
If one were to put this string directly in a script
block, it would violate the
restrictions above:
<script> var example = 'Consider this string: <!-- <script>'; console.log(example); </script>
The bigger problem, though, and the reason why it would violate those restrictions, is that
actually the script would get parsed weirdly: the script block above is not terminated.
That is, what looks like a "</script>
" end tag in this snippet is
actually still part of the script
block. The script doesn't execute (since it's not
terminated); if it somehow were to execute, as it might if the markup looked as follows, it would
fail because the script (highlighted here) is not valid JavaScript:
<script> var example = 'Consider this string: <!-- <script>'; console.log(example); </script> <!-- despite appearances, this is actually part of the script still! --> <script> ... // this is the same script block still... </script>
What is going on here is that for legacy reasons, "<!--
" and "<script
" strings in script
elements in HTML need to be balanced
in order for the parser to consider closing the block.
By escaping the problematic strings as mentioned at the top of this section, the problem is avoided entirely:
<script> var example = 'Consider this string: <\!-- <\script>'; console.log(example); </script> <!-- this is just a comment between script blocks --> <script> ... // this is a new script block </script>
It is possible for these sequences to naturally occur in script expressions, as in the following examples:
if (x<!--y) { ... } if ( player<script ) { ... }
In such cases the characters cannot be escaped, but the expressions can be rewritten so that the sequences don't occur, as in:
if (x < !--y) { ... } if (!--y > x) { ... } if (!(--y) > x) { ... } if (player < script) { ... } if (script > player) { ... }
Doing this also avoids a different pitfall as well: for related historical reasons, the string "<!--" in JavaScript is actually treated as a line comment start, just like "//".
If a script
element's src
attribute is
specified, then the contents of the script
element, if any, must be such that the
value of the text
IDL attribute, which is derived from the
element's contents, matches the documentation
production in the following
ABNF, the character set for which is Unicode. [ABNF]
documentation = *( *( space / tab / comment ) [ line-comment ] newline ) comment = slash star *( not-star / star not-slash ) 1*star slash line-comment = slash slash *not-newline ; characters tab = %x0009 ; "tab" (U+0009) newline = %x000A ; "LF" (U+000A) space = %x0020 ; U+0020 SPACE star = %x002A ; "*" (U+002A) slash = %x002F ; "/" (U+002F) not-newline = %x0000-0009 / %x000B-10FFFF ; a Unicode character other than "LF" (U+000A) not-star = %x0000-0029 / %x002B-10FFFF ; a Unicode character other than "*" (U+002A) not-slash = %x0000-002E / %x0030-10FFFF ; a Unicode character other than "/" (U+002F)
This corresponds to putting the contents of the element in JavaScript comments.
This requirement is in addition to the earlier restrictions on the syntax of
contents of script
elements.
This allows authors to include documentation, such as license information or API information,
inside their documents while still referring to external script files. The syntax is constrained
so that authors don't accidentally include what looks like valid script while also providing a
src
attribute.
<script src="cool-effects.js"> // create new instances using: // var e = new Effect(); // start the effect using .play, stop using .stop: // e.play(); // e.stop(); </script>
script
elements and XSLTThis section is non-normative.
This specification does not define how XSLT interacts with the script
element.
However, in the absence of another specification actually defining this, here are some guidelines
for implementors, based on existing implementations:
When an XSLT transformation program is triggered by an <?xml-stylesheet?>
processing instruction and the browser implements a
direct-to-DOM transformation, script
elements created by the XSLT processor need to
be marked "parser-inserted" and run in document order (modulo scripts marked defer
or async
),
asynchronously while the transformation is occurring.
The XSLTProcessor.transformToDocument()
method
adds elements to a Document
that is not in a browsing context, and,
accordingly, any script
elements they create need to have their "already
started" flag set in the prepare a script algorithm and never get executed
(scripting is disabled). Such script
elements still need to be marked "parser-inserted", though, such that their async
IDL attribute will return false in the absence of an async
content attribute.
The XSLTProcessor.transformToFragment()
method
needs to create a fragment that is equivalent to one built manually by creating the elements
using document.createElementNS()
. For instance,
it needs to create script
elements that aren't "parser-inserted" and
that don't have their "already started" flag set, so that they will execute when the
fragment is inserted into a document.
The main distinction between the first two cases and the last case is that the first two
operate on Document
s and the last operates on a fragment.
noscript
elementhead
element of an HTML document, if there are no ancestor noscript
elements.noscript
elements.head
element: in any order, zero or more link
elements, zero or more style
elements, and zero or more meta
elements.head
element: transparent, but there must be no noscript
element descendants.HTMLElement
.The noscript
element represents nothing if scripting is enabled, and represents its children if
scripting is disabled. It is used to present different
markup to user agents that support scripting and those that don't support scripting, by affecting
how the document is parsed.
When used in HTML documents, the allowed content model is as follows:
head
element, if scripting is
disabled for the noscript
elementThe noscript
element must contain only link
, style
,
and meta
elements.
head
element, if scripting is enabled
for the noscript
elementThe noscript
element must contain only text, except that invoking the
HTML fragment parsing algorithm with
the noscript
element as the context
element and the text contents as the input must result in a list of nodes
that consists only of link
, style
, and meta
elements that
would be conforming if they were children of the noscript
element, and no parse errors.
head
elements, if scripting is
disabled for the noscript
elementThe noscript
element's content model is transparent, with the
additional restriction that a noscript
element must not have a noscript
element as an ancestor (that is, noscript
can't be nested).
head
elements, if scripting is
enabled for the noscript
elementThe noscript
element must contain only text, except that the text must be such
that running the following algorithm results in a conforming document with no
noscript
elements and no script
elements, and such that no step in the
algorithm causes an HTML parser to flag a parse error:
script
element from the document.noscript
element in the document. For every
noscript
element in that list, perform the following steps:
noscript
element.noscript
element, and call these elements the before
children.noscript
element, and call these elements the after
children.Text
node children
of the noscript
element.innerHTML
attribute of the parent element to the value of s. (This, as a side-effect,
causes the noscript
element to be removed from the document.)All these contortions are required because, for historical reasons, the
noscript
element is handled differently by the HTML parser based on
whether scripting was enabled or not when the parser was
invoked.
The noscript
element must not be used in XML documents.
The noscript
element is only effective in the HTML
syntax, it has no effect in the XHTML syntax. This is because the way it works
is by essentially "turning off" the parser when scripts are enabled, so that the contents of the
element are treated as pure text and not as real elements. XML does not define a mechanism by
which to do this.
The noscript
element has no other requirements. In particular, children of the
noscript
element are not exempt from form submission, scripting, and so
forth, even when scripting is enabled for the element.
In the following example, a noscript
element is
used to provide fallback for a script.
<form action="calcSquare.php"> <p> <label for=x>Number</label>: <input id="x" name="x" type="number"> </p> <script> var x = document.getElementById('x'); var output = document.createElement('p'); output.textContent = 'Type a number; it will be squared right then!'; x.form.appendChild(output); x.form.onsubmit = function () { return false; } x.oninput = function () { var v = x.valueAsNumber; output.textContent = v + ' squared is ' + v * v; }; </script> <noscript> <input type=submit value="Calculate Square"> </noscript> </form>
When script is disabled, a button appears to do the calculation on the server side. When script is enabled, the value is computed on-the-fly instead.
The noscript
element is a blunt instrument. Sometimes, scripts might be enabled,
but for some reason the page's script might fail. For this reason, it's generally better to avoid
using noscript
, and to instead design the script to change the page from being a
scriptless page to a scripted page on the fly, as in the next example:
<form action="calcSquare.php"> <p> <label for=x>Number</label>: <input id="x" name="x" type="number"> </p> <input id="submit" type=submit value="Calculate Square"> <script> var x = document.getElementById('x'); var output = document.createElement('p'); output.textContent = 'Type a number; it will be squared right then!'; x.form.appendChild(output); x.form.onsubmit = function () { return false; } x.oninput = function () { var v = x.valueAsNumber; output.textContent = v + ' squared is ' + v * v; }; var submit = document.getElementById('submit'); submit.parentNode.removeChild(submit); </script> </form>
The above technique is also useful in XHTML, since noscript
is not supported in
the XHTML syntax.
template
elementcolgroup
element that doesn't have a span
attribute.ol
and ul
elements.dl
elements.figure
elements.ruby
elements.object
elements.video
and audio
elements.table
elements.colgroup
elements.thead
, tbody
, and tfoot
elements.tr
elements.fieldset
elements.select
elements.details
elements.interface HTMLTemplateElement : HTMLElement { readonly attribute DocumentFragment content; };
The template
element is used to declare fragments of HTML that can be cloned and
inserted in the document by script.
Templates provide a method for declaring inert DOM subtrees and manipulating them to instantiate document fragments with identical contents.
When web pages dynamically alter the contents of their documents (e.g. in response to user interaction or new data arriving from the server), it is common that they require fragments of HTML which may require further modification before use, such as the insertion of values appropriate for the usage context.
The template
element allows for the declaration of document fragments which are
unused by the document when loaded, but are parsed as HTML and are available at runtime for use by
the web page.
In a rendering, the template
element represents nothing.
content
Returns the contents of the template
, which are stored in a
DocumentFragment
associated with a different Document
so as to avoid
the template
contents interfering with the main Document
. (For
example, this avoids form controls from being submitted, scripts from executing, and so
forth.)
Each template
element has an associated DocumentFragment
object that
is its template contents. When a template
element is created, the user
agent must run the following steps to establish the template contents:
Let doc be the template
element's ownerDocument
's appropriate template contents owner
document.
Create a DocumentFragment
object whose ownerDocument
is doc.
Set the template
element's template contents to the newly
created DocumentFragment
object.
A Document
doc's appropriate template contents owner
document is the Document
returned by the following algorithm:
If doc is not a Document
created by this algorithm, run
these substeps:
If doc does not yet have an associated inert template document then run these substeps:
Let new doc be a new Document
(that does not have a
browsing context). This is "a Document
created by this algorithm"
for the purposes of the step above.
If doc is an HTML document, mark new doc as an HTML document also.
Let doc's associated inert template document be new doc.
Set doc to doc's associated inert template document.
Each Document
not created by this algorithm thus gets a single
Document
to act as its proxy for owning the template contents of all
its template
elements, so that they aren't in a browsing context and
thus remain inert (e.g. scripts do not run). Meanwhile, template
elements inside
Document
objects that are created by this algorithm just reuse the same
Document
owner for their contents.
Return doc.
When a template
element changes ownerDocument
, the user agent must run the following
steps:
Let doc be the template
element's new ownerDocument
's appropriate template contents owner
document.
Adopt the template
element's
template contents (a DocumentFragment
object) into doc.
The content
IDL attribute must return the
template
element's template contents.
The cloning steps for a template
element node being cloned to a copy copy must run the
following steps:
If the clone children flag is not set in the calling clone algorithm, abort these steps.
Let copied contents be the result of cloning all the children of node's
template contents, with ownerDocument set to copy's template contents's ownerDocument
, and with the clone children
flag set.
Append copied contents to copy's template contents.
In this example, a script populates a table with data from a data structure, using a
template
to provide the element structure instead of manually generating the
structure from markup.
<!DOCTYPE html> <title>Cat data</title> <script> // Data is hard-coded here, but could come from the server var data = [ { name: 'Pillar', color: 'Ticked Tabby', sex: 'Female (neutered)', legs: 3 }, { name: 'Hedral', color: 'Tuxedo', sex: 'Male (neutered)', legs: 4 }, ]; </script> <table> <thead> <tr> <th>Name <th>Color <th>Sex <th>Legs <tbody> <template id="row"> <tr><td><td><td><td> </template> </table> <script> var template = document.querySelector('#row'); for (var i = 0; i < data.length; i += 1) { var cat = data[i]; var clone = template.content.cloneNode(true); var cells = clone.querySelectorAll('td'); cells[0].textContent = cat.name; cells[1].textContent = cat.color; cells[2].textContent = cat.sex; cells[3].textContent = cat.legs; template.parentNode.appendChild(clone); } </script>
template
elements with XSLT and XPathThis section is non-normative.
This specification does not define how XSLT and XPath interact with the template
element. However, in the absence of another specification actually defining this, here are some
guidelines for implementors, which are intended to be consistent with other processing described
in this specification:
An XSLT processor based on an XML parser that acts as described
in this specification needs to act as if template
elements contain as
descendants their template contents for the purposes of the transform.
An XSLT processor that outputs a DOM needs to ensure that nodes that would go into a
template
element are instead placed into the element's template
contents.
XPath evaluation using the XPath DOM API when applied to a Document
parsed
using the HTML parser or the XML parser described in this specification
needs to ignore template contents.
canvas
elementwidth
height
typedef (CanvasRenderingContext2D or WebGLRenderingContext) RenderingContext;
interface HTMLCanvasElement : HTMLElement {
attribute unsigned long width;
attribute unsigned long height;
RenderingContext? getContext(DOMString contextId, any... arguments);
DOMString toDataURL(optional DOMString type, any... arguments);
void toBlob(FileCallback? _callback, optional DOMString type, any... arguments);
};
The canvas
element provides scripts with a resolution-dependent bitmap canvas,
which can be used for rendering graphs, game graphics, art, or other visual images on the fly.
Authors should not use the canvas
element in a document when a more suitable
element is available. For example, it is inappropriate to use a canvas
element to
render a page heading: if the desired presentation of the heading is graphically intense, it
should be marked up using appropriate elements (typically h1
) and then styled using
CSS and supporting technologies such as XBL.
When authors use the canvas
element, they must also provide content that, when
presented to the user, conveys essentially the same function or purpose as the
canvas
' bitmap. This content may be placed as content of the canvas
element. The contents of the canvas
element, if any, are the element's fallback
content.
In interactive visual media, if scripting is enabled for
the canvas
element, and if support for canvas
elements has been enabled,
the canvas
element represents embedded content consisting
of a dynamically created image, the element's bitmap.
In non-interactive, static, visual media, if the canvas
element has been
previously associated with a rendering context (e.g. if the page was viewed in an interactive
visual medium and is now being printed, or if some script that ran during the page layout process
painted on the element), then the canvas
element represents
embedded content with the element's current bitmap and size. Otherwise, the element
represents its fallback content instead.
In non-visual media, and in visual media if scripting is
disabled for the canvas
element or if support for canvas
elements
has been disabled, the canvas
element represents its fallback
content instead.
When a canvas
element represents embedded content, the
user can still focus descendants of the canvas
element (in the fallback
content). When an element is focused, it is the target of keyboard interaction events (even
though the element itself is not visible). This allows authors to make an interactive canvas
keyboard-accessible: authors should have a one-to-one mapping of interactive regions to focusable
elements in the fallback content. (Focus has no effect on mouse interaction events.)
[DOMEVENTS]
The canvas
element has two attributes to control the size of the element's bitmap:
width
and height
. These attributes, when specified, must have
values that are valid non-negative integers. The rules for parsing non-negative integers must be used to obtain their
numeric values. If an attribute is missing, or if parsing its value returns an error, then the
default value must be used instead. The width
attribute defaults to 300, and the height
attribute
defaults to 150.
The intrinsic dimensions of the canvas
element when it represents
embedded content are equal to the dimensions of the element's bitmap.
A canvas
element can be sized arbitrarily by a style sheet, its
bitmap is then subject to the 'object-fit' CSS property. [CSSIMAGES]
The bitmaps of canvas
elements, as well as some of the bitmaps of rendering
contexts, such as those described in the section on the CanvasRenderingContext2D
object below, have an origin-clean flag, which can
be set to true or false. Initially, when the canvas
element is created, its bitmap's
origin-clean flag must be set to true.
A canvas
bitmap can also have a hit region list, as described in the
CanvasRenderingContext2D
section below.
A canvas
element can have a rendering context bound to it. Initially, it does not
have a bound rendering context. To keep track of whether it has a rendering context or not, and
what kind of rendering context it is, a canvas
also has a canvas context mode, which is initially none but can be changed to either direct-2d, direct-webgl, indirect, or proxied by algorithms defined in this specification.
When its canvas context mode is none, a canvas
element has no rendering context,
and its bitmap must be fully transparent black with an intrinsic width equal to the numeric value
of the element's width
attribute and an intrinsic height
equal to the numeric value of the element's height
attribute, those values being interpreted in CSS pixels, and being updated as the attributes are
set, changed, or removed.
When a canvas
element represents embedded content, it provides
a paint source whose width is the element's intrinsic width, whose height is the element's
intrinsic height, and whose appearance is the element's bitmap.
Whenever the width
and height
content attributes are set, removed, changed, or
redundantly set to the value they already have, if the canvas context mode is direct-2d, the user agent must set bitmap dimensions to the numeric values of
the width
and height
content attributes.
The width
and height
IDL attributes must reflect the
respective content attributes of the same name, with the same defaults.
The bitmaps used with canvas
elements can have arbitrary pixel
densities. Typically, the density will match that of the user's screen.
getContext
(contextId [, ... ])Returns an object that exposes an API for drawing on the canvas. The first argument specifies
the desired API, either "2d
" or "webgl
". Subsequent arguments are handled by that API.
The list of defined contexts is given on the WHATWG Wiki CanvasContexts page. [WHATWGWIKI]
Example contexts are the "2d
" [CANVAS2D] and the "webgl
" context [WEBGL].
Returns null if the given context ID is not supported or if the canvas has already been
initialized with some other (incompatible) context type (e.g. trying to get a "2d
" context after getting a "webgl
" context).
Each rendering context has a context bitmap mode, which is one of fixed, unbound, or bound. Initially, rendering contexts must be in the unbound mode.
The getContext(contextId, arguments...)
method of the canvas
element, when invoked,
must run the steps in the cell of the following table whose column header describes the
canvas
element's canvas context mode
and whose row header describes the method's first argument.
none | direct-2d | direct-webgl | indirect | proxied | |
---|---|---|---|---|---|
"2d "
|
Set the canvas element's context
mode to direct-2d; follow the 2D
context creation algorithm defined in the section below, passing it the
canvas element, to obtain a CanvasRenderingContext2D object; set
that object's context bitmap mode to
fixed, and return the
CanvasRenderingContext2D object
| Return the same object as was return the last time the method was invoked with this same argument. | Return null. |
Throw an InvalidStateError exception.
|
Throw an InvalidStateError exception.
|
"webgl ", if the user agent supports the WebGL feature in its current configuration
|
Follow the instructions given in the WebGL specification's Context Creation section to
obtain either a WebGLRenderingContext or null; if the returned value is null,
then return null and abort these steps, otherwise, set the canvas element's context mode to direct-webgl, set the new
WebGLRenderingContext object's context bitmap mode to fixed, and return the WebGLRenderingContext
object‡ [WEBGL]
| Return null. | Return the same object as was return the last time the method was invoked with this same argument. |
Throw an InvalidStateError exception.
|
Throw an InvalidStateError exception.
|
A vendor-specific extension* | Behave as defined for the extension. | Behave as defined for the extension. | Behave as defined for the extension. |
Throw an InvalidStateError exception.
|
Throw an InvalidStateError exception.
|
An unsupported value† | Return null. | Return null. | Return null. |
Throw an InvalidStateError exception.
|
Throw an InvalidStateError exception.
|
* Vendors may define experimental contexts using the syntax vendorname-context
, for example,
moz-3d
.
† For example, the "webgl
" value in the case of a user agent having exhausted the
graphics hardware's abilities and having no software fallback implementation.
‡ The second (and subsequent) argument(s) to the method, if any, are ignored in all cases except this one. See the WebGL specification for details.
toDataURL
( [ type, ... ] )Returns a data:
URL for the image in
the canvas.
The first argument, if provided, controls the type of the image to be returned (e.g. PNG or
JPEG). The default is image/png
; that type is also used if the given type
isn't supported. The other arguments are specific to the type, and control the way that the
image is generated, as given in the table
below.
When trying to use types other than "image/png
", authors can check if the image
was really returned in the requested format by checking to see if the returned string starts
with one of the exact strings "data:image/png,
" or "data:image/png;
". If it does, the image is PNG, and thus the requested type was
not supported. (The one exception to this is if the canvas has either no height or no width, in
which case the result might simply be "data:,
".)
The toDataURL()
method returns the data at a
resolution of 96dpi.
toBlob
(callback [, type, ... ])Creates a Blob
object representing a file containing the image in the canvas,
and invokes a callback with a handle to that object.
The second argument, if provided, controls the type of the image to be returned (e.g. PNG or
JPEG). The default is image/png
; that type is also used if the given type
isn't supported. The other arguments are specific to the type, and control the way that the
image is generated, as given in the table
below.
The toBlob()
method provides the data at a resolution
of 96dpi.
The toDataURL()
method must run the following
steps:
If the canvas
element's bitmap's origin-clean flag is set to false, throw a
SecurityError
exception and abort these steps.
If the canvas
element's bitmap has no pixels (i.e. either its horizontal
dimension or its vertical dimension is zero) then return the string "data:,
" and abort these steps. (This is the shortest data:
URL; it represents the empty string in a text/plain
resource.)
Let file be a
serialization of the canvas
element's bitmap as a file, using the method's
arguments (if any) as the arguments.
The toBlob()
method must run the following
steps:
If the canvas
element's bitmap's origin-clean flag is set to false, throw a
SecurityError
exception and abort these steps.
Let callback be the first argument.
Let arguments be the second and subsequent arguments to the method, if any.
If the canvas
element's bitmap has no pixels (i.e. either its horizontal
dimension or its vertical dimension is zero) then let result be null.
Otherwise, let result be a Blob
object representing a serialization of the canvas
element's bitmap as a file, using arguments. [FILEAPI]
Return, but continue running these steps asynchronously.
If callback is null, abort these steps.
Queue a task to invoke the FileCallback
callback with result as its argument. The task
source for this task is the canvas blob serialization task source.
The canvas
APIs must perform color correction at only two points: when rendering
images with their own gamma correction and color space information onto a bitmap, to convert the
image to the color space used by the bitmaps (e.g. using the 2D Context's drawImage()
method with an HTMLImageElement
object), and when rendering the actual canvas bitmap to the output device.
Thus, in the 2D context, colors used to draw shapes onto the canvas will exactly
match colors obtained through the getImageDataHD()
method.
The toDataURL()
method must not include color space
information in the resources it returns. Where the output format allows it, the color of pixels
in resources created by toDataURL()
must match those
returned by the getImageData()
method.
In user agents that support CSS, the color space used by a canvas
element must
match the color space used for processing any colors for that element in CSS.
The gamma correction and color space information of images must be handled in such a way that
an image rendered directly using an img
element would use the same colors as one
painted on a canvas
element that is then itself rendered. Furthermore, the rendering
of images that have no color correction information (such as those returned by the toDataURL()
method) must be rendered with no color
correction.
When a user agent is to create a serialization of the bitmap as a file, optionally with some given arguments, it must create an image file in the format given by the first value of arguments, or, if there are no arguments, in the PNG format. [PNG]
If if the bitmap has one pixel per coordinate space unit then the image file must have the same pixel data (before compression, if applicable) as the bitmap, and if the file format used supports encoding resolution metadata, the resolution of that bitmap (device pixels per coordinate space units being interpreted as image pixels per CSS pixel) must be given as well.
Otherwise, the image file's pixel data must be the bitmap's pixel data scaled to one image pixel per coordinate space unit, and if the file format used supports encoding resolution metadata, the resolution must be given as 96dpi (one image pixel per CSS pixel).
If arguments is not empty, the first value must be interpreted as a MIME type giving the format to use. If the type has any parameters, it must be treated as not supported.
For example, the value "image/png
" would mean to generate a PNG
image, the value "image/jpeg
" would mean to generate a JPEG image, and the value
"image/svg+xml
" would mean to generate an SVG image (which would require that the
user agent track how the bitmap was generated, an unlikely, though potentially awesome,
feature).
User agents must support PNG ("image/png
"). User agents may support other types.
If the user agent does not support the requested type, it must create the file using the PNG
format. [PNG]
User agents must convert the provided type to ASCII lowercase before establishing if they support that type.
For image types that do not support an alpha channel, the serialized image must be the bitmap image composited onto a solid black background using the source-over operator.
If the first argument in arguments gives a type corresponding to one of the types given in the first column of the following table, and the user agent supports that type, then the subsequent arguments, if any, must be treated as described in the second cell of that row.
Type | Other arguments | Reference |
---|---|---|
image/jpeg
| The second argument, if it is a number in the range 0.0 to 1.0 inclusive, must be treated as the desired quality level. If it is not a number or is outside that range, the user agent must use its default value, as if the argument had been omitted. | [JPEG] |
For the purposes of these rules, an argument is considered to be a number if it is converted to
an IDL double value by the rules for handling arguments of type any
in the
Web IDL specification. [WEBIDL]
Other arguments must be ignored and must not cause the user agent to throw an exception. A future version of this specification will probably define other parameters to be passed to these methods to allow authors to more carefully control compression settings, image metadata, etc.
canvas
elementsThis section is non-normative.
Information leakage can occur if scripts from one origin can access information (e.g. read pixels) from images from another origin (one that isn't the same).
To mitigate this, bitmaps used with canvas
elements are defined to have a flag
indicating whether they are origin-clean. All
bitmaps start with their origin-clean set to
true. The flag is set to false when cross-origin images or fonts are used.
The toDataURL()
, toBlob()
, getImageData()
, and getImageDataHD()
methods check the flag and will
throw a SecurityError
exception rather than leak cross-origin data.
The flag can be reset in certain situations; for example, when a
CanvasRenderingContext2D
is bound to a new canvas
, the bitmap is cleared
and its flag reset.
HTML does not have a dedicated mechanism for marking up subheadings, alternative titles or taglines. Here are the suggested alternatives.
h1
–h6
elements must not be used to markup subheadings, subtitles, alternative titles and taglines unless intended to be the heading for a new section or subsection.
In the following example the title and subtitles of a web page are grouped using a header
element.
As the author does not want the subtitles to be included the table of contents and they are not intended to signify
the start of a new section, they are marked up using p
elements. A sample CSS styled rendering of the
title and subtitles is provided below the code example.
<header> <h1>HTML 5.1 Nightly</h1> <p>A vocabulary and associated APIs for HTML and XHTML</p> <p>Editor's Draft 9 May 2013</p> </header>
In the following example the subtitle of a book is on the same line as the title separated by a colon. A sample CSS styled rendering of the title and subtitle is provided below the code example.
<h1>The Lord of the Rings: The Two Towers</h1>
In the following example part of an album title is included in a span
element,
allowing it to be styled differently from the rest of the title. A br
element is used to
place the album title on a new line. A sample CSS styled rendering of the heading is provided
below the code example.
<h1>Ramones <br> <span>Hey! Ho! Let's Go</span> </h1>
In the following example the title and tagline for a news article are grouped using a header
element.
The title is marked up using a h2
element and the tagline is in a p
element. A sample CSS styled rendering of the
title and tagline is provided below the code example.
<header> <h2>3D films set for popularity slide </h2> <p>First drop in 3D box office projected for this year despite hotly tipped summer blockbusters, according to Fitch Ratings report</p> </header>
In this last example the title and taglines for a news magazine are grouped using a header
element.
The title is marked up using a h1
element and the taglines are each in a p
element. A sample CSS styled rendering of the
title and taglines is provided below the code example.
<header> <p>Magazine of the Decade</p> <h1>THE MONTH</h1> <p>The Best of UK and Foreign Media</p> </header>
This specification does not provide a machine-readable way of describing bread-crumb navigation
menus. Authors are encouraged to markup bread-crumb navigation as a list. The nav
element can be used to mark the
list containing links as being a navigation block.
In the following example, the current page can be reached via the path indicated. The path is indicated using the right arrow symbol "→". A text label is provided to give the user context. The links are structured as a list, which provides users with an indication of item number.
<nav> <h2>You are here:</h2> <ul id="navlist"> <li><a href="/">Main</a> →</li> <li><a href="/products/">Products</a> →</li> <li><a href="/products/dishwashers/">Dishwashers</a> →</li> <li><a>Second hand</a></li> </ul> </nav>
The breadcrumb code example could be styled as a horizonatal list using CSS:
The use of the right angle bracket symbol ">" to indicate path direction is discouraged as its meaning, in the context used, is not clearly conveyed to all users.
This specification does not define any markup specifically for marking up lists
of keywords that apply to a group of pages (also known as tag clouds). In general, authors
are encouraged to either mark up such lists using ul
elements with explicit inline
counts that are then hidden and turned into a presentational effect using a style sheet, or to use
SVG.
Here, three tags are included in a short tag cloud:
<style> @media screen, print, handheld, tv { /* should be ignored by non-visual browsers */ .tag-cloud > li > span { display: none; } .tag-cloud > li { display: inline; } .tag-cloud-1 { font-size: 0.7em; } .tag-cloud-2 { font-size: 0.9em; } .tag-cloud-3 { font-size: 1.1em; } .tag-cloud-4 { font-size: 1.3em; } .tag-cloud-5 { font-size: 1.5em; } } </style> ... <ul class="tag-cloud"> <li class="tag-cloud-4"><a title="28 instances" href="/t/apple">apple</a> <span>(popular)</span> <li class="tag-cloud-2"><a title="6 instances" href="/t/kiwi">kiwi</a> <span>(rare)</span> <li class="tag-cloud-5"><a title="41 instances" href="/t/pear">pear</a> <span>(very popular)</span> </ul>
The actual frequency of each tag is given using the title
attribute. A CSS style sheet is provided to convert the markup into a cloud of differently-sized
words, but for user agents that do not support CSS or are not visual, the markup contains
annotations like "(popular)" or "(rare)" to categorize the various tags by frequency, thus
enabling all users to benefit from the information.
The ul
element is used (rather than ol
) because the order is not
particularly important: while the list is in fact ordered alphabetically, it would convey the
same information if ordered by, say, the length of the tag.
The tag
rel
-keyword is
not used on these a
elements because they do not represent tags that apply
to the page itself; they are just part of an index listing the tags themselves.
This specification does not define a specific element for marking up conversations, meeting minutes, chat transcripts, dialogues in screenplays, instant message logs, and other situations where different players take turns in discourse.
Instead, authors are encouraged to mark up conversations using p
elements and
punctuation. Authors who need to mark the speaker for styling purposes are encouraged to use
span
or b
. Paragraphs with their text wrapped in the i
element can be used for marking up stage directions.
This example demonstrates this using an extract from Abbot and Costello's famous sketch, Who's on first:
<p> Costello: Look, you gotta first baseman? <p> Abbott: Certainly. <p> Costello: Who's playing first? <p> Abbott: That's right. <p> Costello becomes exasperated. <p> Costello: When you pay off the first baseman every month, who gets the money? <p> Abbott: Every dollar of it.
The following extract shows how an IM conversation log could be marked up, using the
data
element to provide Unix timestamps for each line. Note that the timestamps are
provided in a format that the time
element does not support, so the
data
element is used instead (namely, Unix time_t
timestamps).
Had the author wished to mark up the data using one of the date and time formats supported by the
time
element, that element could have been used instead of data
. This
could be advantageous as it would allow data analysis tools to detect the timestamps
unambiguously, without coordination with the page author.
<p> <data value="1319898155">14:22</data> <b>egof</b> I'm not that nerdy, I've only seen 30% of the star trek episodes <p> <data value="1319898192">14:23</data> <b>kaj</b> if you know what percentage of the star trek episodes you have seen, you are inarguably nerdy <p> <data value="1319898200">14:23</data> <b>egof</b> it's unarguably <p> <data value="1319898228">14:23</data> <i>* kaj blinks</i> <p> <data value="1319898260">14:24</data> <b>kaj</b> you are not helping your case
HTML does not have a good way to mark up graphs, so descriptions of interactive conversations
from games are more difficult to mark up. This example shows one possible convention using
dl
elements to list the possible responses at each point in the conversation.
Another option to consider is describing the conversation in the form of a DOT file, and
outputting the result as an SVG image to place in the document. [DOT]
<p> Next, you meet a fisherman. You can say one of several greetings: <dl> <dt> "Hello there!" <dd> <p> He responds with "Hello, how may I help you?"; you can respond with: <dl> <dt> "I would like to buy a fish." <dd> <p> He sells you a fish and the conversation finishes. <dt> "Can I borrow your boat?" <dd> <p> He is surprised and asks "What are you offering in return?". <dl> <dt> "Five gold." (if you have enough) <dt> "Ten gold." (if you have enough) <dt> "Fifteen gold." (if you have enough) <dd> <p> He lends you his boat. The conversation ends. <dt> "A fish." (if you have one) <dt> "A newspaper." (if you have one) <dt> "A pebble." (if you have one) <dd> <p> "No thanks", he replies. Your conversation options at this point are the same as they were after asking to borrow his boat, minus any options you've suggested before. </dl> </dd> </dl> </dd> <dt> "Vote for me in the next election!" <dd> <p> He turns away. The conversation finishes. <dt> "Sir, are you aware that your fish are running away?" <dd> <p> He looks at you skeptically and says "Fish cannot run, sir". <dl> <dt> "You got me!" <dd> <p> The fisherman sighs and the conversation ends. <dt> "Only kidding." <dd> <p> "Good one!" he retorts. Your conversation options at this point are the same as those following "Hello there!" above. <dt> "Oh, then what are they doing?" <dd> <p> He looks at his fish, giving you an opportunity to steal his boat, which you do. The conversation ends. </dl> </dd> </dl>
In some games, conversations are simpler: each character merely has a fixed set of lines that they say. In this example, a game FAQ/walkthrough lists some of the known possible responses for each character:
<section> <h1>Dialogue</h1> <p><small>Some characters repeat their lines in order each time you interact with them, others randomly pick from amongst their lines. Those who respond in order have numbered entries in the lists below.</small> <h2>The Shopkeeper</h2> <ul> <li>How may I help you? <li>Fresh apples! <li>A loaf of bread for madam? </ul> <h2>The pilot</h2> <p>Before the accident: <ul> </li>I'm about to fly out, sorry! </li>Sorry, I'm just waiting for flight clearance and then I'll be off! </ul> <p>After the accident: <ol> <li>I'm about to fly out, sorry! <li>Ok, I'm not leaving right now, my plane is being cleaned. <li>Ok, it's not being cleaned, it needs a minor repair first. <li>Ok, ok, stop bothering me! Truth is, I had a crash. </ol> <h2>Clan Leader</h2> <p>During the first clan meeting: <ul> <li>Hey, have you seen my daughter? I bet she's up to something nefarious again... <li>Nice weather we're having today, eh? <li>The name is Bailey, Jeff Bailey. How can I help you today? <li>A glass of water? Fresh from the well! </ul> <p>After the earthquake: <ol> <li>Everyone is safe in the shelter, we just have to put out the fire! <li>I'll go and tell the fire brigade, you keep hosing it down! </ol> </section>
HTML does not have a dedicated mechanism for marking up footnotes. Here are the suggested alternatives.
For
annotations, the a
element should be used, pointing to
an element later in the document. The convention is that the
contents of the link be a number in square brackets.
In this example, a footnote in the dialogue links to a paragraph below the dialogue. The paragraph then reciprocally links back to the dialogue, allowing the user to return to the location of the footnote.
<p> Announcer: Number 16: The <i>hand</i>. <p> Interviewer: Good evening. I have with me in the studio tonight Mr Norman St John Polevaulter, who for the past few years has been contradicting people. Mr Polevaulter, why <em>do</em> you contradict people? <p> Norman: I don't. <sup><a href="#fn1" id="r1">[1]</a></sup> <p> Interviewer: You told me you did! ... <section> <p id="fn1"><a href="#r1">[1]</a> This is, naturally, a lie, but paradoxically if it were true he could not say so without contradicting the interviewer and thus making it false.</p> </section>
For side notes, longer annotations that apply to entire sections of the text rather than just
specific words or sentences, the aside
element should be used.
In this example, a sidebar is given after a dialogue, giving it some context.
<p> <span class="speaker">Customer</span>: I will not buy this record, it is scratched. <p> <span class="speaker">Shopkeeper</span>: I'm sorry? <p> <span class="speaker">Customer</span>: I will not buy this record, it is scratched. <p> <span class="speaker">Shopkeeper</span>: No no no, this's'a tobacconist's. <aside> <p>In 1970, the British Empire lay in ruins, and foreign nationalists frequented the streets — many of them Hungarians (not the streets — the foreign nationals). Sadly, Alexander Yalt has been publishing incompetently-written phrase books. </aside>
For figures or tables, footnotes can be included in the relevant figcaption
or
caption
element, or in surrounding prose.
In this example, a table has cells with footnotes that are given in prose. A
figure
element is used to give a single legend to the combination of the table and
its footnotes.
<figure> <figcaption>Table 1. Alternative activities for knights.</figcaption> <table> <tr> <th> Activity <th> Location <th> Cost <tr> <td> Dance <td> Wherever possible <td> £0<sup><a href="#fn1">1</a></sup> <tr> <td> Routines, chorus scenes<sup><a href="#fn2">2</a></sup> <td> Undisclosed <td> Undisclosed <tr> <td> Dining<sup><a href="#fn3">3</a></sup> <td> Camelot <td> Cost of ham, jam, and spam<sup><a href="#fn4">4</a></sup> </table> <p id="fn1">1. Assumed.</p> <p id="fn2">2. Footwork impeccable.</p> <p id="fn3">3. Quality described as "well".</p> <p id="fn4">4. A lot.</p> </figure>
An element is said to be actually disabled if it falls into one of the following categories:
button
elements that are disabledinput
elements that are disabledselect
elements that are disabledtextarea
elements that are disabledoptgroup
elements that have a disabled
attributeoption
elements that are disabledfieldset
elements that have a disabled
attributeThis definition is used to determine what elements can be focused and which elements match the :disabled
pseudo-class.
The Selectors specification leaves the case-sensitivity of IDs, classes, element names, attribute names, and attribute values to be defined by the host language. [SELECTORS]
The unique identifier of HTML elements in documents that are in quirks mode must be treated as ASCII case-insensitive for the purposes of selector matching.
Classes from the class
attribute of HTML elements
in documents that are in quirks mode must be treated as ASCII
case-insensitive for the purposes of selector matching.
When comparing a CSS element type selector to the names of HTML elements in HTML documents, the CSS element type selector must first be converted to ASCII lowercase. The same selector when compared to other elements must be compared according to its original case. In both cases, the comparison is case-sensitive.
When comparing the name part of a CSS attribute selector to the names of namespace-less attributes on HTML elements in HTML documents, the name part of the CSS attribute selector must first be converted to ASCII lowercase. The same selector when compared to other attributes must be compared according to its original case. In both cases, the comparison is case-sensitive.
Everything else (attribute values on HTML elements, IDs and classes in no-quirks mode and limited-quirks mode, and element names, attribute names, and attribute values in XML documents) must be treated as case-sensitive for the purposes of selector matching.
There are a number of dynamic selectors that can be used with HTML. This section defines when these selectors match HTML elements. [SELECTORS] [CSSUI]
:link
:visited
All a
elements that have an href
attribute, all area
elements that have an href
attribute, and all link
elements that have
an href
attribute, must match one of :link
and :visited
.
Other specifications might apply more specific rules regarding how these elements are to match these pseudo-classes, to mitigate some privacy concerns that apply with straightforward implementations of this requirement.
:active
The :active
pseudo-class is defined to match an element
while an
element is being activated by the user
. For the purposes of defining the :active
pseudo-class only, an HTML user agent must consider an
element as being activated if it is:
An element falling into one of the following categories between the time the user begins to indicate an intent to trigger the element's activation behavior and either the time the user stops indicating an intent to trigger the element's activation behavior, or the time the element's activation behavior has finished running, which ever comes first:
a
elements that have an href
attributearea
elements that have an href
attributelink
elements that have an href
attributebutton
elements that are not disabledinput
elements whose type
attribute is
in the Submit Button, Image Button, Reset
Button, or Button stateFor example, if the user is using a keyboard to push a button
element by pressing the space bar, the element would match this pseudo-class in between the
time that the element received the keydown
event and the
time the element received the keyup
event.
An element that the user indicates using a pointing device while that pointing device is in the "down" state (e.g. for a mouse, between the time the mouse button is pressed and the time it is depressed).
An element that has a descendant that is currently matching the :active
pseudo-class.
:hover
The :hover
pseudo-class is defined to match an element while the
user designates an element with a pointing device
. For the purposes of defining the
:hover
pseudo-class only, an HTML user agent must consider
an element as being one that the user designates if it is:
An element that the user indicates using a pointing device.
An element that has a descendant that the user indicates using a pointing device.
An element that is the labeled control of a label
element that is
currently matching :hover.
Consider in particular a fragment such as:
<p> <label for=c> <input id=a> </label> <span id=b> <input id=c> </span> </p>
If the user designates the element with ID "a
" with their pointing
device, then the p
element (and all its ancestors not shown in the snippet above),
the label
element, the element with ID "a
", and the element
with ID "c
" will match the :hover
pseudo-class. The element with ID "a
" matches it from condition 1, the
label
and p
elements match it because of condition 2 (one of their
descendants is designated), and the element with ID "c
" matches it
through condition 3 (its label
element matches :hover). However, the element with ID "b
"
does not match :hover: its descendant is not
designated, even though it matches :hover.
:enabled
The :enabled
pseudo-class must match any element
falling into one of the following categories:
a
elements that have an href
attributearea
elements that have an href
attributelink
elements that have an href
attributebutton
elements that are not disabledinput
elements that are not disabledselect
elements that are not disabledtextarea
elements that are not disabledoptgroup
elements that do not have a disabled
attributeoption
elements that are not disabledfieldset
elements that do not have a disabled
attribute:disabled
The :disabled
pseudo-class must match any element that
is actually disabled.
:checked
The :checked
pseudo-class must match any element
falling into one of the following categories:
input
elements whose type
attribute is in
the Checkbox state and whose checkedness state is trueinput
elements whose type
attribute is in
the Radio Button state and whose checkedness state is trueoption
elements whose selectedness is true:indeterminate
The :indeterminate
pseudo-class must match any
element falling into one of the following categories:
input
elements whose type
attribute is in
the Checkbox state and whose indeterminate
IDL attribute is set to trueinput
elements whose type
attribute is in
the Radio Button state and whose radio button
group contains no input
elements whose checkedness state is true.progress
elements with no value
content attribute:default
The :default
pseudo-class must match any element
falling into one of the following categories:
button
elements that are their form's default buttoninput
elements whose type
attribute is in
the Submit Button or Image Button state, and that are their form's
default buttoninput
elements to which the checked
attribute applies and that have a checked
attributeoption
elements that have a selected
attribute:valid
The :valid
pseudo-class must match any element falling
into one of the following categories:
form
elements that are not the form owner of any elements that
themselves are candidates for constraint
validation but do not satisfy their
constraintsfieldset
elements that have no descendant elements that themselves are candidates for constraint validation but do
not satisfy their constraints:invalid
The :invalid
pseudo-class must match any element
falling into one of the following categories:
form
elements that are the form owner of one or more elements
that themselves are candidates for constraint
validation but do not satisfy their
constraintsfieldset
elements that have of one or more descendant elements that themselves
are candidates for constraint
validation but do not satisfy their
constraints:in-range
The :in-range
pseudo-class must match all elements
that are candidates for constraint
validation, have range limitations, and that are neither suffering
from an underflow nor suffering from an overflow.
:out-of-range
The :out-of-range
pseudo-class must match all
elements that are candidates for constraint
validation, have range limitations, and that are either suffering from
an underflow or suffering from an overflow.
:required
The :required
pseudo-class must match any element
falling into one of the following categories:
:optional
The :optional
pseudo-class must match any element
falling into one of the following categories:
:read-only
:read-write
The :read-write
pseudo-class must match any element
falling into one of the following categories, which for the purposes of Selectors are thus
considered user-alterable: [SELECTORS]
input
elements to which the readonly
attribute applies, and that are mutable (i.e. that do not
have the readonly
attribute specified and that are not
disabled)textarea
elements that do not have a readonly
attribute, and that are not disabledinput
elements nor textarea
elementsThe :read-only
pseudo-class must match all other
HTML elements.
:dir(ltr)
The :dir(ltr)
pseudo-class must match all elements whose
directionality is 'ltr'.
:dir(rtl)
The :dir(rtl)
pseudo-class must match all elements whose
directionality is 'rtl'.
Another section of this specification defines the target element used with
the :target
pseudo-class.
This specification does not define when an element matches the :focus
or :lang()
dynamic
pseudo-classes, as those are all defined in sufficient detail in a language-agnostic fashion in
the Selectors specification. [SELECTORS]
This section describes features that apply most directly to Web browsers. Having said that, except where specified otherwise, the requirements defined in this section do apply to all user agents, whether they are Web browsers or not.
A browsing context is an environment in which Document
objects are
presented to the user.
A tab or window in a Web browser typically contains a browsing
context, as does an iframe
or frame
s in a
frameset
.
Each browsing context has a corresponding WindowProxy
object.
A browsing context has a session history, which lists the
Document
objects that that browsing context has presented, is
presenting, or will present. At any time, one Document
in each browsing
context is designated the active document. A Document
's
browsing context is that browsing context whose session
history contains the Document
, if any. (A Document
created using
an API such as createDocument()
has no
browsing context.)
Each Document
in a browsing context is associated with a Window
object. A
browsing context's WindowProxy
object forwards everything to the
browsing context's active document's Window
object.
In general, there is a 1-to-1 mapping from the Window
object to the
Document
object. There are two exceptions. First, a Window
can be reused
for the presentation of a second Document
in the same browsing context,
such that the mapping is then 1-to-2. This occurs when a browsing context is navigated from the initial about:blank
Document
to another, with replacement enabled. Second, a Document
can end up
being reused for several Window
objects when the document.open()
method is used, such that the mapping is then
many-to-1.
A Document
does not necessarily have a browsing context
associated with it. In particular, data mining tools are likely to never instantiate browsing
contexts.
A browsing context can have a creator browsing context, the browsing context that was responsible for its creation. If a browsing context has a parent browsing context, then that is its creator browsing context. Otherwise, if the browsing context has an opener browsing context, then that is its creator browsing context. Otherwise, the browsing context has no creator browsing context.
If a browsing context A has a creator browsing
context, then the Document
that was the active document of that
creator browsing context at the time A was created is the
creator Document
.
When a browsing context is first created, it must be created with a single
Document
in its session history, whose address is about:blank
, which is marked as being an HTML document, whose character
encoding is UTF-8, and which is both ready for post-load tasks and
completely loaded immediately, along with a new Window
object that
the Document
is associated with. The Document
must have a single child
html
node, which itself has two empty child nodes: a head
element, and a body
element. As soon as this
Document
is created, the user agent must implement the sandboxing for
it. If the browsing context has a creator Document
, then
the browsing context's Document
's referrer must be set to the address
of that creator Document
at the time of the browsing
context's creation.
If the browsing context is created specifically to be immediately navigated, then that initial navigation will have replacement enabled.
The origin and effective script origin of the
about:blank
Document
are set when the Document
is created.
If the new browsing context has a creator browsing context, then the
origin of the about:blank
Document
is an alias to the origin of the creator
Document
and the effective script origin of the
about:blank
Document
is initially an alias to the effective script origin of the
creator Document
. Otherwise, the origin of the
about:blank
Document
is a globally unique identifier assigned when the
new browsing context is created and the effective script origin of the
about:blank
Document
is initially an alias to its origin.
Certain elements (for example, iframe
elements) can instantiate further browsing contexts. These are called nested browsing contexts. If a browsing context P has a
Document
D with an element E that nests
another browsing context C inside it, then C is said to be
nested through D, and E is said to be the browsing context container of C.
If the browsing context container element E is in the Document
D, then P is
said to be the parent browsing context of C and C is said to be a child browsing context of P.
Otherwise, the nested browsing context C has no parent
browsing context.
A browsing context A is said to be an ancestor of a browsing context B if there exists a browsing context A' that is a child browsing context of A and that is itself an ancestor of B, or if the browsing context A is the parent browsing context of B.
A browsing context that is not a nested browsing context has no parent browsing context, and is the top-level browsing context of all the browsing contexts for which it is an ancestor browsing context.
The transitive closure of parent browsing contexts for a nested browsing context gives the list of ancestor browsing contexts.
The list of the descendant browsing contexts of a Document
d is the (ordered) list returned by the following algorithm:
Let list be an empty list.
For each child browsing context of d that is nested through an element that is in the Document
d, in the tree
order of the elements nesting those browsing
contexts, run these substeps:
Append that child browsing context to the list list.
Append the list of the descendant browsing contexts of the active document of that child browsing context to the list list.
Return the constructed list.
A Document
is said to be fully active when it is the active
document of its browsing context, and either its browsing context is a
top-level browsing context, or it has a parent browsing context and the
Document
through which it is
nested is itself fully active.
Because they are nested through an element, child browsing
contexts are always tied to a specific Document
in their parent browsing
context. User agents must not allow the user to interact with child browsing contexts of elements that are in Document
s that are
not themselves fully active.
A nested browsing context can have a seamless browsing context flag
set, if it is embedded through an iframe
element with a seamless
attribute.
A nested browsing context can be put into a delaying load
events mode. This is used when it is navigated, to delay the load event of the browsing
context container iframe
element before the new Document
is
created.
The document family of a browsing context consists of the union of all
the Document
objects in that browsing context's session
history and the document families of all those
Document
objects. The document family of a Document
object
consists of the union of all the document families of the
browsing contexts that are nested through the Document
object.
top
Returns the WindowProxy
for the top-level browsing context.
parent
Returns the WindowProxy
for the parent browsing context.
frameElement
Returns the Element
for the browsing context container.
Returns null if there isn't one.
Throws a SecurityError
exception in cross-origin situations.
The top
IDL attribute on the Window
object
of a Document
in a browsing context b must return
the WindowProxy
object of its top-level browsing context (which would be
its own WindowProxy
object if it was a top-level browsing context
itself), if it has one, or its own WindowProxy
object otherwise (e.g. if it was a
detached nested browsing context).
The parent
IDL attribute on the Window
object of a Document
in a browsing context b must
return the WindowProxy
object of the parent browsing context, if there
is one (i.e. if b is a child browsing context), or the
WindowProxy
object of the browsing context b itself,
otherwise (i.e. if it is a top-level browsing context or a detached nested
browsing context).
The frameElement
IDL attribute on the
Window
object of a Document
d, on getting, must run
the following algorithm:
If d is not a Document
in a nested browsing
context, return null and abort these steps.
If the browsing context container's Document
does not have the
same effective script origin as the effective script origin specified by the entry
settings object, then throw a SecurityError
exception and abort these steps.
Return the browsing context container for b.
It is possible to create new browsing contexts that are related to a top-level browsing context without being nested through an element. Such browsing contexts are called auxiliary browsing contexts. Auxiliary browsing contexts are always top-level browsing contexts.
An auxiliary browsing context has an opener browsing context, which is the browsing context from which the auxiliary browsing context was created.
The opener
IDL attribute on the Window
object, on getting, must return the WindowProxy
object of the browsing
context from which the current browsing context was created (its opener
browsing context), if there is one, if it is still available, and if the current
browsing context has not disowned its opener; otherwise, it must return null.
On setting, if the new value is null then the current browsing context must disown its opener; if the new value is anything else then the
user agent must
call the [[DefineOwnProperty]] internal method of the Window
object, passing the
property name "opener
" as the property key, and the Property Descriptor {
[[Value]]: value, [[Writable]]: true, [[Enumerable]]: true,
[[Configurable]]: true } as the property descriptor,
where value is the new value.
User agents may support secondary browsing contexts, which are browsing contexts that form part of the user agent's interface, apart from the main content area.
A browsing context A is familiar with a second browsing context B if one of the following conditions is true:
A browsing context A is allowed to navigate a second browsing context B if the following algorithm terminates positively:
If A is not the same browsing context as B, and A is not one of the ancestor browsing contexts of B, and B is not a top-level browsing context, and A's active document's active sandboxing flag set has its sandboxed navigation browsing context flag set, then abort these steps negatively.
Otherwise, if B is a top-level browsing context, and is
one of the ancestor browsing contexts of A, and A's Document
's active sandboxing
flag set has its sandboxed top-level navigation browsing context flag set,
then abort these steps negatively.
Otherwise, if B is a top-level browsing context, and is
neither A nor one of the ancestor browsing contexts of A, and A's Document
's active sandboxing
flag set has its sandboxed navigation browsing context flag set, and A is not the one permitted sandboxed navigator of B, then abort these steps negatively.
Otherwise, terminate positively!
An element has a browsing context scope origin if its Document
's
browsing context is a top-level browsing context or if all of its
Document
's ancestor browsing contexts
all have active documents whose origin are the
same origin as the element's Document
's origin. If an
element has a browsing context scope origin, then its value is the
origin of the element's Document
.
Each browsing context is defined as having a list of one or more directly reachable browsing contexts. These are:
The transitive closure of all the browsing contexts that are directly reachable browsing contexts forms a unit of related browsing contexts.
Each unit of related browsing contexts is then further divided into the smallest
number of groups such that every member of each group has an active document with an
effective script origin that, through appropriate manipulation of the document.domain
attribute, could be made to be the same as
other members of the group, but could not be made the same as members of any other group. Each
such group is a unit of related similar-origin browsing contexts.
There is also at most one event loop per unit of related similar-origin browsing contexts (though several units of related similar-origin browsing contexts can have a shared event loop).
Browsing contexts can have a browsing context name. By default, a browsing context has no name (its name is not set).
A valid browsing context name is any string with at least one character that does not start with a U+005F LOW LINE character. (Names starting with an underscore are reserved for special keywords.)
A valid browsing context name or keyword is any string that is either a valid
browsing context name or that is an ASCII case-insensitive match for one of:
_blank
, _self
, _parent
, or _top
.
These values have different meanings based on whether the page is sandboxed or not, as
summarized in the following (non-normative) table. In this table, "current" means the
browsing context that the link or script is in, "parent" means the parent
browsing context of the one the link or script is in, "master" means the nearest
ancestor browsing context of the one the link or script is in that is not itself in a
seamless iframe, "top" means the top-level
browsing context of the one the link or script is in, "new" means a new top-level
browsing context or auxiliary browsing context is to be created, subject to
various user preferences and user agent policies, "none" means that nothing will happen, and
"maybe new" means the same as "new" if the "allow-popups
" keyword is also specified on the
sandbox
attribute (or if the user overrode the
sandboxing), and the same as "none" otherwise.
Keyword | Ordinary effect | Effect in an iframe with...
| ||||
---|---|---|---|---|---|---|
seamless=""
| sandbox=""
| sandbox="" seamless=""
| sandbox="allow-top-navigation"
| sandbox="allow-top-navigation" seamless=""
| ||
none specified, for links and form submissions | current | master | current | master | current | master |
empty string | current | master | current | master | current | master |
_blank
| new | new | maybe new | maybe new | maybe new | maybe new |
_self
| current | current | current | current | current | current |
_parent if there isn't a parent
| current | current | current | current | current | current |
_parent if parent is also top
| parent/top | parent/top | none | none | parent/top | parent/top |
_parent if there is one and it's not top
| parent | parent | none | none | none | none |
_top if top is current
| current | current | current | current | current | current |
_top if top is not current
| top | top | none | none | top | top |
name that doesn't exist | new | new | maybe new | maybe new | maybe new | maybe new |
name that exists and is a descendant | specified descendant | specified descendant | specified descendant | specified descendant | specified descendant | specified descendant |
name that exists and is current | current | current | current | current | current | current |
name that exists and is an ancestor that is top | specified ancestor | specified ancestor | none | none | specified ancestor/top | specified ancestor/top |
name that exists and is an ancestor that is not top | specified ancestor | specified ancestor | none | none | none | none |
other name that exists with common top | specified | specified | none | none | none | none |
name that exists with different top, if familiar and one permitted sandboxed navigator | specified | specified | specified | specified | specified | specified |
name that exists with different top, if familiar but not one permitted sandboxed navigator | specified | specified | none | none | none | none |
name that exists with different top, not familiar | new | new | maybe new | maybe new | maybe new | maybe new |
Most of the restrictions on sandboxed browsing contexts are applied by other algorithms, e.g. the navigation algorithm, not the rules for choosing a browsing context given a browsing context name given below.
An algorithm is allowed to show a popup if any of the following conditions is true:
The task in which the algorithm is running is currently
processing an activation behavior whose click
event
was trusted.
The task in which the algorithm is running is currently running the event listener for a trusted event whose type is in the following list:
change
click
dblclick
mouseup
reset
submit
The task in which the algorithm is running was queued by an algorithm that was allowed to show a popup, and the chain of such algorithms started within a user-agent defined timeframe.
For example, if a user clicked a button, it might be acceptable for a popup to result from that after 4 seconds, but it would likely not be acceptable for a popup to result from that after 4 hours.
The rules for choosing a browsing context given a browsing context name are as follows. The rules assume that they are being applied in the context of a browsing context, as part of the execution of a task.
If the given browsing context name is the empty string or _self
, then
the chosen browsing context must be the current one.
If the given browsing context name is _self
, then this is an
explicit self-navigation override, which overrides the behavior of the
seamless browsing context flag set by the seamless
attribute on iframe
elements.
If the given browsing context name is _parent
, then the chosen
browsing context must be the parent browsing context of the current one,
unless there isn't one, in which case the chosen browsing context must be the current browsing
context.
If the given browsing context name is _top
, then the chosen browsing
context must be the top-level browsing context of the current one, if there is one,
or else the current browsing context.
If the given browsing context name is not _blank
and there exists a
browsing context whose name is the same as the given
browsing context name, and the current browsing context is familiar with that
browsing context, and the user agent determines that the two browsing contexts are related
enough that it is ok if they reach each other, then that browsing context must be the chosen
one. If there are multiple matching browsing contexts, the user agent should select one in some
arbitrary consistent manner, such as the most recently opened, most recently focused, or more
closely related.
If the browsing context is chosen by this step to be the current browsing context, then this is also an explicit self-navigation override.
Otherwise, a new browsing context is being requested, and what happens depends on the user agent's configuration and abilities — it is determined by the rules given for the first applicable option from the following list:
There is no chosen browsing context. The user agent may inform the user that a popup has been blocked.
Typically, there is no chosen browsing context.
The user agent may offer to create a new top-level browsing context or reuse an existing top-level browsing context. If the user picks one of those options, then the designated browsing context must be the chosen one (the browsing context's name isn't set to the given browsing context name). The default behaviour (if the user agent doesn't offer the option to the user, or if the user declines to allow a browsing context to be used) must be that there must not be a chosen browsing context.
If this case occurs, it means that an author has explicitly sandboxed the document that is trying to open a link.
noreferrer
keywordA new top-level browsing context must be created. If the given browsing
context name is not _blank
, then the new top-level browsing context's
name must be the given browsing context name (otherwise, it has no name). The chosen browsing
context must be this new browsing context. The creation of such a browsing context
is a new start for session storage.
If it is immediately navigated, then the navigation will be done with replacement enabled.
noreferrer
keyword doesn't
applyA new auxiliary browsing context must be created, with the opener
browsing context being the current one. If the given browsing context name is not _blank
, then the new auxiliary browsing context's name must be the given
browsing context name (otherwise, it has no name). The chosen browsing context must be this new
browsing context.
If it is immediately navigated, then the navigation will be done with replacement enabled.
The chosen browsing context is the current browsing context.
There must not be a chosen browsing context.
User agent implementors are encouraged to provide a way for users to configure the user agent to always reuse the current browsing context.
If the current browsing context's active document's active sandboxing flag set has the sandboxed navigation browsing context flag set and the chosen browsing context picked above, if any, is a new browsing context (whether top-level or auxiliary), then all the flags that are set in the current browsing context's active document's active sandboxing flag set when the new browsing context is created must be set in the new browsing context's popup sandboxing flag set, and the current browsing context must be set as the new browsing context's one permitted sandboxed navigator.
Window
object[Global] /*sealed*/ interface Window : EventTarget { // the current browsing context [Unforgeable] readonly attribute WindowProxy window; [Replaceable] readonly attribute WindowProxy self; [Unforgeable] readonly attribute Document document; attribute DOMString name; [PutForwards=href, Unforgeable] readonly attribute Location location; readonly attribute History history; [Replaceable] readonly attribute BarProp locationbar; [Replaceable] readonly attribute BarProp menubar; [Replaceable] readonly attribute BarProp personalbar; [Replaceable] readonly attribute BarProp scrollbars; [Replaceable] readonly attribute BarProp statusbar; [Replaceable] readonly attribute BarProp toolbar; attribute DOMString status; void close(); readonly attribute boolean closed; void stop(); void focus(); void blur(); // other browsing contexts [Replaceable] readonly attribute WindowProxy frames; [Replaceable] readonly attribute unsigned long length; [Unforgeable] readonly attribute WindowProxy top; attribute WindowProxy? opener; readonly attribute WindowProxy parent; readonly attribute Element? frameElement; WindowProxy open(optional DOMString url = "about:blank", optional DOMString target = "_blank", optional DOMString features = "", optional boolean replace = false); getter WindowProxy (unsigned long index); getter object (DOMString name); // the user agent readonly attribute Navigator navigator; readonly attribute External external; readonly attribute ApplicationCache applicationCache; // user prompts void alert(optional DOMString message = ""); boolean confirm(optional DOMString message = ""); DOMString? prompt(optional DOMString message = "", optional DOMString default = ""); void print(); any showModalDialog(DOMString url, optional any argument); }; Window implements GlobalEventHandlers; Window implements WindowEventHandlers;
window
frames
self
These attributes all return window.
document
Returns the Document
associated with window.
defaultView
Returns the Window
object of the active document.
The Window
interface must only be exposed to JavaScript if the
JavaScript global environment is a document environment.
The window
, frames
, and self
IDL attributes must all return the Window
object's browsing context's
WindowProxy
object.
The document
IDL attribute must return
the Window
object's newest Document
object.
The defaultView
IDL attribute of the
Document
interface must return the Document
's browsing
context's WindowProxy
object, if there is one, or null otherwise.
For historical reasons, Window
objects must also have a writable, configurable,
non-enumerable property named HTMLDocument
whose value is the
Document
interface object.
This section describes a security model that is underdefined, imperfect, and
does not match implementations. Work is ongoing to attempt to resolve this, but in the meantime,
please do not rely on this section for precision. Implementors are urged to send their feedback on
how cross-origin cross-global access to Window
and Location
objects
should work. See bug 20701.
User agents must throw a SecurityError
exception whenever any
properties of a Window
object are accessed when the incumbent settings object specifies
an effective script origin that is not the same as
the Window
object's
Document
's effective script origin, with the following
exceptions:
location
attribute
postMessage()
method
window
attribute
frames
attribute
self
attribute
top
attribute
parent
attribute
opener
attribute
closed
attribute
close()
method
blur()
method
focus()
method
When the incumbent settings object specifies an effective script origin that is different than
a Window
object's
Document
's effective script origin, the user agent must act as if
any changes to that Window
object's properties, getters, setters, etc, were not
present, and as if all the properties of that Window
object had their [[Enumerable]]
attribute set to false.
For members that return objects (including function objects), each distinct effective
script origin that is not the same as the Window
object's
Document
's effective script origin must be provided with a separate set
of objects. These objects must have the prototype chain appropriate for the script for which the
objects are created (not those that would be appropriate for scripts whose global
object, as specified by their settings object,
is the Window
object in question).
open
( [ url [, target [, features [, replace ] ] ] ] )Opens a window to show url (defaults to about:blank
), and
returns it. The target argument gives the name of the new window. If a
window exists with that name already, it is reused. The replace attribute,
if true, means that whatever page is currently open in that window will be removed from the
window's session history. The features argument is ignored.
name
[ = value ]Returns the name of the window.
Can be set, to change the name.
close
()Closes the window.
closed
Returns true if the window has been closed, false otherwise.
stop
()Cancels the document load.
The open()
method on Window
objects
provides a mechanism for navigating an existing browsing
context or opening and navigating an auxiliary browsing context.
The method has four arguments, though they are all optional.
The first argument, url, must be a valid non-empty URL for a
page to load in the browsing context. If the first argument is the empty string, then the url argument must be interpreted as "about:blank
". Otherwise, the
argument must be resolved to an absolute URL (or
an error), relative to the API base URL specified by the entry settings
object when the method was invoked.
The second argument, target, specifies the name of the browsing context that is to be navigated. It must be a valid browsing context name or keyword.
The third argument, features, has no defined effect and is mentioned for historical reasons only. User agents may interpret this argument as instructions to set the size and position of the browsing context, but are encouraged to instead ignore the argument entirely.
The fourth argument, replace, specifies whether or not the new page will replace the page currently loaded in the browsing context, when target identifies an existing browsing context (as opposed to leaving the current page in the browsing context's session history).
When the method is invoked, the user agent must first select a browsing context to navigate by applying the rules for choosing a browsing context given a browsing context name using the target argument as the name and the browsing context of the script as the context in which the algorithm is executed, unless the user has indicated a preference, in which case the browsing context to navigate may instead be the one indicated by the user.
For example, suppose there is a user agent that supports control-clicking a
link to open it in a new tab. If a user clicks in that user agent on an element whose onclick
handler uses the window.open()
API to open a page in an iframe, but, while doing so, holds
the control key down, the user agent could override the selection of the target browsing context
to instead target a new tab.
If applying the rules for choosing a browsing context given a browsing context
name using the target argument would result in there not being a chosen
browsing context, then throw an InvalidAccessError
exception and abort these
steps.
Otherwise, if url is not "about:blank
", the user agent must
navigate the selected browsing context to the
absolute URL obtained from resolving url earlier, with exceptions enabled. If the replace is true or if the browsing
context was just created as part of the rules for choosing a browsing context given a
browsing context name, then replacement must be
enabled also. The navigation must be done with the responsible
browsing context specified by the incumbent settings object as the source browsing
context. If the resolve a URL algorithm failed, then the user agent may either
instead navigate to an inline error page, with exceptions enabled and using the same replacement behavior and
source browsing context behavior as described earlier in this paragraph; or treat the url as "about:blank
", acting as described in the next paragraph.
If url is "about:blank
", and the browsing
context was just created as part of the rules for choosing a browsing context given a
browsing context name, then the user agent must instead queue a task to
fire a simple event named load
at the selected
browsing context's Window
object, but with its target
set to the selected browsing context's Window
object's Document
object
(and the currentTarget
set to the Window
object).
The method must return the WindowProxy
object of the browsing context
that was navigated, or null if no browsing context was navigated.
The name
attribute of the Window
object
must, on getting, return the current name of the
browsing context, and, on setting, set the name of the browsing context to the new value.
The name gets reset when the browsing context is navigated to another domain.
The close()
method on Window
objects should, if all the following conditions are met, close the browsing context A:
A browsing context is script-closable if it is an auxiliary
browsing context that was created by a script (as opposed to by an action of the user), or
if it is a browsing context whose session history contains only one
Document
.
The closed
attribute on Window
objects must return true if the Window
object's browsing context has
been discarded, and false otherwise.
The stop()
method on Window
objects should, if there is an existing attempt to navigate the browsing
context and that attempt is not currently running the unload a document
algorithm, cancel that navigation; then, it must abort the active document of the browsing context of
the Window
object on which it was invoked.
length
Returns the number of child browsing contexts.
Returns the indicated child browsing context.
The length
IDL attribute on the Window
interface must return the number of child browsing
contexts that are nested through
elements that are in the Document
that is the
active document of that Window
object, if that Window
's
browsing context shares the same event loop as the responsible
document specified by the entry settings object accessing the IDL attribute; otherwise,
it must return zero.
The supported property indices on the Window
object at any instant
are the numbers in the range 0 .. n-1, where n is the number returned by the length
IDL
attribute. If n is zero then there are no supported property
indices.
To determine the value of an indexed property index of a Window
object, the user agent must return the
WindowProxy
object of the indexth child browsing
context of the Document
that is nested through an element that is in the Document
, sorted in the tree order
of the elements nesting those browsing contexts.
These properties are the dynamic nested browsing context properties.
Window
objectReturns the indicated element or collection of elements.
The Window
interface supports named
properties. The supported property names at any moment consist of the
following, in tree order, ignoring later duplicates:
name
content attribute for all a
,
applet
, area
, embed
, form
,
frameset
, img
, and object
elements in the active
document that have a non-empty name
content attribute, andid
content attribute of any HTML element in the active document with a non-empty id
content attribute.To determine the value of a named property name when the Window
object is indexed for property
retrieval, the user agent must return the value obtained using the following steps:
Let objects be the list of named objects with the name name in the active document.
There will be at least one such object, by definition.
If objects contains a nested browsing context, then return
the WindowProxy
object of the nested browsing context corresponding to
the first browsing context container in tree order whose
browsing context is in objects, and abort these steps.
Otherwise, if objects has only one element, return that element and abort these steps.
Otherwise return an HTMLCollection
rooted at the Document
node,
whose filter matches only named objects with
the name name. (By definition, these will all be elements.)
Named objects with the name name, for the purposes of the above algorithm, are those that are either:
a
, applet
, area
, embed
,
form
, frameset
, img
, or object
elements that
have a name
content attribute whose value is name, orid
content attribute
whose value is name.A browsing context has a strong reference to each of its Document
s
and its WindowProxy
object, and the user agent itself has a strong reference to its
top-level browsing contexts.
A Document
has a strong reference to its Window
object.
A Window
object has a strong
reference to its Document
object through its document
attribute. Thus, references from other scripts to either of
those objects will keep both alive. Similarly, both Document
and Window
objects have implied strong references to the
WindowProxy
object.
Each script has a strong reference to its settings object, and each script settings object has strong references to its global object, responsible browsing context, and responsible document.
When a browsing context is to discard a Document
, the user
agent must run the following steps:
Set the Document
's salvageable state to false.
Run any unloading document cleanup steps for the Document
that
are defined by this specification and other applicable specifications.
Remove any tasks associated with the
Document
in any task source, without running those tasks.
Discard all the child browsing contexts of the Document
.
Lose the strong reference from the Document
's browsing context
to the Document
.
Whenever a Document
object is discarded, it is also removed from the list of the worker's
Document
s of each worker whose list contains that Document
.
When a browsing context is discarded, the strong reference
from the user agent itself to the browsing context must be severed, and all the
Document
objects for all the entries in the browsing context's session
history must be discarded as well.
User agents may discard top-level browsing contexts at any time (typically, in
response to user requests, e.g. when a user force-closes a window containing one or more top-level browsing contexts). Other browsing contexts must be discarded once their
WindowProxy
object is eligible for garbage collection.
When the user agent is required to close a browsing context, it must run the following steps:
Let specified browsing context be the browsing context being closed.
Prompt to unload the active document of the specified browsing context. If the user refused to allow the document to be unloaded, then abort these steps.
Unload the active document of the specified browsing context with the recycle parameter set to false.
Remove the specified browsing context from the user interface (e.g. close or hide its tab in a tabbed browser).
Discard the specified browsing context.
User agents should offer users the ability to arbitrarily close any top-level browsing context.
To allow Web pages to integrate with Web browsers, certain Web browser interface elements are exposed in a limited way to scripts in Web pages.
Each interface element is represented by a BarProp
object:
interface BarProp { attribute boolean visible; };
locationbar
. visible
Returns true if the location bar is visible; otherwise, returns false.
menubar
. visible
Returns true if the menu bar is visible; otherwise, returns false.
personalbar
. visible
Returns true if the personal bar is visible; otherwise, returns false.
scrollbars
. visible
Returns true if the scroll bars are visible; otherwise, returns false.
statusbar
. visible
Returns true if the status bar is visible; otherwise, returns false.
toolbar
. visible
Returns true if the toolbar is visible; otherwise, returns false.
The visible attribute, on getting, must return either true or a value determined by the user agent to most accurately represent the visibility state of the user interface element that the object represents, as described below. On setting, the new value must be discarded.
The following BarProp
objects exist for each Document
object in a
browsing context. Some of the user interface elements represented by these objects
might have no equivalent in some user agents; for those user agents, except when otherwise
specified, the object must act as if it was present and visible (i.e. its visible
attribute must return true).
BarProp
objectBarProp
objectBarProp
objectBarProp
objectBarProp
objectvisible
attribute may return false).BarProp
objectvisible
attribute may return false).The locationbar
attribute must return
the location bar BarProp
object.
The menubar
attribute must return the
menu bar BarProp
object.
The personalbar
attribute must return
the personal bar BarProp
object.
The scrollbars
attribute must return
the scrollbar BarProp
object.
The statusbar
attribute must return
the status bar BarProp
object.
The toolbar
attribute must return the
toolbar BarProp
object.
For historical reasons, the status
attribute
on the Window
object must, on getting, return the last string it was set to, and on
setting, must set itself to the new value. When the Window
object is created, the
attribute must be set to the empty string. It does not do anything else.
WindowProxy
objectAs mentioned earlier, each browsing context has a
WindowProxy
object. This object is unusual in that all operations that
would be performed on it must be performed on the Window
object of the browsing
context's active document instead. It is thus indistinguishable from that
Window
object in every way until the browsing context is navigated.
There is no WindowProxy
interface object.
The WindowProxy
object allows scripts to act as if each
browsing context had a single Window
object, while still keeping
separate Window
objects for each Document
.
In the following example, the variable x is set to the
WindowProxy
object returned by the window
accessor
on the global object. All of the expressions following the assignment return true, because in
every respect, the WindowProxy
object acts like the underlying Window
object.
var x = window; x instanceof Window; // true x === this; // true
Origins are the fundamental currency of the Web's security model. Two actors in the Web platform that share an origin are assumed to trust each other and to have the same authority. Actors with differing origins are considered potentially hostile versus each other, and are isolated from each other to varying degrees.
For example, if Example Bank's Web site, hosted at bank.example.com
, tries to examine the DOM of Example Charity's Web site, hosted
at charity.example.org
, a SecurityError
exception will be
raised.
The origin of a resource and the effective script origin of a resource are both either opaque identifiers or tuples consisting of a scheme component, a host component, a port component, and optionally extra data.
The extra data could include the certificate of the site when using encrypted connections, to ensure that if the site's secure certificate changes, the origin is considered to change as well.
An origin or effective script origin can be defined as an alias to another origin or effective script origin. The value of the origin or effective script origin is then the value of the origin or effective script origin to which it is an alias.
These characteristics are defined as follows:
The origin and effective script origin of the URL are the origin defined in The Web Origin Concept. [ORIGIN]
Document
objectsDocument
's active sandboxing flag set has
its sandboxed origin browsing context flag setThe origin is a globally unique identifier assigned when the
Document
is created.
The effective script origin is initially an alias to the origin of the
Document
.
Document
was served over the network and has an address that uses a URL
scheme with a server-based naming authorityThe origin is an alias to the
origin of the Document
's address.
The effective script origin is initially an alias to the origin of the
Document
.
Document
was generated from a data:
URL found in another Document
or in a scriptThe origin is an alias to the
origin specified by the incumbent settings object when the navigate
algorithm was invoked, or, if no script was involved, of
the Document
of the element that initiated the navigation to that URL.
The effective script origin is initially an alias to the effective script origin of that
same script settings object or Document
.
Document
is the initial "about:blank
" documentThe origin and effective script origin of the
Document
are those it was assigned when its
browsing context was created.
Document
was created as part of the processing for javascript:
URLsThe origin is an alias to the origin of the active document of the browsing context being navigated when the navigate algorithm was invoked.
The effective script origin is initially an alias to the effective script origin of that
same Document
.
Document
is an iframe
srcdoc
documentThe origin of the Document
is an alias to the origin of the
Document
's browsing context's browsing context
container's Document
.
The effective script origin is initially an alias to the effective script origin of the
Document
's browsing context's browsing context
container's Document
.
Document
was obtained in some other manner (e.g. a data:
URL typed in by the user or that was returned as
the location of an HTTP redirect (or
equivalent in other protocols), a Document
created using the createDocument()
API, etc)The default behavior as defined in the DOM standard applies. [DOM].
The origin is a globally unique identifier assigned when the
Document
is created, and the effective script origin is initially an
alias to the origin of the
Document
.
The effective script origin of a Document
can be
manipulated using the document.domain
IDL
attribute.
img
elementsimg
element's Document
.Images do not have an effective script origin.
audio
and video
elementsDocument
.Media elements do not have an effective script origin.
The origin of a downloadable Web font is an alias to the origin of the absolute URL used to obtain the font (after any redirects). [CSSFONTS] [CSSFONTLOAD]
The origin of a locally installed system font is an alias to the origin of the
Document
in which that font is being used.
Fonts do not have an effective script origin.
Other specifications can override the above definitions by themselves specifying the origin of
a particular URL, Document
, image, media element, or
font.
The Unicode serialization of an origin is the string obtained by applying the following algorithm to the given origin:
If the origin in question is not a scheme/host/port tuple, then return the
literal string "null
" and abort these steps.
Otherwise, let result be the scheme part of the origin tuple.
Append the string "://
" to result.
Apply the IDNA ToUnicode algorithm to each component of the host part of the origin tuple, and append the results — each component, in the same order, separated by "." (U+002E) characters — to result. [RFC3490]
If the port part of the origin tuple gives a port that is different from the default port for the protocol given by the scheme part of the origin tuple, then append a ":" (U+003A) character and the given port, in base ten, to result.
Return result.
The ASCII serialization of an origin is the string obtained by applying the following algorithm to the given origin:
If the origin in question is not a scheme/host/port tuple, then return the
literal string "null
" and abort these steps.
Otherwise, let result be the scheme part of the origin tuple.
Append the string "://
" to result.
Apply the IDNA ToASCII algorithm to the host part of the origin tuple, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, and append the results to result.
If ToASCII fails to convert one of the components of the string, e.g. because it is too long or because it contains invalid characters, then return the empty string and abort these steps. [RFC3490]
If the port part of the origin tuple gives a port that is different from the default port for the protocol given by the scheme part of the origin tuple, then append a ":" (U+003A) character and the given port, in base ten, to result.
Return result.
Two origins are said to be the same origin if the following algorithm returns true:
Let A be the first origin being compared, and B be the second origin being compared.
If A and B are both opaque identifiers, and their value is equal, then return true.
Otherwise, if either A or B or both are opaque identifiers, return false.
If A and B have scheme components that are not identical, return false.
If A and B have host components that are not identical, return false.
If A and B have port components that are not identical, return false.
If either A or B have additional data, but that data is not identical for both, return false.
Return true.
domain
[ = domain ]Returns the current domain used for security checks.
Can be set to a value that removes subdomains, to change the effective script
origin to allow pages on other subdomains of the same domain (if they do the same thing)
to access each other. (Can't be set in sandboxed iframe
s.)
The domain
attribute on
Document
objects must be initialized to the document's domain, if it has
one, and the empty string otherwise. If the document's domain starts with a "[" (U+005B) character and ends with a "]" (U+005D) character, it is
an IPv6 address; these square brackets must be omitted when initializing the attribute's
value.
On getting, the attribute must return its current value, unless the Document
has
no browsing context, in which case it must return the empty string.
On setting, the user agent must run the following algorithm:
If the Document
has no browsing context, throw a
SecurityError
exception and abort these steps.
If the Document
's active sandboxing flag set has its
sandboxed document.domain
browsing context
flag set, throw a SecurityError
exception and abort these steps.
If the new value is an IPv4 or IPv6 address, let new value be the new value. Otherwise, apply the IDNA ToASCII algorithm to the new value, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, and let new value be the result of the ToASCII algorithm.
If ToASCII fails to convert one of the components of the string, e.g. because it is too long
or because it contains invalid characters, then throw a SecurityError
exception and
abort these steps. [RFC3490]
If new value is not exactly equal to the current value of the document.domain
attribute, then run these substeps:
If the current value is an IPv4 or IPv6 address, throw a SecurityError
exception and abort these steps.
If new value, prefixed by a "." (U+002E), does not exactly
match the end of the current value, throw a SecurityError
exception and abort
these steps.
If the new value is an IPv4 or IPv6 address, it cannot match the new value in this way and thus an exception will be thrown here.
If new value matches a suffix in the Public Suffix List, or, if new value, prefixed by a "." (U+002E), matches the end of a suffix in
the Public Suffix List, then throw a SecurityError
exception and abort these
steps. [PSL]
Suffixes must be compared after applying the IDNA ToASCII algorithm to them, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, in an ASCII case-insensitive manner. [RFC3490]
Release the storage mutex.
Set the attribute's value to new value.
If the effective script origin of the Document
is an alias, set it to the value of the effective script
origin (essentially de-aliasing the effective script origin).
If new value is not the empty string, then run these substeps:
Set the host part of the effective script origin tuple of the
Document
to new value.
Set the port part of the effective script origin tuple of the
Document
to "manual override" (a value that, for the purposes of comparing origins, is identical to "manual override" but not
identical to any other value).
The domain of a Document
is the host part
of the document's origin, if the value of that origin is a
scheme/host/port tuple. If it isn't, then the document does not have a domain.
The domain
attribute is used to enable
pages on different hosts of a domain to access each others' DOMs.
Do not use the document.domain
attribute when using shared hosting. If an untrusted third party is able to host an HTTP server at
the same IP address but on a different port, then the same-origin protection that normally
protects two different sites on the same host will fail, as the ports are ignored when comparing
origins after the document.domain
attribute has been
used.
A sandboxing flag set is a set of zero or more of the following flags, which are used to restrict the abilities that potentially untrusted resources have:
This flag prevents content from navigating browsing contexts other than the sandboxed browsing context itself (or browsing contexts further nested inside it), auxiliary browsing contexts (which are protected by the sandboxed auxiliary navigation browsing context flag defined next), and the top-level browsing context (which is protected by the sandboxed top-level navigation browsing context flag defined below).
If the sandboxed auxiliary navigation browsing context flag is not set, then in certain cases the restrictions nonetheless allow popups (new top-level browsing contexts) to be opened. These browsing contexts always have one permitted sandboxed navigator, set when the browsing context is created, which allows the browsing context that created them to actually navigate them. (Otherwise, the sandboxed navigation browsing context flag would prevent them from being navigated even if they were opened.)
This flag prevents content from creating new auxiliary browsing
contexts, e.g. using the target
attribute, the
window.open()
method, or the showModalDialog()
method.
This flag prevents content from navigating their top-level browsing context and prevents content from closing their top-level browsing context.
When the sandboxed top-level navigation browsing context flag is not set, content can navigate its top-level browsing context, but other browsing contexts are still protected by the sandboxed navigation browsing context flag and possibly the sandboxed auxiliary navigation browsing context flag.
This flag prevents content from instantiating plugins, whether
using the embed
element, the object
element, the applet
element, or through navigation of a nested browsing context, unless
those plugins can be secured.
This flag prevents content from using the seamless
attribute on descendant iframe
elements.
This prevents a page inserted using the allow-same-origin
keyword from using a
CSS-selector-based method of probing the DOM of other pages on the same site (in particular,
pages that contain user-sensitive information).
This flag forces content into a unique origin, thus preventing it from accessing other content from the same origin.
This flag also prevents script from reading from or writing to the
document.cookie
IDL attribute, and blocks access to
localStorage
.
[WEBSTORAGE]
This flag blocks form submission.
This flag disables the Pointer Lock API. [POINTERLOCK]
This flag blocks script execution.
This flag blocks features that trigger automatically, such as automatically playing a video or automatically focusing a form control.
This flag prevents content from using the requestFullscreen()
method.
document.domain
browsing context flagThis flag prevents content from using the document.domain
feature to change the effective script
origin.
When the user agent is to parse a sandboxing directive, given a string input, a sandboxing flag set output, and optionally an allow fullscreen flag, it must run the following steps:
Split input on spaces, to obtain tokens.
Let output be empty.
Add the following flags to output:
The sandboxed auxiliary navigation browsing context flag, unless tokens contains the allow-popups
keyword.
The sandboxed top-level navigation browsing context flag, unless tokens contains the allow-top-navigation
keyword.
The sandboxed origin browsing context flag, unless the tokens contains the allow-same-origin
keyword.
The allow-same-origin
keyword
is intended for two cases.
First, it can be used to allow content from the same site to be sandboxed to disable scripting, while still allowing access to the DOM of the sandboxed content.
Second, it can be used to embed content from a third-party site, sandboxed to prevent that site from opening pop-up windows, etc, without preventing the embedded page from communicating back to its originating site, using the database APIs to store data, etc.
The sandboxed forms browsing context flag, unless tokens contains the allow-forms
keyword.
The sandboxed pointer lock browsing context flag, unless tokens contains the allow-pointer-lock
keyword.
The sandboxed scripts browsing context flag, unless tokens contains the allow-scripts
keyword.
The sandboxed automatic features browsing context flag, unless tokens contains the allow-scripts
keyword (defined above).
This flag is relaxed by the same keyword as scripts, because when scripts are enabled these features are trivially possible anyway, and it would be unfortunate to force authors to use script to do them when sandboxed rather than allowing them to use the declarative features.
The sandboxed fullscreen browsing context flag, unless the allow fullscreen flag was passed to the parse a sandboxing directive flag.
Every top-level browsing context has a popup sandboxing flag set, which is a sandboxing flag set. When a browsing context is created, its popup sandboxing flag set must be empty. It is populated by the rules for choosing a browsing context given a browsing context name.
Every nested browsing context has an iframe
sandboxing flag
set, which is a sandboxing flag set. Which flags in a nested browsing
context's iframe
sandboxing flag set are set at any particular
time is determined by the iframe
element's sandbox
attribute.
Every Document
has an active sandboxing flag set, which is a
sandboxing flag set. When the Document
is created, its active
sandboxing flag set must be empty. It is populated by the navigation
algorithm.
Every resource that is obtained by the navigation algorithm has a forced sandboxing flag set, which is a sandboxing flag set. A resource by default has no flags set in its forced sandboxing flag set, but other specifications can define that certain flags are set.
In particular, the forced sandboxing flag set is used by the Content Security Policy specification. [CSP]
When a user agent is to implement the sandboxing for a Document
, it
must populate Document
's active sandboxing flag set with the union of
the flags that are present in the following sandboxing flag
sets at the time the Document
object is created:
If the Document
's browsing context is a top-level browsing
context, then: the flags set on the browsing context's popup sandboxing
flag set.
If the Document
's browsing context is a nested browsing
context, then: the flags set on the browsing context's
iframe
sandboxing flag set.
If the Document
's browsing context is a nested browsing
context, then: the flags set on the browsing context's parent browsing
context's active document's active sandboxing flag set.
The flags set on the Document
's resource's forced sandboxing flag
set, if it has one.
The sequence of Document
s in a browsing context is its session
history. Each browsing context, including nested browsing contexts, has a distinct session history. A browsing
context's session history consists of a flat list of session history entries. Each session history entry consists, at a
minimum, of a URL, and each entry may in addition have a state object, a
title, a Document
object, form data, a scroll position, and other information
associated with it.
Each entry, when first created, has a Document
. However, when a
Document
is not active, it's possible for it to be
discarded to free resources. The URL and
other data in a session history entry is then used to bring a new
Document
into being to take the place of the original, should the user agent find
itself having to reactivate that Document
.
Titles associated with session history
entries need not have any relation with the current title
of the
Document
. The title of a session history entry is intended to explain
the state of the document at that point, so that the user can navigate the document's history.
URLs without associated state objects are added to the session history as the user (or script) navigates from page to page.
Each Document
object in a browsing context's session
history is associated with a unique History
object which must all model the
same underlying session history.
The history
attribute of the Window
interface must return the object implementing the History
interface for that Window
object's newest
Document
.
A state object is an object representing a user interface state.
Pages can add state objects to the session history. These are then returned to the script when the user (or script) goes back in the history, thus enabling authors to use the "navigation" metaphor even in one-page applications.
State objects are intended to be used for two main purposes:
first, storing a preparsed description of the state in the URL so that in the simple
case an author doesn't have to do the parsing (though one would still need the parsing for
handling URLs passed around by users, so it's only a minor
optimization), and second, so that the author can store state that one wouldn't store in the URL
because it only applies to the current Document
instance and it would have to be
reconstructed if a new Document
were opened.
An example of the latter would be something like keeping track of the precise coordinate from
which a pop-up div
was made to animate, so that if the user goes back, it can be
made to animate to the same location. Or alternatively, it could be used to keep a pointer into a
cache of data that would be fetched from the server based on the information in the
URL, so that when going back and forward, the information doesn't have to be fetched
again.
At any point, one of the entries in the session history is the current entry. This is the entry representing the active document of the browsing context. Which entry is the current entry is changed by the algorithms defined in this specification, e.g. during session history traversal.
The current entry is usually an entry for the address of the Document
. However, it can also be one of
the entries for state objects added to the history by that
document.
An entry with persisted user state is one that also has user-agent defined state. This specification does not specify what kind of state can be stored.
For example, some user agents might want to persist the scroll position, or the values of form controls.
User agents that persist the value of form controls are encouraged to also persist
their directionality (the value of the element's dir
attribute).
This prevents values from being displayed incorrectly after a history traversal when the user had
originally entered the values with an explicit, non-default directionality.
Entries that consist of state objects share the same
Document
as the entry for the page that was active when they were added.
Contiguous entries that differ just by fragment identifier also share the same
Document
.
All entries that share the same Document
(and that are therefore
merely different states of one particular document) are contiguous by definition.
Each Document
in a browsing context can also have a latest
entry. This is the entry or that Document
that was most the recently traversed
to. When a Document
is created, it initially has no latest entry.
User agents may discard the Document
objects of entries other than the current entry that are not referenced from any
script, reloading the pages afresh when the user or script navigates back to such pages. This
specification does not specify when user agents should discard Document
objects and
when they should cache them.
Entries that have had their Document
objects discarded must, for the purposes of
the algorithms given below, act as if they had not. When the user or script navigates back or
forwards to a page which has no in-memory DOM objects, any other entries that shared the same
Document
object with it must share the new object as well.
History
interfaceinterface History { readonly attribute long length; readonly attribute any state; void go(optional long delta); void back(); void forward(); void pushState(any data, DOMString title, optional DOMString? url = null); void replaceState(any data, DOMString title, optional DOMString? url = null); };
history
. length
Returns the number of entries in the joint session history.
history
. state
Returns the current state object.
history
. go
( [ delta ] )Goes back or forward the specified number of steps in the joint session history.
A zero delta will reload the current page.
If the delta is out of range, does nothing.
history
. back
()Goes back one step in the joint session history.
If there is no previous page, does nothing.
history
. forward
()Goes forward one step in the joint session history.
If there is no next page, does nothing.
history
. pushState
(data, title [, url ] )Pushes the given data onto the session history, with the given title, and, if provided and not null, the given URL.
history
. replaceState
(data, title [, url ] )Updates the current entry in the session history to have the given data, title, and, if provided and not null, URL.
The joint session history of a top-level browsing context is the union
of all the session histories of all browsing contexts of all the fully active Document
objects that share that top-level browsing context, with all the entries that are
current entries in their respective session histories removed except for the current entry of the joint session
history.
The current entry of the joint session history is the entry that most recently became a current entry in its session history.
Entries in the joint session history are ordered chronologically by the time they were added to their respective session histories. Each entry has an index; the earliest entry has index 0, and the subsequent entries are numbered with consecutively increasing integers (1, 2, 3, etc).
Since each Document
in a browsing context might have a
different event loop, the actual state of the joint session history can
be someone nebulous. For example, two sibling iframe
elements could both traverse from one unique origin to another at the same time,
so their precise order might not be well-defined; similarly, since they might only find out about
each other later, they might disagree about the length of the joint session
history.
All the getters and setters for attributes, and all the methods, defined on the
History
interface, when invoked on a History
object associated with a
Document
that is not fully active, must throw a
SecurityError
exception instead of operating as described below.
The length
attribute of the
History
interface must return the number of entries in the top-level browsing
context's joint session history.
The actual entries are not accessible from script.
The state
attribute of the
History
interface must return the last value it was set to by the user agent.
Initially, its value must be null.
When the go(delta)
method is
invoked, if the argument to the method was omitted or has the value zero, the user agent must act
as if the location.reload()
method was called instead.
Otherwise, the user agent must traverse the history by a delta whose value is the
value of the method's argument.
When the back()
method is invoked, the user
agent must traverse the history by a delta −1.
When the forward()
method is invoked, the
user agent must traverse the history by a delta +1.
Each top-level browsing context has a session history traversal queue, initially empty, to which tasks can be added.
Each top-level browsing context, when created, must asynchronously begin running the following algorithm, known as the session history event loop for that top-level browsing context:
Wait until this top-level browsing context's session history traversal queue is not empty.
Pull the first task from this top-level browsing context's session history traversal queue, and execute it.
Return to the first step of this algorithm.
The session history event loop helps coordinate cross-browsing-context transitions of the joint session history: since each browsing context might, at any particular time, have a different event loop (this can happen if the user agent has more than one event loop per unit of related browsing contexts), transitions would otherwise have to involve cross-event-loop synchronisation.
To traverse the history by a delta delta, the user agent must append a task to this top-level browsing context's session history traversal queue, the task consisting of running the following steps:
Let delta be the argument to the method.
If the index of the current entry of the joint session history plus delta is less than zero or greater than or equal to the number of items in the joint session history, then abort these steps.
Let specified entry be the entry in the joint session history whose index is the sum of delta and the index of the current entry of the joint session history.
Let specified browsing context be the browsing context of the specified entry.
If the specified browsing context's active document's unload a document algorithm is currently running, abort these steps.
Queue a task that consists of running the following substeps. The relevant event loop is that of the specified browsing context's active document. The task source for the queued task is the history traversal task source.
If there is an ongoing attempt to navigate specified browsing context
that has not yet matured (i.e. it has not passed the
point of making its Document
the active document), then cancel that
attempt to navigate the browsing context.
If the specified browsing context's active document is not
the same Document
as the Document
of the specified
entry, then run these substeps:
Prompt to unload the active document of the specified browsing context. If the user refused to allow the document to be unloaded, then abort these steps.
Unload the active document of the specified browsing context with the recycle parameter set to false.
Traverse the history of the specified browsing context to the specified entry.
When the user navigates through a browsing context, e.g. using a browser's back and forward buttons, the user agent must traverse the history by a delta equivalent to the action specified by the user.
The pushState(data, title, url)
method adds a state object entry to
the history.
The replaceState(data, title, url)
method updates the state object,
title, and optionally the URL of the current entry in the history.
When either of these methods is invoked, the user agent must run the following steps:
Let cloned data be a structured clone of the specified data. If this throws an exception, then rethrow that exception and abort these steps.
If the third argument is not null, run these substeps:
SecurityError
exception and abort these steps.SecurityError
exception and abort these steps.SecurityError
exception
and abort these steps. (This prevents sandboxed content from spoofing other pages on the same
origin.)Let new URL be the resulting absolute URL.
For the purposes of the comparisons in the above substeps, the path and query components can only be the same if the scheme component of both parsed URLs are relative schemes.
If the third argument is null, then let new URL be the URL of the current entry.
If the method invoked was the pushState()
method:
Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.
This doesn't necessarily have to affect the user agent's user interface.
Remove any tasks queued by the history traversal
task source that are associated with any Document
objects in the
top-level browsing context's document family.
If appropriate, update the current entry to reflect any state that the user agent wishes to persist. The entry is then said to be an entry with persisted user state.
Add a state object entry to the session history, after the current entry, with cloned data as the state object, the given title as the title, and new URL as the URL of the entry.
Update the current entry to be this newly added entry.
Otherwise, if the method invoked was the replaceState()
method:
Update the current entry in the session history so that cloned data is the entry's new state object, the given title is the new title, and new URL is the entry's new URL.
If the current entry in the session history represents a non-GET request (e.g. it was the result of a POST submission) then update it to instead represent a GET request (or equivalent).
Set the document's address to new URL.
Since this is neither a navigation of the
browsing context nor a history traversal,
it does not cause a hashchange
event to be fired.
Set history.state
to a structured clone
of cloned data.
Let the latest entry of the Document
of the current
entry be the current entry.
The title is purely advisory. User agents might use the title in the user interface.
User agents may limit the number of state objects added to the session history per page. If a
page hits the UA-defined limit, user agents must remove the entry immediately after the first
entry for that Document
object in the session history after having added the new
entry. (Thus the state history acts as a FIFO buffer for eviction, but as a LIFO buffer for
navigation.)
Consider a game where the user can navigate along a line, such that the user is always at some coordinate, and such that the user can bookmark the page corresponding to a particular coordinate, to return to it later.
A static page implementing the x=5 position in such a game could look like the following:
<!DOCTYPE HTML> <!-- this is http://example.com/line?x=5 --> <title>Line Game - 5</title> <p>You are at coordinate 5 on the line.</p> <p> <a href="?x=6">Advance to 6</a> or <a href="?x=4">retreat to 4</a>? </p>
The problem with such a system is that each time the user clicks, the whole page has to be reloaded. Here instead is another way of doing it, using script:
<!DOCTYPE HTML> <!-- this starts off as http://example.com/line?x=5 --> <title>Line Game - 5</title> <p>You are at coordinate <span id="coord">5</span> on the line.</p> <p> <a href="?x=6" onclick="go(1); return false;">Advance to 6</a> or <a href="?x=4" onclick="go(-1); return false;">retreat to 4</a>? </p> <script> var currentPage = 5; // prefilled by server function go(d) { setupPage(currentPage + d); history.pushState(currentPage, document.title, '?x=' + currentPage); } onpopstate = function(event) { setupPage(event.state); } function setupPage(page) { currentPage = page; document.title = 'Line Game - ' + currentPage; document.getElementById('coord').textContent = currentPage; document.links[0].href = '?x=' + (currentPage+1); document.links[0].textContent = 'Advance to ' + (currentPage+1); document.links[1].href = '?x=' + (currentPage-1); document.links[1].textContent = 'retreat to ' + (currentPage-1); } </script>
In systems without script, this still works like the previous example. However, users that do have script support can now navigate much faster, since there is no network access for the same experience. Furthermore, contrary to the experience the user would have with just a naïve script-based approach, bookmarking and navigating the session history still work.
In the example above, the data argument to the pushState()
method is the same information as would be sent
to the server, but in a more convenient form, so that the script doesn't have to parse the URL
each time the user navigates.
Applications might not use the same title for a session history entry as the
value of the document's title
element at that time. For example, here is a simple
page that shows a block in the title
element. Clearly, when navigating backwards to
a previous state the user does not go back in time, and therefore it would be inappropriate to
put the time in the session history title.
<!DOCTYPE HTML> <TITLE>Line</TITLE> <SCRIPT> setInterval(function () { document.title = 'Line - ' + new Date(); }, 1000); var i = 1; function inc() { set(i+1); history.pushState(i, 'Line - ' + i); } function set(newI) { i = newI; document.forms.F.I.value = newI; } </SCRIPT> <BODY ONPOPSTATE="set(event.state)"> <FORM NAME=F> State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON ONCLICK="inc()"> </FORM>
Location
interfaceEach Document
object in a browsing context's session history is
associated with a unique instance of a Location
object.
location
[ = value ]location
[ = value ]Returns a Location
object with the current page's location.
Can be set, to navigate to another page.
The location
attribute of the
Document
interface must return the Location
object for that
Document
object, if it is in a browsing context, and null otherwise.
The location
attribute of the Window
interface must return the Location
object for that Window
object's
Document
.
Location
objects provide a representation of the address of the active document of their Document
's
browsing context, and allow the current entry of the browsing
context's session history to be changed, by adding or replacing entries in the history
object.
[Unforgeable] interface Location { void assign(DOMString url); void replace(DOMString url); void reload(); }; Location implements URLUtils;
assign
(url)Navigates to the given page.
replace
(url)Removes the current page from the session history and navigates to the given page.
reload
()Reloads the current page.
The relevant Document
is the Location
object's associated
Document
object's browsing context's active document.
When the assign(url)
method is invoked, the UA must resolve the argument, relative
to the API base URL specified by the entry settings object, and if that is
successful, must navigate the browsing
context to the specified url, with exceptions enabled. If the browsing context's
session history contains only one Document
, and that was the
about:blank
Document
created when the browsing context was
created, then the navigation must be done with replacement enabled.
When the replace(url)
method is invoked, the UA must resolve the argument, relative
to the API base URL specified by the entry settings object, and if that is
successful, navigate the browsing
context to the specified url with replacement enabled and exceptions enabled.
Navigation for the assign()
and replace()
methods must be done with the responsible browsing context specified by
the incumbent settings object as the source
browsing context.
If the resolving step of the assign()
and replace()
methods is not successful, then the user agent must
instead throw a SyntaxError
exception.
When the reload()
method is invoked, the
user agent must run the appropriate steps from the following list:
resize
event in response to the user resizing the browsing
contextRepaint the browsing context and abort these steps.
iframe
srcdoc
documentReprocess the iframe
attributes of the browsing context's browsing context
container.
Perform an overridden reload, with the browsing context being navigated as the responsible browsing context.
Navigate the browsing context to the document's address with replacement enabled and exceptions enabled. The source browsing context must be the browsing context being navigated.
When a user requests that the active document of a browsing context
be reloaded through a user interface element, the user agent should navigate the browsing context to the same resource as that
Document
, with replacement enabled. In the case of non-idempotent
methods (e.g. HTTP POST), the user agent should prompt the user to confirm the operation first,
since otherwise transactions (e.g. purchases or database modifications) could be repeated. User
agents may allow the user to explicitly override any caches when reloading. If browsing
context's active document's reload override flag is set, then the
user agent may instead perform an overridden reload rather than the navigation
described in this paragraph (with the browsing context being reloaded as the
source browsing context).
The Location
interface also supports the URLUtils
interface. [URL]
When the object is created, and whenever the the
address of the relevant Document
changes, the user agent must invoke
the object's URLUtils
interface's set the
input algorithm with the address of the
relevant Document
as the given value.
The object's URLUtils
interface's get the
base algorithm must return the API base URL specified by the entry
settings object, if there is one, or null otherwise.
The object's URLUtils
interface's query
encoding is the document's character encoding.
When the object's URLUtils
interface invokes its update steps with the string value, the user
agent must run the following steps:
If any of the following conditions are met, let mode be normal navigation; otherwise, let it be replace navigation:
Location
object's relevant Document
has
completely loaded, orclick
event was trusted,
orclick
event is being handled.If mode is normal navigation, then act as if the assign()
method had been called with value
as its argument. Otherwise, act as if the replace()
method had been called with value as its argument.
This section describes a security model that is underdefined, imperfect, and
does not match implementations. Work is ongoing to attempt to resolve this, but in the meantime,
please do not rely on this section for precision. Implementors are urged to send their feedback on
how cross-origin cross-global access to Window
and Location
objects
should work. See bug 20701.
User agents must throw a SecurityError
exception whenever any
properties of a Location
object are accessed when the entry settings object specifies
an effective script origin that is not the same as
the Location
object's associated Document
's browsing
context's active document's effective script origin, with the
following exceptions:
href
setter, if the responsible browsing context
specified by the entry
settings object is familiar with the browsing
context with which the Location
object is associated
replace()
method, if the responsible
browsing context specified by the entry
settings object is familiar with the
browsing context with which the Location
object is associated
Location
object or indirectly via
one of those properties (e.g. toString()
, which is defined via the stringifier
keyword), if the effective script
origin specified by the entry settings object is the same origin as the Location
object's associated
Document
's effective script origin
When the effective script origin specified by the entry settings object is different than a
Location
object's associated Document
's effective script
origin, the user agent must act as if any changes to that Location
object's
properties, getters, setters, etc, were not present, and as if all the properties of that
Location
object had their [[Enumerable]] attribute set to false.
For members that return objects (including function objects), each distinct effective
script origin that is not the same origin as the Location
object's Document
's effective script origin must be provided with a
separate set of objects. These objects must have the prototype chain appropriate for the script
for which the objects are created (not those that would be appropriate for scripts whose
settings object specifies a global object that is the Location
object's Document
's
Window
object).
This section is non-normative.
The History
interface is not meant to place restrictions on how implementations
represent the session history to the user.
For example, session history could be implemented in a tree-like manner, with each page having
multiple "forward" pages. This specification doesn't define how the linear list of pages in the
history
object are derived from the actual session history as
seen from the user's perspective.
Similarly, a page containing two iframe
s has a history
object distinct from the iframe
s' history
objects, despite the fact that typical Web browsers present the
user with just one "Back" button, with a session history that interleaves the navigation of the
two inner frames and the outer page.
Security: It is suggested that to avoid letting a page "hijack" the history
navigation facilities of a UA by abusing pushState()
,
the UA provide the user with a way to jump back to the previous page (rather than just going back
to the previous state). For example, the back button could have a drop down showing just the pages
in the session history, and not showing any of the states. Similarly, an aural browser could have
two "back" commands, one that goes back to the previous state, and one that jumps straight back to
the previous page.
In addition, a user agent could ignore calls to pushState()
that are invoked on a timer, or from event
listeners that are not triggered in response to a clear user action, or that are invoked in rapid
succession.
Certain actions cause the browsing context to navigate to a new resource. A user agent may provide various ways for the user to explicitly cause a browsing context to navigate, in addition to those defined in this specification.
For example, following a hyperlink,
form submission, and the window.open()
and location.assign()
methods can all cause a browsing context to
navigate.
A resource has a URL, but that might not be the only information necessary
to identify it. For example, a form submission that uses HTTP POST would also have the HTTP method
and payload. Similarly, an iframe
srcdoc
document needs to know the data it is to use.
Navigation always involves source browsing context, which is the browsing context which was responsible for starting the navigation.
When a browsing context is navigated to a new resource, the user agent must run the following steps:
Release the storage mutex.
If the source browsing context is not allowed to navigate the browsing context being navigated, then abort these steps.
If these steps are aborted here, the user agent may instead offer to open the new resource in a new top-level browsing context or in the top-level browsing context of the source browsing context, at the user's option, in which case the user agent must navigate that designated top-level browsing context to the new resource as if the user had requested it independently.
Doing so, however, can be dangerous, as it means that the user is overriding the author's explicit request to sandbox the content.
If the navigate algorithm was invoked with exceptions enabled, and it
is aborted on this step, then in addition to aborting this algorithm, the user agent must also
throw a SecurityError
exception.
If the source browsing context is the same as the browsing context being navigated, and this browsing context has its seamless browsing context flag set, and the browsing context being navigated was not chosen using an explicit self-navigation override, then find the nearest ancestor browsing context that does not have its seamless browsing context flag set, and continue these steps as if that browsing context was the one that was going to be navigated instead.
If there is a preexisting attempt to navigate the browsing context, and the source browsing context is the same as the browsing context being navigated, and that attempt is currently running the unload a document algorithm, and the origin of the URL of the resource being loaded in that navigation is not the same origin as the origin of the URL of the resource being loaded in this navigation, then abort these steps without affecting the preexisting attempt to navigate the browsing context.
If a task queued by the traverse the history by a delta algorithm is running the unload a document algorithm for the active document of the browsing context being navigated, then abort these steps without affecting the unload a document algorithm or the aforementioned history traversal task.
If the prompt to unload a document algorithm is being run for the active document of the browsing context being navigated, then abort these steps without affecting the prompt to unload a document algorithm.
Let gone async be false.
The handle redirects step later in this algorithm can in certain cases jump back to the step labeled fragment identifiers. Since, between those two steps, this algorithm goes from operating synchronously in the context of the calling task to operating asynchronously independent of the event loop, some of the intervening steps need to be able to handle both being synchronous and being asynchronous. The gone async flag is thus used to make these steps aware of which mode they are operating in.
If gone async is false, cancel any preexisting but not yet mature attempt to navigate the browsing
context, including canceling any instances of the fetch algorithm started by
those attempts. If one of those attempts has already created a new Document
object, abort that Document
also. (Navigation attempts that have matured already have session history entries, and are
therefore handled during the update the session history with the new page algorithm,
later.)
If the new resource is to be handled using a mechanism that does not affect the browsing context, e.g. ignoring the navigation request altogether because the specified scheme is not one of the supported protocols, then abort these steps and proceed with that mechanism instead.
If gone async is false, prompt
to unload the Document
object. If the user refused to allow the
document to be unloaded, then abort these steps.
If this instance of the navigation algorithm gets canceled while this step is running, the prompt to unload a document algorithm must nonetheless be run to completion.
If gone async is false, abort the active document of the browsing context.
If the new resource is to be handled by displaying some sort of inline content, e.g. an error message because the specified scheme is not one of the supported protocols, or an inline prompt to allow the user to select a registered handler for the given scheme, then display the inline content and abort these steps.
In the case of a registered handler being used, the algorithm will be reinvoked with a new URL to handle the request.
If the browsing context being navigated is a nested browsing
context, then put it in the delaying load
events
mode.
The user agent must take this nested browsing context out of the delaying
load
events mode when this navigation algorithm later matures, or when it terminates (whether due to having
run all the steps, or being canceled, or being aborted), whichever happens first.
This is the step that attempts to obtain the resource, if necessary. Jump to the first appropriate substep:
object
element's new child browsing context)Skip this step. The data is already available.
javascript
Queue a task to run these "javascript:
URL" steps, associated with the active
document of the browsing context being navigated:
If the origin of the source browsing context is not the same origin as the origin of the active document of the browsing context being navigated, then act as if the result of evaluating the script was the void value, and jump to the step labeled process results below.
Apply the URL parser to the URL being navigated.
Let parsed URL be the result of the URL parser.
Let script source be the empty string.
Append parsed URL's scheme data component to script source.
If parsed URL's query component is not null, then first append a "?" (U+003F) character to script source, and then append parsed URL's query component to script source.
If parsed URL's fragment component is not null, then first append a "#" (U+0023) character to script source, and then append parsed URL's fragment component to script source.
Replace script source with the result of applying the percent decode algorithm to script source.
Replace script source with the result of applying the UTF-8 decode algorithm to script source.
Let address be the address of the active document of the browsing context being navigated.
Create a script, using script source as the script
source, address as the script source URL, JavaScript as the scripting
language, and the script settings object of the Window
object of
the active document of the browsing context being navigated.
Let result be the return value of the code entry-point of this script. If an exception was thrown, let result be void instead. (The result will be void also if scripting is disabled.)
Process results: If the result of executing the script is void (there is no return value), then the result of obtaining the resource for the URL is equivalent to an HTTP resource with an HTTP 204 No Content response.
Otherwise, the result of obtaining the resource for the URL is equivalent to an HTTP resource with a 200 OK
response whose Content-Type metadata is
text/html
and whose response body is the return value converted to a string
value.
When it comes time to set the document's address in the navigation algorithm, use address as the override URL.
The task source for this task is the DOM manipulation task source.
So for example a javascript:
URL in an href
attribute of an
a
element would only be evaluated when the link was followed, while such a URL in the src
attribute of an iframe
element would be
evaluated in the context of the iframe
's own nested browsing
context when the iframe
is being set up; once evaluated, its return value
(if it was not void) would replace that browsing context's document, thus also
changing the Window
object of that browsing context.
Fetch the resource from the most appropriate application cache of those that match.
For example, imagine an HTML page with an associated application cache displaying an image and a form, where the image is also used by several other application caches. If the user right-clicks on the image and chooses "View Image", then the user agent could decide to show the image from any of those caches, but it is likely that the most useful cache for the user would be the one that was used for the aforementioned HTML page. On the other hand, if the user submits the form, and the form does a POST submission, then the user agent will not use an application cache at all; the submission will be made to the network.
Fetch the new resource, with the manual redirect flag set.
If the steps above invoked the fetch algorith, the following requirements also apply:
If the resource is being fetched using a method other than one equivalent to HTTP's GET, or, if the navigation algorithm was invoked as a result of the form submission algorithm, then the fetching algorithm must be invoked from the origin of the active document of the source browsing context, if any.
Otherwise, if the browsing context being navigated is a child browsing context, then the fetching algorithm must be invoked from the browsing context scope origin of the browsing context container of the browsing context being navigated, if it has one.
If gone async is false, return to whatever algorithm invoked the navigation steps and continue running these steps asynchronously.
Let gone async be true.
Wait for one or more bytes to be available or for the user agent to establish that the resource in question is empty. During this time, the user agent may allow the user to cancel this navigation attempt or start other navigation attempts.
Fallback in prefer-online mode: If the resource was not fetched from an application cache, and was to be fetched using HTTP GET or equivalent, and there are relevant application caches that are identified by a URL with the same origin as the URL in question, and that have this URL as one of their entries, excluding entries marked as foreign, and whose mode is prefer-online, and the user didn't cancel the navigation attempt during the earlier step, and the navigation attempt failed (e.g. the server returned a 4xx or 5xx status code or equivalent, or there was a DNS error), then:
Let candidate be the resource identified by the URL in question from the most appropriate application cache of those that match.
If candidate is not marked as foreign, then the user agent must discard the failed load and instead continue along these steps using candidate as the resource. The user agent may indicate to the user that the original page load failed, and that the page used was a previously cached resource.
This does not affect the address of the resource from which Request-URIs are obtained, as used to set the document's referrer in the create a Document object steps below; they still use the value as computed by the original fetch algorithm.
Fallback for fallback entries: If the resource was not fetched from an application cache, and was to be fetched using HTTP GET or equivalent, and its URL matches the fallback namespace of one or more relevant application caches, and the most appropriate application cache of those that match does not have an entry in its online whitelist that has the same origin as the resource's URL and that is a prefix match for the resource's URL, and the user didn't cancel the navigation attempt during the previous step, and the navigation attempt failed (e.g. the server returned a 4xx or 5xx status code or equivalent, or there was a DNS error), then:
Let candidate be the fallback resource specified for the fallback namespace in question. If multiple application caches match, the user agent must use the fallback of the most appropriate application cache of those that match.
If candidate is not marked as foreign, then the user agent must discard the failed load and instead continue along these steps using candidate as the resource. The document's address, if appropriate, will still be the originally requested URL, not the fallback URL, but the user agent may indicate to the user that the original page load failed, that the page used was a fallback resource, and what the URL of the fallback resource actually is.
This does not affect the address of the resource from which Request-URIs are obtained, as used to set the document's referrer in the create a Document object steps below; they still use the value as computed by the original fetch algorithm.
Resource handling: If the resource's out-of-band metadata (e.g. HTTP headers), not counting any type information (such as the Content-Type HTTP header), requires some sort of processing that will not affect the browsing context, then perform that processing and abort these steps.
Such processing might be triggered by, amongst other things, the following:
Responses with HTTP Content-Disposition
headers
specifying the attachment
disposition type must be handled as a
download.
HTTP 401 responses that do not include a challenge recognized by the user agent must be processed as if they had no challenge, e.g. rendering the entity body as if the response had been 200 OK.
User agents may show the entity body of an HTTP 401 response even when the response does include a recognized challenge, with the option to login being included in a non-modal fashion, to enable the information provided by the server to be used by the user before authenticating. Similarly, user agents should allow the user to authenticate (in a non-modal fashion) against authentication challenges included in other responses such as HTTP 200 OK responses, effectively allowing resources to present HTTP login forms without requiring their use.
Let type be the sniffed type of the resource.
If the user agent has been configured to process resources of the given type using some mechanism other than rendering the content in a browsing context, then skip this step. Otherwise, if the type is one of the following types, jump to the appropriate entry in the following list, and process the resource as described there:
text/html
"application/xml
"text/xml
"image/svg+xml
"application/xhtml+xml
"+xml
" that is not an explicitly
supported XML typetext/plain
"multipart/x-mixed-replace
"An explicitly supported XML type is one for which the user agent is configured to
use an external application to render the content (either a plugin rendering
directly in the browsing context, or a separate application), or one for which the
user agent has dedicated processing rules (e.g. a Web browser with a built-in Atom feed viewer
would be said to explicitly support the application/atom+xml
MIME type), or one for
which the user agent has a dedicated handler (e.g. one registered using registerContentHandler()
).
Setting the document's address: If there is no
override URL, then any Document
created by these steps must have its
address set to the URL that was
originally to be fetched, ignoring any other data that was used to
obtain the resource (e.g. the entity body in the case of a POST submission is not part of
the document's address, nor is the URL of the fallback resource in the case of the
original load having failed and that URL having been found to match a fallback namespace). However, if there is
an override URL, then any Document
created by these steps must have
its address set to that URL
instead.
An override URL is set when dereferencing a javascript:
URL and when
performing an overridden reload.
Creating a new Document
object: when
a Document
is created as part of the above steps, the user agent must additionally
run the following algorithm as part of creating the new object:
Create a new Window
object, and associate it with the
Document
, with one exception: if the browsing context's only entry in
its session history is the about:blank
Document
that was
added when the browsing context was created, and navigation is occurring with
replacement enabled, and that Document
has the same
origin as the new Document
, then use the Window
object of that
Document
instead, and change the document
attribute of the Window
object to point to the new Document
.
Set the document's referrer to the address of the resource from which Request-URIs are obtained as determined when the fetch algorithm obtained the resource, if that algorithm was used and determined such a value; otherwise, set it to the empty string.
Implement the sandboxing for the Document
.
If the active sandboxing flag set of the Document
's
browsing context or any of its ancestor
browsing contexts (if any) have the sandboxed fullscreen browsing context
flag set, then skip this step.
If the Document
's browsing context has a browsing context
container and either it is not an iframe
element, or its
Document
does not have the fullscreen enabled flag set, then also
skip this step.
Otherwise, set the Document
's fullscreen enabled flag.
Otherwise, the document's type is such that the resource will not affect the browsing context, e.g. because the resource is to be handed to an external application or because it is an unknown type that will be processed as a download. Process the resource appropriately.
Some of the sections below, to which the above algorithm defers in certain cases, require the
user agent to update the session history with the new page. When a user agent is
required to do this, it must queue a task (associated with the Document
object of the current entry, not the new one) to run the following steps:
Unload the Document
object of the
current entry, with the recycle parameter set to false.
If this instance of the navigation algorithm is canceled while this step is running the unload a document algorithm, then the unload a document algorithm must be allowed to run to completion, but this instance of the navigation algorithm must not run beyond this step. (In particular, for instance, the cancelation of this algorithm does not abort any event dispatch or script execution occurring as part of unloading the document or its descendants.)
Replace the Document
of the entry being updated, and any other entries
that referenced the same document as that entry, with the new Document
.
Traverse the history to the new entry.
This can only happen if the entry being updated is not the current
entry, and can never happen with replacement enabled. (It happens when the
user tried to traverse to a session history entry that no longer had a Document
object.)
Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.
This doesn't necessarily have to affect the user agent's user interface.
Append a new entry at the end of the History
object representing the new
resource and its Document
object and related state.
Traverse the history to the new entry. If the navigation was initiated with replacement enabled, then the traversal must itself be initiated with replacement enabled.
The navigation algorithm has now matured.
Fragment identifier loop: Spin the event loop for a user-agent-defined amount of time, as desired by the user agent implementor. (This is intended to allow the user agent to optimize the user experience in the face of performance concerns.)
If the Document
object has no parser, or its parser has stopped parsing, or the user agent has reason to believe the user is no longer
interested in scrolling to the fragment identifier, then abort these steps.
Scroll to the fragment identifier given in the document's address. If this fails to find an indicated part of the document, then return to the fragment identifier loop step.
The task source for this task is the networking task source.
When an HTML document is to be loaded in a browsing context, the user agent must
queue a task to create a Document
object, mark it as being
an HTML document, set its content type to "text/html
",
create an HTML parser, and associate it with the document. Each task that the networking task source places on the
task queue while the fetching algorithm runs must then
fill the parser's input byte stream with the fetched bytes and cause the HTML
parser to perform the appropriate processing of the input stream.
The input byte stream converts bytes into characters for use in the tokenizer. This process relies, in part, on character encoding information found in the real Content-Type metadata of the resource; the "sniffed type" is not used for this purpose.
When no more bytes are available, the user agent must queue a task for the parser
to process the implied EOF character, which eventually causes a load
event to be fired.
After creating the Document
object, but before any script execution, certainly
before the parser stops, the user agent must update the
session history with the new page.
Application cache selection happens in the HTML parser.
The task source for the two tasks mentioned in this section must be the networking task source.
When faced with displaying an XML file inline, user agents must first create a
Document
object, following the requirements of the XML and Namespaces in XML
recommendations, RFC 3023, DOM, and other relevant specifications. [XML] [XMLNS] [RFC3023] [DOM]
The actual HTTP headers and other metadata, not the headers as mutated or implied by the algorithms given in this specification, are the ones that must be used when determining the character encoding according to the rules given in the above specifications. Once the character encoding is established, the document's character encoding must be set to that character encoding.
If the root element, as parsed according to the XML specifications cited above, is found to be
an html
element with an attribute manifest
whose value is not the empty string, then, as soon as the element is inserted into the document, the user agent must resolve the value of that attribute relative to that element, and if
that is successful, must apply the URL serializer
algorithm to the resulting parsed URL with the exclude fragment flag set to
obtain manifest URL, and then run the application cache selection algorithm with manifest URL as the manifest URL, passing in the newly-created
Document
. Otherwise, if the attribute is absent, its value is the empty string, or
resolving its value fails, then as soon as the root element is inserted into the document, the user agent must run the application cache selection algorithm with no manifest, and
passing in the Document
.
Because the processing of the manifest
attribute happens only once the root element is parsed, any URLs referenced by processing
instructions before the root element (such as <?xml-stylesheet?>
and
<?xbl?>
PIs) will be fetched from the network and cannot be
cached.
User agents may examine the namespace of the root Element
node of this
Document
object to perform namespace-based dispatch to alternative processing tools,
e.g. determining that the content is actually a syndication feed and passing it to a feed handler.
If such processing is to take place, abort the steps in this section, and jump to the next step (labeled non-document content) in the
navigate steps above.
Otherwise, then, with the newly created Document
, the user agent must update
the session history with the new page. User agents may do this before the complete document
has been parsed (thus achieving incremental rendering), and must do this before any scripts
are to be executed.
Error messages from the parse process (e.g. XML namespace well-formedness errors) may be
reported inline by mutating the Document
.
When a plain text document is to be loaded in a browsing context, the user agent
must queue a task to create a Document
object, mark it as
being an HTML document, set its content type to "text/plain
",
create an HTML parser, associate it with the document, act as if the tokenizer had
emitted a start tag token with the tag name "pre" followed by a single "LF" (U+000A)
character, and switch the HTML parser's tokenizer to the PLAINTEXT
state. Each task that the networking task
source places on the task queue while the fetching
algorithm runs must then fill the parser's input byte stream with the fetched
bytes and cause the HTML parser to perform the appropriate processing of the input
stream.
The rules for how to convert the bytes of the plain text document into actual characters, and the rules for actually rendering the text to the user, are defined in RFC 2046, RFC 3676, and subsequent versions thereof. [RFC2046] [RFC3676]
The document's character encoding must be set to the character encoding used to decode the document.
Upon creation of the Document
object, the user agent must run the application cache selection algorithm with no manifest, and
passing in the newly-created Document
.
When no more bytes are available, the user agent must queue a task for the parser
to process the implied EOF character, which eventually causes a load
event to be fired.
After creating the Document
object, but potentially before the page has finished
parsing, the user agent must update the session history with the new page.
User agents may add content to the head
element of the Document
, e.g.
linking to a style sheet or an XBL binding, providing script, giving the document a
title
, etc.
In particular, if the user agent supports the Format=Flowed
feature of RFC 3676 then the user agent would need to apply extra styling to cause the text to
wrap correctly and to handle the quoting feature. This could be performed using, e.g., an XBL
binding or a CSS extension.
The task source for the two tasks mentioned in this section must be the networking task source.
multipart/x-mixed-replace
resourcesWhen a resource with the type multipart/x-mixed-replace
is to be loaded in a
browsing context, the user agent must parse the resource using the rules for
multipart types. [RFC2046]
For each body part obtained from the resource, the user agent must run a new instance of the
navigate algorithm, starting from the resource handling step, using the new
body part as the resource being navigated, with replacement enabled if a previous
body part from the same resource resulted in a Document
object being created, and otherwise using the same setup as the
navigate attempt that caused this section to be invoked in the first place.
For the purposes of algorithms processing these body parts as if they were complete stand-alone resources, the user agent must act as if there were no more bytes for those resources whenever the boundary following the body part is reached.
Thus, load
events (and for that matter unload
events) do fire for each body part loaded.
When an image, video, or audio resource is to be loaded in a browsing context, the
user agent should create a Document
object, mark it as being an HTML document, set its content type to the sniffed MIME type of the resource
(type in the navigate algorithm), append an html
element to the Document
, append a head
element and a body
element to the html
element, append an element host element for
the media, as described below, to the body
element, and set the appropriate attribute
of the element host element, as described below, to the address of the image,
video, or audio resource.
The element host element to create for the media is the element given in the table below in the second cell of the row whose first cell describes the media. The appropriate attribute to set is the one given by the third cell in that same row.
Type of media | Element for the media | Appropriate attribute |
---|---|---|
Image | img
| src
|
Video | video
| src
|
Audio | audio
| src
|
Then, the user agent must act as if it had stopped parsing.
Upon creation of the Document
object, the user agent must run the application cache selection algorithm with no manifest, and
passing in the newly-created Document
.
After creating the Document
object, but potentially before the page has finished
fully loading, the user agent must update the session history with the new page.
User agents may add content to the head
element of the Document
, or
attributes to the element host element, e.g. to link to a style sheet or an
XBL binding, to provide a script, to give the document a title
, to make the media
autoplay, etc.
When a resource that requires an external resource to be rendered is to be loaded in a
browsing context, the user agent should create a Document
object, mark it as being an HTML document and mark it
as being a plugin document, set its content
type to the sniffed MIME type of the resource (type in the
navigate algorithm), append an html
element to the
Document
, append a head
element and a body
element to the
html
element, append an embed
to the body
element, and set
the src
attribute of the embed
element to the
address of the resource.
The term plugin document is used by the Content Security Policy
specification as part of the mechanism that ensures iframe
s can't be used to evade
plugin-types
directives. [CSP]
Then, the user agent must act as if it had stopped parsing.
Upon creation of the Document
object, the user agent must run the application cache selection algorithm with no manifest, and
passing in the newly-created Document
.
After creating the Document
object, but potentially before the page has finished
fully loading, the user agent must update the session history with the new page.
User agents may add content to the head
element of the Document
, or
attributes to the embed
element, e.g. to link to a style sheet or an XBL binding, or
to give the document a title
.
When the user agent is to display a user agent page inline in a browsing context,
the user agent should create a Document
object, mark it as being an
HTML document, set its content type to "text/html
",
and then either associate that Document
with a custom rendering that is not rendered
using the normal Document
rendering rules, or mutate that Document
until
it represents the content the user agent wants to render.
Once the page has been set up, the user agent must act as if it had stopped parsing.
Upon creation of the Document
object, the user agent must run the application cache selection algorithm with no manifest,
passing in the newly-created Document
.
After creating the Document
object, but potentially before the page has been
completely set up, the user agent must update the session history with the new
page.
When a user agent is supposed to navigate to a fragment identifier, then the user agent must run the following steps:
Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.
This doesn't necessarily have to affect the user agent's user interface.
Remove any tasks queued by the history traversal
task source that are associated with any Document
objects in the
top-level browsing context's document family.
Append a new entry at the end of the History
object representing the new
resource and its Document
object and related state. Its URL must be set
to the address to which the user agent was navigating. The title
must be left unset.
Traverse the history to the new entry, with the asynchronous events flag set. This will scroll to the fragment identifier given in what is now the document's address.
If the scrolling fails because the relevant ID has not yet been parsed, then the original navigation algorithm will take care of the scrolling instead, as the last few steps of its update the session history with the new page algorithm.
When the user agent is required to scroll to the fragment identifier and the indicated part of the document, if any, is being rendered, the user agent must either change the scrolling position of the document using the following algorithm, or perform some other action such that the indicated part of the document is brought to the user's attention. If there is no indicated part, or if the indicated part is not being rendered, then the user agent must do nothing. The aforementioned algorithm is as follows:
Let target be the indicated part of the document, as defined below.
If target is the top of the document, then scroll to the
beginning of the document for the Document
, and abort these steps. [CSSOMVIEW]
Use the scroll an element into view algorithm to scroll target into view, with the align to top flag set. [CSSOMVIEW]
If target is a focusable element, run the focusing steps for that element.
The indicated part of the document is the one that the fragment identifier, if any,
identifies. The semantics of the fragment identifier in terms of mapping it to a specific DOM Node
is defined by the specification that defines the MIME type used by the
Document
(for example, the processing of fragment identifiers for XML MIME types is the responsibility of RFC3023). [RFC3023]
For HTML documents (and HTML MIME types), the following processing model must be followed to determine what the indicated part of the document is.
Apply the URL parser algorithm to the URL, and let fragid be the fragment component of the resulting parsed URL.
If fragid is the empty string, then the indicated part of the document is the top of the document; stop the algorithm here.
Let fragid bytes be the result of percent-decoding fragid.
Let decoded fragid be the result of applying the UTF-8 decoder algorithm to fragid bytes. If the UTF-8 decoder emits a decoder error, abort the decoder and instead jump to the step labeled no decoded fragid.
If there is an element in the DOM that has an ID exactly equal to decoded fragid, then the first such element in tree order is the indicated part of the document; stop the algorithm here.
No decoded fragid: If there is an a
element in the DOM that has a name
attribute whose value is exactly equal to fragid (not decoded fragid), then the first such
element in tree order is the indicated part of the document; stop the algorithm
here.
If fragid is an ASCII case-insensitive match for the
string top
, then the indicated part of the document is the top
of the document; stop the algorithm here.
Otherwise, there is no indicated part of the document.
For the purposes of the interaction of HTML with Selectors' :target
pseudo-class, the target element is
the indicated part of the document, if that is an element; otherwise there is no
target element. [SELECTORS]
The task source for the task mentioned in this section must be the DOM manipulation task source.
When a user agent is required to traverse the history to a specified entry, optionally with replacement enabled, and optionally with the asynchronous events flag set, the user agent must act as follows.
This algorithm is not just invoked when explicitly going back or forwards in the session history — it is also invoked in other situations, for example when navigating a browsing context, as part of updating the session history with the new page.
If there is no longer a Document
object for the entry in question,
navigate the browsing
context to the resource for that entry to perform an entry update of that
entry, and abort these steps. The "navigate" algorithm reinvokes this "traverse"
algorithm to complete the traversal, at which point there is a Document
object and so this step gets skipped. The navigation must be done using the same source
browsing context as was used the first time this entry was created. (This can never
happen with replacement enabled.)
If the resource was obtained usign a non-idempotent action, for example a POST form submission, or if the resource is no longer available, for example because the computer is now offline and the page wasn't cached, navigating to it again might not be possible. In this case, the navigation will result in a different page than previously; for example, it might be an error message explaining the problem or offering to resubmit the form.
If the current entry's title was not set by the pushState()
or replaceState()
methods, then set its title to the value
returned by the document.title
IDL attribute.
If appropriate, update the current entry in the browsing
context's Document
object's History
object to reflect any state
that the user agent wishes to persist. The entry is then said to be an entry with persisted
user state.
If the specified entry has a different Document
object
than the current entry, then run the following substeps:
Remove any tasks queued by the history traversal
task source that are associated with any Document
objects in the
top-level browsing context's document family.
If the origin of the Document
of the specified
entry is not the same as the origin of the
Document
of the current entry, then run the following
sub-sub-steps:
The current browsing context name must be stored with all the entries in
the history that are associated with Document
objects with the same
origin as the active document and that are contiguous with the
current entry.
If the browsing context is a top-level browsing context, but not an auxiliary browsing context, then the browsing context's browsing context name must be unset.
Make the specified entry's
Document
object the active document of the browsing
context.
If the specified entry has a browsing context name stored with it, then run the following sub-sub-steps:
Set the browsing context's browsing context name to the name stored with the specified entry.
Clear any browsing context names stored
with all entries in the history that are associated with Document
objects with
the same origin as the new active document and that are contiguous
with the specified entry.
If the specified entry's
Document
has any form controls whose autofill field name is "off
", invoke the reset algorithm of each of those elements.
If the current document readiness of the specified entry's
Document
is "complete
", queue a task to run
the following sub-sub-steps:
If the Document
's page showing flag is true, then abort this
task (i.e. don't fire the event below).
Set the Document
's page showing flag to true.
Run any session history document visibility change steps for Document
that
are defined by other applicable specifications.
This is specifically intended for use by the Page Visibility specification. [PAGEVIS]
Fire a trusted event with the name pageshow
at the Window
object of that
Document
, but with its target
set to the
Document
object (and the currentTarget
set to the Window
object),
using the PageTransitionEvent
interface, with the persisted
attribute initialized to true.
This event must not bubble, must not be cancelable, and has no default action.
Set the document's address to the URL of the specified entry.
If the specified entry has a URL whose fragment identifier differs
from that of the current entry's when compared in a case-sensitive
manner, and the two share the same Document
object, then let hash
changed be true, and let old URL be the URL of the current
entry and new URL be the URL of the specified
entry. Otherwise, let hash changed be false.
If the traversal was initiated with replacement enabled, remove the entry immediately before the specified entry in the session history.
If the specified entry is not an entry with persisted user state, but its URL has a fragment identifier, scroll to the fragment identifier.
If the entry is an entry with persisted user state, the user agent may update aspects of the document and its rendering, for instance the scroll position or values of form fields, that it had previously recorded.
This can even include updating the dir
attribute
of textarea
elements or input
elements whose type
attribute is in either the Text state or the Search state, if the persisted state includes the
directionality of user input in such controls.
If the entry is a state object entry, let state be a structured clone of that state object. Otherwise, let state be null.
Set history.state
to state.
Let state changed be true if the Document
of the specified entry has a latest entry, and that entry is not the specified entry; otherwise let it be false.
Let the latest entry of the Document
of the specified entry be the specified entry.
If the asynchronous events flag is not set, then run the following steps synchronously. Otherwise, the asynchronous events flag is set; queue a task to run the following substeps.
If state changed is true, fire a trusted
event with the name popstate
at the Window
object of the Document
, using the PopStateEvent
interface, with the
state
attribute initialized to the value of state. This event must bubble but not be cancelable and has no default
action.
If hash changed is true, then fire a trusted
event with the name hashchange
at the browsing
context's Window
object, using the HashChangeEvent
interface,
with the oldURL
attribute initialized to old URL and the newURL
attribute
initialized to new URL. This event must bubble but not be cancelable and
has no default action.
The current entry is now the specified entry.
The task source for the tasks mentioned above is the DOM manipulation task source.
The popstate
event is fired in certain cases
when navigating to a session history entry.
[Constructor(DOMString type, optional PopStateEventInit eventInitDict)] interface PopStateEvent : Event { readonly attribute any state; }; dictionary PopStateEventInit : EventInit { any state; };
state
Returns a copy of the information that was provided to pushState()
or replaceState()
.
The state
attribute must return the
value it was initialized to. When the object is created, this attribute must be initialized to
null. It represents the context information for the event, or null, if the state represented is
the initial state of the Document
.
The hashchange
event is fired when navigating
to a session history entry whose URL differs from that of the previous
one only in the fragment identifier.
[Constructor(DOMString type, optional HashChangeEventInit eventInitDict)] interface HashChangeEvent : Event { readonly attribute DOMString oldURL; readonly attribute DOMString newURL; }; dictionary HashChangeEventInit : EventInit { DOMString oldURL; DOMString newURL; };
oldURL
Returns the URL of the session history entry that was previously current.
newURL
Returns the URL of the session history entry that is now current.
The oldURL
attribute must return the
value it was initialized to. When the object is created, this attribute must be initialized to
null. It represents context information for the event, specifically the URL of the session
history entry that was traversed from.
The newURL
attribute must return the
value it was initialized to. When the object is created, this attribute must be initialized to
null. It represents context information for the event, specifically the URL of the session
history entry that was traversed to.
The pageshow
event is fired when traversing to a session history entry.
The pagehide
event is fired when traversing
from a session history entry. The specification uses the page
showing flag to ensure that scripts receive these events in a consistent manner (e.g. that
they never receive two pagehide
events in a row without an
intervening pageshow
, or vice versa).
[Constructor(DOMString type, optional PageTransitionEventInit eventInitDict)] interface PageTransitionEvent : Event { readonly attribute boolean persisted; }; dictionary PageTransitionEventInit : EventInit { boolean persisted; };
persisted
For the pageshow
event, returns false if the page is
newly being loaded (and the load
event will fire). Otherwise,
returns true.
For the pagehide
event, returns false if the page is
going away for the last time. Otherwise, returns true, meaning that (if nothing conspires to
make the page unsalvageable) the page might be reused if the user navigates back to this
page.
Things that can cause the page to be unsalvageable include:
document.open()
beforeunload
events
unload
events
iframe
s that are not salvageable
WebSocket
objects
Document
The persisted
attribute must
return the value it was initialized to. When the object is created, this attribute must be
initialized to false. It represents the context information for the event.
A Document
has a salvageable state, which must initially be true,
a fired unload flag, which must initially be false, and a page showing flag,
which must initially be false.
Event loops have a termination nesting level counter, which must initially be zero.
When a user agent is to prompt to unload a document, it must run the following steps.
Increase the event loop's termination nesting level by one.
Increase the Document
's ignore-opens-during-unload counter by
one.
Let event be a new trusted
BeforeUnloadEvent
event object with the name beforeunload
, which does not bubble but is cancelable.
Decrease the event loop's termination nesting level by one.
Release the storage mutex.
If any event listeners were triggered by the earlier dispatch step, then set the
Document
's salvageable state to
false.
If the returnValue
attribute of the
event object is not the empty string, or if the event was canceled, then the
user agent should ask the user to confirm that they wish to unload the document.
The prompt shown by the user agent may include the string of the returnValue
attribute, or some leading subset
thereof. (A user agent may want to truncate the string to 1024 characters for display, for
instance.)
The user agent must pause while waiting for the user's response.
If the user did not confirm the page navigation, then the user agent refused to allow the document to be unloaded.
If this algorithm was invoked by another instance of the "prompt to unload a document" algorithm (i.e. through the steps below that invoke this algorithm for all descendant browsing contexts), then jump to the step labeled end.
Let descendants be the list of the descendant browsing
contexts of the Document
.
If descendants is not an empty list, then for each browsing context b in descendants run the following substeps:
Prompt to unload the active document of the browsing context b. If the user refused to allow the document to be unloaded, then the user implicitly also refused to allow this document to be unloaded; jump to the step labeled end.
If the salvageable state of the active document of the browsing context b is false, then set the salvageable state of this document to false also.
End: Decrease the Document
's ignore-opens-during-unload
counter by one.
When a user agent is to unload a document, it must run the following steps. These
steps are passed an argument, recycle, which is either true or false,
indicating whether the Document
object is going to be re-used. (This is set by the
document.open()
method.)
Increase the event loop's termination nesting level by one.
Increase the Document
's ignore-opens-during-unload counter by
one.
If the Document
's page showing flag is false, then jump to the
step labeled unload event below (i.e. skip firing the pagehide
event and don't rerun the unloading document
visibility change steps).
Set the Document
's page showing flag to false.
Fire a trusted event with the name pagehide
at the Window
object of the
Document
, but with its target
set to the
Document
object (and the currentTarget
set to the Window
object), using the PageTransitionEvent
interface,
with the persisted
attribute initialized
to true if the Document
object's salvageable state is true, and false otherwise. This
event must not bubble, must not be cancelable, and has no default action.
Run any unloading document visibility change steps for Document
that
are defined by other applicable specifications.
This is specifically intended for use by the Page Visibility specification. [PAGEVIS]
Unload event: If the Document
's fired unload flag is
false, fire a simple event named unload
at the
Document
's Window
object.
Decrease the event loop's termination nesting level by one.
Release the storage mutex.
If any event listeners were triggered by the earlier unload event step, then set
the Document
object's salvageable state
to false and set the Document
's fired unload flag to true.
Run any unloading document cleanup steps for Document
that are
defined by this specification and other applicable specifications.
If this algorithm was invoked by another instance of the "unload a document" algorithm (i.e. by the steps below that invoke this algorithm for all descendant browsing contexts), then jump to the step labeled end.
Let descendants be the list of the descendant browsing
contexts of the Document
.
If descendants is not an empty list, then for each browsing context b in descendants run the following substeps:
Unload the active document of the browsing context b with the recycle parameter set to false.
If the salvageable state of the active document of the browsing context b is false, then set the salvageable state of this document to false also.
If both the Document
's salvageable state and recycle are
false, then the Document
's browsing context must discard the Document
.
End: Decrease the Document
's ignore-opens-during-unload
counter by one.
This specification defines the following unloading document cleanup steps. Other specifications can define more.
Make disappear any WebSocket
objects that were created by the WebSocket()
constructor from the
Document
's Window
object.
If this affected any WebSocket
objects, then set Document
's salvageable state to false.
If the Document
's salvageable
state is false, forcibly close any
EventSource
objects that whose constructor was invoked from the
Document
's Window
object.
If the Document
's salvageable
state is false, empty the Document
's Window
's list of active
timers.
interface BeforeUnloadEvent : Event { attribute DOMString returnValue; };
returnValue
[ = value ]Returns the current return value of the event (the message to show the user).
Can be set, to update the message.
There are no BeforeUnloadEvent
-specific initialization methods.
The returnValue
attribute
represents the message to show the user. When the event is created, the attribute must be set to
the empty string. On getting, it must return the last value it was set to. On setting, the
attribute must be set to the new value.
If a Document
is aborted, the user agent must
run the following steps:
Abort the active
documents of every child browsing context. If this results in any of those
Document
objects having their salvageable state set to false, then set this
Document
's salvageable state to false
also.
Cancel any instances of the fetch algorithm in the context of
this Document
, discarding any tasks queued for them, and discarding any further data received from the
network for them. If this resulted in any instances of the fetch
algorithm being canceled or any queued tasks or any network data getting discarded, then set the
Document
's salvageable state to
false.
If the Document
has an active parser, then abort that parser and set the Document
's salvageable state to false.
User agents may allow users to explicitly invoke the abort a
document algorithm for a Document
. If the user does so, then, if that
Document
is an active document, the user agent should queue a
task to fire a simple event named abort
at
that Document
's Window
object before invoking the abort algorithm.
This section is non-normative.
In order to enable users to continue interacting with Web applications and documents even when their network connection is unavailable — for instance, because they are traveling outside of their ISP's coverage area — authors can provide a manifest which lists the files that are needed for the Web application to work offline and which causes the user's browser to keep a copy of the files for use offline.
To illustrate this, consider a simple clock applet consisting of an HTML page "clock.html
", a CSS style sheet "clock.css
", and a JavaScript
script "clock.js
".
Before adding the manifest, these three files might look like this:
EXAMPLE offline/clock/clock1.html
EXAMPLE offline/clock/clock1.css
EXAMPLE offline/clock/clock1.js
If the user tries to open the "clock.html
" page while offline, though,
the user agent (unless it happens to have it still in the local cache) will fail with an
error.
The author can instead provide a manifest of the three files, say "clock.appcache
":
EXAMPLE offline/clock/clock2.appcache
With a small change to the HTML file, the manifest (served as text/cache-manifest
)
is linked to the application:
EXAMPLE offline/clock/clock2.html
Now, if the user goes to the page, the browser will cache the files and make them available even when the user is offline.
Authors are encouraged to include the main page in the manifest also, but in practice the page that referenced the manifest is automatically cached even if it isn't explicitly mentioned.
With the exception of "no-store" directive, HTTP cache headers and restrictions on
caching pages served over TLS (encrypted, using https:
) are overridden by
manifests. Thus, pages will not expire from an application cache before the user agent has updated
it, and even applications served over TLS can be made to work offline.
This section is non-normative.
The application cache feature works best if the application logic is separate from the
application and user data, with the logic (markup, scripts, style sheets, images, etc) listed in
the manifest and stored in the application cache, with a finite number of static HTML pages for
the application, and with the application and user data stored in Web Storage or a client-side
Indexed Database, updated dynamically using Web Sockets, XMLHttpRequest
, server-sent
events, or some other similar mechanism.
This model results in a fast experience for the user: the application immediately loads, and fresh data is obtained as fast as the network will allow it (possibly while stale data shows).
Legacy applications, however, tend to be designed so that the user data and the logic are mixed together in the HTML, with each operation resulting in a new HTML page from the server.
For example, consider a news application. The typical architecture of such an application, when not using the application cache feature, is that the user fetches the main page, and the server returns a dynamically-generated page with the current headlines and the user interface logic mixed together.
A news application designed for the application cache feature, however, would instead have the
main page just consist of the logic, and would then have the main page fetch the data separately
from the server, e.g. using XMLHttpRequest
.
The mixed-content model does not work well with the application cache feature: since the content is cached, it would result in the user always seeing the stale data from the previous time the cache was updated.
While there is no way to make the legacy model work as fast as the separated model, it
can at least be retrofitted for offline use using the prefer-online application cache mode. To do so, list all the static
resources used by the HTML page you want to have work offline in an application cache manifest, use the manifest
attribute to select that manifest from the HTML file,
and then add the following line at the bottom of the manifest:
SETTINGS: prefer-online NETWORK: *
This causes the application cache to only be used for master entries when the user is offline, and causes the application cache to be used as an atomic HTTP cache (essentially pinning resources listed in the manifest), while allowing all resources not listed in the manifest to be accessed normally when the user is online.
This section is non-normative.
When the user visits a page that declares a manifest, the browser will try to update the cache. It does this by fetching a copy of the manifest and, if the manifest has changed since the user agent last saw it, redownloading all the resources it mentions and caching them anew.
As this is going on, a number of events get fired on the ApplicationCache
object
to keep the script updated as to the state of the cache update, so that the user can be notified
appropriately. The events are as follows:
Event name | Interface | Fired when... | Next events |
---|---|---|---|
checking
| Event
| The user agent is checking for an update, or attempting to download the manifest for the first time. This is always the first event in the sequence. | noupdate , downloading , obsolete , error
|
noupdate
| Event
| The manifest hadn't changed. | Last event in sequence. |
downloading
| Event
| The user agent has found an update and is fetching it, or is downloading the resources listed by the manifest for the first time. | progress , error , cached , updateready
|
progress
| ProgressEvent
| The user agent is downloading resources listed by the manifest.
The event object's total attribute returns the total number of files to be downloaded.
The event object's loaded attribute returns the number of files processed so far.
| progress , error , cached , updateready
|
cached
| Event
| The resources listed in the manifest have been downloaded, and the application is now cached. | Last event in sequence. |
updateready
| Event
| The resources listed in the manifest have been newly redownloaded, and the script can use
swapCache() to switch to the new cache.
| Last event in sequence. |
obsolete
| Event
| The manifest was found to have become a 404 or 410 page, so the application cache is being deleted. | Last event in sequence. |
error
| Event
| The manifest was a 404 or 410 page, so the attempt to cache the application has been aborted. | Last event in sequence. |
The manifest hadn't changed, but the page referencing the manifest failed to download properly. | |||
A fatal error occurred while fetching the resources listed in the manifest. | |||
The manifest changed while the update was being run. | The user agent will try fetching the files again momentarily. |
These events are cancelable; their default action is for the user agent to show download progress information. If the page shows its own update UI, canceling the events will prevent the user agent from showing redundant progress information.
An application cache is a set of cached resources consisting of:
One or more resources (including their out-of-band metadata, such as HTTP headers, if any), identified by URLs, each falling into one (or more) of the following categories:
These are documents that were added to the cache because a browsing
context was navigated to that document and the document
indicated that this was its cache, using the manifest
attribute.
This is the resource corresponding to the URL that was given in a master
entry's html
element's manifest
attribute.
The manifest is fetched and processed during the application cache download
process. All the master entries have the
same origin as the manifest.
These are the resources that were listed in the cache's manifest in an explicit section.
These are the resources that were listed in the cache's manifest in a fallback section.
Explicit entries and Fallback entries can be marked as foreign, which means that they have a manifest
attribute but that it doesn't point at this cache's
manifest.
A URL in the list can be flagged with multiple different types, and thus an entry can end up being categorized as multiple entries. For example, an entry can be a manifest entry and an explicit entry at the same time, if the manifest is listed within the manifest.
Zero or more fallback namespaces, each of which is mapped to a fallback entry.
These are URLs used as prefix match patterns for resources that are to be fetched from the network if possible, or to be replaced by the corresponding fallback entry if not. Each namespace URL has the same origin as the manifest.
Zero or more URLs that form the online whitelist namespaces.
These are used as prefix match patterns, and declare URLs for which the user agent will ignore the application cache, instead fetching them normally (i.e. from the network or local HTTP cache as appropriate).
An online whitelist wildcard flag, which is either open or blocking.
The open state indicates that any URL not listed as cached is to be implicitly treated as being in the online whitelist namespaces; the blocking state indicates that URLs not listed explicitly in the manifest are to be treated as unavailable.
A cache mode flag, which is either in the fast state or the prefer-online state.
Each application cache has a completeness flag, which is either complete or incomplete.
An application cache group is a group of application caches, identified by the absolute URL of a resource manifest which is used to populate the caches in the group.
An application cache is newer than another if it was created after the other (in other words, application caches in an application cache group have a chronological order).
Only the newest application cache in an application cache group can have its completeness flag set to incomplete; the others are always all complete.
Each application cache group has an update status, which is one of the following: idle, checking, downloading.
A relevant application cache is an application cache that is the newest in its group to be complete.
Each application cache group has a list of pending master entries. Each entry in this
list consists of a resource and a corresponding Document
object. It is used during
the application cache download process to ensure that new master entries are cached
even if the application cache download process was already running for their
application cache group when they were loaded.
An application cache group can be marked as obsolete, meaning that it must be ignored when looking at what application cache groups exist.
A cache host is a Document
or a SharedWorkerGlobalScope
object. A cache host can be associated with an application cache.
[WEBWORKERS]
A Document
initially is not associated with an application cache, but
can become associated with one early during the page load process, when steps in the parser and in the navigation
sections cause cache selection to occur.
A SharedWorkerGlobalScope
can be associated with an application cache
when it is created.
[WEBWORKERS]
Each cache host has an associated ApplicationCache
object.
Multiple application caches in different application cache groups can contain the same resource, e.g. if the manifests all reference that resource. If the user agent is to select an application cache from a list of relevant application caches that contain a resource, the user agent must use the application cache that the user most likely wants to see the resource from, taking into account the following:
A URL matches a fallback namespace if there exists a relevant application cache whose manifest's URL has the same origin as the URL in question, and that has a fallback namespace that is a prefix match for the URL being examined. If multiple fallback namespaces match the same URL, the longest one is the one that matches. A URL looking for a fallback namespace can match more than one application cache at a time, but only matches one namespace in each cache.
If a manifest http://example.com/app1/manifest
declares that http://example.com/resources/images
is a fallback namespace, and the user
navigates to HTTP://EXAMPLE.COM:80/resources/images/cat.png
, then the user
agent will decide that the application cache identified by http://example.com/app1/manifest
contains a namespace with a match for that
URL.
This section is non-normative.
This example manifest requires two images and a style sheet to be cached and whitelists a CGI script.
CACHE MANIFEST # the above line is required # this is a comment # there can be as many of these anywhere in the file # they are all ignored # comments can have spaces before them # but must be alone on the line # blank lines are ignored too # these are files that need to be cached they can either be listed # first, or a "CACHE:" header could be put before them, as is done # lower down. images/sound-icon.png images/background.png # note that each file has to be put on its own line # here is a file for the online whitelist -- it isn't cached, and # references to this file will bypass the cache, always hitting the # network (or trying to, if the user is offline). NETWORK: comm.cgi # here is another set of files to cache, this time just the CSS file. CACHE: style/default.css
It could equally well be written as follows:
CACHE MANIFEST NETWORK: comm.cgi CACHE: style/default.css images/sound-icon.png images/background.png
Offline application cache manifests can use absolute paths or even absolute URLs:
CACHE MANIFEST /main/home /main/app.js /settings/home /settings/app.js http://img.example.com/logo.png http://img.example.com/check.png http://img.example.com/cross.png
The following manifest defines a catch-all error page that is displayed for any page on the site while the user is offline. It also specifies that the online whitelist wildcard flag is open, meaning that accesses to resources on other sites will not be blocked. (Resources on the same site are already not blocked because of the catch-all fallback namespace.)
So long as all pages on the site reference this manifest, they will get cached locally as they are fetched, so that subsequent hits to the same page will load the page immediately from the cache. Until the manifest is changed, those pages will not be fetched from the server again. When the manifest changes, then all the files will be redownloaded.
Subresources, such as style sheets, images, etc, would only be cached using the regular HTTP caching semantics, however.
CACHE MANIFEST FALLBACK: / /offline.html NETWORK: *
Manifests must be served using the text/cache-manifest
MIME type. All
resources served using the text/cache-manifest
MIME type must follow the
syntax of application cache manifests, as described in this section.
An application cache manifest is a text file, whose text is encoded using UTF-8. Data in application cache manifests is line-based. Newlines must be represented by "LF" (U+000A) characters, "CR" (U+000D) characters, or "CR" (U+000D) "LF" (U+000A) pairs. [RFC3629]
This is a willful violation of RFC 2046, which requires all text/*
types to only allow CRLF line breaks. This requirement, however, is
outdated; the use of CR, LF, and CRLF line breaks is commonly supported and indeed sometimes CRLF
is not supported by text editors. [RFC2046]
The first line of an application cache manifest must consist of the string "CACHE", a single U+0020 SPACE character, the string "MANIFEST", and either a U+0020 SPACE character, a "tab" (U+0009) character, a "LF" (U+000A) character, or a "CR" (U+000D) character. The first line may optionally be preceded by a "BOM" (U+FEFF) character. If any other text is found on the first line, it is ignored.
Subsequent lines, if any, must all be one of the following:
Blank lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters only.
Comment lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters, followed by a single "#" (U+0023) character, followed by zero or more characters other than "LF" (U+000A) and "CR" (U+000D) characters.
Comments must be on a line on their own. If they were to be included on a line with a URL, the "#" would be mistaken for part of a fragment identifier.
Section headers change the current section. There are four possible section headers:
CACHE:
FALLBACK:
NETWORK:
SETTINGS:
Section header lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters, followed by one of the names above (including the ":)" (U+003A) character followed by zero or more U+0020 SPACE and "tab" (U+0009) characters.
Ironically, by default, the current section is the explicit section.
The format that data lines must take depends on the current section.
When the current section is the explicit section, data lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters, a valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and "tab" (U+0009) characters.
When the current section is the fallback section, data lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters, a valid URL identifying a resource other than the manifest itself, one or more U+0020 SPACE and "tab" (U+0009) characters, another valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and "tab" (U+0009) characters.
When the current section is the online whitelist section, data lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters, either a single "*" (U+002A) character or a valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and "tab" (U+0009) characters.
When the current section is the settings section, data lines must consist of zero or more U+0020 SPACE and "tab" (U+0009) characters, a setting, and then zero or more U+0020 SPACE and "tab" (U+0009) characters.
Currently only one setting is defined:
prefer-online
". It sets the cache mode to prefer-online. (The cache mode defaults to fast.)Within a settings section, each setting must occur no more than once.
Manifests may contain sections more than once. Sections may be empty.
URLs that are to be fallback pages associated with fallback namespaces, and those namespaces themselves, must be given in fallback sections, with the namespace being the first URL of the data line, and the corresponding fallback page being the second URL. All the other pages to be cached must be listed in explicit sections.
Fallback namespaces and fallback entries must have the same origin as the manifest itself.
A fallback namespace must not be listed more than once.
Namespaces that the user agent is to put into the online whitelist must all be specified in online whitelist sections. (This is needed for any URL that the page is intending to use to communicate back to the server.) To specify that all URLs are automatically whitelisted in this way, a "*" (U+002A) character may be specified as one of the URLs.
Authors should not include namespaces in the online whitelist for which another namespace in the online whitelist is a prefix match.
Relative URLs must be given relative to the manifest's own URL. All URLs in the manifest must have the same scheme as the manifest itself (either explicitly or implicitly, through the use of relative URLs). [URL]
URLs in manifests must not have fragment identifiers (i.e. the U+0023 NUMBER SIGN character isn't allowed in URLs in manifests).
Fallback namespaces and namespaces in the online whitelist are matched by prefix match.
When a user agent is to parse a manifest, it means that the user agent must run the following steps:
UTF-8 decode the byte stream corresponding with the manifest to be parsed.
The UTF-8 decode algorithm strips a leading BOM, if any.
Let base URL be the absolute URL representing the manifest.
Apply the URL parser steps to the base URL, so that the components from its parsed URL can be used by the subseqent steps of this algorithm.
Let explicit URLs be an initially empty list of absolute URLs for explicit entries.
Let fallback URLs be an initially empty mapping of fallback namespaces to absolute URLs for fallback entries.
Let online whitelist namespaces be an initially empty list of absolute URLs for an online whitelist.
Let online whitelist wildcard flag be blocking.
Let cache mode flag be fast.
Let input be the decoded text of the manifest's byte stream.
Let position be a pointer into input, initially pointing at the first character.
If the characters starting from position are "CACHE", followed by a U+0020 SPACE character, followed by "MANIFEST", then advance position to the next character after those. Otherwise, this isn't a cache manifest; abort this algorithm with a failure while checking for the magic signature.
If the character at position is neither a U+0020 SPACE character, a "tab" (U+0009) character, "LF" (U+000A) character, nor a "CR" (U+000D) character, then this isn't a cache manifest; abort this algorithm with a failure while checking for the magic signature.
This is a cache manifest. The algorithm cannot fail beyond this point (though bogus lines can get ignored).
Collect a sequence of characters that are not "LF" (U+000A) or "CR" (U+000D) characters, and ignore those characters. (Extra text on the first line, after the signature, is ignored.)
Let mode be "explicit".
Start of line: If position is past the end of input, then jump to the last step. Otherwise, collect a sequence of characters that are "LF" (U+000A), "CR" (U+000D), U+0020 SPACE, or "tab" (U+0009) characters.
Now, collect a sequence of characters that are not "LF" (U+000A) or "CR" (U+000D) characters, and let the result be line.
Drop any trailing U+0020 SPACE and "tab" (U+0009) characters at the end of line.
If line is the empty string, then jump back to the step labeled start of line.
If the first character in line is a "#" (U+0023) character, then jump back to the step labeled start of line.
If line equals "CACHE:" (the word "CACHE" followed by a ":)" (U+003A) character, then set mode to "explicit" and jump back to the step labeled start of line.
If line equals "FALLBACK:" (the word "FALLBACK" followed by a ":)" (U+003A) character, then set mode to "fallback" and jump back to the step labeled start of line.
If line equals "NETWORK:" (the word "NETWORK" followed by a ":)" (U+003A) character, then set mode to "online whitelist" and jump back to the step labeled start of line.
If line equals "SETTINGS:" (the word "SETTINGS" followed by a ":)" (U+003A) character, then set mode to "settings" and jump back to the step labeled start of line.
If line ends with a ":" (U+003A) character, then set mode to "unknown" and jump back to the step labeled start of line.
This is either a data line or it is syntactically incorrect.
Let position be a pointer into line, initially pointing at the start of the string.
Let tokens be a list of strings, initially empty.
While position doesn't point past the end of line:
Let current token be an empty string.
While position doesn't point past the end of line and the character at position is neither a U+0020 SPACE nor a "tab" (U+0009) character, add the character at position to current token and advance position to the next character in input.
Add current token to the tokens list.
While position doesn't point past the end of line and the character at position is either a U+0020 SPACE or a "tab" (U+0009) character, advance position to the next character in input.
Process tokens as follows:
Resolve the first item in tokens, relative to base URL, with the URL character encoding set to UTF-8; ignore the rest.
If this fails, then jump back to the step labeled start of line.
If the resulting parsed URL has a different scheme component than base URL (the manifest's URL), then jump back to the step labeled start of line.
Let new URL be the result of applying the URL serializer algorithm to the resulting parsed URL, with the exclude fragment flag set.
Add new URL to the explicit URLs.
Let part one be the first token in tokens, and let part two be the second token in tokens.
Resolve part one and part two, relative to base URL, with the URL character encoding set to UTF-8.
If either fails, then jump back to the step labeled start of line.
If the absolute URL corresponding to either part one or part two does not have the same origin as the manifest's URL, then jump back to the step labeled start of line.
Let part one be the result of applying the URL serializer algorithm to the first resulting parsed URL, with the exclude fragment flag set.
Let part two be the result of applying the URL serializer algorithm to the second resulting parsed URL, with the exclude fragment flag set.
If part one is already in the fallback URLs mapping as a fallback namespace, then jump back to the step labeled start of line.
Otherwise, add part one to the fallback URLs mapping as a fallback namespace, mapped to part two as the fallback entry.
If the first item in tokens is a "*" (U+002A) character, then set online whitelist wildcard flag to open and jump back to the step labeled start of line.
Otherwise, resolve the first item in tokens, relative to base URL, with the URL character encoding set to UTF-8; ignore the rest.
If this fails, then jump back to the step labeled start of line.
If the resulting parsed URL has a different scheme component than base URL (the manifest's URL), then jump back to the step labeled start of line.
Let new URL be the result of applying the URL serializer algorithm to the resulting parsed URL, with the exclude fragment flag set.
Add new URL to the online whitelist namespaces.
If tokens contains a single token, and that token is a
case-sensitive match for the string "prefer-online
", then
set cache mode flag to prefer-online and jump back to the
step labeled start of line.
Otherwise, the line is an unsupported setting: do nothing; the line is ignored.
Do nothing. The line is ignored.
Jump back to the step labeled start of line. (That step jumps to the next, and last, step when the end of the file is reached.)
Return the explicit URLs list, the fallback URLs mapping, the online whitelist namespaces, the online whitelist wildcard flag, and the cache mode flag.
The resource that declares the manifest (with the manifest
attribute) will always get taken from the cache,
whether it is listed in the cache or not, even if it is listed in an online whitelist namespace.
If a resource is listed in the explicit section or as a fallback entry in the fallback section, the resource will always be taken from the cache, regardless of any other matching entries in the fallback namespaces or online whitelist namespaces.
When a fallback namespace and an online whitelist namespace overlap, the online whitelist namespace has priority.
The online whitelist wildcard flag is applied last, only for URLs that match neither the online whitelist namespace nor the fallback namespace and that are not listed in the explicit section.
When the user agent is required (by other parts of this specification) to start the application cache download process for an absolute URL purported to identify a manifest, or for an application cache group, potentially given a particular cache host, and potentially given a master resource, the user agent must run the steps below. These steps are always run asynchronously, in parallel with the event loop tasks.
Some of these steps have requirements that only apply if the user agent shows caching
progress. Support for this is optional. Caching progress UI could consist of a progress bar
or message panel in the user agent's interface, or an overlay, or something else. Certain events
fired during the application cache download process allow the script to override the
display of such an interface. (Such events are delayed until after the load
event has fired.)
The goal of this is to allow Web applications to provide more
seamless update mechanisms, hiding from the user the mechanics of the application cache mechanism.
User agents may display user interfaces independent of this, but are encouraged to not show
prominent update progress notifications for applications that cancel the relevant events.
The application cache download process steps are as follows:
Optionally, wait until the permission to start the application cache download process has been obtained from the user and until the user agent is confident that the network is available. This could include doing nothing until the user explicitly opts-in to caching the site, or could involve prompting the user for permission. The algorithm might never get past this point. (This step is particularly intended to be used by user agents running on severely space-constrained devices or in highly privacy-sensitive environments).
Atomically, so as to avoid race conditions, perform the following substeps:
Pick the appropriate substeps:
Let manifest URL be that absolute URL.
If there is no application cache group identified by manifest URL, then create a new application cache group identified by manifest URL. Initially, it has no application caches. One will be created later in this algorithm.
Let manifest URL be the absolute URL of the manifest used to identify the application cache group to be updated.
If that application cache group is obsolete, then abort this instance of the application cache download process. This can happen if another instance of this algorithm found the manifest to be 404 or 410 while this algorithm was waiting in the first step above.
Let cache group be the application cache group identified by manifest URL.
If these steps were invoked with a master
resource, then add the resource, along with the resource's Document
, to cache group's list of pending
master entries.
If these steps were invoked with a cache host, and the status of cache group is
checking or downloading, then queue a post-load task to fire a
simple event named checking
that is
cancelable at the ApplicationCache
singleton of that cache host. The
default action of this event must be, if the user agent shows caching progress,
the display of some sort of user interface indicating to the user that the user agent is
checking to see if it can download the application.
If these steps were invoked with a cache host, and the status of cache group is
downloading, then also queue a post-load task to fire a simple
event named downloading
that is
cancelable at the ApplicationCache
singleton of that cache host. The
default action of this event must be, if the user agent shows caching progress,
the display of some sort of user interface indicating to the user the application is being
downloaded.
If the status of the cache group is either checking or downloading, then abort this instance of the application cache download process, as an update is already in progress.
Set the status of cache group to checking.
For each cache host associated with an application cache in
cache group, queue a post-load task to fire a simple
event that is cancelable named checking
at
the ApplicationCache
singleton of the cache host. The default action
of these events must be, if the user agent shows caching progress, the display of
some sort of user interface indicating to the user that the user agent is checking for the
availability of updates.
The remainder of the steps run asynchronously.
If cache group already has an application cache in it, then this is an upgrade attempt. Otherwise, this is a cache attempt.
If this is a cache attempt, then this
algorithm was invoked with a cache host; queue a post-load task to
fire a simple event named checking
that
is cancelable at the ApplicationCache
singleton of that cache host. The
default action of this event must be, if the user agent shows caching progress, the
display of some sort of user interface indicating to the user that the user agent is checking for
the availability of updates.
Fetching the manifest: Fetch the resource from manifest URL with the synchronous flag set, and let manifest be that resource. HTTP caching semantics should be honored for this request.
Parse manifest according to the rules for parsing manifests, obtaining a list of explicit entries, fallback entries and the fallback namespaces that map to them, entries for the online whitelist, and values for the online whitelist wildcard flag and the cache mode flag.
The MIME type of the resource is ignored — it is assumed to
be text/cache-manifest
. In the future, if new manifest formats are supported, the
different types will probably be distinguished on the basis of the file signatures (for the
current format, that is the "CACHE MANIFEST
" string at the top of the
file).
If fetching the manifest fails due to a 404 or 410 response or equivalent, then run these substeps:
Mark cache group as obsolete. This cache group no
longer exists for any purpose other than the processing of Document
objects
already associated with an application cache in the cache
group.
Let task list be an empty list of tasks.
For each cache host associated with an application cache in
cache group, create a task to fire
a simple event named obsolete
that is
cancelable at the ApplicationCache
singleton of the cache host, and
append it to task list. The default action of these events must be, if the
user agent shows caching progress, the display of some sort of user interface
indicating to the user that the application is no longer available for offline use.
For each entry in cache group's list of pending master entries, create a task to fire a simple event that is cancelable named
error
(not obsolete
!) at the ApplicationCache
singleton of the Document
for this entry, if there still is one, and append it to
task list. The default action of this event must be, if the user agent
shows caching progress, the display of some sort of user interface indicating to
the user that the user agent failed to save the application for offline use.
If cache group has an application cache whose completeness flag is incomplete, then discard that application cache.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Let the status of cache group be idle.
For each task in task list, queue that task as a post-load task.
Abort the application cache download process.
Otherwise, if fetching the manifest fails in some other way (e.g. the server returns another 4xx or 5xx response or equivalent, or there is a DNS error, or the connection times out, or the user cancels the download, or the parser for manifests fails when checking the magic signature), or if the server returned a redirect, then run the cache failure steps. [HTTP]
If this is an upgrade attempt and the newly downloaded manifest is byte-for-byte identical to the manifest found in the newest application cache in cache group, or the server reported it as "304 Not Modified" or equivalent, then run these substeps:
Let cache be the newest application cache in cache group.
Let task list be an empty list of tasks.
For each entry in cache group's list of pending master entries, wait for the resource for this entry to have either completely downloaded or failed.
If the download failed (e.g. the server returns a 4xx or 5xx response or equivalent, or there is a DNS error, the
connection times out, or the user cancels the download), or if the resource is labeled with
the "no-store" cache directive, then create a task to
fire a simple event that is cancelable named error
at the ApplicationCache
singleton of
the Document
for this entry, if there still is one, and append it to task list. The default action of this event must be, if the user agent
shows caching progress, the display of some sort of user interface indicating to
the user that the user agent failed to save the application for offline use.
Otherwise, associate the Document
for this entry with cache; store the resource for this entry in cache, if it
isn't already there, and categorize its entry as a master entry. If applying the URL parser
algorithm to the resource's URL results in a parsed URL that has a
non-null fragment component, the URL
used for the entry in cache must instead be the absolute URL
obtained from applying the URL serializer
algorithm to the parsed URL with the exclude fragment flag set
(application caches never include fragment identifiers).
For each cache host associated with an application cache in
cache group, create a task to fire
a simple event that is cancelable named noupdate
at the ApplicationCache
singleton
of the cache host, and append it to task list. The default
action of these events must be, if the user agent shows caching progress, the
display of some sort of user interface indicating to the user that the application is up to
date.
Empty cache group's list of pending master entries.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Let the status of cache group be idle.
For each task in task list, queue that task as a post-load task.
Abort the application cache download process.
Let new cache be a newly created application cache in cache group. Set its completeness flag to incomplete.
For each entry in cache group's list of pending master entries, associate the
Document
for this entry with new cache.
Set the status of cache group to downloading.
For each cache host associated with an application cache in cache group, queue a post-load task to fire a simple
event that is cancelable named downloading
at the ApplicationCache
singleton of the cache host. The default action
of these events must be, if the user agent shows caching progress, the display of
some sort of user interface indicating to the user that a new version is being
downloaded.
Let file list be an empty list of URLs with flags.
Add all the URLs in the list of explicit entries obtained by parsing manifest to file list, each flagged with "explicit entry".
Add all the URLs in the list of fallback entries obtained by parsing manifest to file list, each flagged with "fallback entry".
If this is an upgrade attempt, then add all the URLs of master entries in the newest application cache in cache group whose completeness flag is complete to file list, each flagged with "master entry".
If any URL is in file list more than once, then merge the entries into one entry for that URL, that entry having all the flags that the original entries had.
For each URL in file list, run the following steps. These steps may be
run in parallel for two or more of the URLs at a time. If, while running these steps, the
ApplicationCache
object's abort()
method
sends a signal to this instance of the application
cache download process algorithm, then run the cache failure steps
instead.
If the resource URL being processed was flagged as neither an "explicit entry" nor or a "fallback entry", then the user agent may skip this URL.
This is intended to allow user agents to expire resources not listed in the manifest from the cache. Generally, implementors are urged to use an approach that expires lesser-used resources first.
For each cache host associated with an application cache in
cache group, queue a post-load task to fire a trusted
event with the name progress
, which does not
bubble, which is cancelable, and which uses the ProgressEvent
interface, at the
ApplicationCache
singleton of the cache host. The lengthComputable
attribute must be set to
true, the total
attribute must be set to the
number of files in file list, and the loaded
attribute must be set to the number of files in
file list that have been either downloaded or skipped so far. The default
action of these events must be, if the user agent shows caching progress, the
display of some sort of user interface indicating to the user that a file is being downloaded
in preparation for updating the application. [XHR]
Fetch the resource, from the origin of the URL manifest URL, with the synchronous flag set and the manual redirect flag set. If this is an upgrade attempt, then use the newest application cache in cache group as an HTTP cache, and honor HTTP caching semantics (such as expiration, ETags, and so forth) with respect to that cache. User agents may also have other caches in place that are also honored.
If the resource in question is already being downloaded for other reasons then the existing download process can sometimes be used for the purposes of this step, as defined by the fetching algorithm.
An example of a resource that might already be being downloaded is a large
image on a Web page that is being seen for the first time. The image would get downloaded to
satisfy the img
element on the page, as well as being listed in the cache
manifest. According to the rules for fetching that image only need
be downloaded once, and it can be used both for the cache and for the rendered Web page.
If the previous step fails (e.g. the server returns a 4xx or 5xx response or equivalent, or there is a DNS error, or the connection times out, or the user cancels the download), or if the server returned a redirect, or if the resource is labeled with the "no-store" cache directive, then run the first appropriate step from the following list: [HTTP]
If these steps are being run in parallel for any other URLs in file list, then abort these steps for those other URLs. Run the cache failure steps.
Redirects are fatal because they are either indicative of a network problem (e.g. a captive portal); or would allow resources to be added to the cache under URLs that differ from any URL that the networking model will allow access to, leaving orphan entries; or would allow resources to be stored under URLs different than their true URLs. All of these situations are bad.
Skip this resource. It is dropped from the cache.
Copy the resource and its metadata from the newest application cache in cache group whose completeness flag is complete, and act as if that was the fetched resource, ignoring the resource obtained from the network.
User agents may warn the user of these errors as an aid to development.
These rules make errors for resources listed in the manifest fatal, while making it possible for other resources to be removed from caches when they are removed from the server, without errors, and making non-manifest resources survive server-side errors.
Except for the "no-store" directive, HTTP caching rules that would cause a file to be expired or otherwise not cached are ignored for the purposes of the application cache download process.
Otherwise, the fetching succeeded. Store the resource in the new cache.
If the user agent is not able to store the resource (e.g. because of quota restrictions), the user agent may prompt the user or try to resolve the problem in some other manner (e.g. automatically pruning content in other caches). If the problem cannot be resolved, the user agent must run the cache failure steps.
If the URL being processed was flagged as an "explicit entry" in file list, then categorize the entry as an explicit entry.
If the URL being processed was flagged as a "fallback entry" in file list, then categorize the entry as a fallback entry.
If the URL being processed was flagged as an "master entry" in file list, then categorize the entry as a master entry.
As an optimization, if the resource is an HTML or XML file whose root element is an
html
element with a manifest
attribute
whose value doesn't match the manifest URL of the application cache being processed, then the
user agent should mark the entry as being foreign.
For each cache host associated with an application cache in cache group, queue a post-load task to fire a trusted
event with the name progress
, which does not bubble,
which is cancelable, and which uses the ProgressEvent
interface, at the
ApplicationCache
singleton of the cache host. The lengthComputable
attribute must be set to
true, the total
and the loaded
attributes must be set to the number of files in
file list. The default action of these events must be, if the user agent
shows caching progress, the display of some sort of user interface indicating to the
user that all the files have been downloaded. [XHR]
Store the list of fallback namespaces, and the URLs of the fallback entries that they map to, in new cache.
Store the URLs that form the new online whitelist in new cache.
Store the value of the new online whitelist wildcard flag in new cache.
Store the value of the new cache mode flag in new cache.
For each entry in cache group's list of pending master entries, wait for the resource for this entry to have either completely downloaded or failed.
If the download failed (e.g. the server returns a 4xx or 5xx response or equivalent, or there is a DNS error, the connection times out, or the user cancels the download), or if the resource is labeled with the "no-store" cache directive, then run these substeps:
Unassociate the Document
for this entry from new
cache.
Queue a post-load task to fire a simple event that is
cancelable named error
at the
ApplicationCache
singleton of the Document
for this entry, if there
still is one. The default action of this event must be, if the user agent shows caching
progress, the display of some sort of user interface indicating to the user that the
user agent failed to save the application for offline use.
If this is a cache attempt and this entry is the last entry in cache group's list of pending master entries, then run these further substeps:
Discard cache group and its only application cache, new cache.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Abort the application cache download process.
Otherwise, remove this entry from cache group's list of pending master entries.
Otherwise, store the resource for this entry in new cache, if it isn't already there, and categorize its entry as a master entry.
Fetch the resource from manifest URL again, with the synchronous flag set, and let second manifest be that resource. HTTP caching semantics should again be honored for this request.
Since caching can be honored, authors are encouraged to avoid setting the cache headers on the manifest in such a way that the user agent would simply not contact the network for this second request; otherwise, the user agent would not notice if the cache had changed during the cache update process.
If the previous step failed for any reason, or if the fetching attempt involved a redirect, or if second manifest and manifest are not byte-for-byte identical, then schedule a rerun of the entire algorithm with the same parameters after a short delay, and run the cache failure steps.
Otherwise, store manifest in new cache, if it's not there already, and categorize its entry as the manifest.
Set the completeness flag of new cache to complete.
Let task list be an empty list of tasks.
If this is a cache attempt, then for each
cache host associated with an application cache in cache
group, create a task to fire a simple event
that is cancelable named cached
at the
ApplicationCache
singleton of the cache host, and append it to task list. The default action of these events must be, if the user agent
shows caching progress, the display of some sort of user interface indicating to
the user that the application has been cached and that they can now use it offline.
Otherwise, it is an upgrade attempt. For each
cache host associated with an application cache in cache
group, create a task to fire a simple event
that is cancelable named updateready
at the
ApplicationCache
singleton of the cache host, and append it to task list. The default action of these events must be, if the user agent
shows caching progress, the display of some sort of user interface indicating to
the user that a new version is available and that they can activate it by reloading the
page.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Set the update status of cache group to idle.
For each task in task list, queue that task as a post-load task.
The cache failure steps are as follows:
Let task list be an empty list of tasks.
For each entry in cache group's list of pending master entries, run the following further substeps. These steps may be run in parallel for two or more entries at a time.
Wait for the resource for this entry to have either completely downloaded or failed.
Unassociate the Document
for this entry from its application
cache, if it has one.
Create a task to fire a simple event that
is cancelable named error
at the
ApplicationCache
singleton of the Document
for this entry, if there
still is one, and append it to task list. The default action of these
events must be, if the user agent shows caching progress, the display of some sort
of user interface indicating to the user that the user agent failed to save the application for
offline use.
For each cache host still associated with an application cache
in cache group, create a task to fire
a simple event that is cancelable named error
at
the ApplicationCache
singleton of the cache host, and append it to task list. The default action of these events must be, if the user agent
shows caching progress, the display of some sort of user interface indicating to the
user that the user agent failed to save the application for offline use.
Empty cache group's list of pending master entries.
If cache group has an application cache whose completeness flag is incomplete, then discard that application cache.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Let the status of cache group be idle.
If this was a cache attempt, discard cache group altogether.
For each task in task list, queue that task as a post-load task.
Abort the application cache download process.
Attempts to fetch resources as part of the application cache download process may be done with cache-defeating semantics, to avoid problems with stale or inconsistent intermediary caches.
User agents may invoke the application cache download process, in the background, for any application cache group, at any time (with no cache host). This allows user agents to keep caches primed and to update caches even before the user visits a site.
Each Document
has a list of pending application cache download process
tasks that is used to delay events fired by the algorithm above until the document's load
event has fired. When the Document
is created, the
list must be empty.
When the steps above say to queue a post-load task task, where
task is a task that dispatches an event on a
target ApplicationCache
object target, the user agent must run
the appropriate steps from the following list:
Document
is
ready for post-load tasksQueue the task task.
Add task to target's Document
's list
of pending application cache download process tasks.
The task source for these tasks is the networking task source.
When the application cache selection algorithm
algorithm is invoked with a Document
document and optionally a
manifest URL manifest URL, the user agent must run the first
applicable set of steps from the following list:
Mark the entry for the resource from which document was taken in the application cache from which it was loaded as foreign.
Restart the current navigation from the top of the navigation algorithm, undoing any changes that were made as part of the initial load (changes can be avoided by ensuring that the step to update the session history with the new page is only ever completed after this application cache selection algorithm is run, though this is not required).
The navigation will not result in the same resource being loaded, because "foreign" entries are never picked during navigation.
User agents may notify the user of the inconsistency between the cache manifest and the document's own metadata, to aid in application development.
Associate document with the application cache from which it was loaded. Invoke, in the background, the application cache download process for that application cache's application cache group, with document as the cache host.
Invoke, in the background, the application cache download process for manifest URL, with document as the cache host and with the resource from which document was parsed as the master resource.
If there are relevant application caches that are identified by a URL with the same origin as the URL of document, and that have this URL as one of their entries, excluding entries marked as foreign, then the user agent should use the most appropriate application cache of those that match as an HTTP cache for any subresource loads. User agents may also have other caches in place that are also honored.
The Document
is not associated with any application cache.
If there was a manifest URL, the user agent may report to the user that it was ignored, to aid in application development.
When a cache host is associated with an application cache whose completeness flag is complete, any and all loads for resources related to that cache host other than those for child browsing contexts must go through the following steps instead of immediately invoking the mechanisms appropriate to that resource's scheme:
If the resource is not to be fetched using the HTTP GET mechanism or equivalent, or if applying the URL parser algorithm to both its URL and the application cache's manifest's URL results in two parsed URLs with different scheme components, then fetch the resource normally and abort these steps.
If the resource's URL is a master entry, the manifest, an explicit entry, or a fallback entry in the application cache, then get the resource from the cache (instead of fetching it), and abort these steps.
If there is an entry in the application cache's online whitelist that has the same origin as the resource's URL and that is a prefix match for the resource's URL, then fetch the resource normally and abort these steps.
If the resource's URL has the same origin as the manifest's URL, and there is a fallback namespace f in the application cache that is a prefix match for the resource's URL, then:
Fetch the resource normally. If this results in a redirect to a resource with another origin (indicative of a captive portal), or a 4xx or 5xx status code or equivalent, or if there were network errors (but not if the user canceled the download), then instead get, from the cache, the resource of the fallback entry corresponding to the fallback namespace f. Abort these steps.
If the application cache's online whitelist wildcard flag is open, then fetch the resource normally and abort these steps.
Fail the resource load as if there had been a generic network error.
The above algorithm ensures that so long as the online whitelist wildcard flag is blocking, resources that are not present in the manifest will always fail to load (at least, after the application cache has been primed the first time), making the testing of offline applications simpler.
As a general rule, user agents should not expire application caches, except on request from the user, or after having been left unused for an extended period of time.
Application caches and cookies have similar implications with respect to privacy (e.g. if the site can identify the user when providing the cache, it can store data in the cache that can be used for cookie resurrection). Implementors are therefore encouraged to expose application caches in a manner related to HTTP cookies, allowing caches to be expunged together with cookies and other origin-specific data.
For example, a user agent could have a "delete site-specific data" feature that clears all cookies, application caches, local storage, databases, etc, from an origin all at once.
User agents should consider applying constraints on disk usage of application caches, and care should be taken to ensure that the restrictions cannot be easily worked around using subdomains.
User agents should allow users to see how much space each domain is using, and may offer the user the ability to delete specific application caches.
For predictability, quotas should be based on the uncompressed size of data stored.
How quotas are presented to the user is not defined by this specification. User agents are encouraged to provide features such as allowing a user to indicate that certain sites are trusted to use more than the default quota, e.g. by asynchronously presenting a user interface while a cache is being updated, or by having an explicit whitelist in the user agent's configuration interface.
interface ApplicationCache : EventTarget { // update status const unsigned short UNCACHED = 0; const unsigned short IDLE = 1; const unsigned short CHECKING = 2; const unsigned short DOWNLOADING = 3; const unsigned short UPDATEREADY = 4; const unsigned short OBSOLETE = 5; readonly attribute unsigned short status; // updates void update(); void abort(); void swapCache(); // events attribute EventHandler onchecking; attribute EventHandler onerror; attribute EventHandler onnoupdate; attribute EventHandler ondownloading; attribute EventHandler onprogress; attribute EventHandler onupdateready; attribute EventHandler oncached; attribute EventHandler onobsolete; };
applicationCache
(In a window.) Returns the ApplicationCache
object that applies to the
active document of that Window
.
applicationCache
(In a shared worker.) Returns the ApplicationCache
object that applies to the
current shared worker.
status
Returns the current status of the application cache, as given by the constants defined below.
update
()Invokes the application cache download process.
Throws an InvalidStateError
exception if there is no application cache to
update.
Calling this method is not usually necessary, as user agents will generally take care of updating application caches automatically.
The method can be useful in situations such as long-lived applications. For example, a Web mail application might stay open in a browser tab for weeks at a time. Such an application could want to test for updates each day.
abort
()Cancels the application cache download process.
This method is intended to be used by Web application showing their own caching progress UI, in case the user wants to stop the update (e.g. because bandwidth is limited).
swapCache
()Switches to the most recent application cache, if there is a newer one. If there isn't,
throws an InvalidStateError
exception.
This does not cause previously-loaded resources to be reloaded; for example, images do not suddenly get reloaded and style sheets and scripts do not get reparsed or reevaluated. The only change is that subsequent requests for cached resources will obtain the newer copies.
The updateready
event will fire before this
method can be called. Once it fires, the Web application can, at its leisure, call this method
to switch the underlying cache to the one with the more recent updates. To make proper use of
this, applications have to be able to bring the new features into play; for example, reloading
scripts to enable new features.
An easier alternative to swapCache()
is just to
reload the entire page at a time suitable for the user, using location.reload()
.
There is a one-to-one mapping from cache hosts to
ApplicationCache
objects. The applicationCache
attribute on Window
objects must return the ApplicationCache
object associated with the
Window
object's active document. The applicationCache
attribute
on SharedWorkerGlobalScope
objects must return the ApplicationCache
object associated with the worker.
A Window
or SharedWorkerGlobalScope
object has an
associated ApplicationCache
object even if that cache host has no actual
application cache.
The status
attribute, on getting, must
return the current state of the application cache that the
ApplicationCache
object's cache host is associated with, if any. This
must be the appropriate value from the following list:
UNCACHED
(numeric value 0)The ApplicationCache
object's cache host is not associated with
an application cache at this time.
IDLE
(numeric value 1)The ApplicationCache
object's cache host is associated with an
application cache whose application cache group's update status is idle, and that application
cache is the newest cache in its
application cache group, and the application cache group is not marked
as obsolete.
CHECKING
(numeric value 2)The ApplicationCache
object's cache host is associated with an
application cache whose application cache group's update status is checking.
DOWNLOADING
(numeric value 3)The ApplicationCache
object's cache host is associated with an
application cache whose application cache group's update status is downloading.
UPDATEREADY
(numeric value 4)The ApplicationCache
object's cache host is associated with an
application cache whose application cache group's update status is idle, and whose application
cache group is not marked as obsolete, but
that application cache is not the newest cache in its group.
OBSOLETE
(numeric value 5)The ApplicationCache
object's cache host is associated with an
application cache whose application cache group is marked as obsolete.
If the update()
method is invoked, the user
agent must invoke the application cache download process, in the background, for the
application cache group of the application cache with which the
ApplicationCache
object's cache host is associated, but without giving
that cache host to the algorithm. If there is no such application cache,
or if its application cache group is marked as obsolete, then the method must throw an
InvalidStateError
exception instead.
If the abort()
method is invoked, the user
agent must send a signal to the current application cache download process
for the application cache group of the application cache with which the
ApplicationCache
object's cache host is associated, if any. If there is
no such application cache, or it does not have a current application cache
download process, then do nothing.
If the swapCache()
method is invoked,
the user agent must run the following steps:
Check that ApplicationCache
object's cache host is associated
with an application cache. If it is not, then throw an
InvalidStateError
exception and abort these steps.
Let cache be the application cache with which the
ApplicationCache
object's cache host is associated. (By definition,
this is the same as the one that was found in the previous step.)
If cache's application cache group is marked as obsolete, then unassociate the
ApplicationCache
object's cache host from cache and
abort these steps. (Resources will now load from the network instead of the cache.)
Check that there is an application cache in the same application cache group
as cache whose completeness
flag is complete and that is newer than
cache. If there is not, then throw an InvalidStateError
exception and abort these steps.
Let new cache be the newest application cache in the same application cache group as cache whose completeness flag is complete.
Unassociate the ApplicationCache
object's cache host from cache and instead associate it with new cache.
The following are the event handlers (and their corresponding event handler event types) that must be
supported, as event handler IDL attributes, by all objects implementing the
ApplicationCache
interface:
Event handler | Event handler event type |
---|---|
onchecking | checking
|
onerror | error
|
onnoupdate | noupdate
|
ondownloading | downloading
|
onprogress | progress
|
onupdateready | updateready
|
oncached | cached
|
onobsolete | obsolete
|
[NoInterfaceObject] interface NavigatorOnLine { readonly attribute boolean onLine; };
navigator
. onLine
Returns false if the user agent is definitely offline (disconnected from the network). Returns true if the user agent might be online.
The events online
and offline
are fired when the value of this attribute changes.
The navigator.onLine
attribute must return
false if the user agent will not contact the network when the user follows links or when a script
requests a remote page (or knows that such an attempt would fail), and must return true
otherwise.
When the value that would be returned by the navigator.onLine
attribute of a Window
or
WorkerGlobalScope
changes from true to false, the user agent must queue a
task to fire a simple event named offline
at the Window
or
WorkerGlobalScope
object.
On the other hand, when the value that would be returned by the navigator.onLine
attribute of a Window
or
WorkerGlobalScope
changes from false to true, the user agent must queue a
task to fire a simple event named online
at the Window
or
WorkerGlobalScope
object.
The task source for these tasks is the networking task source.
This attribute is inherently unreliable. A computer can be connected to a network without having Internet access.
In this example, an indicator is updated as the browser goes online and offline.
<!DOCTYPE HTML> <html> <head> <title>Online status</title> <script> function updateIndicator() { document.getElementById('indicator').textContent = navigator.onLine ? 'online' : 'offline'; } </script> </head> <body onload="updateIndicator()" ononline="updateIndicator()" onoffline="updateIndicator()"> <p>The network is: <span id="indicator">(state unknown)</span> </body> </html>
Various mechanisms can cause author-provided executable code to run in the context of a document. These mechanisms include, but are probably not limited to:
script
elements.javascript:
URLs.addEventListener()
, by explicit event handler content attributes, by
event handler IDL attributes, or otherwise.Scripting is enabled in a browsing context when all of the following conditions are true:
Scripting is disabled in a browsing context when any of the above conditions are false (i.e. when scripting is not enabled).
Scripting is enabled for a node if the
Document
object of the node (the node itself, if it is itself a Document
object) has an associated browsing context, and scripting is enabled in that browsing context.
Scripting is disabled for a node if there is no such browsing context, or if scripting is disabled in that browsing context.
This specification describes three kinds of JavaScript global environments: the document environment, the dedicated worker environment, and the shared worker environment. The dedicated worker environment and the shared worker environment are both types of worker environments.
Except where otherwise specified, a JavaScript global environment is a document environment.
A script has:
A code entry-point represents a block of executable code that the script exposes to other scripts and to the user agent. Typically, the code corresponding to the code entry-point is executed immediately after the script is parsed, but for event handlers, it is called each time the handler is invoked.
In JavaScript script
blocks, this corresponds to the execution
context of the global code.
A flag which, if set, means that error information will not be provided for errors in this script (used to mute errors for cross-origin scripts, since that can leak private information).
A script settings object, various settings that are shared with other scripts in the same context.
A script settings object specifies algorithms for obtaining the following:
The characteristics of the script execution environment depend on the language, and are not defined by this specification.
In JavaScript, the script execution environment consists of the interpreter,
the stack of execution contexts, the global code and function code and the
Function
objects resulting, and so forth.
An object that provides the APIs that can be called by the code in scripts that use this settings object.
This is typically a Window
object or a
WorkerGlobalScope
object. When a global object is an empty object, it
can't do anything that interacts with the environment.
If the global object is a Window
object, then, in
JavaScript, the ThisBinding of the global execution context for this script must be the
Window
object's WindowProxy
object, rather than the global object. [ECMA262]
This is a willful violation of the JavaScript specification current
at the time of writing (ECMAScript edition 5, as defined in section 10.4.1.1 Initial Global
Execution Context, step 3). The JavaScript specification requires that the this
keyword in the global scope return the global object, but this is not
compatible with the security design prevalent in implementations as specified herein. [ECMA262]
A browsing context that is assigned responsibility for actions taken by the scripts that use this script settings object.
When a script creates and navigates a new
top-level browsing context, the opener
attribute
of the new browsing context's Window
object will be set to the
responsible browsing context's WindowProxy
object.
A Document
that is assigned responsibility for actions taken by the scripts that
use this script settings object.
For example, the address of the
responsible document is used to set the address of any Document
s created using createDocument()
.
An event loop that is used when it would not be immediately clear what event loop to use.
Either a Document
(specifically, the responsible document), or a
URL, which is used by some APIs to determine what value to use for the Referer
(sic) header in calls to the fetching algorithm.
A character encoding used to encode URLs by APIs called by scripts that use this script settings object.
An absolute URL used by APIs called by scripts that use this script settings object to resolve relative URLs.
An instrument used in security checks.
The relevant settings object for a global object o is the script settings object whose global object is o. (There is always a 1:1 mapping of global objects to script settings objects.)
The relevant settings object for a script s is the settings object of s.
Whenever a new Window
object is created, it must also create a script
settings object whose algorithms are defined as follows:
When the script settings object is created, for each language supported by the user agent, create an appropriate execution environment as defined by the relevant specification.
When a script execution environment is needed, return the appropriate one from those created when the script settings object was created.
Return the Window
object itself.
Return the browsing context with which the Window
object is
associated.
Return the Document
with which the Window
is currently
associated.
Return the event loop that is associated with the unit of related
similar-origin browsing contexts to which the Window
object's browsing
context belongs.
Return the Document
with which the Window
is currently
associated.
Return the current character encoding of
the Document
with which the Window
is currently associated.
Return the current base URL of the
Document
with which the Window
is currently associated.
Return the origin of the Document
with which the
Window
is currently associated.
Return the effective script origin of the Document
with which the
Window
is currently associated.
Each unit of related similar-origin browsing contexts has a stack of script settings objects, which must be initially empty. When a new script settings object is pushed onto this stack, the specified script settings object is to be added to the stack; when the script settings object on this stack that was most recently pushed onto it is to be popped from the stack, it must be removed. Entries on this stack can be labeled as candidate entry settings objects.
When a user agent is to jump to a code entry-point for a script s, the user agent must run the following steps:
Let context be the settings object of s.
Prepare to run a callback with context as the script settings object. If this returns "do not run" then abort these steps.
Make the appropriate script execution environment specified by context execute the s's code entry-point.
The steps to prepare to run a callback with a script settings object o are as follows. They return either "run" or "do not run".
If the global object specified by o
is a Window
object whose Document
object is not fully
active, then return "do not run" and abort these steps.
If scripting is disabled for the responsible browsing context specified by o, then return "do not run" and abort these steps.
Push o onto the stack of script settings objects, and label it as a candidate entry settings object.
Return "run".
The steps to clean up after running a callback are as follows:
Pop the current incumbent settings object from the stack of script settings objects.
If the stack of script settings objects is now empty, run the global script clean-up jobs. (These cannot run scripts.)
If the stack of script settings objects is now empty, perform a microtask checkpoint. (If this runs scripts, these algorithms will be invoked reentrantly.)
These algorithms are not invoked by one script directly calling another, but they can be invoked reentrantly in an indirect manner, e.g. if a script dispatches an event which has event listeners registered.
When a JavaScript SourceElements production is to be evaluated, the settings object of the script corresponding to that SourceElements must be pushed onto the stack of script settings objects before the evaluation begins, and popped when the evaluation ends (regardless of whether it's an abrupt completion or not).
The entry settings object is the most-recently added script settings object in the stack of script settings objects that is labeled as a candidate entry settings object. If the stack is empty, or has no entries labeled as such, then there is no entry settings object. It is used to obtain, amongst other things, the API base URL to resolve relative URLs used in scripts running in that unit of related similar-origin browsing contexts.
The incumbent settings object is the script settings object in the stack of script settings objects that was most-recently added (i.e. the last one on the stack). If the stack is empty, then there is no incumbent settings object. It is used in some security checks.
The WebIDL specification also uses these algorithms. [WEBIDL]
Each unit of related similar-origin browsing contexts has a performing
a microtask checkpoint flag, which must initially be false. It is used to prevent reentrant invocation of
the algorithm to invoke MutationObserver
objects. For the purposes of MutationObserver
objects, each unit of
related similar-origin browsing contexts is a distinct scripting environment.
Each unit of related similar-origin browsing contexts has a global script
clean-up jobs list, which must initially be empty. A global script clean-up job cannot run
scripts, and cannot be sensitive to the order in which other clean-up jobs are executed. The File
API uses this to release blob:
URLs. [FILEAPI]
When the user agent is to run the global script clean-up jobs, the user agent must perform each of the jobs in the global script clean-up jobs list and then empty the list.
When the specification says that a script is to be created, given some script source, a script source URL, its scripting language, a script settings object, and optionally a muted errors flag, the user agent must run the following steps:
Let script be a new script that this algorithm will subsequently initialize.
If scripting is disabled for browsing context passed to this algorithm, then abort these steps, as if the script source described a program that did nothing but return void.
Obtain the appropriate script execution environment for the given scripting language from the script settings object provided.
Parse/compile/initialize the source of the script using the script execution environment, as appropriate for the scripting language, and thus obtain script's code entry-point.
Let script's settings object be the script settings object provided.
If the muted errors flag was set, then set script's muted errors flag.
If all the steps above succeeded (in particular, if the script was compiled successfully), Jump to script's code entry-point.
Otherwise, report the error for script, with the problematic position (line number and column number), using the global object specified by the script settings object as the target. If the error is still not handled after this, then the error may be reported to the user.
User agents may impose resource limitations on scripts, for example CPU quotas, memory limits,
total execution time limits, or bandwidth limitations. When a script exceeds a limit, the user
agent may either throw a QuotaExceededError
exception, abort the script without an
exception, prompt the user, or throttle script execution.
For example, the following script never terminates. A user agent could, after waiting for a few seconds, prompt the user to either terminate the script or let it continue.
<script> while (true) { /* loop */ } </script>
User agents are encouraged to allow users to disable scripting whenever the user is prompted
either by a script (e.g. using the window.alert()
API) or because
of a script's actions (e.g. because it has exceeded a time limit).
If scripting is disabled while a script is executing, the script should be terminated immediately.
User agents may allow users to specifically disable scripts just for the purposes of closing a browsing context.
For example, the prompt mentioned in the example above could also offer the
user with a mechanism to just close the page entirely, without running any unload
event handlers.
When the user agent is required to report an error for a particular script script with a particular position line:col, using a particular target target, it must run these steps, after which the error is either handled or not handled:
If target is in error reporting mode, then abort these steps; the error is not handled.
Let target be in error reporting mode.
Let message be a user-agent-defined string describing the error in a
helpful manner.
Let error object be the object that represents the error: in the case
of an uncaught exception, that would be the object that was thrown; in the case of a JavaScript
error that would be an Error
object. If there is no corresponding object, then the
null value must be used instead.
Let location be an absolute URL that corresponds to the resource from which script was obtained.
The resource containing the script will typically be the file from which the
Document
was parsed, e.g. for inline script
elements or event
handler content attributes; or the JavaScript file that the script was in, for external
scripts. Even for dynamically-generated scripts, user agents are strongly encouraged to attempt
to keep track of the original source of a script. For example, if an external script uses the
document.write()
API to insert an inline
script
element during parsing, the URL of the resource containing the script would
ideally be reported as being the external script, and the line number might ideally be reported
as the line with the document.write()
call or where the
string passed to that call was first constructed. Naturally, implementing this can be somewhat
non-trivial.
User agents are similarly encouraged to keep careful track of the original line
numbers, even in the face of document.write()
calls
mutating the document as it is parsed, or event handler content attributes spanning
multiple lines.
If script has muted errors, then set message to "Script error.
", set location
to the empty string, set line and col to 0, and set error object to null.
Let event be a new trusted
ErrorEvent
object that does not bubble but is cancelable, and which has the event
name error
.
Initialize event's message
attribute to message.
Initialize event's filename
attribute to location.
Initialize event's lineno
attribute to line.
Initialize event's colno
attribute to col.
Initialize event's error
attribute to error object.
Dispatch event at target.
Let target no longer be in error reporting mode.
If event was canceled, then the error is handled. Otherwise, the error is not handled.
Whenever an uncaught runtime script error occurs in one of the scripts associated with a
Document
, the user agent must report the error for the relevant script, with the problematic position (line number and column
number) in the resource containing the script, using the global object specified by the script's settings object as
the target. If the error is still not handled after this,
then the error may be reported to the user.
ErrorEvent
interface[Constructor(DOMString type, optional ErrorEventInit eventInitDict)] interface ErrorEvent : Event { readonly attribute DOMString message; readonly attribute DOMString filename; readonly attribute unsigned long lineno; readonly attribute unsigned long colno; readonly attribute any error; }; dictionary ErrorEventInit : EventInit { DOMString message; DOMString filename; unsigned long lineno; unsigned long colno; any error; };
The message
attribute must return the
value it was initialized to. When the object is created, this attribute must be initialized to the
empty string. It represents the error message.
The filename
attribute must return the
value it was initialized to. When the object is created, this attribute must be initialized to the
empty string. It represents the absolute URL of the script in which the error
originally occurred.
The lineno
attribute must return the
value it was initialized to. When the object is created, this attribute must be initialized to
zero. It represents the line number where the error occurred in the script.
The colno
attribute must return the value
it was initialized to. When the object is created, this attribute must be initialized to zero. It
represents the column number where the error occurred in the script.
The error
attribute must return the value
it was initialized to. When the object is created, this attribute must be initialized to null.
Where appropriate, it is set to the object representing the error (e.g. the exception object in
the case of an uncaught DOM exception).
To coordinate events, user interaction, scripts, rendering, networking, and so forth, user agents must use event loops as described in this section.
There must be at least one event loop per user agent, and at most one event loop per unit of related similar-origin browsing contexts.
When there is more than one event loop for a unit of related browsing contexts, complications arise when a browsing context in that group is navigated such that it switches from one unit of related similar-origin browsing contexts to another. This specification does not currently describe how to handle these complications.
An event loop always has at least one browsing context. If an event loop's browsing contexts all go away, then the event loop goes away as well. A browsing context always has an event loop coordinating its activities.
An event loop has one or more task queues. A task queue is an ordered list of tasks, which are algorithms that are responsible for such work as:
Asynchronously dispatching an Event
object at a particular
EventTarget
object is often done by a dedicated task.
Not all events are dispatched using the task queue, many are dispatched synchronously during other tasks.
The HTML parser tokenizing one or more bytes, and then processing any resulting tokens, is typically a task.
Calling a callback asynchronously is often done by a dedicated task.
When an algorithm fetches a resource, if the fetching occurs asynchronously then the processing of the resource once some or all of the resource is available is performed by a task.
Some elements have tasks that trigger in response to DOM manipulation, e.g. when that element is inserted into the document.
Each task is associated with a Document
; if the
task was queued in the context of an element, then it is the element's Document
; if
the task was queued in the context of a browsing context, then it is the
browsing context's active document at the time the task was queued; if
the task was queued by or for a script then the document is
the responsible document specified by the script's settings object.
A task is intended for a specific event loop:
the event loop that is handling tasks for the task's associated Document
.
When a user agent is to queue a task, it must add the given task to one of the task queues of the relevant event loop.
Each task is defined as coming from a specific task
source. All the tasks from one particular task source and destined to a
particular event loop (e.g. the callbacks generated by timers of a
Document
, the events fired for mouse movements over that Document
, the
tasks queued for the parser of that Document
) must always be added to the same
task queue, but tasks from different task sources may be placed in different task
queues.
For example, a user agent could have one task queue for mouse and key events (the user interaction task source), and another for everything else. The user agent could then give keyboard and mouse events preference over other tasks three quarters of the time, keeping the interface responsive but not starving other task queues, and never processing events from any one task source out of order.
A user agent may have one storage mutex. This mutex is used to control access to shared state like cookies. At any one point, the storage mutex is either free, or owned by a particular event loop or instance of the fetching algorithm.
If a user agent does not implement a storage mutex, it is exempt from implementing the requirements that require it to acquire or release it.
User agent implementors have to make a choice between two evils. On the one hand, not implementing the storage mutex means that there is a risk of data corruption: a site could, for instance, try to read a cookie, increment its value, then write it back out, using the new value of the cookie as a unique identifier for the session; if the site does this twice in two different browser windows at the same time, it might end up using the same "unique" identifier for both sessions, with potentially disastrous effects. On the other hand, implementing the storage mutex has potentially serious performance implications: whenever a site uses Web Storage or cookies, all other sites that try to use Web Storage or cookies are blocked until the first site finishes.
Whenever a script calls into a plugin, and whenever a plugin calls into a script, the user agent must release the storage mutex.
An event loop must continually run through the following steps for as long as it exists:
Run the oldest task on one of the event
loop's task queues, if any, ignoring tasks whose
associated Document
s are not fully active. The user agent may pick any
task queue.
If the storage mutex is now owned by the event loop, release it so that it is once again free.
If a task was run in the first step above, remove that task from its task queue.
If this event loop is not a worker's event loop, run these substeps:
If necessary, update the rendering or user interface of any Document
or
browsing context to reflect the current state.
Otherwise, if this event loop is running for a
WorkerGlobalScope
, but there are no events in the event loop's task queues and the WorkerGlobalScope
object's closing flag is true, then destroy the event
loop, aborting these steps.
Return to the first step of the event loop.
When a user agent is to perform a microtask checkpoint, if the performing a microtask checkpoint flag is false, then the user agent must run the following steps:
Let the performing a microtask checkpoint flag be true.
Perform a custom elements checkpoint. [CUSTOM]
Sort the tables with pending sorts.
Invoke MutationObserver
objects for the
unit of related similar-origin browsing contexts to which the responsible
browsing context specified by the script's settings object belongs, using the task wrapper algorithm as the steps to
invoke each callback.
This will typically invoke scripted callbacks, which eventually calls the clean up after running a callback steps, which call this perform a microtask checkpoint algorithm again, which is why we use the performing a microtask checkpoint flag to avoid reentrancy.
Let the performing a microtask checkpoint flag be false.
When the user agent is to provide a stable state, if any asynchronously-running algorithms are awaiting a stable state, then the user agent must run their synchronous section and then resume running their asynchronous algorithm (if appropriate).
A synchronous section never mutates the DOM, runs any script, or has any side-effects detectable from another synchronous section, and thus synchronous sections can be run in any order, and cannot spin the event loop.
Steps in synchronous sections are marked with ⌛.
The task wrapper algorithm, which is implicitly invoked in the context of an event loop and is used to invoke a given callback in a specific way, is as follows:
Invoke callback as specified.
The above will change in due course; see bug 20821.
When an algorithm says to spin the event loop until a condition goal is met, the user agent must run the following steps:
Let task source be the task source of the currently running task.
Let old stack of script settings objects be a copy of the stack of script settings objects.
Empty the stack of script settings objects.
Stop the currently running task, allowing the event loop to resume, but continue these steps asynchronously.
This causes the event loop to move on to the second step of its processing model (defined above).
Wait until the condition goal is met.
Queue a task to continue running these steps, using the task source task source. Wait until this task runs before continuing these steps.
Replace the stack of script settings objects with the old stack of script settings objects.
Return to the caller.
Some of the algorithms in this specification, for historical reasons, require the user agent to pause while running a task until a condition goal is met. This means running the following steps:
If any asynchronously-running algorithms are awaiting a stable state, then run their synchronous section and then resume running their asynchronous algorithm. (See the event loop processing model definition above for details.)
If necessary, update the rendering or user interface of any Document
or
browsing context to reflect the current state.
Wait until the condition goal is met. While a user agent has a paused task, the corresponding event loop must not run further tasks, and any script in the currently running task must block. User agents should remain responsive to user input while paused, however, albeit in a reduced capacity since the event loop will not be doing anything.
When a user agent is to obtain the storage mutex as part of running a task, it must run through the following steps:
If the storage mutex is already owned by this task's event loop, then abort these steps.
Otherwise, pause until the storage mutex can be taken by the event loop.
Take ownership of the storage mutex.
The following task sources are used by a number of mostly unrelated features in this and other specifications.
This task source is used for features that react to DOM manipulations, such as things that happen asynchronously when an element is inserted into the document.
This task source is used for features that react to user interaction, for example keyboard or mouse input.
Asynchronous events sent in response to user input (e.g. click
events) must be fired using tasks queued with the user
interaction task source. [DOMEVENTS]
This task source is used for features that trigger in response to network activity.
This task source is used to queue calls to history.back()
and similar APIs.
Many objects can have event handlers specified. These act as non-capture event listeners for the object on which they are specified. [DOM]
An event handler has a name, which always starts with
"on
" and is followed by the name of the event for which it is intended.
An event handler can either have the value null, or be set
to a callback object, or be set to an internal raw uncompiled
handler. The EventHandler
callback function type describes how this is
exposed to scripts. Initially, event handlers must be set to null.
Event handlers are exposed in one of two ways.
The first way, common to all event handlers, is as an event handler IDL attribute.
The second way is as an event handler content
attribute. Event handlers on HTML elements and some of the event handlers on
Window
objects are exposed in this way.
An event handler IDL attribute is an IDL attribute for a specific event handler. The name of the IDL attribute is the same as the name of the event handler.
Event handler IDL attributes, on setting, must set the corresponding event handler to their new value, and on getting, must return the result of getting the current value of the event handler in question (this can throw an exception, in which case the getting propagates it to the caller, it does not catch it).
If an event handler IDL attribute exposes an event handler of an object that doesn't exist, it must always return null on getting and must do nothing on setting.
This can happen in particular for event
handler IDL attribute on body
elements that do not have corresponding
Window
objects.
Certain event handler IDL attributes have additional requirements, in particular
the onmessage
attribute of
MessagePort
objects.
An event handler content attribute is a content attribute for a specific event handler. The name of the content attribute is the same as the name of the event handler.
Event handler content attributes, when specified, must contain valid JavaScript
code which, when parsed, would match the FunctionBody
production after
automatic semicolon insertion. [ECMA262]
When an event handler content attribute is set, the user agent must set the corresponding event handler to an internal raw uncompiled handler consisting of the attribute's new value and the script location where the attribute was set to this value
When an event handler content attribute is removed, the user agent must set the corresponding event handler to null.
When an event handler H of an element
or object T implementing the EventTarget
interface is first set
to a non-null value, the user agent must append an event
listener to the list of event listeners
associated with T with type set to the event handler event
type corresponding to H, capture set to false, and
listener set to the event handler processing algorithm defined below. [DOM]
The listener is emphatically not the event handler itself. Every event handler ends up registering the same listener, the algorithm defined below, which takes care of invoking the right callback, and processing the callback's return value.
This only happens the first time the event
handler's value is set. Since listeners are called in the order they were registered, the
order of event listeners for a particular event type will always be first the event listeners
registered with addEventListener()
before
the first time the event handler was set to a non-null value,
then the callback to which it is currently set, if any, and finally the event listeners registered
with addEventListener()
after the
first time the event handler was set to a non-null value.
This example demonstrates the order in which event listeners are invoked. If the button in this example is clicked by the user, the page will show four alerts, with the text "ONE", "TWO", "THREE", and "FOUR" respectively.
<button id="test">Start Demo</button> <script> var button = document.getElementById('test'); button.addEventListener('click', function () { alert('ONE') }, false); button.setAttribute('onclick', "alert('NOT CALLED')"); // event handler listener is registered here button.addEventListener('click', function () { alert('THREE') }, false); button.onclick = function () { alert('TWO'); }; button.addEventListener('click', function () { alert('FOUR') }, false); </script>
The interfaces implemented by the event object do not influence whether an event handler is triggered or not.
The event handler processing algorithm for an event
handler H and an Event
object E is as
follows:
Let callback be the result of getting the current value of the event handler H.
If callback is null, then abort these steps.
Process the Event
object E as follows:
ErrorEvent
object and the event handler IDL attribute's type is
OnErrorEventHandler
Invoke callback with five arguments,
the first one having the value of E's message
attribute,
the second having the value of E's filename
attribute,
the third having the value of E's lineno
attribute,
the fourth having the value of E's colno
attribute,
the fifth having the value of E's error
attribute, and
with the callback this value set to E's currentTarget
. Let
return value be the callback's return value. [WEBIDL]
Invoke callback with one argument, the value of which is the
Event
object E, with the callback this value set to E's currentTarget
. Let return value be the callback's return value. [WEBIDL]
In this step, invoke means to run the jump to a code entry-point algorithm.
Process return value as follows:
mouseover
error
and E is an ErrorEvent
objectIf return value is a WebIDL boolean true value, then cancel the event.
beforeunload
The event handler IDL
attribute's type is OnBeforeUnloadEventHandler
, and the return value will therefore have been coerced into either the value null or a
DOMString.
If the return value is null, then cancel the event.
Otherwise, If the Event
object E is a
BeforeUnloadEvent
object, and the Event
object E's returnValue
attribute's value is the empty string, then set the returnValue
attribute's value to return value.
If return value is a WebIDL boolean false value, then cancel the event.
The EventHandler
callback function type represents a callback used for event
handlers. It is represented in Web IDL as follows:
[TreatNonCallableAsNull] callback EventHandlerNonNull = any (Event event); typedef EventHandlerNonNull? EventHandler;
In JavaScript, any Function
object implements this interface.
For example, the following document fragment:
<body onload="alert(this)" onclick="alert(this)">
...leads to an alert saying "[object Window]
" when the document is
loaded, and an alert saying "[object HTMLBodyElement]
" whenever the
user clicks something in the page.
The return value of the function affects whether the event is canceled or not:
as described above, if the return value is false, the event is canceled
(except for mouseover
events, where the return value has to
be true to cancel the event). With beforeunload
events,
the value is instead used to determine the message to show the user.
For historical reasons, the onerror
handler has different
arguments:
[TreatNonCallableAsNull] callback OnErrorEventHandlerNonNull = any ((Event or DOMString) event, optional DOMString source, optional unsigned long lineno, optional unsigned long column, optional any error); typedef OnErrorEventHandlerNonNull? OnErrorEventHandler;
Similarly, the onbeforeunload
handler has a
different return value:
[TreatNonCallableAsNull] callback OnBeforeUnloadEventHandlerNonNull = DOMString? (Event event); typedef OnBeforeUnloadEventHandlerNonNull? OnBeforeUnloadEventHandler;
An internal raw uncompiled handler is a tuple with the following information:
When the user agent is to get the current value of the event handler H, it must run these steps:
If H's value is an internal raw uncompiled handler, run these substeps:
If H is an element's event
handler, then let element be the element, and document be the element's Document
.
Otherwise, H is a Window
object's event handler: let element be null, and let document be the Document
most recently associated with that
Window
object.
If document is not in a browsing context, or if scripting is enabled for document's browsing context, then return null and abort the algorithm for getting the current value of the event handler.
Let body be the uncompiled script body in the internal raw uncompiled handler.
Let location be the location where the script body originated, as given by the internal raw uncompiled handler.
If element is not null and element has a form owner, let form owner be that form owner. Otherwise, let form owner be null.
Let script settings be the script settings object
created for the Window
object with which document is
currently associated.
Obtain the script execution environment for JavaScript from script settings.
If body is not parsable as FunctionBody or if parsing detects an early error, then follow these substeps:
Set H's value to null.
Report the error for the appropriate script and with the appropriate position (line number and column number) given by location, using the global object specified by script settings as the target. If the error is still not handled after this, then the error may be reported to the user.
Jump to the step labeled end below.
FunctionBody is defined in ECMAScript edition 5 section 13 Function Definition. Early error is defined in ECMAScript edition 5 section 16 Errors. [ECMA262]
If body begins with a Directive Prologue that contains a Use Strict Directive then let strict be true, otherwise let strict be false.
The terms "Directive Prologue" and "Use Strict Directive" are defined in ECMAScript edition 5 section 14.1 Directive Prologues and the Use Strict Directive. [ECMA262]
Using the script execution environment obtained above, create a function object (as defined in ECMAScript edition 5 section 13.2 Creating Function Objects), with:
onerror
event handler of a Window
objectevent
, source
, lineno
, colno
, and
error
.event
.NewObjectEnvironment() is defined in ECMAScript edition 5 section 10.2.2.3 NewObjectEnvironment (O, E). [ECMA262]
Let function be this new function.
Let script be a new script.
Let script's code entry-point be function.
Let script's settings object be script settings.
Set H to function.
End: Return H's value.
Document
objects, and Window
objectsThe following are the event handlers (and their corresponding event handler event types) that must be
supported by all HTML elements, as both event handler content attributes
and event handler IDL attributes; and that must be
supported by all Document
and Window
objects, as event handler IDL
attributes:
Event handler | Event handler event type |
---|---|
onabort | abort
|
oncancel | cancel
|
oncanplay | canplay
|
oncanplaythrough | canplaythrough
|
onchange | change
|
onclick | click
|
onclose | close
|
oncuechange | cuechange
|
ondblclick | dblclick
|
ondrag | drag
|
ondragend | dragend
|
ondragenter | dragenter
|
ondragexit | dragexit
|
ondragleave | dragleave
|
ondragover | dragover
|
ondragstart | dragstart
|
ondrop | drop
|
ondurationchange | durationchange
|
onemptied | emptied
|
onended | ended
|
oninput | input
|
oninvalid | invalid
|
onkeydown | keydown
|
onkeypress | keypress
|
onkeyup | keyup
|
onloadeddata | loadeddata
|
onloadedmetadata | loadedmetadata
|
onloadstart | loadstart
|
onmousedown | mousedown
|
onmouseenter | mouseenter
|
onmouseleave | mouseleave
|
onmousemove | mousemove
|
onmouseout | mouseout
|
onmouseover | mouseover
|
onmouseup | mouseup
|
onmousewheel | mousewheel
|
onpause | pause
|
onplay | play
|
onplaying | playing
|
onprogress | progress
|
onratechange | ratechange
|
onreset | reset
|
onseeked | seeked
|
onseeking | seeking
|
onselect | select
|
onshow | show
|
onstalled | stalled
|
onsubmit | submit
|
onsuspend | suspend
|
ontimeupdate | timeupdate
|
ontoggle | toggle
|
onvolumechange | volumechange
|
onwaiting | waiting
|
The following are the event handlers (and their corresponding event handler event types) that must be
supported by all HTML elements other than body
and frameset
elements, as both event handler content attributes and event handler IDL
attributes; that must be supported by all Document
objects, as event handler IDL attributes; and that must be
supported by all Window
objects, as event handler IDL attributes on the
Window
objects themselves, and with corresponding event handler content
attributes and event handler IDL attributes exposed on all body
and frameset
elements that are owned by that
Window
object's Document
s:
Event handler | Event handler event type |
---|---|
onblur | blur
|
onerror | error
|
onfocus | focus
|
onload | load
|
onresize | resize
|
onscroll | scroll
|
The following are the event handlers (and their corresponding event handler event types) that must be
supported by Window
objects, as event handler IDL attributes on the
Window
objects themselves, and with corresponding event handler content
attributes and event handler IDL attributes exposed on all body
and frameset
elements that are owned by that
Window
object's Document
s:
Event handler | Event handler event type |
---|---|
onafterprint | afterprint
|
onbeforeprint | beforeprint
|
onbeforeunload | beforeunload
|
onhashchange | hashchange
|
onmessage | message
|
onoffline | offline
|
ononline | online
|
onpagehide | pagehide
|
onpageshow | pageshow
|
onpopstate | popstate
|
onstorage | storage
|
onunload | unload
|
The following are the event handlers (and their corresponding event handler event types) that must be
supported on Document
objects as event handler IDL attributes:
Event handler | Event handler event type |
---|---|
onreadystatechange | readystatechange
|
[NoInterfaceObject] interface GlobalEventHandlers { attribute EventHandler onabort; attribute EventHandler onblur; attribute EventHandler oncancel; attribute EventHandler oncanplay; attribute EventHandler oncanplaythrough; attribute EventHandler onchange; attribute EventHandler onclick; attribute EventHandler onclose; attribute EventHandler oncuechange; attribute EventHandler ondblclick; attribute EventHandler ondrag; attribute EventHandler ondragend; attribute EventHandler ondragenter; attribute EventHandler ondragexit; attribute EventHandler ondragleave; attribute EventHandler ondragover; attribute EventHandler ondragstart; attribute EventHandler ondrop; attribute EventHandler ondurationchange; attribute EventHandler onemptied; attribute EventHandler onended; attribute OnErrorEventHandler onerror; attribute EventHandler onfocus; attribute EventHandler oninput; attribute EventHandler oninvalid; attribute EventHandler onkeydown; attribute EventHandler onkeypress; attribute EventHandler onkeyup; attribute EventHandler onload; attribute EventHandler onloadeddata; attribute EventHandler onloadedmetadata; attribute EventHandler onloadstart; attribute EventHandler onmousedown; [LenientThis] attribute EventHandler onmouseenter; [LenientThis] attribute EventHandler onmouseleave; attribute EventHandler onmousemove; attribute EventHandler onmouseout; attribute EventHandler onmouseover; attribute EventHandler onmouseup; attribute EventHandler onmousewheel; attribute EventHandler onpause; attribute EventHandler onplay; attribute EventHandler onplaying; attribute EventHandler onprogress; attribute EventHandler onratechange; attribute EventHandler onreset; attribute EventHandler onresize; attribute EventHandler onscroll; attribute EventHandler onseeked; attribute EventHandler onseeking; attribute EventHandler onselect; attribute EventHandler onshow; attribute EventHandler onstalled; attribute EventHandler onsubmit; attribute EventHandler onsuspend; attribute EventHandler ontimeupdate; attribute EventHandler ontoggle; attribute EventHandler onvolumechange; attribute EventHandler onwaiting; }; [NoInterfaceObject] interface WindowEventHandlers { attribute EventHandler onafterprint; attribute EventHandler onbeforeprint; attribute OnBeforeUnloadEventHandler onbeforeunload; attribute EventHandler onhashchange; attribute EventHandler onmessage; attribute EventHandler onoffline; attribute EventHandler ononline; attribute EventHandler onpagehide; attribute EventHandler onpageshow; attribute EventHandler onpopstate; attribute EventHandler onstorage; attribute EventHandler onunload; };
Certain operations and methods are defined as firing events on elements. For example, the click()
method on the HTMLElement
interface is defined as
firing a click
event on the element. [DOMEVENTS]
Firing a simple event named e means
that a trusted event with the name e, which does not bubble (except where otherwise stated) and is not cancelable
(except where otherwise stated), and which uses the Event
interface, must be created
and dispatched at the given target.
Firing a synthetic mouse event named e means that an event with the name e, which is trusted (except where otherwise stated), does not bubble
(except where otherwise stated), is not cancelable (except where otherwise stated), and which uses
the MouseEvent
interface, must be created and dispatched at the given target. The
event object must have its screenX
, screenY
, clientX
, clientY
, and button
attributes initialized to 0, its ctrlKey
, shiftKey
,
altKey
, and metaKey
attributes initialized according
to the current state of the key input device, if any (false for any keys that are not available),
its detail
attribute initialized to 1, and its relatedTarget
attribute initialized to null (except where otherwise stated). The
getModifierState()
method on the object must return values appropriately
describing the state of the key input device at the time the event is created.
Firing a click
event
means firing a synthetic mouse event named click
, which bubbles and is cancelable.
The default action of these events is to do nothing except where otherwise stated.
Window
objectWhen an event is dispatched at a DOM node in a Document
in a browsing
context, if the event is not a load
event, the user agent
must act as if, for the purposes of event dispatching,
the Window
object is the parent of the Document
object. [DOM]
The atob()
and btoa()
methods allow authors to transform content to and from
the base64 encoding.
[NoInterfaceObject] interface WindowBase64 { DOMString btoa(DOMString btoa); DOMString atob(DOMString atob); }; Window implements WindowBase64;
In these APIs, for mnemonic purposes, the "b" can be considered to stand for "binary", and the "a" for "ASCII". In practice, though, for primarily historical reasons, both the input and output of these functions are Unicode strings.
btoa
( data )Takes the input data, in the form of a Unicode string containing only characters in the range U+0000 to U+00FF, each representing a binary byte with values 0x00 to 0xFF respectively, and converts it to its base64 representation, which it returns.
Throws an InvalidCharacterError
exception if the input string contains any
out-of-range characters.
atob
( data )Takes the input data, in the form of a Unicode string containing base64-encoded binary data, decodes it, and returns a string consisting of characters in the range U+0000 to U+00FF, each representing a binary byte with values 0x00 to 0xFF respectively, corresponding to that binary data.
Throws an InvalidCharacterError
exception if the input string is not valid
base64 data.
The WindowBase64
interface adds to the Window
interface
and the WorkerGlobalScope
interface (part of Web workers).
The btoa()
method must throw an
InvalidCharacterError
exception if the method's first argument contains any character
whose code point is greater than U+00FF. Otherwise, the user agent must convert that argument to a
sequence of octets whose nth octet is the eight-bit representation of the code
point of the nth character of the argument, and then must apply the base64
algorithm to that sequence of octets, and return the result. [RFC4648]
The atob()
method must run the following
steps to parse the string passed in the method's first argument:
Let input be the string being parsed.
Let position be a pointer into input, initially pointing at the start of the string.
Remove all space characters from input.
If the length of input divides by 4 leaving no remainder, then: if input ends with one or two "=" (U+003D) characters, remove them from input.
If the length of input divides by 4 leaving a remainder of 1, throw an
InvalidCharacterError
exception and abort these steps.
If input contains a character that is not in the following list of
characters and character ranges, throw an InvalidCharacterError
exception and abort
these steps:
Let output be a string, initially empty.
Let buffer be a buffer that can have bits appended to it, initially empty.
While position does not point past the end of input, run these substeps:
Find the character pointed to by position in the first column of the following table. Let n be the number given in the second cell of the same row.
Character | Number |
---|---|
A | 0 |
B | 1 |
C | 2 |
D | 3 |
E | 4 |
F | 5 |
G | 6 |
H | 7 |
I | 8 |
J | 9 |
K | 10 |
L | 11 |
M | 12 |
N | 13 |
O | 14 |
P | 15 |
Q | 16 |
R | 17 |
S | 18 |
T | 19 |
U | 20 |
V | 21 |
W | 22 |
X | 23 |
Y | 24 |
Z | 25 |
a | 26 |
b | 27 |
c | 28 |
d | 29 |
e | 30 |
f | 31 |
g | 32 |
h | 33 |
i | 34 |
j | 35 |
k | 36 |
l | 37 |
m | 38 |
n | 39 |
o | 40 |
p | 41 |
q | 42 |
r | 43 |
s | 44 |
t | 45 |
u | 46 |
v | 47 |
w | 48 |
x | 49 |
y | 50 |
z | 51 |
0 | 52 |
1 | 53 |
2 | 54 |
3 | 55 |
4 | 56 |
5 | 57 |
6 | 58 |
7 | 59 |
8 | 60 |
9 | 61 |
+ | 62 |
/ | 63 |
Append to buffer the six bits corresponding to number, most significant bit first.
If buffer has accumulated 24 bits, interpret them as three 8-bit big-endian numbers. Append the three characters with code points equal to those numbers to output, in the same order, and then empty buffer.
Advance position by one character.
If buffer is not empty, it contains either 12 or 18 bits. If it contains 12 bits, discard the last four and interpret the remaining eight as an 8-bit big-endian number. If it contains 18 bits, discard the last two and interpret the remaining 16 as two 8-bit big-endian numbers. Append the one or two characters with code points equal to those one or two numbers to output, in the same order.
The discarded bits mean that, for instance, atob("YQ")
and
atob("YR")
both return "a
".
Return output.
APIs for dynamically inserting markup into the document interact with the parser, and thus their behavior varies depending on whether they are used with HTML documents (and the HTML parser) or XHTML in XML documents (and the XML parser).
The open()
method comes in several variants
with different numbers of arguments.
open
( [ type [, replace ] ] )Causes the Document
to be replaced in-place, as if it was a new
Document
object, but reusing the previous object, which is then returned.
If the type argument is omitted or has the value
"text/html
", then the resulting Document
has an HTML parser associated
with it, which can be given data to parse using document.write()
. Otherwise, all content passed to document.write()
will be parsed as plain text.
If the replace argument is present and has the value "replace
", the existing entries in the session history for the
Document
object are removed.
The method has no effect if the Document
is still being parsed.
Throws an InvalidStateError
exception if the Document
is an XML document.
open
( url, name, features [, replace ] )Works like the window.open()
method.
Document
objects have an ignore-opens-during-unload counter, which is
used to prevent scripts from invoking the document.open()
method (directly or indirectly) while the document is being
unloaded. Initially, the counter must be set to zero.
When called with two arguments, the document.open()
method must act as follows:
If the Document
object is not flagged as an HTML
document, throw an InvalidStateError
exception and abort these steps.
If the Document
object is not an active document, then abort
these steps.
Let type be the value of the first argument.
If the second argument is an ASCII case-insensitive match for the value "replace", then let replace be true.
Otherwise, if the browsing context's session history contains only
one Document
, and that was the about:blank
Document
created when the browsing context was created, and that Document
has
never had the unload a document algorithm invoked on it (e.g. by a previous call to
document.open()
), then let replace be
true.
Otherwise, let replace be false.
If the Document
has an active parser whose script nesting
level is greater than zero, then the method does nothing. Abort these steps and return
the Document
object on which the method was invoked.
This basically causes document.open()
to
be ignored when it's called in an inline script found during parsing, while still letting it
have an effect when called asynchronously.
Similarly, if the Document
's ignore-opens-during-unload counter is
greater than zero, then the method does nothing. Abort these steps and return the
Document
object on which the method was invoked.
This basically causes document.open()
to
be ignored when it's called from a beforeunload
pagehide
, or unload
event
handler while the Document
is being unloaded.
Release the storage mutex.
Set the Document
's salvageable state to false.
Prompt to unload the
Document
object. If the user refused to allow the document to be
unloaded, then abort these steps and return the Document
object on which the
method was invoked.
Unload the Document
object, with the
recycle parameter set to true.
Unregister all event listeners registered on the Document
node and its
descendants.
Remove any tasks associated with the
Document
in any task source.
Remove all child nodes of the document, without firing any mutation events.
Replace the Document
's singleton objects with new instances of those objects.
(This includes in particular the Window
, Location
,
History
, ApplicationCache
, and Navigator
, objects, the
various BarProp
objects, the two Storage
objects, the various
HTMLCollection
objects, and objects defined by other specifications, like
Selection
and the document's UndoManager
. It also includes all the Web
IDL prototypes in the JavaScript binding, including the Document
object's
prototype.)
The new Window
object has a new script settings
object.
Change the document's character encoding to UTF-8.
If the Document
is ready for post-load tasks, then set the
Document
object's reload override flag and set the
Document
's reload override buffer to the empty string.
Set the Document
's salvageable state back to true.
Change the document's address to the address of the responsible document specified by the entry settings object.
If the Document
's iframe load in progress flag is set, set the
Document
's mute iframe load flag.
Create a new HTML parser and associate it with the document. This is a
script-created parser (meaning that it can be closed by the document.open()
and document.close()
methods, and that the tokenizer will wait for
an explicit call to document.close()
before emitting an
end-of-file token). The encoding confidence is
irrelevant.
Set the current document readiness of the document to "loading
".
If type is an ASCII case-insensitive match for the string
"replace
", then, for historical reasons, set it to the string "text/html
".
Otherwise:
If the type string contains a ";" (U+003B) character, remove the first such character and all characters from it up to the end of the string.
Strip leading and trailing whitespace from type.
If type is not now an ASCII case-insensitive match
for the string "text/html
", then act as if the tokenizer had emitted a start tag
token with the tag name "pre" followed by a single "LF" (U+000A) character, then switch the
HTML parser's tokenizer to the PLAINTEXT state.
Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.
This doesn't necessarily have to affect the user agent's user interface.
Remove any tasks queued by the history traversal
task source that are associated with any Document
objects in the
top-level browsing context's document family.
Document
.If replace is false, then add a new entry, just before the last entry,
and associate with the new entry the text that was parsed by the previous parser associated with
the Document
object, as well as the state of the document at the start of these
steps. This allows the user to step backwards in the session history to see the page before it
was blown away by the document.open()
call. This new entry
does not have a Document
object, so a new one will be created if the session history
is traversed to that entry.
Finally, set the insertion point to point at just before the end of the input stream (which at this point will be empty).
Return the Document
on which the method was invoked.
The document.open()
method does not affect
whether a Document
is ready for post-load tasks or completely
loaded.
When called with four arguments, the open()
method on
the Document
object must call the open()
method on the
Window
object of the Document
object, with the same arguments as the
original call to the open()
method, and return whatever
that method returned. If the Document
object has no Window
object, then
the method must throw an InvalidAccessError
exception.
close
()Closes the input stream that was opened by the document.open()
method.
Throws an InvalidStateError
exception if the
Document
is an XML
document.
The close()
method must run the following
steps:
If the Document
object is not flagged as an HTML
document, throw an InvalidStateError
exception and abort these
steps.
If there is no script-created parser associated with the document, then abort these steps.
Insert an explicit "EOF" character at the end of the parser's input stream.
If there is a pending parsing-blocking script, then abort these steps.
Run the tokenizer, processing resulting tokens as they are emitted, and stopping when the tokenizer reaches the explicit "EOF" character or spins the event loop.
document.write()
write
(text...)In general, adds the given string(s) to the Document
's input stream.
This method has very idiosyncratic behavior. In some cases, this method can
affect the state of the HTML parser while the parser is running, resulting in a DOM
that does not correspond to the source of the document (e.g. if the string written is the string
"<plaintext>
" or "<!--
"). In other cases,
the call can clear the current page first, as if document.open()
had been called. In yet more cases, the method
is simply ignored, or throws an exception. To make matters worse, the exact behavior of this
method can in some cases be dependent on network latency, which can lead to failures that are very hard to debug. For all these reasons, use
of this method is strongly discouraged.
This method throws an InvalidStateError
exception when invoked on XML
documents.
Document
objects have an ignore-destructive-writes counter, which is
used in conjunction with the processing of script
elements to prevent external
scripts from being able to use document.write()
to blow
away the document by implicitly calling document.open()
.
Initially, the counter must be set to zero.
The document.write(...)
method must act as
follows:
If the method was invoked on an XML document, throw an
InvalidStateError
exception and abort these steps.
If the Document
object is not an active document, then abort
these steps.
If the insertion point is undefined and either the Document
's
ignore-opens-during-unload counter is greater than zero or the
Document
's ignore-destructive-writes counter is greater than zero,
abort these steps.
If the insertion point is undefined, call the open()
method on the document
object (with no arguments). If the user refused to allow the document to be
unloaded, then abort these steps. Otherwise, the insertion point will point
at just before the end of the (empty) input stream.
Insert the string consisting of the concatenation of all the arguments to the method into the input stream just before the insertion point.
If the Document
object's reload override flag is set, then append
the string consisting of the concatenation of all the arguments to the method to the
Document
's reload override buffer.
If there is no pending parsing-blocking script, have the HTML
parser process the characters that were inserted, one at a time, processing resulting
tokens as they are emitted, and stopping when the tokenizer reaches the insertion point or when
the processing of the tokenizer is aborted by the tree construction stage (this can happen if a
script
end tag token is emitted by the tokenizer).
If the document.write()
method was
called from script executing inline (i.e. executing because the parser parsed a set of
script
tags), then this is a reentrant invocation of the
parser.
Finally, return from the method.
document.writeln()
writeln
(text...)Adds the given string(s) to the Document
's input stream, followed by a newline
character. If necessary, calls the open()
method
implicitly first.
This method throws an InvalidStateError
exception when invoked on XML
documents.
The document.writeln(...)
method, when
invoked, must act as if the document.write()
method had
been invoked with the same argument(s), plus an extra argument consisting of a string containing a
single line feed character (U+000A).
The setTimeout()
and setInterval()
methods allow authors to schedule timer-based callbacks.
[NoInterfaceObject] interface WindowTimers { long setTimeout(Function handler, optional long timeout, any... arguments); long setTimeout(DOMString handler, optional long timeout, any... arguments); void clearTimeout(long handle); long setInterval(Function handler, optional long timeout, any... arguments); long setInterval(DOMString handler, optional long timeout, any... arguments); void clearInterval(long handle); }; Window implements WindowTimers;
setTimeout
( handler [, timeout [, arguments... ] ] )Schedules a timeout to run handler after timeout milliseconds. Any arguments are passed straight through to the handler.
setTimeout
( code [, timeout ] )Schedules a timeout to compile and run code after timeout milliseconds.
clearTimeout
( handle )Cancels the timeout set with setTimeout()
identified by handle.
setInterval
( handler [, timeout [, arguments... ] ] )Schedules a timeout to run handler every timeout milliseconds. Any arguments are passed straight through to the handler.
setInterval
( code [, timeout ] )Schedules a timeout to compile and run code every timeout milliseconds.
clearInterval
( handle )Cancels the timeout set with setInterval()
identified by handle.
Timers can be nested; after five such nested timers, however, the interval is forced to be at least four milliseconds.
This API does not guarantee that timers will run exactly on schedule. Delays due to CPU load, other tasks, etc, are to be expected.
The WindowTimers
interface adds to the Window
interface
and the WorkerGlobalScope
interface (part of Web workers).
Each object that implements the WindowTimers
interface has a list of active
timers. Each entry in this lists is identified by a number, which must be unique within the
list for the lifetime of the object that implements the WindowTimers
interface.
The setTimeout()
method must return
the value returned by the timer initialization steps, passing them the method's
arguments, the object on which the method for which the algorithm is running is implemented (a
Window
or WorkerGlobalScope
object) as the method
context, and the repeat flag set to false.
The setInterval()
method must
return the value returned by the timer initialization steps, passing them the
method's arguments, the object on which the method for which the algorithm is running is
implemented (a Window
or WorkerGlobalScope
object) as the method context, and the repeat flag set to true.
The clearTimeout()
and clearInterval()
methods must clear the
entry identified as handle from the list of active timers of the
WindowTimers
object on which the method was invoked, where handle
is the argument passed to the method, if any. (If handle does not identify an
entry in the list of active timers of the WindowTimers
object on which
the method was invoked, the method does nothing.)
The timer initialization steps, which are invoked with some method arguments, a method context, a repeat flag which can be true or false, and optionally (and only if the repeat flag is true) a previous handle, are as follows:
Let method context proxy be method context if that
is a WorkerGlobalScope
object, or else the WindowProxy
that corresponds
to method context.
If previous handle was provided, let handle be previous handle; otherwise, let handle be a user-agent-defined integer that is greater than zero that will identify the timeout to be set by this call in the list of active timers.
If previous handle was not provided, add an entry to the list of active timers for handle.
Let task be a task that runs the following substeps:
If the entry for handle in the list of active timers has been cleared, then abort this task's substeps.
Run the appropriate set of steps from the following list:
Function
Call the Function
. Use the third and subsequent method arguments (if any) as
the arguments for invoking the Function
. Use method context
proxy as the thisArg for invoking the Function
. [ECMA262]
Let script source be the first method argument.
Let script language be JavaScript.
Let settings object be method context's script settings object.
Create a script using script source as the script source, the URL where script source can be found, scripting language as the scripting language, and settings object as the script settings object.
If the repeat flag is true, then call timer initialization steps again, passing them the same method arguments, the same method context, with the repeat flag still set to true, and with the previous handle set to handler.
Let timeout be the second method argument, or zero if the argument was omitted.
If the currently running task is a task that was created by this algorithm, then let nesting level be the task's timer nesting level. Otherwise, let nesting level be zero.
If nesting level is greater than 5, and timeout is less than 4, then increase timeout to 4.
Increment nesting level by one.
Let task's timer nesting level be nesting level.
Return handle, and then continue running this algorithm asynchronously.
If method context is a Window
object, wait until the
Document
associated with method context has been fully
active for a further timeout milliseconds (not necessarily
consecutively).
Otherwise, method context is a WorkerGlobalScope
object;
wait until timeout milliseconds have passed with the worker not suspended
(not necessarily consecutively).
Wait until any invocations of this algorithm that had the same method context, that started before this one, and whose timeout is equal to or less than this one's, have completed.
Argument conversion as defined by Web IDL (for example, invoking toString()
methods on objects passed as the first argument) happens in the
algorithms defined in Web IDL, before this algorithm is invoked.
So for example, the following rather silly code will result in the log containing "ONE TWO
":
var log = ''; function logger(s) { log += s + ' '; } setTimeout({ toString: function () { setTimeout("logger('ONE')", 100); return "logger('TWO')"; } }, 100);
Optionally, wait a further user-agent defined length of time.
This is intended to allow user agents to pad timeouts as needed to optimise the power usage of the device. For example, some processors have a low-power mode where the granularity of timers is reduced; on such platforms, user agents can slow timers down to fit this schedule instead of requiring the processor to use the more accurate mode with its associated higher power usage.
Once the task has been processed, if the repeat flag is false, it is safe to remove the entry for handle from the list of active timers (there is no way for the entry's existence to be detected past this point, so it does not technically matter one way or the other).
The task source for these tasks is the timer task source.
To run tasks of several milliseconds back to back without any delay, while still yielding back to the browser to avoid starving the user interface (and to avoid the browser killing the script for hogging the CPU), simply queue the next timer before performing work:
function doExpensiveWork() { var done = false; // ... // this part of the function takes up to five milliseconds // set done to true if we're done // ... return done; } function rescheduleWork() { var handle = setTimeout(rescheduleWork, 0); // preschedule next iteration if (doExpensiveWork()) clearTimeout(handle); // clear the timeout if we don't need it } function scheduleWork() { setTimeout(rescheduleWork, 0); } scheduleWork(); // queues a task to do lots of work
alert
(message)Displays a modal alert with the given message, and waits for the user to dismiss it.
A call to the navigator.yieldForStorageUpdates()
method is
implied when this method is invoked.
confirm
(message)Displays a modal OK/Cancel prompt with the given message, waits for the user to dismiss it, and returns true if the user clicks OK and false if the user clicks Cancel.
A call to the navigator.yieldForStorageUpdates()
method is
implied when this method is invoked.
prompt
(message [, default] )Displays a modal text field prompt with the given message, waits for the user to dismiss it, and returns the value that the user entered. If the user cancels the prompt, then returns null instead. If the second argument is present, then the given value is used as a default.
A call to the navigator.yieldForStorageUpdates()
method is
implied when this method is invoked.
The alert(message)
method, when
invoked, must run the following steps:
If the event loop's termination nesting level is non-zero, optionally abort these steps.
Release the storage mutex.
Optionally, abort these steps. (For example, the user agent might give the user the option to ignore all alerts, and would thus abort at this step whenever the method was invoked.)
Show the given message to the user.
Optionally, pause while waiting for the user to acknowledge the message.
The confirm(message)
method,
when invoked, must run the following steps:
If the event loop's termination nesting level is non-zero, optionally abort these steps, returning false.
Release the storage mutex.
Optionally, return false and abort these steps. (For example, the user agent might give the user the option to ignore all prompts, and would thus abort at this step whenever the method was invoked.)
Show the given message to the user, and ask the user to respond with a positive or negative response.
Pause until the user responds either positively or negatively.
If the user responded positively, return true; otherwise, the user responded negatively: return false.
The prompt(message, default)
method, when invoked, must run the following steps:
If the event loop's termination nesting level is non-zero, optionally abort these steps, returning null.
Release the storage mutex.
Optionally, return null and abort these steps. (For example, the user agent might give the user the option to ignore all prompts, and would thus abort at this step whenever the method was invoked.)
Show the given message to the user, and ask the user to either respond with a string value or abort. The response must be defaulted to the value given by default.
Pause while waiting for the user's response.
If the user aborts, then return null; otherwise, return the string that the user responded with.
print
()Prompts the user to print the page.
A call to the navigator.yieldForStorageUpdates()
method is
implied when this method is invoked.
When the print()
method is invoked, if the
Document
is ready for post-load tasks, then the user agent must
synchronously run the printing steps. Otherwise, the user agent must only set the
print when loaded flag on the Document
.
User agents should also run the printing steps whenever the user asks for the opportunity to obtain a physical form (e.g. printed copy), or the representation of a physical form (e.g. PDF copy), of a document.
The printing steps are as follows:
The user agent may display a message to the user or abort these steps (or both).
For instance, a kiosk browser could silently ignore any invocations of the
print()
method.
For instance, a browser on a mobile device could detect that there are no printers in the vicinity and display a message saying so before continuing to offer a "save to PDF" option.
The user agent must fire a simple event named beforeprint
at the Window
object of the
Document
that is being printed, as well as any nested browsing contexts in it.
The beforeprint
event can be used to
annotate the printed copy, for instance adding the time at which the document was printed.
The user agent must release the storage mutex.
The user agent should offer the user the opportunity to obtain a physical form (or the representation of a physical form) of the document. The user agent may wait for the user to either accept or decline before returning; if so, the user agent must pause while the method is waiting. Even if the user agent doesn't wait at this point, the user agent must use the state of the relevant documents as they are at this point in the algorithm if and when it eventually creates the alternate form.
The user agent must fire a simple event named afterprint
at the Window
object of the
Document
that is being printed, as well as any nested browsing contexts in it.
The afterprint
event can be used to
revert annotations added in the earlier event, as well as showing post-printing UI. For
instance, if a page is walking the user through the steps of applying for a home loan, the
script could automatically advance to the next step after having printed a form or other.
showModalDialog
(url [, argument] )Prompts the user with the given page, waits for that page to close, and returns the return value.
A call to the navigator.yieldForStorageUpdates()
method is implied when this method is invoked.
The showModalDialog(url, argument)
method, when invoked,
must cause the user agent to run the following steps:
Resolve url relative to the API base URL specified by the entry settings object.
If this fails, then throw a SyntaxError
exception and abort these steps.
If the event loop's termination nesting level is non-zero, optionally abort these steps, returning the empty string.
Release the storage mutex.
If the user agent is configured such that this invocation of showModalDialog()
is somehow disabled, then return the empty
string and abort these steps.
User agents are expected to disable this method in certain cases to avoid user annoyance (e.g. as part of their popup blocker feature). For instance, a user agent could require that a site be white-listed before enabling this method, or the user agent could be configured to only allow one modal dialog at a time.
If the active sandboxing flag set of the active document of the responsible browsing context specified by the incumbent settings object has its sandboxed auxiliary navigation browsing context flag set, then return the empty string and abort these steps.
Let incumbent origin be the effective script origin specified by the
incumbent settings object at the time the showModalDialog()
method was called.
Let the list of background browsing contexts be a list of all the browsing contexts that:
Window
object on which the showModalDialog()
method was called, and that...as well as any browsing contexts that are nested inside any of the browsing contexts matching those conditions.
Disable the user interface for all the browsing contexts in the list of background browsing contexts. This should prevent the user from navigating those browsing contexts, causing events to be sent to those browsing context, or editing any content in those browsing contexts. However, it does not prevent those browsing contexts from receiving events from sources other than the user, from running scripts, from running animations, and so forth.
Create a new auxiliary browsing context, with the opener browsing
context being the browsing context of the Window
object on which the showModalDialog()
method was called. The new auxiliary
browsing context has no name.
This browsing context's Document
s' Window
objects all implement the WindowModal
interface.
Set all the flags in the new browsing context's popup sandboxing flag set that are set in the active sandboxing flag set of the active document of the responsible browsing context specified by the incumbent settings object. The responsible browsing context specified by the incumbent settings object must be set as the new browsing context's one permitted sandboxed navigator.
Let the dialog arguments of the new browsing context be set to the value of argument, or the undefined value if the argument was omitted.
Let the dialog arguments' origin be incumbent origin.
Let the return value of the new browsing context be the undefined value.
Let the return value origin be incumbent origin.
Navigate the new browsing context to the absolute URL that resulted from resolving url earlier, with replacement enabled, and with the responsible browsing context specified by the incumbent settings object as the source browsing context.
Spin the event loop until the new browsing context is closed. The user agent must allow the user to indicate that the browsing context is to be closed.
Reenable the user interface for all the browsing contexts in the list of background browsing contexts.
If the auxiliary browsing context's return value origin at the time the browsing context was closed was the same as incumbent origin, then let return value be the auxiliary browsing context's return value as it stood when the browsing context was closed.
Otherwise, let return value be undefined.
Return return value.
The Window
objects of Document
s hosted by browsing contexts created by the above algorithm must also implement the
WindowModal
interface.
When this happens, the members of the WindowModal
interface, in
JavaScript environments, appear to actually be part of the Window
interface (e.g.
they are on the same prototype chain as the window.alert()
method).
[NoInterfaceObject] interface WindowModal { readonly attribute any dialogArguments; attribute any returnValue; };
dialogArguments
Returns the argument argument that was passed to the showModalDialog()
method.
returnValue
[ = value ]Returns the current return value for the window.
Can be set, to change the value that will be returned by the showModalDialog()
method.
Such browsing contexts have associated dialog arguments, which are stored along with
the dialog arguments' origin. These values are set by the showModalDialog()
method in the algorithm above, when the
browsing context is created, based on the arguments provided to the method.
The dialogArguments
IDL
attribute, on getting, must check whether its browsing context's active document's
effective script origin is the same as the dialog arguments'
origin. If it is, then the browsing context's dialog arguments must be
returned unchanged. Otherwise, the IDL attribute must return undefined.
These browsing contexts also have an associated return value and return value
origin. As with the previous two values, these values are set by the showModalDialog()
method in the algorithm above, when the
browsing context is created.
The returnValue
IDL attribute, on
getting, must check whether its browsing context's active document's effective
script origin is the same as the current return
value origin. If it is, then the browsing context's return value must be
returned unchanged. Otherwise, the IDL attribute must return undefined. On setting, the
attribute must set the return value to the given new value, and the return
value origin to the browsing context's active document's effective
script origin.
The window.close()
method can be used to
close the browsing context.
Navigator
objectThe navigator
attribute of the
Window
interface must return an instance of the Navigator
interface,
which represents the identity and state of the user agent (the client), and allows Web pages to
register themselves as potential protocol and content handlers:
interface Navigator { // objects implementing this interface also implement the interfaces given below }; Navigator implements NavigatorID; Navigator implements NavigatorLanguage; Navigator implements NavigatorOnLine; Navigator implements NavigatorContentUtils; Navigator implements NavigatorStorageUtils; Navigator implements NavigatorPlugins;
These interfaces are defined separately so that other specifications can re-use parts of the
Navigator
interface.
[NoInterfaceObject] interface NavigatorID { readonly attribute DOMString appCodeName; // constant "Mozilla" readonly attribute DOMString appName; readonly attribute DOMString appVersion; readonly attribute DOMString platform; readonly attribute DOMString product; // constant "Gecko" boolean taintEnabled(); // constant false readonly attribute DOMString userAgent; };
In certain cases, despite the best efforts of the entire industry, Web browsers have bugs and limitations that Web authors are forced to work around.
This section defines a collection of attributes that can be used to determine, from script, the kind of user agent in use, in order to work around these issues.
Client detection should always be limited to detecting known current versions; future versions and unknown versions should always be assumed to be fully compliant.
navigator
. appCodeName
Returns the string "Mozilla
".
navigator
. appName
Returns the name of the browser.
navigator
. appVersion
Returns the version of the browser.
navigator
. platform
Returns the name of the platform.
navigator
. product
Returns the string "Gecko
".
navigator
. taintEnabled
()Returns false.
navigator
. userAgent
Returns the complete User-Agent header.
appCodeName
Must return the string "Mozilla
".
appName
Must return either the string "Netscape
" or the full name of the
browser, e.g. "Mellblom Browsernator
".
appVersion
Must return either the string "4.0
" or a string representing the
version of the browser in detail, e.g. "1.0 (VMS; en-US)
Mellblomenator/9000
".
platform
Must return either the empty string or a string representing the platform on which the
browser is executing, e.g. "MacIntel
", "Win32
",
"FreeBSD i386
", "WebTV OS
".
product
Must return the string "Gecko
".
taintEnabled()
Must return false.
userAgent
Must return the string used for the value of the "User-Agent
" header
in HTTP requests, or the empty string if no such header is ever sent.
Any information in this API that varies from user to user can be used to
profile the user. In fact, if enough such information is available, a user can actually be
uniquely identified. For this reason, user agent implementors are strongly urged to include as
little information in this API as possible.
[NoInterfaceObject] interface NavigatorLanguage { readonly attribute DOMString? language; };
navigator
. language
Returns a language tag representing the user's preferred language.
language
Must return a valid BCP 47 language tag representing either a plausible language or the user's preferred language. [BCP47]
To determine a plausible language, the user agent should bear in mind the following:
en-US
" is
suggested; if all users of the service use that same value, that reduces the possibility of
distinguishing the users from each other.[NoInterfaceObject] interface NavigatorContentUtils { // content handler registration void registerProtocolHandler(DOMString scheme, DOMString url, DOMString title); void registerContentHandler(DOMString mimeType, DOMString url, DOMString title); DOMString isProtocolHandlerRegistered(DOMString scheme, DOMString url); DOMString isContentHandlerRegistered(DOMString mimeType, DOMString url); void unregisterProtocolHandler(DOMString scheme, DOMString url); void unregisterContentHandler(DOMString mimeType, DOMString url); };
The registerProtocolHandler()
method
allows Web sites to register themselves as possible handlers for particular schemes. For example,
an online telephone messaging service could register itself as a handler of the sms:
scheme, so that if the user clicks on such a link, he is given the opportunity to use that Web
site. Analogously, the registerContentHandler()
method
allows Web sites to register themselves as possible handlers for content in a particular
MIME type. For example, the same online telephone messaging service could register
itself as a handler for text/vcard
files, so that if the user has no native
application capable of handling vCards, his Web browser can instead suggest he use that site to
view contact information stored on vCards that he opens. [RFC5724] [RFC6350]
navigator
. registerProtocolHandler
(scheme, url, title)navigator
. registerContentHandler
(mimeType, url, title)Registers a handler for the given scheme or content type, at the given URL, with the given title.
The string "%s
" in the URL is used as a placeholder for where to put
the URL of the content to be handled.
Throws a SecurityError
exception if the user agent blocks the registration (this
might happen if trying to register as a handler for "http", for instance).
Throws a SyntaxError
exception if the "%s
" string is
missing in the URL.
User agents may, within the constraints described in this section, do whatever they like when the methods are called. A UA could, for instance, prompt the user and offer the user the opportunity to add the site to a shortlist of handlers, or make the handlers his default, or cancel the request. UAs could provide such a UI through modal UI or through a non-modal transient notification interface. UAs could also simply silently collect the information, providing it only when relevant to the user.
User agents should keep track of which sites have registered handlers (even if the user has declined such registrations) so that the user is not repeatedly prompted with the same request.
The arguments to the methods have the following meanings and corresponding implementation requirements. The requirements that involve throwing exceptions must be processed in the order given below, stopping at the first exception thrown. (So the exceptions for the first argument take precedence over the exceptions for the second argument.)
registerProtocolHandler()
only)A scheme, such as mailto
or web+auth
. The scheme must be compared
in an ASCII case-insensitive manner by user agents for the purposes of comparing
with the scheme part of URLs that they consider against the list of registered handlers.
The scheme value, if it contains a colon (as in "mailto:
"),
will never match anything, since schemes don't contain colons.
If the registerProtocolHandler()
method is invoked with a scheme that is neither a whitelisted scheme nor a scheme
whose value starts with the substring "web+
" and otherwise contains only
lowercase ASCII letters, and whose length is at least five characters (including
the "web+
" prefix), the user agent must throw a SecurityError
exception.
The following schemes are the whitelisted schemes:
bitcoin
geo
im
irc
ircs
magnet
mailto
mms
news
nntp
sip
sms
smsto
ssh
tel
urn
webcal
wtai
xmpp
This list can be changed. If there are schemes that should be added, please send feedback.
This list excludes any schemes that could reasonably be expected to be supported
inline, e.g. in an iframe
, such as http
or (more
theoretically) gopher
. If those were supported, they could potentially be
used in man-in-the-middle attacks, by replacing pages that have frames with such content with
content under the control of the protocol handler. If the user agent has native support for the
schemes, this could further be used for cookie-theft attacks.
registerContentHandler()
only)A MIME type, such as model/vnd.flatland.3dml
or
application/vnd.google-earth.kml+xml
. The MIME type must be compared
in an ASCII case-insensitive manner by user agents for the purposes of comparing
with MIME types of documents that they consider against the list of registered handlers.
User agents must compare the given values only to the MIME type/subtype parts of content types, not to the complete type including parameters. Thus, if mimeType values passed to this method include characters such as commas or whitespace, or include MIME parameters, then the handler being registered will never be used.
The type is compared to the MIME type used by the user agent after the sniffing algorithms have been applied.
If the registerContentHandler()
method is invoked with a MIME type that is in the type blacklist or
that the user agent has deemed a privileged type, the user agent must throw a
SecurityError
exception.
The following MIME types are in the type blacklist:
application/x-www-form-urlencoded
application/xhtml+xml
application/xml
image/gif
image/jpeg
image/png
image/svg+xml
multipart/x-mixed-replace
text/cache-manifest
text/css
text/html
text/ping
text/plain
text/xml
application/rss+xml
and application/atom+xml
This list can be changed. If there are MIME types that should be added, please send feedback.
A string used to build the URL of the page that will handle the requests.
User agents must throw a SyntaxError
exception if the url
argument passed to one of these methods does not contain the exact literal string
"%s
".
User agents must throw a SyntaxError
exception if resolving the url argument relative to the
API base URL specified by the entry settings object is not successful.
The resulting absolute URL would by definition not be a valid
URL as it would include the string "%s
" which is not a valid
component in a URL.
User agents must throw a SecurityError
exception if the resulting absolute
URL has an origin that differs from the origin specified by the
entry settings object.
This is forcibly the case if the %s
placeholder is in the
scheme, host, or port parts of the URL.
The resulting absolute URL is the proto-URL. It identifies the handler for the purposes of the methods described below.
When the user agent uses this handler, it must replace the first occurrence of the exact
literal string "%s
" in the url argument with an
escaped version of the absolute URL of the content in question (as defined below),
then resolve the resulting URL, relative to the API
base URL specified by the entry settings object at the time the registerContentHandler()
or registerProtocolHandler()
methods were
invoked, and then navigate an appropriate browsing
context to the resulting URL using the GET method (or equivalent for non-HTTP URLs).
To get the escaped version of the absolute URL of the content in question, the user agent must replace every character in that absolute URL that is not a character in the URL default encode set with the result of UTF-8 percent encoding that character.
If the user had visited a site at http://example.com/
that made the
following call:
navigator.registerContentHandler('application/x-soup', 'soup?url=%s', 'SoupWeb™')
...and then, much later, while visiting http://www.example.net/
,
clicked on a link such as:
<a href="chickenkïwi.soup">Download our Chicken Kïwi soup!</a>
...then, assuming this chickenkïwi.soup
file was served with the
MIME type application/x-soup
, the UA might navigate to the following
URL:
http://example.com/soup?url=http://www.example.net/chickenk%C3%AFwi.soup
This site could then fetch the chickenkïwi.soup
file and do whatever it is
that it does with soup (synthesize it and ship it to the user, or whatever).
A descriptive title of the handler, which the UA might use to remind the user what the site in question is.
This section does not define how the pages registered by these methods are used, beyond the requirements on how to process the url value (see above). To some extent, the processing model for navigating across documents defines some cases where these methods are relevant, but in general UAs may use this information wherever they would otherwise consider handing content to native plugins or helper applications.
UAs must not use registered content handlers to handle content that was returned as part of a non-GET transaction (or rather, as part of any non-idempotent transaction), as the remote site would not be able to fetch the same data.
In addition to the registration methods, there are also methods for determining if particular handlers have been registered, and for unregistering handlers.
navigator
. isProtocolHandlerRegistered
(scheme, url)navigator
. isContentHandlerRegistered
(mimeType, url)Returns one of the following strings describing the state of the handler given by the arguments:
new
registered
declined
navigator
. unregisterProtocolHandler
(scheme, url)navigator
. unregisterContentHandler
(mimeType, url)Unregisters the handler given by the arguments.
The isProtocolHandlerRegistered()
method must return the handler state string that most closely describes the current
state of the handler described by the two arguments to the method, where the first argument gives
the scheme and the second gives the string used to build the URL of the page that
will handle the requests.
The first argument must be compared to the schemes for which custom protocol handlers are registered in an ASCII case-insensitive manner to find the relevant handlers.
The second argument must be preprocessed as described below, and if that is successful, must then be matched against the proto-URLs of the relevant handlers to find the described handler.
The isContentHandlerRegistered()
method must return the handler state string that most closely describes the current
state of the handler described by the two arguments to the method, where the first argument gives
the MIME type and the second gives the string used to build the URL of
the page that will handle the requests.
The first argument must be compared to the MIME types for which custom content handlers are registered in an ASCII case-insensitive manner to find the relevant handlers.
The second argument must be preprocessed as described below, and if that is successful, must then be matched against the proto-URLs of the relevant handlers to find the described handler.
The handler state strings are the following strings. Each string describes several situations, as given by the following list.
new
registered
declined
The unregisterProtocolHandler()
method must unregister the handler described by the two arguments to the method, where the first
argument gives the scheme and the second gives the string used to build the URL of
the page that will handle the requests.
The first argument must be compared to the schemes for which custom protocol handlers are registered in an ASCII case-insensitive manner to find the relevant handlers.
The second argument must be preprocessed as described below, and if that is successful, must then be matched against the proto-URLs of the relevant handlers to find the described handler.
The unregisterContentHandler()
method must unregister the handler described by the two arguments to the method, where the first
argument gives the MIME type and the second gives the string used to build the
URL of the page that will handle the requests.
The first argument must be compared to the MIME types for which custom content handlers are registered in an ASCII case-insensitive manner to find the relevant handlers.
The second argument must be preprocessed as described below, and if that is successful, must then be matched against the proto-URLs of the relevant handlers to find the described handler.
The second argument of the four methods described above must be preprocessed as follows:
If the string does not contain the substring "%s
", abort these
steps. There's no matching handler.
Resolve the string relative to the API base URL specified by the entry settings object.
If this fails, then throw a SyntaxError
exception, aborting the
method.
If the resulting absolute URL's origin is not the same
origin as the origin specified by the entry settings object, throw a SecurityError
exception, aborting the method.
Return the resulting absolute URL as the result of preprocessing the argument.
These mechanisms can introduce a number of concerns, in particular privacy concerns.
Hijacking all Web usage. User agents should not allow schemes that are key to
its normal operation, such as http
or https
, to be rerouted through
third-party sites. This would allow a user's activities to be trivially tracked, and would allow
user information, even in secure connections, to be collected.
Hijacking defaults. User agents are strongly urged to not automatically change any defaults, as this could lead the user to send data to remote hosts that the user is not expecting. New handlers registering themselves should never automatically cause those sites to be used.
Registration spamming. User agents should consider the possibility that a site
will attempt to register a large number of handlers, possibly from multiple domains (e.g. by
redirecting through a series of pages each on a different domain, and each registering a handler
for video/mpeg
— analogous practices abusing other Web browser features have
been used by pornography Web sites for many years). User agents should gracefully handle such
hostile attempts, protecting the user.
Misleading titles. User agents should not rely wholly on the title argument to the methods when presenting the registered handlers to the user,
since sites could easily lie. For example, a site hostile.example.net
could claim
that it was registering the "Cuddly Bear Happy Content Handler". User agents should therefore use
the handler's domain in any UI along with any title.
Hostile handler metadata. User agents should protect against typical attacks against strings embedded in their interface, for example ensuring that markup or escape characters in such strings are not executed, that null bytes are properly handled, that over-long strings do not cause crashes or buffer overruns, and so forth.
Leaking Intranet URLs. The mechanism described in this section can result in secret Intranet URLs being leaked, in the following manner:
No actual confidential file data is leaked in this manner, but the URLs themselves could
contain confidential information. For example, the URL could be
http://www.corp.example.com/upcoming-aquisitions/the-sample-company.egf
, which might
tell the third party that Example Corporation is intending to merge with The Sample Company.
Implementors might wish to consider allowing administrators to disable this feature for certain
subdomains, content types, or schemes.
Leaking secure URLs. User agents should not send HTTPS URLs to third-party
sites registered as content handlers without the user's informed consent, for the same reason that
user agents sometimes avoid sending Referer
(sic) HTTP headers
from secure sites to third-party sites.
Leaking credentials. User agents must never send username or password information in the URLs that are escaped and included sent to the handler sites. User agents may even avoid attempting to pass to Web-based handlers the URLs of resources that are known to require authentication to access, as such sites would be unable to access the resources in question without prompting the user for credentials themselves (a practice that would require the user to know whether to trust the third-party handler, a decision many users are unable to make or even understand).
Interface interference. User agents should be prepared to handle intentionally long arguments to the methods. For example, if the user interface exposed consists of an "accept" button and a "deny" button, with the "accept" binding containing the name of the handler, it's important that a long name not cause the "deny" button to be pushed off the screen.
Fingerprinting users. Since a site can detect if it has attempted to register a particular handler or not, whether or not the user responds, the mechanism can be used to store data. User agents are therefore strongly urged to treat registrations in the same manner as cookies: clearing cookies for a site should also clear all registrations for that site, and disabling cookies for a site should also disable registrations.
This section is non-normative.
A simple implementation of this feature for a desktop Web browser might work as follows.
The registerContentHandler()
method
could display a modal dialog box:
In this dialog box, "Kittens at work" is the title of the page that invoked the method,
"http://kittens.example.org/" is the URL of that page, "application/x-meowmeow" is the string that
was passed to the registerContentHandler()
method as its first
argument (mimeType), "http://kittens.example.org/?show=%s" was the second
argument (url), and "Kittens-at-work displayer" was the third argument (title).
If the user clicks the Cancel button, then nothing further happens. If the user clicks the "Trust" button, then the handler is remembered.
When the user then attempts to fetch a URL that uses the "application/x-meowmeow" MIME type, then it might display a dialog as follows:
In this dialog, the third option is the one that was primed by the site registering itself earlier.
If the user does select that option, then the browser, in accordance with the requirements described in the previous two sections, will redirect the user to "http://kittens.example.org/?show=data%3Aapplication/x-meowmeow;base64,S2l0dGVucyBhcmUgdGhlIGN1dGVzdCE%253D".
The registerProtocolHandler()
method
would work equivalently, but for schemes instead of unknown content types.
[NoInterfaceObject] interface NavigatorStorageUtils { readonly attribute boolean cookieEnabled; void yieldForStorageUpdates(); };
navigator
. cookieEnabled
Returns false if setting a cookie will be ignored, and true otherwise.
navigator
. yieldForStorageUpdates
()If a script uses the document.cookie
API, or the
localStorage
API, the browser will block other scripts
from accessing cookies or storage until the first script finishes.
[WEBSTORAGE]
Calling the navigator.yieldForStorageUpdates()
method
tells the user agent to unblock any other scripts that may be blocked, even though the script
hasn't returned.
Values of cookies and items in the Storage
objects of localStorage
attributes can change after calling this method,
whence its name.
[WEBSTORAGE]
The cookieEnabled
attribute must
return true if the user agent attempts to handle cookies according to the cookie specification,
and false if it ignores cookie change requests. [COOKIES]
The yieldForStorageUpdates()
method,
when invoked, must, if the storage mutex is owned by the event loop of
the task that resulted in the method being called, release the
storage mutex so that it is once again free. Otherwise, it must do nothing.
[NoInterfaceObject] interface NavigatorPlugins { readonly attribute PluginArray plugins; readonly attribute MimeTypeArray mimeTypes; readonly attribute boolean javaEnabled; }; interface PluginArray { void refresh(optional boolean reload = false); readonly attribute unsigned long length; getter Plugin? item(unsigned long index); getter Plugin? namedItem(DOMString name); }; interface MimeTypeArray { readonly attribute unsigned long length; getter MimeType? item(unsigned long index); getter MimeType? namedItem(DOMString name); }; interface Plugin { readonly attribute DOMString name; readonly attribute DOMString description; readonly attribute DOMString filename; readonly attribute unsigned long length; getter MimeType? item(unsigned long index); getter MimeType? namedItem(DOMString name); }; interface MimeType { readonly attribute DOMString type; readonly attribute DOMString description; readonly attribute DOMString suffixes; // comma-separated readonly attribute Plugin enabledPlugin; };
navigator
. plugins
. refresh
( [ refresh ] )Updates the lists of supported plugins and MIME types for this page, and reloads the page if the lists have changed.
navigator
. plugins
. length
Returns the number of plugins, represented by Plugin
objects, that the user agent reports.
navigator
. plugins
. item
(index)navigator
. plugins
[index]Returns the specified Plugin
object.
navigator
. plugins
. item
(name)navigator
. plugins
[name]Returns the Plugin
object for the plugin with the given name.
navigator
. mimeTypes
. length
Returns the number of MIME types, represented by MimeType
objects, supported by the plugins that the user agent reports.
navigator
. mimeTypes
. item
(index)navigator
. mimeTypes
[index]Returns the specified MimeType
object.
navigator
. mimeTypes
. item
(name)navigator
. mimeTypes
[name]Returns the MimeType
object for the given MIME type.
name
Returns the plugin's name.
description
Returns the plugin's description.
filename
Returns the plugin library's filename, if applicable on the current platform.
length
Returns the number of MIME types, represented by MimeType
objects, supported by the plugin.
item
(index)Returns the specified MimeType
object.
item
(name)Returns the MimeType
object for the given MIME type.
type
Returns the MIME type.
description
Returns the MIME type's description.
suffixes
Returns the MIME type's typical file extensions, in a comma-separated list.
enabledPlugin
Returns the Plugin
object that implements this MIME type.
navigator
. javaEnabled
Returns true if there's a plugin that supports the MIME type "application/x-java-vm
".
The navigator.plugins
attribute must
return a PluginArray
object. The same object must be returned each time.
The navigator.mimeTypes
attribute must
return a MimeTypeArray
object. The same object must be returned each time.
A PluginArray
object represents none, some, or all of the plugins supported by the user agent, each of which is represented by a Plugin
object. Each of these Plugin
objects may be hidden plugins. A hidden plugin can't
be enumerated, but can still be inspected by using its name.
The fewer plugins are represented by the
PluginArray
object, and of those, the more that are hidden, the more the user's privacy will be protected. Each exposed plugin
increases the number of bits that can be derived for fingerprinting. Hiding a plugin helps, but
unless it is an extremely rare plugin, it is likely that a site attempting to derive the list of
plugins can still determine whether the plugin is supported or not by probing for it by name (the
names of popular plugins are widely known). Therefore not exposing a plugin at all is preferred.
Unfortunately, many legacy sites use this feature to determine, for example, which plugin to use
to play video. Not exposing any plugins at all might therefore not be entirely plausible.
The PluginArray
objects created by a user agent must not be live. The
set of plugins represented by the objects must not change once an object is created, except when
it is updated by the refresh()
method.
Each plugin represented by a PluginArray
can support a number of
MIME types. For each such plugin, the user agent must
pick one or more of these MIME types to be those that are
explicitly supported.
The explicitly supported MIME types of
a plugin are those that are exposed through the Plugin
and MimeTypeArray
interfaces. As with plugins themselves, any variation between users regarding what is exposed
allows sites to fingerprint users. User agents are therefore encouraged to expose the same MIME types for all users of a plugin, regardless of the
actual types supported... at least, within the constraints imposed by compatibility with legacy
content.
The supported property indices of a PluginArray
object are the
numbers from zero to the number of non-hidden plugins represented by the object, if any.
The length
attribute must return the
number of non-hidden plugins
represented by the object.
The item()
method of a
PluginArray
object must return null if the argument is not one of the object's
supported property indices, and otherwise must return the result of running the
following steps, using the method's argument as index:
Let list be the Plugin
objects
representing the non-hidden plugins represented by the PluginArray
object.
Return the indexth entry in list.
It is important for privacy that the order of plugins not leak additional information, e.g. the order in which plugins were installed.
The supported property names of a PluginArray
object are the values
of the name
attributes of all the Plugin
objects represented by the PluginArray
object. The
properties exposed in this way must not be enumerable.
The namedItem()
method of a
PluginArray
object must return null if the argument is not one of the object's
supported property names, and otherwise must return the Plugin
object, of those represented by the PluginArray
object, that has a name
equal to the method's argument.
The refresh()
method of the
PluginArray
object of a Navigator
object, when invoked, must check to
see if any plugins have been installed or reconfigured since the user
agent created the PluginArray
object. If so, and the method's argument is true, then
the user agent must act as if the location.reload()
method was called instead. Otherwise, the user agent must update the PluginArray
object and MimeTypeArray
object created for attributes of that Navigator
object, and the Plugin
and MimeType
objects created
for those PluginArray
and MimeTypeArray
objects, using the same Plugin
objects for cases where the name
is the same, and the same MimeType
objects for
cases where the type
is the same, and creating new objects
for cases where there were no matching objects immediately prior to the refresh()
call. Old Plugin
and MimeType
objects must continue to return the same values that they had prior to
the update, though naturally now the data is stale and may appear inconsistent (for example, an
old MimeType
entry might list as its enabledPlugin
a Plugin
object that no longer lists that MimeType
as a supported MimeType
).
A MimeTypeArray
object represents the MIME types
explicitly supported by plugins supported by the user
agent, each of which is represented by a MimeType
object.
The MimeTypeArray
objects created by a user agent must not be live.
The set of MIME types represented by the objects must not change once an object is created, except
when it is updated by the PluginArray
object's refresh()
method.
The supported property indices of a MimeTypeArray
object are the
numbers from zero to the number of MIME types explicitly
supported by non-hidden plugins represented by the corresponding PluginArray
object, if
any.
The length
attribute must return the
number of MIME types explicitly supported by non-hidden plugins represented by the
corresponding PluginArray
object, if any.
The item()
method of a
MimeTypeArray
object must return null if the argument is not one of the object's
supported property indices, and otherwise must return the result of running the
following steps, using the method's argument as index:
Let list be the MimeType
objects representing the MIME types explicitly supported by non-hidden plugins represented by the corresponding
PluginArray
object, if any.
Return the indexth entry in list.
It is important for privacy that the order of MIME types not leak additional information, e.g. the order in which plugins were installed.
The supported property names of a MimeTypeArray
object are the values
of the type
attributes of all the MimeType
objects represented by the MimeTypeArray
object. The properties exposed in this way
must not be enumerable.
The namedItem()
method of a
MimeTypeArray
object must return null if the argument is not one of the object's
supported property names, and otherwise must return the MimeType
object
that has a type
equal to the method's argument.
A Plugin
object represents a plugin. It has
several attributes to provide details about the plugin, and can be enumerated to obtain the list
of MIME types that it explicitly
supports.
The Plugin
objects created by a user agent must not be
live. The set of MIME types represented by the objects, and the values of the
objects' attributes, must not change once an object is created, except when updated by the
PluginArray
object's refresh()
method.
The reported MIME types for a Plugin
object are the
MIME types explicitly supported by the corresponding
plugin when this object was last created or updated by PluginArray.refresh()
, whichever happened most
recently.
The supported property indices of a Plugin
object
are the numbers from zero to the number of reported MIME types.
The length
attribute must return the number
of reported MIME types.
The item()
method of a Plugin
object must return null if the argument is not one of the
object's supported property indices, and otherwise must return the result of running
the following steps, using the method's argument as index:
Let list be the MimeType
objects representing the
reported MIME types.
Return the indexth entry in list.
It is important for privacy that the order of MIME types not leak additional information, e.g. the order in which plugins were installed.
The supported property names of a Plugin
object
are the values of the type
attributes of the
MimeType
objects representing the reported MIME types. The properties
exposed in this way must not be enumerable.
The namedItem()
method of a Plugin
object must return null if the argument is not one of the
object's supported property names, and otherwise must return the
MimeType
object that has a type
equal to the
method's argument.
The name
attribute must return the
plugin's name.
The description
and filename
attributes must return user-agent-defined
(or, in all likelihood, plugin-defined) strings. In each case, the same string must
be returned each time, except that the strings returned may change when the PluginArray.refresh()
method updates the object.
If the values returned by the description
or filename
attributes vary between versions of a
plugin, they can be used both as a fingerprinting vector and, even more importantly,
as a trivial way to determine what security vulnerabilities a plugin (and thus a
browser) may have. It is thus highly recommended that the description
attribute just return the same value as the
name
attribute, and that the filename
attribute return the empty string.
A MimeType
object represents a MIME type that is, or was,
explicitly supported by a plugin.
The MimeType
objects created by a user agent must not be live. The
values of the objects' attributes must not change once an object is created, except when updated
by the PluginArray
object's refresh()
method.
The type
attribute must return the
valid MIME type with no parameters describing the MIME type.
The description
and suffixes
attributes must return
user-agent-defined (or, in all likelihood, plugin-defined) strings. In each case, the
same string must be returned each time, except that the strings returned may change when the PluginArray.refresh()
method updates the object.
If the values returned by the description
or suffxies
attributes vary between versions of a
plugin, they can be used both as a fingerprinting vector and, even more importantly,
as a trivial way to determine what security vulnerabilities a plugin (and thus a
browser) may have. It is thus highly recommended that the description
attribute just return the same value as the
type
attribute, and that the suffixes
attribute return the empty string.
Commas in the suffixes
attribute are
interpreted as separating subsequent filename extensions, as in "htm,html
".
The enabledPlugin
attribute must
return the Plugin
object that represents the plugin
that explicitly supported the MIME type that this MimeType
object represents when this object was last created or updated by PluginArray.refresh()
, whichever happened most
recently.
The navigator.javaEnabled
attribute
must return true if the user agent supports a plugin that supports the MIME
type "application/x-java-vm
".
External
interfaceThe external
attribute of the Window
interface must return an instance of the External
interface. The same object must be
returned each time.
interface External { void AddSearchProvider(DOMString engineURL); unsigned long IsSearchProviderInstalled(DOMString engineURL); };
external
. AddSearchProvider
( url )Adds the search engine described by the OpenSearch description document at url. [OPENSEARCH]
The OpenSearch description document has to be on the same server as the script that calls this method.
external
. IsSearchProviderInstalled
( url )Returns a value based on comparing url to the URLs of the results pages of the installed search engines.
The url is compared to the URLs of the results pages of the installed search engines using a prefix match. Only results pages on the same domain as the script that calls this method are checked.
Another way of exposing search engines using OpenSearch description documents is
using a link
element with the search
link type.
The AddSearchProvider()
method,
when invoked, must run the following steps:
Optionally, abort these steps. User agents may implement the method as a stub method that never does anything, or may arbitrarily ignore invocations with particular arguments for security, privacy, or usability reasons.
Resolve the value of the method's first argument relative to the API base URL specified by the entry settings object.
If this fails, abort these steps.
Process the resulting absolute URL as the URL to an OpenSearch description document. [OPENSEARCH]
The IsSearchProviderInstalled()
method, when invoked, must run the following steps:
Optionally, return 0 and abort these steps. User agents may implement the method as a stub method that never returns a non-zero value, or may arbitrarily ignore invocations with particular arguments for security, privacy, or usability reasons.
If the origin specified by the entry settings object is an opaque identifier (i.e. it has no host component), then return 0 and abort these steps.
Let host1 be the host component of the origin specified by the entry settings object.
Resolve the scriptURL argument relative to the API base URL specified by the entry settings object.
If this fails, return 0 and abort these steps.
Let host2 be the host component of the resulting parsed URL.
If the longest suffix in the Public Suffix List that matches the end of host1 is different than the longest suffix in the Public Suffix List that matches the end of host2, then return 0 and abort these steps. [PSL]
If the next domain component of host1 and host2 after their common suffix are not the same, then return 0 and abort these steps.
Let search engines be the list of search engines known by the user
agent and made available to the user by the user agent for which the resulting absolute
URL is a prefix match of the search engine's URL, if any. For
search engines registered using OpenSearch description documents, the URL of the
search engine corresponds to the URL given in a Url
element whose rel
attribute is "results
" (the default). [OPENSEARCH]
If search engines is empty, return 0 and abort these steps.
If the user's default search engine (as determined by the user agent) is one of the search engines in search engines, then return 2 and abort these steps.
Return 1.
hidden
attributeAll HTML elements may have the hidden
content
attribute set. The hidden
attribute is a boolean
attribute. When specified on an element, it indicates that the element is not yet, or is no
longer, directly relevant to the page's current state, or that it is being used to declare content
to be reused by other parts of the page as opposed to being directly accessed by the user. User agents should not render elements that have the hidden
attribute specified. This requirement may be implemented
indirectly through the style layer. For example, an HTML+CSS user agent could implement these
requirements using the rules suggested in the Rendering
section.
Because this attribute is typically implemented using CSS, it's also possible to
override it using CSS. For instance, a rule that applies 'display: block' to all elements will
cancel the effects of the hidden
attribute. Authors therefore
have to take care when writing their style sheets to make sure that the attribute is still styled
as expected.
In the following skeletal example, the attribute is used to hide the Web game's main screen until the user logs in:
<h1>The Example Game</h1> <section id="login"> <h2>Login</h2> <form> ... <!-- calls login() once the user's credentials have been checked --> </form> <script> function login() { // switch screens document.getElementById('login').hidden = true; document.getElementById('game').hidden = false; } </script> </section> <section id="game" hidden> ... </section>
The hidden
attribute must not be used to hide content that
could legitimately be shown in another presentation. For example, it is incorrect to use hidden
to hide panels in a tabbed dialog, because the tabbed interface
is merely a kind of overflow presentation — one could equally well just show all the form
controls in one big page with a scrollbar. It is similarly incorrect to use this attribute to hide
content just from one presentation — if something is marked hidden
, it is hidden from all
presentations, including, for instance, printers.
Elements that are not themselves hidden
must not
hyperlink to elements that are hidden
. The for
attributes of label
and output
elements that are not
themselves hidden
must similarly not refer to elements that are
hidden
. In both cases, such references would cause user
confusion.
Elements and scripts may, however, refer to elements that are hidden
in other contexts.
For example, it would be incorrect to use the href
attribute to link to a
section marked with the hidden
attribute. If the content is not applicable or relevant, then there
is no reason to link to it.
It would be fine, however, to use the ARIA aria-describedby
attribute to
refer to descriptions that are themselves hidden
. While hiding the descriptions
implies that they are not useful alone, they could be written in
such a way that they are useful in the specific context of being
referenced from the images that they describe.
Similarly, a canvas
element with the hidden
attribute could be used by a
scripted graphics engine as an off-screen buffer, and a form
control could refer to a hidden form
element using its
form
attribute.
Accessibility APIs are encouraged to provide a way to expose structured content while marking it as hidden in the default view. Such content should not be perceivable to users in the normal document flow in any modality, whether using Assistive Technology (AT) or mainstream User Agents.
When such features are available, User Agents may use them to
expose the full semantics of hidden
elements to AT when appropriate, if such content is referenced
indirectly by an ID reference or
valid hash-name reference. This allows ATs to access the
structure of these hidden
elements
upon user request, while keeping the content hidden in all
presentations of the normal document flow. Authors who wish to prevent
user-initiated viewing of a hidden
element should not reference the element with such a mechanism.
Because some User Agents have flattened hidden content when
exposing such content to AT, authors should not reference hidden
content which would lose essential
meaning when flattened.
For example, it would be incorrect to use the href
attribute to link to a section marked with the hidden
attribute.
If the content is not applicable or relevant, then there is no reason to link to it.
It would be fine, however, to use the ARIA aria-describedby
attribute to refer to descriptions that are
themselves hidden
. While hiding the descriptions implies that
they are not useful alone, they could be written in such a way that they are useful in the
specific context of being referenced from the images that they describe.
Similarly, a canvas
element with the hidden
attribute could be used by a scripted graphics engine as an off-screen buffer, and a form control
could refer to a hidden form
element using its form
attribute.
Elements in a section hidden by the hidden
attribute are still
active, e.g. scripts and form controls in such sections still execute and submit respectively.
Only their presentation to the user changes.
The hidden
IDL attribute must reflect
the content attribute of the same name.
A node (in particular elements and text nodes) can be marked as inert. When a node is inert, then the user agent must act as if the node was absent for the purposes of targeting user interaction events, may ignore the node for the purposes of text search user interfaces (commonly known as "find in page"), and may prevent the user from selecting text in that node. User agents should allow the user to override the restrictions on search and text selection, however.
For example, consider a page that consists of just a single inert
paragraph positioned in the middle of a body
. If a user moves their pointing device
from the body
over to the inert paragraph and clicks on the paragraph,
no mouseover
event would be fired, and the mousemove
and click
events would
be fired on the body
element rather than the paragraph.
When a node is inert, it also can't be focusable.
An entire Document
can be marked as blocked by a modal dialog subject. While a Document
is so marked, every node that is in the Document
, with the exception of the subject element and its descendants, must be marked
inert. (The elements excepted by this paragraph can additionally be marked
inert through other means; being part of a modal dialog does not "protect" a node
from being marked inert.)
Only one element at a time can mark a Document
as being blocked by a modal
dialog. When a new dialog
is made to block a Document
, the previous element, if any, stops blocking the
Document
.
The dialog
element's showModal()
method makes use of this mechanism.
click
()Acts as if the element was clicked.
The click()
method must run synthetic click
activation steps on the element.
When an element is focused, key events received by the document must be targeted at that
element. There may be no element focused; when no element is focused, key events received by the
document must be targeted at the body element, if there is one, or else at the
Document
's root element, if there is one. If there is no root element, key events
must not be fired.
User agents may track focus for each browsing context or Document
individually, or may support only one focused element per top-level browsing context
— user agents should follow platform conventions in this regard.
Which elements within a top-level browsing context currently have focus must be independent of whether or not the top-level browsing context itself has the system focus.
When a child browsing context is focused, its browsing context container must also have focus.
When an element is focused, the element matches the CSS :focus
pseudo-class.
tabindex
attributeThe tabindex
content attribute allows authors to
control whether an element is supposed to be focusable, whether it is supposed to be reachable
using sequential focus navigation, and what is to be the relative order of the element for the
purposes of sequential focus navigation. The name "tab index" comes from the common use of the
"tab" key to navigate through the focusable elements. The term "tabbing" refers to moving forward
through the focusable elements that can be reached using sequential focus navigation.
The tabindex
attribute, if specified, must have a value that
is a valid integer.
Each element can have a tabindex focus flag set, as defined below. This flag is a factor that contributes towards determining whether an element is focusable, as described in the next section.
If the attribute is specified, it must be parsed using the rules for parsing integers. The attribute's values have the following meanings:
The user agent should follow platform conventions to determine if the element's tabindex focus flag is set and, if so, whether the element can be reached using sequential focus navigation, and if so, what its relative order should be.
Modulo platform conventions, it is suggested that for the following elements, the tabindex focus flag be set:
a
elements that have an href
attributelink
elements that have an href
attributebutton
elementsinput
elements whose type
attribute are
not in the Hidden stateselect
elementstextarea
elementsdraggable
attribute set, if that would
enable the user agent to allow the user to begin a drag operations for those elements without
the use of a pointing deviceOne valid reason to ignore the platform conventions and always allow an element to be focused (by setting its tabindex focus flag) would be if the user's only mechanism for activating an element is through a keyboard action that triggers the focused element.
The user agent must set the element's tabindex focus flag, but should not allow the element to be reached using sequential focus navigation.
One valid reason to ignore the requirement that sequential focus navigation not
allow the author to lead to the element would be if the user's only mechanism for moving the
focus is sequential focus navigation. For instance, a keyboard-only user would be unable to
click on a text field with a negative tabindex
, so that
user's user agent would be well justified in allowing the user to tab to the control
regardless.
The user agent must set the element's tabindex focus flag, should allow the element to be reached using sequential focus navigation, and should follow platform conventions to determine the element's relative order.
The user agent must set the element's tabindex focus flag, should allow the element to be reached using sequential focus navigation, and should place the element in the sequential focus navigation order so that it is:
tabindex
attribute has been omitted or whose value, when parsed, returns an error,tabindex
attribute has a value equal to or less than zero,tabindex
attribute has a value
greater than zero but less than the value of the tabindex
attribute on the element,tabindex
attribute has a value
equal to the value of the tabindex
attribute on the element
but that is earlier in the document in tree order than the element,tabindex
attribute has a value
equal to the value of the tabindex
attribute on the element
but that is later in the document in tree order than the element, andtabindex
attribute has a value
greater than the value of the tabindex
attribute on the
element.An element that has its tabindex focus flag set but does not otherwise have an activation behavior defined has an activation behavior that does nothing.
This means that an element that is only focusable because of its tabindex
attribute will fire a click
event in response to a non-mouse activation (e.g. hitting the "enter" key while the element is
focused).
The tabIndex
IDL attribute must
reflect the value of the tabindex
content
attribute. Its default value is 0 for elements that are focusable and −1 for elements that
are not focusable.
An element is focusable if all of the following conditions are met:
canvas
element that represents embedded
content.In addition, each shape that is generated for an area
element, any
user-agent-provided interface components of media elements
(e.g. a play button), and distinct user interface components of form controls (e.g. "up" and
"down" buttons on an <input type=number>
spin
control), should be focusable, unless platform conventions dictate otherwise or
unless their corresponding element is disabled. (A
single area
element can correspond to multiple shapes, since image maps can be reused
with multiple images on a page.)
The user agent may also make part of a details
element's rendering
focusable, to enable the element to be opened or closed using keyboard input.
However, this is distinct from the details
or summary
element being
focusable.
Notwithstanding the above, user agents may make any element or part of an element focusable, especially to aid with accessibility or to better match platform conventions.
The focusing steps for an element are as follows:
If the element is not in a Document
, or if
the element's Document
has no browsing context, or if the element's
Document
's browsing context has no top-level browsing
context, or if the element is not focusable, or if the element is already
focused, then abort these steps.
If focusing the element will remove the focus from another element, then run the unfocusing steps for that element.
Make the element the currently focused element in its top-level browsing context.
Some elements, most notably area
, can correspond to more than one distinct
focusable area. If a particular area was indicated when the element was focused, then that is
the area that must get focus; otherwise, e.g. when using the focus()
method, the first such region in tree order is the one that
must be focused.
The user agent may apply relevant platform-specific conventions for focusing widgets.
For example, some platforms select the contents of a text field when that field is focused.
Fire a simple event named focus
at the element.
User agents must synchronously run the focusing steps for an element whenever the user moves the focus to a focusable element.
The unfocusing steps for an element are as follows:
If the element is an input
element, and the change
event applies to the element, and the element does not
have a defined activation behavior, and the user has changed the element's value or its list of selected files while the control was focused
without committing that change, then fire a simple event that bubbles named change
at the element.
Unfocus the element.
Fire a simple event named blur
at the element.
When an element that is focused stops being a focusable element, or stops being focused without another element being explicitly focused in its stead, the user agent should synchronously run the unfocusing steps for the affected element only.
For example, this might happen because the element is removed from its
Document
, or has a hidden
attribute added. It would
also happen to an input
element when the element gets disabled.
activeElement
Returns the currently focused element.
hasFocus
()Returns true if the document has focus; otherwise, returns false.
focus
()Focuses the window. Use of this method is discouraged. Allow the user to control window focus instead.
blur
()Unfocuses the window. Use of this method is discouraged. Allow the user to control window focus instead.
The activeElement
attribute on
Document
objects must return the element in the document that is focused. If no
element in the Document
is focused, this must return the body
element.
When a child browsing context is focused, its browsing context
container is also focused, by definition. For
example, if the user moves the focus to a text field in an iframe
, the
iframe
is the element with focus in the parent browsing context.
The hasFocus()
method on
Document
objects must return true if the Document
's browsing
context is focused, and all its ancestor browsing
contexts are also focused, and the top-level browsing context has the
system focus. If the Document
has no browsing context or if its
browsing context has no top-level browsing context, then the method will
always return false.
The focus()
method on the Window
object, when invoked, provides a hint to the user agent that the script believes the user might be
interested in the contents of the browsing context of the Window
object
on which the method was invoked.
User agents are encouraged to have this focus()
method
trigger some kind of notification.
The blur()
method on the Window
object, when invoked, provides a hint to the user agent that the script believes the user probably
is not currently interested in the contents of the browsing context of the
Window
object on which the method was invoked, but that the contents might become
interesting again in the future.
User agents are encouraged to ignore calls to this blur()
method entirely.
Historically the focus()
and blur()
methods actually affected the system focus, but hostile
sites widely abuse this behavior to the user's detriment.
focus
()Focuses the element.
blur
()Unfocuses the element. Use of this method is discouraged. Focus another element instead.
Do not use this method to hide the focus ring. Do not use any other method that hides the focus ring from keyboard users, in particular do not use a CSS rule to override the 'outline' property. Removal of the focus ring leads to serious accessibility issues for users who navigate and interact with interactive content using the keyboard.
The focus()
method, when invoked, must run the
following algorithm:
If the element is marked as locked for focus, then abort these steps.
Mark the element as locked for focus.
Run the focusing steps for the element.
Unmark the element as locked for focus.
The blur()
method, when invoked, should run the
unfocusing steps for the element on which the method was called instead. User agents
may selectively or uniformly ignore calls to this method for usability reasons.
For example, if the blur()
method is unwisely
being used to remove the focus ring for aesthetics reasons, the page would become unusable by
keyboard users. Ignoring calls to this method would thus allow keyboard users to interact with the
page.
This section is non-normative.
Each element that can be activated or focused can be assigned a single key combination to
activate it, using the accesskey
attribute.
The exact shortcut is determined by the user agent, based on information about the user's
keyboard, what keyboard shortcuts already exist on the platform, and what other shortcuts have
been specified on the page, using the information provided in the accesskey
attribute as a guide.
In order to ensure that a relevant keyboard shortcut is available on a wide variety of input
devices, the author can provide a number of alternatives in the accesskey
attribute.
Each alternative consists of a single character, such as a letter or digit.
User agents can provide users with a list of the keyboard shortcuts, but authors are encouraged
to do so also. The accessKeyLabel
IDL attribute returns a
string representing the actual key combination assigned by the user agent.
In this example, an author has provided a button that can be invoked using a shortcut key. To support full keyboards, the author has provided "C" as a possible key. To support devices equipped only with numeric keypads, the author has provided "1" as another possibly key.
<input type=button value=Collect onclick="collect()" accesskey="C 1" id=c>
To tell the user what the shortcut key is, the author has this script here opted to explicitly add the key combination to the button's label:
function addShortcutKeyLabel(button) { if (button.accessKeyLabel != '') button.value += ' (' + button.accessKeyLabel + ')'; } addShortcutKeyLabel(document.getElementById('c'));
Browsers on different platforms will show different labels, even for the same key combination, based on the convention prevalent on that platform. For example, if the key combination is the Control key, the Shift key, and the letter C, a Windows browser might display "Ctrl+Shift+C", whereas a Mac browser might display "^⇧C", while an Emacs browser might just display "C-C". Similarly, if the key combination is the Alt key and the Escape key, Windows might use "Alt+Esc", Mac might use "⌥⎋", and an Emacs browser might use "M-ESC" or "ESC ESC".
In general, therefore, it is unwise to attempt to parse the value returned from the accessKeyLabel
IDL attribute.
accesskey
attributeAll HTML elements may have the accesskey
content attribute set. The accesskey
attribute's value is used
by the user agent as a guide for creating a keyboard shortcut that activates or focuses the
element.
If specified, the value must be an ordered set of unique space-separated tokens that are case-sensitive, each of which must be exactly one Unicode code point in length.
In the following example, a variety of links are given with access keys so that keyboard users familiar with the site can more quickly navigate to the relevant pages:
<nav> <p> <a title="Consortium Activities" accesskey="A" href="/Consortium/activities">Activities</a> | <a title="Technical Reports and Recommendations" accesskey="T" href="/TR/">Technical Reports</a> | <a title="Alphabetical Site Index" accesskey="S" href="/Consortium/siteindex">Site Index</a> | <a title="About This Site" accesskey="B" href="/Consortium/">About Consortium</a> | <a title="Contact Consortium" accesskey="C" href="/Consortium/contact">Contact</a> </p> </nav>
In the following example, the search field is given two possible access keys, "s" and "0" (in that order). A user agent on a device with a full keyboard might pick Ctrl+Alt+S as the shortcut key, while a user agent on a small device with just a numeric keypad might pick just the plain unadorned key 0:
<form action="/search"> <label>Search: <input type="search" name="q" accesskey="s 0"></label> <input type="submit"> </form>
In the following example, a button has possible access keys described. A script then tries to update the button's label to advertise the key combination the user agent selected.
<input type=submit accesskey="N @ 1" value="Compose"> ... <script> function labelButton(button) { if (button.accessKeyLabel) button.value += ' (' + button.accessKeyLabel + ')'; } var inputs = document.getElementsByTagName('input'); for (var i = 0; i < inputs.length; i += 1) { if (inputs[i].type == "submit") labelButton(inputs[i]); } </script>
On one user agent, the button's label might become "Compose (⌘N)". On another, it might become "Compose (Alt+⇧+1)". If the user agent doesn't assign a key, it will be just "Compose". The exact string depends on what the assigned access key is, and on how the user agent represents that key combination.
An element's assigned access key is a key combination derived from the element's
accesskey
content attribute. Initially, an element must not
have an assigned access key.
Whenever an element's accesskey
attribute is set, changed,
or removed, the user agent must update the element's assigned access key by running
the following steps:
If the element has no accesskey
attribute, then skip
to the fallback step below.
Otherwise, split the attribute's value on spaces, and let keys be the resulting tokens.
For each value in keys in turn, in the order the tokens appeared in the attribute's value, run the following substeps:
If the value is not a string exactly one Unicode code point in length, then skip the remainder of these steps for this value.
If the value does not correspond to a key on the system's keyboard, then skip the remainder of these steps for this value.
If the user agent can find a mix of zero or more modifier keys that, combined with the key that corresponds to the value given in the attribute, can be used as the access key, then the user agent may assign that combination of keys as the element's assigned access key and abort these steps.
Fallback: Optionally, the user agent may assign a key combination of its choosing as the element's assigned access key and then abort these steps.
If this step is reached, the element has no assigned access key.
Once a user agent has selected and assigned an access key for an element, the user agent should
not change the element's assigned access key unless the accesskey
content attribute is changed or the element is moved to
another Document
.
User agents might expose elements that have
an accesskey
attribute in other ways as well, e.g. in a menu
displayed in response to a specific key combination.
The accessKey
IDL attribute must
reflect the accesskey
content attribute.
The accessKeyLabel
IDL attribute must return
a string that represents the element's assigned access key, if any. If the element
does not have one, then the IDL attribute must return the empty string.
contenteditable
content attributeThe contenteditable
attribute is an
enumerated attribute whose keywords are the empty string, true
,
and false
. The empty string and the true
keyword map
to the true state. The false
keyword maps to the false state.
In addition, there is a third state, the inherit state, which is the missing value
default (and the invalid value default).
The true state indicates that the element is editable. The inherit state indicates that the element is editable if its parent is. The false state indicates that the element is not editable.
contentEditable
[ = value ]Returns "true
", "false
", or "inherit
", based on the state of the contenteditable
attribute.
Can be set, to change that state.
Throws a SyntaxError
exception if the new value isn't one of those strings.
isContentEditable
Returns true if the element is editable; otherwise, returns false.
The contentEditable
IDL attribute, on
getting, must return the string "true
" if the content attribute is set to
the true state, "false
" if the content attribute is set to the false state,
and "inherit
" otherwise. On setting, if the new value is an ASCII
case-insensitive match for the string "inherit
" then the content
attribute must be removed, if the new value is an ASCII case-insensitive match for
the string "true
" then the content attribute must be set to the string
"true
", if the new value is an ASCII case-insensitive match for
the string "false
" then the content attribute must be set to the string
"false
", and otherwise the attribute setter must throw a
SyntaxError
exception.
The isContentEditable
IDL attribute, on
getting, must return true if the element is either an editing host or
editable, and false otherwise.
designMode
IDL attributeDocuments have a designMode
, which can be either enabled or
disabled.
designMode
[ = value ]Returns "on
" if the document is editable, and "off
" if it isn't.
Can be set, to change the document's current state. This focuses the document and resets the selection in that document.
The designMode
IDL attribute on the
Document
object takes two values, "on
" and "off
". On setting, the new value must be compared in an ASCII
case-insensitive manner to these two values; if it matches the "on
"
value, then designMode
must be enabled, and if it
matches the "off
" value, then designMode
must be disabled. Other values must be
ignored.
On getting, if designMode
is enabled, the IDL
attribute must return the value "on
"; otherwise it is disabled, and the
attribute must return the value "off
".
The last state set must persist until the document is destroyed or the state is changed.
Initially, documents must have their designMode
disabled.
When the designMode
changes from being disabled to
being enabled, the user agent must synchronously reset the document's active range's
start and end boundary points to be at the start of the Document
and then run the
focusing steps for the root element of the Document
, if any.
Authors are encouraged to set the 'white-space' property on editing hosts and on markup that was originally created through these editing mechanisms to the value 'pre-wrap'. Default HTML whitespace handling is not well suited to WYSIWYG editing, and line wrapping will not work correctly in some corner cases if 'white-space' is left at its default value.
As an example of problems that occur if the default 'normal' value is used instead, consider the case of the user typing "yellow␣␣ball", with two spaces (here represented by "␣") between the words. With the editing rules in place for the default value of 'white-space' ('normal'), the resulting markup will either consist of "yellow ball" or "yellow ball"; i.e., there will be a non-breaking space between the two words in addition to the regular space. This is necessary because the 'normal' value for 'white-space' requires adjacent regular spaces to be collapsed together.
In the former case, "yellow⍽" might wrap to the next line ("⍽" being used here to represent a non-breaking space) even though "yellow" alone might fit at the end of the line; in the latter case, "⍽ball", if wrapped to the start of the line, would have visible indentation from the non-breaking space.
When 'white-space' is set to 'pre-wrap', however, the editing rules will instead simply put two regular spaces between the words, and should the two words be split at the end of a line, the spaces would be neatly removed from the rendering.
The definition of the terms active range, editing host, and
editable, the user interface requirements of elements that are editing hosts or editable, the
execCommand()
,
queryCommandEnabled()
,
queryCommandIndeterm()
,
queryCommandState()
,
queryCommandSupported()
, and
queryCommandValue()
methods, text selections, and the delete the selection algorithm are defined in the
HTML Editing APIs specification. The interaction of editing and the undo/redo features in user
agents is defined by the UndoManager and DOM Transaction specification. [EDITING] [UNDO]
User agents can support the checking of spelling and grammar of editable text, either in form
controls (such as the value of textarea
elements), or in elements in an editing
host (e.g. using contenteditable
).
For each element, user agents must establish a default behavior, either through defaults or through preferences expressed by the user. There are three possible default behaviors for each element:
The spellcheck
attribute is an enumerated
attribute whose keywords are the empty string, true
and false
. The empty string and the true
keyword map to the
true state. The false
keyword maps to the false state. In
addition, there is a third state, the default state, which is the missing value
default (and the invalid value default).
The true state indicates that the element is to have its spelling and
grammar checked. The default state indicates that the element is to act according to a
default behavior, possibly based on the parent element's own spellcheck
state, as defined below. The false state
indicates that the element is not to be checked.
spellcheck
[ = value ]Returns true if the element is to have its spelling and grammar checked; otherwise, returns false.
Can be set, to override the default and set the spellcheck
content attribute.
The spellcheck
IDL attribute, on getting, must
return true if the element's spellcheck
content attribute is
in the true state, or if the element's spellcheck
content attribute is in the default state and the element's default behavior is true-by-default, or if the element's spellcheck
content attribute is in the default state and the
element's default behavior is inherit-by-default and the element's parent
element's spellcheck
IDL attribute would return true;
otherwise, if none of those conditions applies, then the attribute must instead return false.
The spellcheck
IDL attribute is not affected
by user preferences that override the spellcheck
content
attribute, and therefore might not reflect the actual spellchecking state.
On setting, if the new value is true, then the element's spellcheck
content attribute must be set to the literal string
"true
", otherwise it must be set to the literal string "false
".
User agents must only consider the following pieces of text as checkable for the purposes of this feature:
input
elements whose type
attributes are in the Text, Search,
URL, or E-mail states and that are mutable (i.e. that do not have the readonly
attribute specified and that are not disabled).textarea
elements that do not
have a readonly
attribute and that are not disabled.Text
nodes that are children of editing
hosts or editable elements.For text that is part of a Text
node, the element with which the text is
associated is the element that is the immediate parent of the first character of the word,
sentence, or other piece of text. For text in attributes, it is the attribute's element. For the
values of input
and textarea
elements, it is the element itself.
To determine if a word, sentence, or other piece of text in an applicable element (as defined above) is to have spelling- and grammar-checking enabled, the UA must use the following algorithm:
spellcheck
content attribute, then: if that attribute is in the
true state, then checking is enabled; otherwise, if that attribute is in the false
state, then checking is disabled.spellcheck
content attribute that is not in the default
state, then: if the nearest such ancestor's spellcheck
content attribute is in the true state, then checking is enabled; otherwise, checking is
disabled.If the checking is enabled for a word/sentence/text, the user agent should indicate spelling
and grammar errors in that text. User agents should take into account the other semantics given in
the document when suggesting spelling and grammar corrections. User agents may use the language of
the element to determine what spelling and grammar rules to use, or may use the user's preferred
language settings. UAs should use input
element attributes such as pattern
to ensure that the resulting value is valid, where
possible.
If checking is disabled, the user agent should not indicate spelling or grammar errors for that text.
Even when checking is enabled, user agents may opt to not report spelling or grammar errors in text that the user agent deems the user has no interest in having checked (e.g. text that was already present when the page was loaded, or that the user did not type, or text in controls that the user has not focused, or in parts of e-mail addresses that the user agent is not confident were misspelt).
The element with ID "a" in the following example would be the one used to determine if the word "Hello" is checked for spelling errors. In this example, it would not be.
<div contenteditable="true"> <span spellcheck="false" id="a">Hell</span><em>o!</em> </div>
The element with ID "b" in the following example would have checking enabled (the leading
space character in the attribute's value on the input
element causes the attribute
to be ignored, so the ancestor's value is used instead, regardless of the default).
<p spellcheck="true"> <label>Name: <input spellcheck=" false" id="b"></label> </p>
This specification does not define the user interface for spelling and grammar checkers. A user agent could offer on-demand checking, could perform continuous checking while the checking is enabled, or could use other interfaces.
This section defines an event-based drag-and-drop mechanism.
This specification does not define exactly what a drag-and-drop operation actually is.
On a visual medium with a pointing device, a drag operation could be the default action of a
mousedown
event that is followed by a series of mousemove
events, and the drop could be triggered by the mouse
being released.
When using an input modality other than a pointing device, users would probably have to explicitly indicate their intention to perform a drag-and-drop operation, stating what they wish to drag and where they wish to drop it, respectively.
However it is implemented, drag-and-drop operations must have a starting point (e.g. where the mouse was clicked, or the start of the selection or element that was selected for the drag), may have any number of intermediate steps (elements that the mouse moves over during a drag, or elements that the user picks as possible drop points as he cycles through possibilities), and must either have an end point (the element above which the mouse button was released, or the element that was finally selected), or be canceled. The end point must be the last element selected as a possible drop point before the drop occurs (so if the operation is not canceled, there must be at least one element in the middle step).
This section is non-normative.
To make an element draggable is simple: give the element a draggable
attribute, and set an event listener for dragstart
that stores the data being dragged.
The event handler typically needs to check that it's not a text selection that is being
dragged, and then needs to store data into the DataTransfer
object and set the
allowed effects (copy, move, link, or some combination).
For example:
<p>What fruits do you like?</p> <ol ondragstart="dragStartHandler(event)"> <li draggable="true" data-value="fruit-apple">Apples</li> <li draggable="true" data-value="fruit-orange">Oranges</li> <li draggable="true" data-value="fruit-pear">Pears</li> </ol> <script> var internalDNDType = 'text/x-example'; // set this to something specific to your site function dragStartHandler(event) { if (event.target instanceof HTMLLIElement) { // use the element's data-value="" attribute as the value to be moving: event.dataTransfer.setData(internalDNDType, event.target.dataset.value); event.dataTransfer.effectAllowed = 'move'; // only allow moves } else { event.preventDefault(); // don't allow selection to be dragged } } </script>
To accept a drop, the drop target has to have a dropzone
attribute and listen to the drop
event.
The value of the dropzone
attribute specifies what kind of
data to accept (e.g. "string:text/plain
" to accept any text strings, or
"file:image/png
" to accept a PNG image file) and what kind of feedback to give (e.g.
"move
" to indicate that the data will be moved).
Instead of using the dropzone
attribute, a drop
target can handle the dragenter
event (to report whether or
not the drop target is to accept the drop) and the dragover
event (to specify what feedback is to be shown to the user).
The drop
event allows the actual drop to be performed. This
event needs to be canceled, so that the dropEffect
attribute's value can be used by the source
(otherwise it's reset).
For example:
<p>Drop your favorite fruits below:</p> <ol dropzone="move string:text/x-example" ondrop="dropHandler(event)"> <!-- don't forget to change the "text/x-example" type to something specific to your site --> </ol> <script> var internalDNDType = 'text/x-example'; // set this to something specific to your site function dropHandler(event) { var li = document.createElement('li'); var data = event.dataTransfer.getData(internalDNDType); if (data == 'fruit-apple') { li.textContent = 'Apples'; } else if (data == 'fruit-orange') { li.textContent = 'Oranges'; } else if (data == 'fruit-pear') { li.textContent = 'Pears'; } else { li.textContent = 'Unknown Fruit'; } event.target.appendChild(li); } </script>
To remove the original element (the one that was dragged) from the display, the dragend
event can be used.
For our example here, that means updating the original markup to handle that event:
<p>What fruits do you like?</p> <ol ondragstart="dragStartHandler(event)" ondragend="dragEndHandler(event)"> ...as before... </ol> <script> function dragStartHandler(event) { // ...as before... } function dragEndHandler(event) { if (event.dataTransfer.dropEffect == 'move') { // remove the dragged element event.target.parentNode.removeChild(event.target); } } </script>
The data that underlies a drag-and-drop operation, known as the drag data store, consists of the following information:
A drag data store item list, which is a list of items representing the dragged data, each consisting of the following information:
The kind of data:
Text.
Binary data with a file name.
A Unicode string giving the type or format of the data, generally given by a MIME type. Some values that are not MIME types are special-cased for legacy reasons. The API does not enforce the use of MIME types; other values can be used as well. In all cases, however, the values are all converted to ASCII lowercase by the API.
Strings that contain space characters
cannot be used with the dropzone
attribute, so authors are
encouraged to use only MIME types or custom strings (without
spaces).
There is a limit of one Plain Unicode string item per item type string.
A Unicode or binary string, in some cases with a file name (itself a Unicode string), as per the drag data item kind.
The drag data store item list is ordered in the order that the items were added to the list; most recently added last.
The following information, used to generate the UI feedback during the drag:
A drag data store mode, which is one of the following:
For the dragstart
event. New data can be added to the
drag data store.
For the drop
event. The list of items representing dragged
data can be read, including the data. No new data can be added.
For all other events. The formats and kinds in the drag data store list of items representing dragged data can be enumerated, but the data itself is unavailable and no new data can be added.
A drag data store allowed effects state, which is a string.
When a drag data store is created, it
must be initialized such that its drag data store item list is empty, it has no
drag data store default feedback, it has no drag data store bitmap and
drag data store hot spot coordinate, its drag data store mode is protected mode, and its drag data store allowed effects
state is the string "uninitialized
".
DataTransfer
interfaceDataTransfer
objects are used to expose the drag data store that
underlies a drag-and-drop operation.
interface DataTransfer { attribute DOMString dropEffect; attribute DOMString effectAllowed; readonly attribute DataTransferItemList items; void setDragImage(Element image, long x, long y); /* old interface */ readonly attribute DOMString[] types; DOMString getData(DOMString format); void setData(DOMString format, DOMString data); void clearData(optional DOMString format); readonly attribute FileList files; };
dropEffect
[ = value ]Returns the kind of operation that is currently selected. If the kind of operation isn't one
of those that is allowed by the effectAllowed
attribute, then the operation will
fail.
Can be set, to change the selected operation.
The possible values are "none
", "copy
", "link
", and "move
".
effectAllowed
[ = value ]Returns the kinds of operations that are to be allowed.
Can be set (during the dragstart
event), to change the
allowed operations.
The possible values are "none
", "copy
", "copyLink
", "copyMove
", "link
",
"linkMove
", "move
", "all
", and
"uninitialized
",
items
Returns a DataTransferItemList
object, with the drag data.
setDragImage
(element, x, y)Uses the given element to update the drag feedback, replacing any previously specified feedback.
types
Returns an array listing the formats that were set in the dragstart
event. In addition, if any files are being dragged,
then one of the types will be the string "Files
".
getData
(format)Returns the specified data. If there is no such data, returns the empty string.
setData
(format, data)Adds the specified data.
clearData
( [ format ] )Removes the data of the specified formats. Removes all data if the argument is omitted.
files
Returns a FileList
of the files being dragged, if any.
DataTransfer
objects are used during the drag-and-drop
events, and are only valid while those events are being fired.
A DataTransfer
object is associated with a drag data store while it
is valid.
The dropEffect
attribute controls
the drag-and-drop feedback that the user is given during a drag-and-drop operation. When the
DataTransfer
object is created, the dropEffect
attribute is set to a string value. On
getting, it must return its current value. On setting, if the new value is one of "none
", "copy
", "link
", or "move
", then the attribute's current value must be set to the new value. Other
values must be ignored.
The effectAllowed
attribute is
used in the drag-and-drop processing model to initialize the dropEffect
attribute during the dragenter
and dragover
events.
When the DataTransfer
object is created, the effectAllowed
attribute is set to a string value. On
getting, it must return its current value. On setting, if drag data store's mode is the read/write
mode and the new value is one of "none
", "copy
", "copyLink
", "copyMove
", "link
", "linkMove
", "move
", "all
", or "uninitialized
", then the attribute's current value
must be set to the new value. Otherwise it must be left unchanged.
The items
attribute must return a
DataTransferItemList
object associated with the DataTransfer
object. The
same object must be returned each time.
The setDragImage(element,
x, y)
method must run the following
steps:
If the DataTransfer
object is no longer associated with a drag data
store, abort these steps. Nothing happens.
If the drag data store's mode is not the read/write mode, abort these steps. Nothing happens.
If the element argument is an img
element, then set the
drag data store bitmap to the element's image (at its intrinsic size); otherwise,
set the drag data store bitmap to an image generated from the given element (the
exact mechanism for doing so is not currently specified).
Set the drag data store hot spot coordinate to the given x, y coordinate.
The types
attribute must return a
live read only array giving the strings that
the following steps would produce. The same object must be returned each time.
Start with an empty list L.
If the DataTransfer
object is no longer associated with a drag data
store, the array is empty. Abort these steps; return the empty list L.
For each item in the drag data store item list whose kind is Plain Unicode string, add an entry to the list L consisting of the item's type string.
If there are any items in the drag data store item list whose kind is File, then add an entry to the list L consisting of the string "Files
". (This value can be
distinguished from the other values because it is not lowercase.)
The strings produced by these steps are those in the list L.
The getData(format)
method must run the following steps:
If the DataTransfer
object is no longer associated with a drag data
store, return the empty string and abort these steps.
If the drag data store's mode is the protected mode, return the empty string and abort these steps.
Let format be the first argument, converted to ASCII lowercase.
Let convert-to-URL be false.
If format equals "text
", change it to "text/plain
".
If format equals "url
", change it to "text/uri-list
" and set convert-to-URL to true.
If there is no item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, return the empty string and abort these steps.
Let result be the data of the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format.
If convert-to-URL is true, then parse result as
appropriate for text/uri-list
data, and then set result
to the first URL from the list, if any, or the empty string otherwise. [RFC2483]
Return result.
The setData(format, data)
method must run the following steps:
If the DataTransfer
object is no longer associated with a drag data
store, abort these steps. Nothing happens.
If the drag data store's mode is not the read/write mode, abort these steps. Nothing happens.
Let format be the first argument, converted to ASCII lowercase.
If format equals "text
", change it to "text/plain
".
If format equals "url
", change it to "text/uri-list
".
Remove the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, if there is one.
Add an item to the drag data store item list whose kind is Plain Unicode string, whose type string is equal to format, and whose data is the string given by the method's second argument.
The clearData()
method must run the
following steps:
If the DataTransfer
object is no longer associated with a drag data
store, abort these steps. Nothing happens.
If the drag data store's mode is not the read/write mode, abort these steps. Nothing happens.
If the method was called with no arguments, remove each item in the drag data store item list whose kind is Plain Unicode string, and abort these steps.
Let format be the first argument, converted to ASCII lowercase.
If format equals "text
", change it to "text/plain
".
If format equals "url
", change it to "text/uri-list
".
Remove the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, if there is one.
The clearData()
method does not
affect whether any files were included in the drag, so the types
attribute's list might still not be empty after
calling clearData()
(it would still contain the
"Files
" string if any files were included in the drag).
The files
attribute must return a
live FileList
sequence consisting of File
objects
representing the files found by the following steps. The same object must be returned each time.
Furthermore, for a given FileList
object and a given underlying file, the same
File
object must be used each time.
Start with an empty list L.
If the DataTransfer
object is no longer associated with a drag data
store, the FileList
is empty. Abort these steps; return the empty list L.
If the drag data store's mode is the protected mode, abort these steps; return the empty list L.
For each item in the drag data store item list whose kind is File , add the item's data (the file, in particular its name and contents, as well as its type) to the list L.
The files found by these steps are those in the list L.
This version of the API does not expose the types of the files during the drag.
DataTransferItemList
interfaceEach DataTransfer
object is associated with a DataTransferItemList
object.
interface DataTransferItemList { readonly attribute unsigned long length; getter DataTransferItem (unsigned long index); DataTransferItem? add(DOMString data, DOMString type); DataTransferItem? add(File data); void remove(unsigned long index); void clear(); };
length
Returns the number of items in the drag data store.
Returns the DataTransferItem
object representing the indexth
entry in the drag data store.
remove
(index)Removes the indexth entry in the drag data store.
clear
()Removes all the entries in the drag data store.
add
(data)add
(data, type)Adds a new entry for the given data to the drag data store. If the data is plain text then a type string has to be provided also.
While the DataTransferItemList
object's DataTransfer
object is
associated with a drag data store, the DataTransferItemList
object's
mode is the same as the drag data store mode. When the
DataTransferItemList
object's DataTransfer
object is not
associated with a drag data store, the DataTransferItemList
object's
mode is the disabled mode. The drag data store referenced in this
section (which is used only when the DataTransferItemList
object is not in the
disabled mode) is the drag data store with which the
DataTransferItemList
object's DataTransfer
object is associated.
The length
attribute must
return zero if the object is in the disabled mode; otherwise it must return the number of
items in the drag data store item list.
When a DataTransferItemList
object is not in the disabled mode, its
supported property indices are the numbers in the range
0 .. n-1,
where n is the number of items in the drag data store item
list.
To determine the value of an indexed property
i of a DataTransferItemList
object, the user agent must return a
DataTransferItem
object representing the ith item in the
drag data store. The same object must be returned each time a particular item is
obtained from this DataTransferItemList
object. The DataTransferItem
object must be associated with the same DataTransfer
object as the
DataTransferItemList
object when it is first created.
The add()
method must run the
following steps:
If the DataTransferItemList
object is not in the read/write mode, return null and abort these steps.
Jump to the appropriate set of steps from the following list:
If there is already an item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to the value of the
method's second argument, converted to ASCII lowercase, then throw a
NotSupportedError
exception and abort these steps.
Otherwise, add an item to the drag data store item list whose kind is Plain Unicode string, whose type string is equal to the value of the method's second argument, converted to ASCII lowercase, and whose data is the string given by the method's first argument.
File
Add an item to the drag data store item list whose kind is File, whose type
string is the type
of the File
,
converted to ASCII lowercase, and whose data is the same as the
File
's data.
Determine the value of the indexed
property corresponding to the newly added item, and return that value (a newly created
DataTransferItem
object).
The remove()
method, when
invoked with the argument i, must run these steps:
If the DataTransferItemList
object is not in the read/write mode, throw an InvalidStateError
exception and
abort these steps.
Remove the ith item from the drag data store.
The clear
method, if the
DataTransferItemList
object is in the read/write mode,
must remove all the items from the drag data store. Otherwise, it must do
nothing.
DataTransferItem
interfaceEach DataTransferItem
object is associated with a DataTransfer
object.
interface DataTransferItem { readonly attribute DOMString kind; readonly attribute DOMString type; void getAsString(FunctionStringCallback? _callback); File? getAsFile(); }; callback FunctionStringCallback = void (DOMString data);
kind
Returns the drag data item kind, one of: "string", "file".
type
Returns the drag data item type string.
getAsString
(callback)Invokes the callback with the string data as the argument, if the drag data item kind is Plain Unicode string.
getAsFile
()Returns a File
object, if the drag data item kind is File.
While the DataTransferItem
object's DataTransfer
object is associated
with a drag data store and that drag data store's drag data store
item list still contains the item that the DataTransferItem
object represents,
the DataTransferItem
object's mode is the same as the drag data store
mode. When the DataTransferItem
object's DataTransfer
object is
not associated with a drag data store, or if the item that the
DataTransferItem
object represents has been removed from the relevant drag data
store item list, the DataTransferItem
object's mode is the disabled
mode. The drag data store referenced in this section (which is used only when the
DataTransferItem
object is not in the disabled mode) is the drag data
store with which the DataTransferItem
object's DataTransfer
object is associated.
The kind
attribute must return the
empty string if the DataTransferItem
object is in the disabled mode; otherwise
it must return the string given in the cell from the second column of the following table from the
row whose cell in the first column contains the drag data item kind of the item
represented by the DataTransferItem
object:
Kind | String |
---|---|
Plain Unicode string | "string "
|
File | "file "
|
The type
attribute must return the
empty string if the DataTransferItem
object is in the disabled mode; otherwise
it must return the drag data item type string of the item represented by the
DataTransferItem
object.
The getAsString(callback)
method must run the following steps:
If the callback is null, abort these steps.
If the DataTransferItem
object is not in the read/write mode or the read-only mode,
abort these steps. The callback is never invoked.
If the drag data item kind is not Plain Unicode string, abort these steps. The callback is never invoked.
Otherwise, queue a task to invoke callback, passing the
actual data of the item represented by the DataTransferItem
object as the
argument.
The getAsFile()
method must run the following steps:
If the DataTransferItem
object is not in the read/write mode or the read-only mode,
return null and abort these steps.
If the drag data item kind is not File, then return null and abort these steps.
Return a new File
object representing the actual data of the item represented
by the DataTransferItem
object.
DragEvent
interfaceThe drag-and-drop processing model involves several events. They all use the
DragEvent
interface.
[Constructor(DOMString type, optional DragEventInit eventInitDict)] interface DragEvent : MouseEvent { readonly attribute DataTransfer? dataTransfer; }; dictionary DragEventInit : MouseEventInit { DataTransfer? dataTransfer; };
dataTransfer
Returns the DataTransfer
object for the event.
Although, for consistency with other event interfaces, the DragEvent
interface has a constructor, it is not particularly useful. In particular, there's no way to
create a useful DataTransfer
object from script, as DataTransfer
objects
have a processing and security model that is coordinated by the browser during drag-and-drops.
The dataTransfer
attribute of the
DragEvent
interface must return the value it was initialized to. When the object is
created, this attribute must be initialized to null. It represents the context information for the
event.
When a user agent is required to fire a DND event named e at an element, using a particular drag data store, the user agent must run the following steps:
If e is dragstart
, set the
drag data store mode to the read/write
mode.
If e is drop
, set the drag data
store mode to the read-only mode.
Let dataTransfer be a newly created DataTransfer
object
associated with the given drag data store.
Set the effectAllowed
attribute to the drag data
store's drag data store allowed effects state.
Set the dropEffect
attribute to "none
"
if e is dragstart
, drag
, dragexit
, or dragleave
; to the value corresponding to the current drag
operation if e is drop
or dragend
; and to a value based on the effectAllowed
attribute's value and the
drag-and-drop source, as given by the following table, otherwise (i.e. if e
is dragenter
or dragover
):
effectAllowed |
dropEffect |
---|---|
"none " |
"none " |
"copy " |
"copy " |
"copyLink " |
"copy ", or, if appropriate, "link " |
"copyMove " |
"copy ", or, if appropriate, "move " |
"all " |
"copy ", or, if appropriate, either "link " or "move " |
"link " |
"link " |
"linkMove " |
"link ", or, if appropriate, "move " |
"move " |
"move " |
"uninitialized " when what is being dragged is a selection from a text field |
"move ", or, if appropriate, either "copy " or "link " |
"uninitialized " when what is being dragged is a selection |
"copy ", or, if appropriate, either "link " or "move " |
"uninitialized " when what is being dragged is an a element with an href attribute |
"link ", or, if appropriate, either "copy " or "move " |
Any other case | "copy ", or, if appropriate, either "link " or "move " |
Where the table above provides possibly appropriate alternatives, user agents may instead use the listed alternative values if platform conventions dictate that the user has requested those alternate effects.
For example, Windows platform conventions are such that dragging while
holding the "alt" key indicates a preference for linking the data, rather than moving or copying
it. Therefore, on a Windows system, if "link
" is an option according to
the table above while the "alt" key is depressed, the user agent could select that instead of
"copy
" or "move
".
Create a trusted DragEvent
object
and initialize it to have the given name e, to bubble, to be cancelable
unless e is dragexit
, dragleave
, or dragend
, and to
have the detail
attribute initialized to zero, the mouse
and key attributes initialized according to the state of the input devices as they would be for
user interaction events, the relatedTarget
attribute initialized to null,
and the dataTransfer
attribute initialized to
dataTransfer, the DataTransfer
object created above.
If there is no relevant pointing device, the object must have its screenX
, screenY
, clientX
, clientY
, and button
attributes set to 0.
Dispatch the newly created
DragEvent
object at the specified target element.
Set the drag data store allowed effects state to the current value of dataTransfer's effectAllowed
attribute. (It can only have changed value if e is dragstart
.)
Set the drag data store mode back to the protected mode if it was changed in the first step.
Break the association between dataTransfer and the drag data store.
When the user attempts to begin a drag operation, the user agent must run the following steps. User agents must act as if these steps were run even if the drag actually started in another document or application and the user agent was not aware that the drag was occurring until it intersected with a document under the user agent's purview.
Determine what is being dragged, as follows:
If the drag operation was invoked on a selection, then it is the selection that is being dragged.
Otherwise, if the drag operation was invoked on a Document
, it is the first
element, going up the ancestor chain, starting at the node that the user tried to drag, that has
the IDL attribute draggable
set to true. If there is no such
element, then nothing is being dragged; abort these steps, the drag-and-drop operation is never
started.
Otherwise, the drag operation was invoked outside the user agent's purview. What is being dragged is defined by the document or application where the drag was started.
img
elements and a
elements with an href
attribute have their draggable
attribute set to true by default.
Create a drag data store. All the DND events fired subsequently by the steps in this section must use this drag data store.
Establish which DOM node is the source node, as follows:
If it is a selection that is being dragged, then the source node is the
Text
node that the user started the drag on (typically the Text
node
that the user originally clicked). If the user did not specify a particular node, for example if
the user just told the user agent to begin a drag of "the selection", then the source
node is the first Text
node containing a part of the selection.
Otherwise, if it is an element that is being dragged, then the source node is the element that is being dragged.
Otherwise, the source node is part of another document or application. When this specification requires that an event be dispatched at the source node in this case, the user agent must instead follow the platform-specific conventions relevant to that situation.
Multiple events are fired on the source node during the course of the drag-and-drop operation.
Determine the list of dragged nodes, as follows:
If it is a selection that is being dragged, then the list of dragged nodes contains, in tree order, every node that is partially or completely included in the selection (including all their ancestors).
Otherwise, the list of dragged nodes contains only the source node, if any.
If it is a selection that is being dragged, then add an item to the drag data store item list, with its properties set as follows:
text/plain
"Otherwise, if any files are being dragged, then add one item per file to the drag data store item list, with their properties set as follows:
application/octet-stream
" otherwise.Dragging files can currently only happen from outside a browsing context, for example from a file system manager application.
If the drag initiated outside of the application, the user agent must add items to the drag data store item list as appropriate for the data being dragged, honoring platform conventions where appropriate; however, if the platform conventions do not use MIME types to label dragged data, the user agent must make a best-effort attempt to map the types to MIME types, and, in any case, all the drag data item type strings must be converted to ASCII lowercase.
User agents may also add one or more items representing the selection or dragged element(s) in other forms, e.g. as HTML.
Run the following substeps:
Let urls be an empty list of absolute URLs.
For each node in the list of dragged nodes:
If urls is still empty, abort these substeps.
Let url string be the result of concatenating the strings in urls, in the order they were added, separated by a U+000D CARRIAGE RETURN U+000A LINE FEED character pair (CRLF).
Add one item to the drag data store item list, with its properties set as follows:
text/uri-list
Update the drag data store default feedback as appropriate for the user agent (if the user is dragging the selection, then the selection would likely be the basis for this feedback; if the user is dragging an element, then that element's rendering would be used; if the drag began outside the user agent, then the platform conventions for determining the drag feedback should be used).
Fire a DND event named dragstart
at the
source node.
If the event is canceled, then the drag-and-drop operation should not occur; abort these steps.
Since events with no event listeners registered are, almost by definition, never canceled, drag-and-drop is always available to the user if the author does not specifically prevent it.
Initiate the drag-and-drop operation in a manner consistent with platform conventions, and as described below.
The drag-and-drop feedback must be generated from the first of the following sources that is available:
From the moment that the user agent is to initiate the drag-and-drop operation, until the end of the drag-and-drop operation, device input events (e.g. mouse and keyboard events) must be suppressed.
During the drag operation, the element directly indicated by the user as the drop target is called the immediate user selection. (Only elements can be selected by the user; other nodes must not be made available as drop targets.) However, the immediate user selection is not necessarily the current target element, which is the element currently selected for the drop part of the drag-and-drop operation.
The immediate user selection changes as the user selects different elements (either by pointing at them with a pointing device, or by selecting them in some other way). The current target element changes when the immediate user selection changes, based on the results of event listeners in the document, as described below.
Both the current target element and the immediate user selection can be null, which means no target element is selected. They can also both be elements in other (DOM-based) documents, or other (non-Web) programs altogether. (For example, a user could drag text to a word-processor.) The current target element is initially null.
In addition, there is also a current drag operation, which can take on the values
"none
", "copy
", "link
", and
"move
". Initially, it has the value "none
". It is
updated by the user agent as described in the steps below.
User agents must, as soon as the drag operation is initiated and every 350ms (±200ms) thereafter for as long as the drag operation is ongoing, queue a task to perform the following steps in sequence:
If the user agent is still performing the previous iteration of the sequence (if any) when the next iteration becomes due, abort these steps for this iteration (effectively "skipping missed frames" of the drag-and-drop operation).
Fire a DND event named drag
at the
source node. If this event is canceled, the user agent must set the current
drag operation to "none
" (no drag operation).
If the drag
event was not canceled and the user has not ended
the drag-and-drop operation, check the state of the drag-and-drop operation, as follows:
If the user is indicating a different immediate user selection than during the
last iteration (or if this is the first iteration), and if this immediate user
selection is not the same as the current target element, then fire a
DND event named dragexit
at the current
target element, and then update the current target element as follows:
Set the current target element to null also.
Set the current target element to the immediate user selection.
Fire a DND event named dragenter
at the
immediate user selection.
If the event is canceled, then set the current target element to the immediate user selection.
Otherwise, run the appropriate step from the following list:
textarea
, or an input
element whose type
attribute is in the Text state) or an editing host or
editable element, and the drag data store item list has an item
with the drag data item type string "text/plain
" and the
drag data item kind Plain Unicode stringSet the current target element to the immediate user selection anyway.
dropzone
attribute that matches the drag data storeSet the current target element to the immediate user selection anyway.
dropzone
attribute that matches the drag data storeLet new target be the nearest (deepest) such ancestor element.
If the immediate user selection is new target, then leave the current target element unchanged.
Otherwise, fire a DND event named dragenter
at new target. Then, set the
current target element to new target, regardless of
whether that event was canceled or not.
Leave the current target element unchanged.
Fire a DND event named dragenter
at
the body element, if there is one, or at the Document
object, if
not. Then, set the current target element to the body element,
regardless of whether that event was canceled or not.
If the previous step caused the current target element to change, and if the
previous target element was not null or a part of a non-DOM document, then fire a DND
event named dragleave
at the previous target
element.
If the current target element is a DOM element, then fire a DND
event named dragover
at this current target
element.
If the dragover
event is not canceled, run the
appropriate step from the following list:
textarea
,
or an input
element whose type
attribute is
in the Text state) or an editing host
or editable element, and the drag data store item list has an item
with the drag data item type string "text/plain
" and the drag
data item kind Plain Unicode stringSet the current drag operation to either "copy
" or
"move
", as appropriate given the platform conventions.
dropzone
attribute that matches the drag data store and specifies an operationSet the current drag operation to the operation specified by the dropzone
attribute of the current target
element.
dropzone
attribute that matches the drag data store and does not
specify an operationSet the current drag operation to "copy
".
Reset the current drag operation to "none
".
Otherwise (if the dragover
event is canceled),
set the current drag operation based on the values of the effectAllowed
and dropEffect
attributes of the DragEvent
object's dataTransfer
object as they stood
after the event dispatch finished, as per the
following table:
effectAllowed |
dropEffect |
Drag operation |
---|---|---|
"uninitialized ", "copy ", "copyLink ", "copyMove ", or "all " |
"copy " |
"copy " |
"uninitialized ", "link ", "copyLink ", "linkMove ", or "all " |
"link " |
"link " |
"uninitialized ", "move ", "copyMove ", "linkMove ", or "all " |
"move " |
"move " |
Any other case | "none " |
Otherwise, if the current target element is not a DOM element, use platform-specific mechanisms to determine what drag operation is being performed (none, copy, link, or move), and set the current drag operation accordingly.
Update the drag feedback (e.g. the mouse cursor) to match the current drag operation, as follows:
Drag operation | Feedback |
---|---|
"copy " |
Data will be copied if dropped here. |
"link " |
Data will be linked if dropped here. |
"move " |
Data will be moved if dropped here. |
"none " |
No operation allowed, dropping here will cancel the drag-and-drop operation. |
Otherwise, if the user ended the drag-and-drop operation (e.g. by releasing the mouse button
in a mouse-driven drag-and-drop interface), or if the drag
event
was canceled, then this will be the last iteration. Run the following steps, then stop the
drag-and-drop operation:
If the current drag operation is "none
" (no drag
operation), or, if the user ended the drag-and-drop operation by canceling it (e.g. by hitting
the Escape key), or if the current target element is null, then the
drag operation failed. Run these substeps:
Let dropped be false.
If the current target element is a DOM element, fire a DND
event named dragleave
at it; otherwise, if it is
not null, use platform-specific conventions for drag cancellation.
Set the current drag operation to "none
".
Otherwise, the drag operation might be a success; run these substeps:
Let dropped be true.
If the current target element is a DOM element, fire a DND
event named drop
at it; otherwise, use
platform-specific conventions for indicating a drop.
If the event is canceled, set the current drag operation to the value of the
dropEffect
attribute of the
DragEvent
object's dataTransfer
object as it stood after the event dispatch
finished.
Otherwise, the event is not canceled; perform the event's default action, which depends on the exact target as follows:
textarea
,
or an input
element whose type
attribute
is in the Text state) or an editing
host or editable element, and the drag data store item
list has an item with the drag data item type string
"text/plain
" and the drag data item kind Plain Unicode
stringInsert the actual data of the first item in the drag data store item
list to have a drag data item type
string of "text/plain
" and a drag
data item kind that is Plain Unicode string into the text field or
editing host or editable element in a manner consistent with
platform-specific conventions (e.g. inserting it at the current mouse cursor position, or
inserting it at the end of the field).
Reset the current drag operation to "none
".
Fire a DND event named dragend
at the
source node.
Run the appropriate steps from the following list as the default action of the dragend
event:
move
", and the source of the drag-and-drop operation is a selection in the
DOM that is entirely contained within an editing hostmove
", and the source of the drag-and-drop operation is a selection in a text
fieldThe user agent should delete the dragged selection from the relevant text field.
none
"The drag was canceled. If the platform conventions dictate that this be represented to the user (e.g. by animating the dragged selection going back to the source of the drag-and-drop operation), then do so.
The event has no default action.
For the purposes of this step, a text field is a textarea
element or an
input
element whose type
attribute is in one
of the
Text,
Search,
Tel,
URL,
E-mail,
Password, or
Number
states.
User agents are encouraged to consider how to react to drags near the edge of scrollable regions. For example, if a user drags a link to the bottom of the viewport on a long page, it might make sense to scroll the page so that the user can drop the link lower on the page.
This model is independent of which Document
object the nodes involved
are from; the events are fired as described above and the rest of the processing model runs as
described above, irrespective of how many documents are involved in the operation.
This section is non-normative.
The following events are involved in the drag-and-drop model.
Event Name | Target | Cancelable? | Drag data store mode | dropEffect |
Default Action |
---|---|---|---|---|---|
dragstart |
Source node | ✓ Cancelable | Read/write mode | "none " |
Initiate the drag-and-drop operation |
drag |
Source node | ✓ Cancelable | Protected mode | "none " |
Continue the drag-and-drop operation |
dragenter |
Immediate user selection or the body element | ✓ Cancelable | Protected mode | Based on effectAllowed value |
Reject immediate user selection as potential target element |
dragexit |
Previous target element | — | Protected mode | "none " |
None |
dragleave |
Previous target element | — | Protected mode | "none " |
None |
dragover |
Current target element | ✓ Cancelable | Protected mode | Based on effectAllowed value |
Reset the current drag operation to "none" |
drop |
Current target element | ✓ Cancelable | Read-only mode | Current drag operation | Varies |
dragend |
Source node | — | Protected mode | Current drag operation | Varies |
Not shown in the above table: all these events bubble, and the effectAllowed
attribute always has the value it had
after the dragstart
event, defaulting to "uninitialized
" in the dragstart
event.
draggable
attributeAll HTML elements may have the draggable
content attribute set. The draggable
attribute is an
enumerated attribute. It has three states. The first state is true and it has
the keyword true
. The second state is false and it has the keyword
false
. The third state is auto; it has no keywords but it is the
missing value default.
The true state means the element is draggable; the false state means that it is not. The auto state uses the default behavior of the user agent.
An element with a draggable
attribute should also have a
title
attribute that names the element for the purpose of
non-visual interactions.
draggable
[ = value ]Returns true if the element is draggable; otherwise, returns false.
Can be set, to override the default and set the draggable
content attribute.
The draggable
IDL attribute, whose value depends
on the content attribute's in the way described below, controls whether or not the element is
draggable. Generally, only text selections are draggable, but elements whose draggable
IDL attribute is true become draggable as well.
If an element's draggable
content attribute has the state
true, the draggable
IDL attribute must return true.
Otherwise, if the element's draggable
content attribute has
the state false, the draggable
IDL attribute must return
false.
Otherwise, the element's draggable
content attribute has
the state auto. If the element is an img
element, an object
element that represents an image, or an a
element with an href
content attribute, the draggable
IDL attribute must return true; otherwise, the draggable
IDL attribute must return false.
If the draggable
IDL attribute is set to the value false,
the draggable
content attribute must be set to the literal
value false
. If the draggable
IDL
attribute is set to the value true, the draggable
content
attribute must be set to the literal value true
.
dropzone
attributeAll HTML elements may have the dropzone
content
attribute set. When specified, its value must be an unordered set of unique space-separated
tokens that are ASCII case-insensitive. The allowed values are the
following:
copy
Indicates that dropping an accepted item on the element will result in a copy of the dragged data.
move
Indicates that dropping an accepted item on the element will result in the dragged data being moved to the new location.
link
Indicates that dropping an accepted item on the element will result in a link to the original data.
string:
"Indicates that items with the drag data item kind Plain Unicode string and the drag data item type string set to a value that matches the remainder of the keyword are accepted.
file:
"Indicates that items with the drag data item kind File and the drag data item type string set to a value that matches the remainder of the keyword are accepted.
The dropzone
content attribute's values must not have more
than one of the three feedback values (copy
, move
, and link
)
specified. If none are specified, the copy
value is
implied.
An element with a dropzone
attribute should also have a
title
attribute that names the element for the purpose of
non-visual interactions.
A dropzone
attribute matches a drag data store if the dropzone
processing steps result in a match.
A dropzone
attribute specifies an operation if the dropzone
processing steps result in a specified operation. The
specified operation is as given by those steps.
The dropzone
processing steps are as follows.
They either result in a match or not, and separate from this result either in a specified
operation or not, as defined below.
Let value be the value of the dropzone
attribute.
Let keywords be the result of splitting value on spaces.
Let matched be false.
Let operation be unspecified.
For each value in keywords, if any, in the order that they were found in value, run the following steps.
Let keyword be the keyword.
If keyword is one of "copy
",
"move
", or "link
", then: run the following substeps:
If operation is still unspecified, then let operation be the string given by keyword.
Skip to the step labeled end of keyword below.
If keyword does not contain a ":" (U+003A) character, or if the first such character in keyword is either the first character or the last character in the string, then skip to the step labeled end of keyword below.
Let kind code be the substring of keyword from the first character in the string to the last character in the string that is before the first ":" (U+003A) character in the string, converted to ASCII lowercase.
Jump to the appropriate step from the list below, based on the value of kind code:
string
"Let kind be Plain Unicode string.
file
"Let kind be File.
Skip to the step labeled end of keyword below.
Let type be the substring of keyword from the first character after the first ":" (U+003A) character in the string, to the last character in the string, converted to ASCII lowercase.
If there exist any items in the drag data store item list whose drag data item kind is the kind given in kind and whose drag data item type string is type, then let matched be true.
End of keyword: Go on to the next keyword, if any, or the next step in the overall algorithm, if there are no more.
The algorithm results in a match if matched is true, and does not otherwise.
The algorithm results in a specified operation if operation is not unspecified. The specified operation, if one is specified, is the one given by operation.
The dropzone
IDL attribute must
reflect the content attribute of the same name.
In this example, a div
element is made into a drop target for image files using
the dropzone
attribute. Images dropped into the target are
then displayed.
<div dropzone="copy file:image/png file:image/gif file:image/jpeg" ondrop="receive(event, this)"> <p>Drop an image here to have it displayed.</p> </div> <script> function receive(event, element) { var data = event.dataTransfer.items; for (var i = 0; i < data.length; i += 1) { if ((data[i].kind == 'file') && (data[i].type.match('^image/'))) { var img = new Image(); img.src = window.createObjectURL(data[i].getAsFile()); element.appendChild(img); } } } </script>
User agents must not make the data added to the DataTransfer
object during the
dragstart
event available to scripts until the drop
event, because otherwise, if a user were to drag sensitive
information from one document to a second document, crossing a hostile third document in the
process, the hostile document could intercept the data.
For the same reason, user agents must consider a drop to be successful only if the user
specifically ended the drag operation — if any scripts end the drag operation, it must be
considered unsuccessful (canceled) and the drop
event must not be
fired.
User agents should take care to not start drag-and-drop operations in response to script actions. For example, in a mouse-and-window environment, if a script moves a window while the user has his mouse button depressed, the UA would not consider that to start a drag. This is important because otherwise UAs could cause data to be dragged from sensitive sources and dropped into hostile documents without the user's consent.
User agents should filter potentially active (scripted) content (e.g. HTML) when it is dragged and when it is dropped, using a whitelist of known-safe features. Similarly, relative URLs should be turned into absolute URLs to avoid references changing in unexpected ways. This specification does not specify how this is performed.
Consider a hostile page providing some content and getting the user to select and drag and
drop (or indeed, copy and paste) that content to a victim page's contenteditable
region. If the browser does not ensure that
only safe content is dragged, potentially unsafe content such as scripts and event handlers in
the selection, once dropped (or pasted) into the victim site, get the privileges of the victim
site. This would thus enable a cross-site scripting attack.
This section only describes the rules for resources labeled with an HTML MIME type. Rules for XML resources are discussed in the section below entitled "The XHTML syntax".
This section only applies to documents, authoring tools, and markup generators. In particular, it does not apply to conformance checkers; conformance checkers must use the requirements given in the next section ("parsing HTML documents").
Documents must consist of the following parts, in the given order:
html
element.The various types of content mentioned above are described in the next few sections.
In addition, there are some restrictions on how character encoding declarations are to be serialized, as discussed in the section on that topic.
Space characters before the root html
element, and space characters at the start
of the html
element and before the head
element, will be dropped when
the document is parsed; space characters after the root html
element will
be parsed as if they were at the end of the body
element. Thus, space characters
around the root element do not round-trip.
It is suggested that newlines be inserted after the DOCTYPE, after any comments that are
before the root element, after the html
element's start tag (if it is not omitted), and after any comments that are inside the
html
element but before the head
element.
Many strings in the HTML syntax (e.g. the names of elements and their attributes) are case-insensitive, but only for uppercase ASCII letters and lowercase ASCII letters. For convenience, in this section this is just referred to as "case-insensitive".
A DOCTYPE is a required preamble.
DOCTYPEs are required for legacy reasons. When omitted, browsers tend to use a different rendering mode that is incompatible with some specifications. Including the DOCTYPE in a document ensures that the browser makes a best-effort attempt at following the relevant specifications.
A DOCTYPE must consist of the following components, in this order:
<!DOCTYPE
".html
".In other words, <!DOCTYPE html>
, case-insensitively.
For the purposes of HTML generators that cannot output HTML markup with the short DOCTYPE
"<!DOCTYPE html>
", a DOCTYPE legacy string may be inserted
into the DOCTYPE (in the position defined above). This string must consist of:
SYSTEM
".about:legacy-compat
".In other words, <!DOCTYPE html SYSTEM "about:legacy-compat">
or
<!DOCTYPE html SYSTEM 'about:legacy-compat'>
, case-insensitively except for the
part in single or double quotes.
The DOCTYPE legacy string should not be used unless the document is generated from a system that cannot output the shorter string.
To help authors transition from HTML4 and XHTML1, an obsolete permitted DOCTYPE string can be inserted into the DOCTYPE (in the position defined above). This string must consist of:
PUBLIC
".Public identifier | System identifier | System identifier optional? |
---|---|---|
-//W3C//DTD HTML 4.0//EN
| http://www.w3.org/TR/REC-html40/strict.dtd
| Yes |
-//W3C//DTD HTML 4.01//EN
| http://www.w3.org/TR/html4/strict.dtd
| Yes |
-//W3C//DTD XHTML 1.0 Strict//EN
| http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd
| No |
-//W3C//DTD XHTML 1.1//EN
| http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd
| No |
A DOCTYPE containing an obsolete permitted DOCTYPE string is an obsolete permitted DOCTYPE. Authors should not use obsolete permitted DOCTYPEs, as they are unnecessarily long.
There are five different kinds of elements: void elements, raw text elements, escapable raw text elements, foreign elements, and normal elements.
area
, base
, br
, col
, embed
,
hr
, img
, input
, keygen
, link
,
meta
, param
, source
,
track
, wbr
script
, style
textarea
, title
Tags are used to delimit the start and end of elements in the markup. Raw text, escapable raw text, and normal elements have a start tag to indicate where they begin, and an end tag to indicate where they end. The start and end tags of certain normal elements can be omitted, as described below in the section on optional tags. Those that cannot be omitted must not be omitted. Void elements only have a start tag; end tags must not be specified for void elements. Foreign elements must either have a start tag and an end tag, or a start tag that is marked as self-closing, in which case they must not have an end tag.
The contents of the element must be placed between just after the start tag (which might be implied, in certain cases) and just before the end tag (which again, might be implied in certain cases). The exact allowed contents of each individual element depend on the content model of that element, as described earlier in this specification. Elements must not contain content that their content model disallows. In addition to the restrictions placed on the contents by those content models, however, the five types of elements have additional syntactic requirements.
Void elements can't have any contents (since there's no end tag, no content can be put between the start tag and the end tag).
Raw text elements can have text, though it has restrictions described below.
Escapable raw text elements can have text and character references, but the text must not contain an ambiguous ampersand. There are also further restrictions described below.
Foreign elements whose start tag is marked as self-closing can't have any contents (since, again, as there's no end tag, no content can be put between the start tag and the end tag). Foreign elements whose start tag is not marked as self-closing can have text, character references, CDATA sections, other elements, and comments, but the text must not contain the character "<" (U+003C) or an ambiguous ampersand.
The HTML syntax does not support namespace declarations, even in foreign elements.
For instance, consider the following HTML fragment:
<p> <svg> <metadata> <!-- this is invalid --> <cdr:license xmlns:cdr="http://www.example.com/cdr/metadata" name="MIT"/> </metadata> </svg> </p>
The innermost element, cdr:license
, is actually in the SVG namespace, as
the "xmlns:cdr
" attribute has no effect (unlike in XML). In fact, as the
comment in the fragment above says, the fragment is actually non-conforming. This is because the
SVG specification does not define any elements called "cdr:license
" in the
SVG namespace.
Normal elements can have text, character references, other elements, and comments, but the text must not contain the character "<" (U+003C) or an ambiguous ampersand. Some normal elements also have yet more restrictions on what content they are allowed to hold, beyond the restrictions imposed by the content model and those described in this paragraph. Those restrictions are described below.
Tags contain a tag name, giving the element's name. HTML elements all have names that only use alphanumeric ASCII characters. In the HTML syntax, tag names, even those for foreign elements, may be written with any mix of lower- and uppercase letters that, when converted to all-lowercase, matches the element's tag name; tag names are case-insensitive.
Start tags must have the following format:
End tags must have the following format:
Attributes for an element are expressed inside the element's start tag.
Attributes have a name and a value. Attribute names must consist of one or more characters other than the space characters, U+0000 NULL, U+0022 QUOTATION MARK ("), U+0027 APOSTROPHE ('), ">" (U+003E), "/" (U+002F), and "=" (U+003D) characters, the control characters, and any characters that are not defined by Unicode. In the HTML syntax, attribute names, even those for foreign elements, may be written with any mix of lower- and uppercase letters that are an ASCII case-insensitive match for the attribute's name.
Attribute values are a mixture of text and character references, except with the additional restriction that the text cannot contain an ambiguous ampersand.
Attributes can be specified in four different ways:
Just the attribute name. The value is implicitly the empty string.
In the following example, the disabled
attribute is
given with the empty attribute syntax:
<input disabled>
If an attribute using the empty attribute syntax is to be followed by another attribute, then there must be a space character separating the two.
The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal space characters, any U+0022 QUOTATION MARK characters ("), U+0027 APOSTROPHE characters ('), "=" (U+003D) characters, "<" (U+003C) characters, ">" (U+003E) characters, or U+0060 GRAVE ACCENT characters (`), and must not be the empty string.
In the following example, the value
attribute is given
with the unquoted attribute value syntax:
<input value=yes>
If an attribute using the unquoted attribute syntax is to be followed by another attribute or by the optional "/" (U+002F) character allowed in step 6 of the start tag syntax above, then there must be a space character separating the two.
The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by a single "'" (U+0027) character, followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal "'" (U+0027) characters, and finally followed by a second single "'" (U+0027) character.
In the following example, the type
attribute is given
with the single-quoted attribute value syntax:
<input type='checkbox'>
If an attribute using the single-quoted attribute syntax is to be followed by another attribute, then there must be a space character separating the two.
The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by a single """ (U+0022) character, followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal U+0022 QUOTATION MARK characters ("), and finally followed by a second single """ (U+0022) character.
In the following example, the name
attribute is given with
the double-quoted attribute value syntax:
<input name="be evil">
If an attribute using the double-quoted attribute syntax is to be followed by another attribute, then there must be a space character separating the two.
There must never be two or more attributes on the same start tag whose names are an ASCII case-insensitive match for each other.
When a foreign element has one of the namespaced attributes given by the local name and namespace of the first and second cells of a row from the following table, it must be written using the name given by the third cell from the same row.
Local name | Namespace | Attribute name |
---|---|---|
actuate | XLink namespace | xlink:actuate
|
arcrole | XLink namespace | xlink:arcrole
|
href | XLink namespace | xlink:href
|
role | XLink namespace | xlink:role
|
show | XLink namespace | xlink:show
|
title | XLink namespace | xlink:title
|
type | XLink namespace | xlink:type
|
base | XML namespace | xml:base
|
lang | XML namespace | xml:lang
|
space | XML namespace | xml:space
|
xmlns | XMLNS namespace | xmlns
|
xlink | XMLNS namespace | xmlns:xlink
|
No other namespaced attribute can be expressed in the HTML syntax.
Whether the attributes in the table above are conforming or not is defined by other specifications (e.g. the SVG and MathML specifications); this section only describes the syntax rules if the attributes are serialized using the HTML syntax.
Certain tags can be omitted.
Omitting an element's start tag in the
situations described below does not mean the element is not present; it is implied, but it is
still there. For example, an HTML document always has a root html
element, even if
the string <html>
doesn't appear anywhere in the markup.
An html
element's start tag may be omitted
if the first thing inside the html
element is not a comment.
An html
element's end tag may be omitted if
the html
element is not immediately followed by a comment.
A head
element's start tag may be omitted if
the element is empty, or if the first thing inside the head
element is an
element.
A head
element's end tag may be omitted if the
head
element is not immediately followed by a space character or a comment.
A body
element's start tag may be omitted if
the element is empty, or if the first thing inside the body
element is not a
space character or a comment, except if the
first thing inside the body
element is a meta
, link
, script
, style
, or template
element.
A body
element's end tag may be omitted if the
body
element is not immediately followed by a comment.
An li
element's end tag may be omitted if the
li
element is immediately followed by another li
element or if there is
no more content in the parent element.
A dt
element's end tag may be omitted if the
dt
element is immediately followed by another dt
element or a
dd
element.
A dd
element's end tag may be omitted if the
dd
element is immediately followed by another dd
element or a
dt
element, or if there is no more content in the parent element.
A p
element's end tag may be omitted if the
p
element is immediately followed by an address
, article
,
aside
, blockquote
, div
, dl
,
fieldset
, footer
, form
, h1
, h2
,
h3
, h4
, h5
, h6
, header
,
hgroup
, hr
, main
, nav
,
ol
, p
, pre
, section
, table
, or
ul
, element, or if there is no more content in the parent element and the parent
element is not an a
element.
An rb
element's end tag may be omitted if the
rb
element is immediately followed by an rb
, rt
,
rtc
or rp
element, or if there is no more content in the parent
element.
An rt
element's end tag may be omitted if the
rt
element is immediately followed by an rb
, rt
or
rp
element, or if there is no more content in the parent element.
An rtc
element's end tag may be omitted if
the rtc
element is immediately followed by an rb
, rt
,
rtc
or rp
element, or if there is no more content in the parent
element.
An rp
element's end tag may be omitted if the
rp
element is immediately followed by an rb
, rt
,
rtc
or rp
element, or if there is no more content in the parent
element.
An optgroup
element's end tag may be omitted
if the optgroup
element is
immediately followed by another optgroup
element, or if there is no more content in
the parent element.
An option
element's end tag may be omitted if
the option
element is immediately followed by another option
element, or
if it is immediately followed by an optgroup
element, or if there is no more content
in the parent element.
A colgroup
element's start tag may be
omitted if the first thing inside the colgroup
element is a col
element,
and if the element is not immediately preceded by another colgroup
element whose
end tag has been omitted. (It can't be omitted if the element
is empty.)
A colgroup
element's end tag may be omitted if
the colgroup
element is not immediately followed by a space character or
a comment.
A thead
element's end tag may be omitted if
the thead
element is immediately followed by a tbody
or
tfoot
element.
A tbody
element's start tag may be omitted
if the first thing inside the tbody
element is a tr
element, and if the
element is not immediately preceded by a tbody
, thead
, or
tfoot
element whose end tag has been omitted. (It
can't be omitted if the element is empty.)
A tbody
element's end tag may be omitted if
the tbody
element is immediately followed by a tbody
or
tfoot
element, or if there is no more content in the parent element.
A tfoot
element's end tag may be omitted if
the tfoot
element is immediately followed by a tbody
element, or if
there is no more content in the parent element.
A tr
element's end tag may be omitted if the
tr
element is immediately followed by another tr
element, or if there is
no more content in the parent element.
A td
element's end tag may be omitted if the
td
element is immediately followed by a td
or th
element,
or if there is no more content in the parent element.
A th
element's end tag may be omitted if the
th
element is immediately followed by a td
or th
element,
or if there is no more content in the parent element.
However, a start tag must never be omitted if it has any attributes.
For historical reasons, certain elements have extra restrictions beyond even the restrictions given by their content model.
A table
element must not contain tr
elements, even though these
elements are technically allowed inside table
elements according to the content
models described in this specification. (If a tr
element is put inside a
table
in the markup, it will in fact imply a tbody
start tag before
it.)
A single newline may be placed immediately after the start tag of pre
and textarea
elements.
If the element's contents are intended to start with a newline,
two consecutive newlines thus need to be included by the author.
The text in raw text and escapable raw text
elements must not contain any occurrences of the string "</
"
(U+003C LESS-THAN SIGN, U+002F SOLIDUS) followed by characters that case-insensitively match the
tag name of the element followed by one of "tab" (U+0009), "LF" (U+000A), "FF" (U+000C), "CR" (U+000D), U+0020 SPACE, ">" (U+003E), or "/" (U+002F).
Text is allowed inside elements, attribute values, and comments. Extra constraints are placed on what is and what is not allowed in text based on where the text is to be put, as described in the other sections.
Newlines in HTML may be represented either as "CR" (U+000D) characters, "LF" (U+000A) characters, or pairs of "CR" (U+000D), "LF" (U+000A) characters in that order.
Where character references are allowed, a character reference of a "LF" (U+000A) character (but not a "CR" (U+000D) character) also represents a newline.
In certain cases described in other sections, text may be mixed with character references. These can be used to escape characters that couldn't otherwise legally be included in text.
Character references must start with a U+0026 AMPERSAND character (&). Following this, there are three possible kinds of character references:
The numeric character reference forms described above are allowed to reference any Unicode code point other than U+0000, U+000D, permanently undefined Unicode characters (noncharacters), surrogates (U+D800–U+DFFF), and control characters other than space characters.
An ambiguous ampersand is a U+0026 AMPERSAND character (&) that is followed by one or more alphanumeric ASCII characters, followed by a ";" (U+003B) character, where these characters do not match any of the names given in the named character references section.
CDATA sections must consist of the following components, in this order:
<![CDATA[
".]]>
".]]>
".CDATA sections can only be used in foreign content (MathML or SVG). In this example, a CDATA
section is used to escape the contents of an ms
element:
<p>You can add a string to a number, but this stringifies the number:</p> <math> <ms><![CDATA[x<y]]></ms> <mo>+</mo> <mn>3</mn> <mo>=</mo> <ms><![CDATA[x<y3]]></ms> </math>
Comments must start with the four character sequence U+003C
LESS-THAN SIGN, U+0021 EXCLAMATION MARK, U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS (<!--
). Following this sequence, the comment may have text, with the additional restriction that the text must not start with
a single ">" (U+003E) character, nor start with a U+002D HYPHEN-MINUS character
(-) followed by a ">" (U+003E) character, nor contain two consecutive U+002D
HYPHEN-MINUS characters (--
), nor end with a U+002D HYPHEN-MINUS character
(-). Finally, the comment must be ended by the three character sequence U+002D HYPHEN-MINUS,
U+002D HYPHEN-MINUS, U+003E GREATER-THAN SIGN (-->
).
This section only applies to user agents, data mining tools, and conformance checkers.
The rules for parsing XML documents into DOM trees are covered by the next section, entitled "The XHTML syntax".
User agents must use the parsing rules described in this section to generate the DOM trees from
text/html
resources. Together, these rules define what is referred to as the
HTML parser.
While the HTML syntax described in this specification bears a close resemblance to SGML and XML, it is a separate language with its own parsing rules.
Some earlier versions of HTML (in particular from HTML2 to HTML4) were based on SGML and used SGML parsing rules. However, few (if any) web browsers ever implemented true SGML parsing for HTML documents; the only user agents to strictly handle HTML as an SGML application have historically been validators. The resulting confusion — with validators claiming documents to have one representation while widely deployed Web browsers interoperably implemented a different representation — has wasted decades of productivity. This version of HTML thus returns to a non-SGML basis.
Authors interested in using SGML tools in their authoring pipeline are encouraged to use XML tools and the XML serialization of HTML.
This specification defines the parsing rules for HTML documents, whether they are syntactically correct or not. Certain points in the parsing algorithm are said to be parse errors. The error handling for parse errors is well-defined (that's the processing rules described throughout this specification), but user agents, while parsing an HTML document, may abort the parser at the first parse error that they encounter for which they do not wish to apply the rules described in this specification.
Conformance checkers must report at least one parse error condition to the user if one or more parse error conditions exist in the document and must not report parse error conditions if none exist in the document. Conformance checkers may report more than one parse error condition if more than one parse error condition exists in the document.
Parse errors are only errors with the syntax of HTML. In addition to checking for parse errors, conformance checkers will also verify that the document obeys all the other conformance requirements described in this specification.
For the purposes of conformance checkers, if a resource is determined to be in the HTML syntax, then it is an HTML document.
As stated in the terminology
section, references to element types that do not
explicitly specify a namespace always refer to elements in the HTML namespace. For
example, if the spec talks about "a div
element", then that is an element with
the local name "div
", the namespace "http://www.w3.org/1999/xhtml
", and the interface HTMLDivElement
.
Where possible, references to such elements are hyperlinked to their definition.
The input to the HTML parsing process consists of a stream of Unicode code points, which is passed through a tokenization stage
followed by a tree construction stage. The output is a Document
object.
Implementations that do not support scripting do not
have to actually create a DOM Document
object, but the DOM tree in such cases is
still used as the model for the rest of the specification.
In the common case, the data handled by the tokenization stage comes from the network, but
it can also come from script running in the user
agent, e.g. using the document.write()
API.
There is only one set of states for the tokenizer stage and the tree construction stage, but the tree construction stage is reentrant, meaning that while the tree construction stage is handling one token, the tokenizer might be resumed, causing further tokens to be emitted and processed before the first token's processing is complete.
In the following example, the tree construction stage will be called upon to handle a "p" start tag token while handling the "script" end tag token:
... <script> document.write('<p>'); </script> ...
To handle these cases, parsers have a script nesting level, which must be initially set to zero, and a parser pause flag, which must be initially set to false.
The stream of Unicode code points that comprises the input to the tokenization stage will be initially seen by the user agent as a stream of bytes (typically coming over the network or from the local file system). The bytes encode the actual characters according to a particular character encoding, which the user agent uses to decode the bytes into characters.
For XML documents, the algorithm user agents must use to determine the character encoding is given by the XML specification. This section does not apply to XML documents. [XML]
Usually, the encoding sniffing algorithm defined below is used to determine the character encoding.
Given a character encoding, the bytes in the input byte stream must be converted to Unicode code points for the tokenizer's input stream, as described by the rules for that encoding's decoder.
Bytes or sequences of bytes in the original byte stream that did not conform to the encoding specification (e.g. invalid UTF-8 byte sequences in a UTF-8 input byte stream) are errors that conformance checkers are expected to report.
Leading Byte Order Marks (BOMs) are not stripped by the decoder algorithms, they are stripped by the algorithm below.
The decoder algorithms describe how to handle invalid input; for security reasons, it is imperative that those rules be followed precisely. Differences in how invalid byte sequences are handled can result in, amongst other problems, script injection vulnerabilities ("XSS").
When the HTML parser is decoding an input byte stream, it uses a character encoding and a confidence. The confidence is either tentative, certain, or irrelevant. The encoding used, and whether the confidence in that encoding is tentative or certain, is used during the parsing to determine whether to change the encoding. If no encoding is necessary, e.g. because the parser is operating on a Unicode stream and doesn't have to use a character encoding at all, then the confidence is irrelevant.
Some algorithms feed the parser by directly adding characters to the input stream rather than adding bytes to the input byte stream.
When the HTML parser is to operate on an input byte stream that has a known definite encoding, then the character encoding is that encoding and the confidence is certain.
In some cases, it might be impractical to unambiguously determine the encoding before parsing the document. Because of this, this specification provides for a two-pass mechanism with an optional pre-scan. Implementations are allowed, as described below, to apply a simplified parsing algorithm to whatever bytes they have available before beginning to parse the document. Then, the real parser is started, using a tentative encoding derived from this pre-parse and other out-of-band metadata. If, while the document is being loaded, the user agent discovers a character encoding declaration that conflicts with this information, then the parser can get reinvoked to perform a parse of the document with the real encoding.
User agents must use the following algorithm, called the encoding sniffing algorithm, to determine the character encoding to use when decoding a document in the first pass. This algorithm takes as input any out-of-band metadata available to the user agent (e.g. the Content-Type metadata of the document) and all the bytes available so far, and returns a character encoding and a confidence that is either tentative or certain.
If the user has explicitly instructed the user agent to override the document's character encoding with a specific encoding, optionally return that encoding with the confidence certain and abort these steps.
Typically, user agents remember such user requests across sessions, and in some
cases apply them to documents in iframe
s as well.
The user agent may wait for more bytes of the resource to be available, either in this step or at any later step in this algorithm. For instance, a user agent might wait 500ms or 1024 bytes, whichever came first. In general preparsing the source to find the encoding improves performance, as it reduces the need to throw away the data structures used when parsing upon finding the encoding information. However, if the user agent delays too long to obtain data to determine the encoding, then the cost of the delay could outweigh any performance improvements from the preparse.
The authoring conformance requirements for character encoding declarations limit them to only appearing in the first 1024 bytes. User agents are therefore encouraged to use the prescan algorithm below (as invoked by these steps) on the first 1024 bytes, but not to stall beyond that.
For each of the rows in the following table, starting with the first one and going down, if there are as many or more bytes available than the number of bytes in the first column, and the first bytes of the file match the bytes given in the first column, then return the encoding given in the cell in the second column of that row, with the confidence certain, and abort these steps:
Bytes in Hexadecimal | Encoding |
---|---|
FE FF | Big-endian UTF-16 |
FF FE | Little-endian UTF-16 |
EF BB BF | UTF-8 |
This step looks for Unicode Byte Order Marks (BOMs).
That this step happens before the next one honoring the HTTP
Content-Type
header is a willful violation of the HTTP specification,
motivated by a desire to be maximally compatible with legacy content. [HTTP]
If the transport layer specifies a character encoding, and it is supported, return that encoding with the confidence certain, and abort these steps.
Optionally prescan the byte stream to determine its encoding. The end condition is that the user agent decides that scanning further bytes would not be efficient. User agents are encouraged to only prescan the first 1024 bytes. User agents may decide that scanning any bytes is not efficient, in which case these substeps are entirely skipped.
The aforementioned algorithm either aborts unsuccessfully or returns a character encoding. If it returns a character encoding, then this algorithm must be aborted, returning the same encoding, with confidence tentative.
If the HTML parser for which this algorithm is being run is associated with a
Document
that is itself in a nested browsing context, run these
substeps:
Let new document be the Document
with which the
HTML parser is associated.
Let parent document be the Document
through which new document is
nested (the active document of the parent browsing context of
new document).
If parent document's origin is not the same origin as new document's origin, then abort these substeps.
If parent document's character encoding is not an ASCII-compatible character encoding, then abort these substeps.
Return parent document's character encoding, with the confidence tentative, and abort the encoding sniffing algorithm's steps.
Otherwise, if the user agent has information on the likely encoding for this page, e.g. based on the encoding of the page when it was last visited, then return that encoding, with the confidence tentative, and abort these steps.
The user agent may attempt to autodetect the character encoding from applying frequency analysis or other algorithms to the data stream. Such algorithms may use information about the resource other than the resource's contents, including the address of the resource. If autodetection succeeds in determining a character encoding, and that encoding is a supported encoding, then return that encoding, with the confidence tentative, and abort these steps. [UNIVCHARDET]
The UTF-8 encoding has a highly detectable bit pattern. Documents that contain bytes with values greater than 0x7F which match the UTF-8 pattern are very likely to be UTF-8, while documents with byte sequences that do not match it are very likely not. User-agents are therefore encouraged to search for this common encoding. [PPUTF8] [UTF8DET]
Otherwise, return an implementation-defined or user-specified default character encoding, with the confidence tentative.
In controlled environments or in environments where the encoding of documents can be
prescribed (for example, for user agents intended for dedicated use in new networks), the
comprehensive UTF-8
encoding is suggested.
In other environments, the default encoding is typically dependent on the user's locale (an approximation of the languages, and thus often encodings, of the pages that the user is likely to frequent). The following table gives suggested defaults based on the user's locale, for compatibility with legacy content. Locales are identified by BCP 47 language tags. [BCP47] [ENCODING]
Locale language | Suggested default encoding | |
---|---|---|
ar | Arabic | windows-1256 |
ba | Bashkir | windows-1251 |
be | Belarusian | windows-1251 |
bg | Bulgarian | windows-1251 |
cs | Czech | windows-1250 |
el | Greek | ISO-8859-7 |
et | Estonian | windows-1257 |
fa | Persian | windows-1256 |
he | Hebrew | windows-1255 |
hr | Croatian | windows-1250 |
hu | Hungarian | ISO-8859-2 |
ja | Japanese | Shift_JIS |
kk | Kazakh | windows-1251 |
ko | Korean | euc-kr |
ku | Kurdish | windows-1254 |
ky | Kyrgyz | windows-1251 |
lt | Lithuanian | windows-1257 |
lv | Latvian | windows-1257 |
mk | Macedonian | windows-1251 |
pl | Polish | ISO-8859-2 |
ru | Russian | windows-1251 |
sah | Yakut | windows-1251 |
sk | Slovak | windows-1250 |
sl | Slovenian | ISO-8859-2 |
sr | Serbian | windows-1251 |
tg | Tajik | windows-1251 |
th | Thai | windows-874 |
tr | Turkish | windows-1254 |
tt | Tatar | windows-1251 |
uk | Ukrainian | windows-1251 |
vi | Vietnamese | windows-1258 |
zh-CN | Chinese (People's Republic of China) | GB18030 |
zh-TW | Chinese (Taiwan) | Big5 |
All other locales | windows-1252 |
The contents of this table are derived from the intersection of Windows, Chrome, and Firefox defaults.
The document's character encoding must immediately be set to the value returned from this algorithm, at the same time as the user agent uses the returned value to select the decoder to use for the input byte stream.
When an algorithm requires a user agent to prescan a byte stream to determine its encoding, given some defined end condition, then it must run the following steps. These steps either abort unsuccessfully or return a character encoding. If at any point during these steps (including during instances of the get an attribute algorithm invoked by this one) the user agent either runs out of bytes (meaning the position pointer created in the first step below goes beyond the end of the byte stream obtained so far) or reaches its end condition, then abort the prescan a byte stream to determine its encoding algorithm unsuccessfully.
Let position be a pointer to a byte in the input byte stream, initially pointing at the first byte.
Loop: If position points to:
Advance the position pointer so that it points at the first 0x3E byte which is preceded by two 0x2D bytes (i.e. at the end of an ASCII '-->' sequence) and comes after the 0x3C byte that was found. (The two 0x2D bytes can be the same as the those in the '<!--' sequence.)
Advance the position pointer so that it points at the next 0x09, 0x0A, 0x0C, 0x0D, 0x20, or 0x2F byte (the one in sequence of characters matched above).
Let attribute list be an empty list of strings.
Let got pragma be false.
Let need pragma be null.
Let charset be the null value (which, for the purposes of this algorithm, is distinct from an unrecognised encoding or the empty string).
Attributes: Get an attribute and its value. If no attribute was sniffed, then jump to the processing step below.
If the attribute's name is already in attribute list, then return to the step labeled attributes.
Add the attribute's name to attribute list.
Run the appropriate step from the following list, if one applies:
http-equiv
"If the attribute's value is "content-type
", then set got pragma to true.
content
"Apply the algorithm for extracting a character encoding from a
meta
element, giving the attribute's value as the string to parse. If a
character encoding is returned, and if charset is still set to null,
let charset be the encoding returned, and set need
pragma to true.
charset
"Let charset be the result of getting an encoding from the attribute's value, and set need pragma to false.
Return to the step labeled attributes.
Processing: If need pragma is null, then jump to the step below labeled next byte.
If need pragma is true but got pragma is false, then jump to the step below labeled next byte.
If charset is a UTF-16 encoding, change the value of charset to UTF-8.
If charset is not a supported character encoding, then jump to the step below labeled next byte.
Abort the prescan a byte stream to determine its encoding algorithm, returning the encoding given by charset.
Advance the position pointer so that it points at the next 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), 0x20 (ASCII space), or 0x3E (ASCII >) byte.
Repeatedly get an attribute until no further attributes can be found, then jump to the step below labeled next byte.
Advance the position pointer so that it points at the first 0x3E byte (ASCII >) that comes after the 0x3C byte that was found.
Do nothing with that byte.
When the prescan a byte stream to determine its encoding algorithm says to get an attribute, it means doing this:
If the byte at position is one of 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), 0x20 (ASCII space), or 0x2F (ASCII /) then advance position to the next byte and redo this step.
If the byte at position is 0x3E (ASCII >), then abort the get an attribute algorithm. There isn't one.
Otherwise, the byte at position is the start of the attribute name. Let attribute name and attribute value be the empty string.
Process the byte at position as follows:
Advance position to the next byte and return to the previous step.
Spaces: If the byte at position is one of 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), or 0x20 (ASCII space) then advance position to the next byte, then, repeat this step.
If the byte at position is not 0x3D (ASCII =), abort the get an attribute algorithm. The attribute's name is the value of attribute name, its value is the empty string.
Advance position past the 0x3D (ASCII =) byte.
Value: If the byte at position is one of 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), or 0x20 (ASCII space) then advance position to the next byte, then, repeat this step.
Process the byte at position as follows:
Process the byte at position as follows:
Advance position to the next byte and return to the previous step.
For the sake of interoperability, user agents should not use a pre-scan algorithm that returns different results than the one described above. (But, if you do, please at least let us know, so that we can improve this algorithm and benefit everyone...)
User agents must support the encodings defined in the Encoding standard. User agents should not support other encodings.
User agents must not support the CESU-8, UTF-7, BOCU-1 and SCSU encodings. [CESU8] [UTF7] [BOCU1] [SCSU]
Support for encodings based on EBCDIC is especially discouraged. This encoding is rarely used for publicly-facing Web content. Support for UTF-32 is also especially discouraged. This encoding is rarely used, and frequently implemented incorrectly.
This specification does not make any attempt to support EBCDIC-based encodings and UTF-32 in its algorithms; support and use of these encodings can thus lead to unexpected behavior in implementations of this specification.
When the parser requires the user agent to change the encoding, it must run the following steps. This might happen if the encoding sniffing algorithm described above failed to find a character encoding, or if it found a character encoding that was not the actual encoding of the file.
The input stream consists of the characters pushed into it as the input byte stream is decoded or from the various APIs that directly manipulate the input stream.
One leading U+FEFF BYTE ORDER MARK character must be ignored if any are present in the input stream.
The requirement to strip a U+FEFF BYTE ORDER MARK character regardless of whether that character was used to determine the byte order is a willful violation of Unicode, motivated by a desire to increase the resilience of user agents in the face of naïve transcoders.
Any occurrences of any characters in the ranges U+0001 to U+0008, U+000E to U+001F, U+007F to U+009F, U+FDD0 to U+FDEF, and characters U+000B, U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, U+2FFFE, U+2FFFF, U+3FFFE, U+3FFFF, U+4FFFE, U+4FFFF, U+5FFFE, U+5FFFF, U+6FFFE, U+6FFFF, U+7FFFE, U+7FFFF, U+8FFFE, U+8FFFF, U+9FFFE, U+9FFFF, U+AFFFE, U+AFFFF, U+BFFFE, U+BFFFF, U+CFFFE, U+CFFFF, U+DFFFE, U+DFFFF, U+EFFFE, U+EFFFF, U+FFFFE, U+FFFFF, U+10FFFE, and U+10FFFF are parse errors. These are all control characters or permanently undefined Unicode characters (noncharacters).
Any character that is a not a Unicode character, i.e. any isolated
surrogate, is a parse error. (These can only find their way into the input stream via
script APIs such as document.write()
.)
"CR" (U+000D) characters and "LF" (U+000A) characters are treated specially. All CR characters must be converted to LF characters, and any LF characters that immediately follow a CR character must be ignored. Thus, newlines in HTML DOMs are represented by LF characters, and there are never any CR characters in the input to the tokenization stage.
The next input character is the first character in the input stream that has not yet been consumed or explicitly ignored by the requirements in this section. Initially, the next input character is the first character in the input. The current input character is the last character to have been consumed.
The insertion point is the position (just before a character or just before the end
of the input stream) where content inserted using document.write()
is actually inserted. The insertion point is
relative to the position of the character immediately after it, it is not an absolute offset into
the input stream. Initially, the insertion point is undefined.
The "EOF" character in the tables below is a conceptual character representing the end of the
input stream. If the parser is a script-created parser, then the end of
the input stream is reached when an explicit "EOF" character (inserted by
the document.close()
method) is consumed. Otherwise, the
"EOF" character is not a real character in the stream, but rather the lack of any further
characters.
The handling of U+0000 NULL characters varies based on where the characters are found. In general, they are ignored except where doing so could plausibly introduce an attack vector. This handling is, by necessity, spread across both the tokenization stage and the tree construction stage.
The insertion mode is a state variable that controls the primary operation of the tree construction stage.
Initially, the insertion mode is "initial". It can change to "before html", "before head", "in head", "in head noscript", "after head", "in body", "text", "in table", "in table text", "in caption", "in column group", "in table body", "in row", "in cell", "in select", "in select in table", "in template", "after body", "in frameset", "after frameset", "after after body", and "after after frameset" during the course of the parsing, as described in the tree construction stage. The insertion mode affects how tokens are processed and whether CDATA sections are supported.
Several of these modes, namely "in head", "in body", "in table", and "in select", are special, in that the other modes defer to them at various times. When the algorithm below says that the user agent is to do something "using the rules for the m insertion mode", where m is one of these modes, the user agent must use the rules described under the m insertion mode's section, but must leave the insertion mode unchanged unless the rules in m themselves switch the insertion mode to a new value.
When the insertion mode is switched to "text" or "in table text", the original insertion mode is also set. This is the insertion mode to which the tree construction stage will return.
Similarly, to parse nested template
elements, a stack of template insertion
modes is used. It is initially empty. The current template insertion mode is the
insertion mode that was most recently added to the stack of template insertion modes.
The algorithms in the sections below will push insertion modes onto this stack, meaning
that the specified insertion mode is to be added to the stack, and pop insertion modes from
the stack, which means that the most recently added insertion mode must be removed from the
stack.
When the steps below require the UA to reset the insertion mode appropriately, it means the UA must follow these steps:
Let last be false.
Let node be the last node in the stack of open elements.
Loop: If node is the first node in the stack of open elements, then set last to true, and, if the parser was originally created as part of the HTML fragment parsing algorithm (fragment case) set node to the context element.
If node is a select
element, run these substeps:
If last is true, jump to the step below labeled done.
Let ancestor be node.
Loop: If ancestor is the first node in the stack of open elements, jump to the step below labeled done.
Let ancestor be the node before ancestor in the stack of open elements.
If ancestor is a template
node, jump to the step below
labeled done.
If ancestor is a table
node, switch the insertion
mode to "in select in table" and
abort these steps.
Jump back to the step labeled loop.
Done: Switch the insertion mode to "in select" and abort these steps.
If node is a td
or th
element and last is false, then switch the insertion mode to "in cell" and abort these steps.
If node is a tr
element, then switch the insertion
mode to "in row" and abort these
steps.
If node is a tbody
, thead
, or
tfoot
element, then switch the insertion mode to "in table body" and abort these steps.
If node is a caption
element, then switch the
insertion mode to "in caption" and
abort these steps.
If node is a colgroup
element, then switch the
insertion mode to "in column
group" and abort these steps.
If node is a table
element, then switch the
insertion mode to "in table" and abort
these steps.
If node is a template
element, then switch the
insertion mode to the current template insertion mode and abort these
steps.
head
element
and last is true,
then switch the insertion mode to "in body" ("in body"! not "in head"!) and abort
these steps. (fragment case)If node is a head
element and last is
false, then switch the insertion mode to "in
head" and abort these steps.
If node is a body
element, then switch the
insertion mode to "in body" and abort
these steps.
If node is a frameset
element, then switch the
insertion mode to "in frameset" and
abort these steps. (fragment case)
If node is an html
element, run these substeps:
If the head
element pointer is null, switch the
insertion mode to "before head"
and abort these steps. (fragment case)
Otherwise, the head
element pointer is not null, switch the
insertion mode to "after head" and
abort these steps.
If last is true, then switch the insertion mode to "in body" and abort these steps. (fragment case)
Let node now be the node before node in the stack of open elements.
Return to the step labeled loop.
Initially, the stack of open elements is empty. The stack grows downwards; the topmost node on the stack is the first one added to the stack, and the bottommost node of the stack is the most recently added node in the stack (notwithstanding when the stack is manipulated in a random access fashion as part of the handling for misnested tags).
The "before html" insertion
mode creates the html
root element node, which is then added to the stack.
In the fragment case, the stack of open elements is
initialized to contain an html
element that is created as part of that algorithm. (The fragment case skips the
"before html" insertion mode.)
The html
node, however it is created, is the topmost node of the stack. It only
gets popped off the stack when the parser finishes.
The current node is the bottommost node in this stack of open elements.
The adjusted current node is the context element if the stack of open elements has only one element in it and the parser was created by the HTML fragment parsing algorithm; otherwise, the adjusted current node is the current node.
Elements in the stack of open elements fall into the following categories:
The following elements have varying levels of special parsing rules: HTML's
address
, applet
, area
, article
,
aside
, base
, basefont
, bgsound
,
blockquote
, body
, br
, button
,
caption
, center
, col
, colgroup
,
dd
, details
, dir
, div
, dl
,
dt
, embed
, fieldset
, figcaption
,
figure
, footer
, form
, frame
,
frameset
, h1
, h2
, h3
, h4
,
h5
, h6
, head
, header
, hgroup
,
hr
, html
, iframe
,
img
, input
, isindex
, li
, link
,
listing
, main
, marquee
,
meta
, nav
, noembed
,
noframes
, noscript
, object
, ol
,
p
, param
, plaintext
, pre
,
script
, section
, select
, source
,
style
, summary
, table
, tbody
,
td
, template
, textarea
, tfoot
,
th
, thead
, title
, tr
, track
,
ul
, wbr
, and xmp
; MathML's mi
, mo
, mn
, ms
, mtext
, and annotation-xml
; and SVG's foreignObject
, desc
, and title
.
The following HTML elements are those that end up in the list of active formatting
elements: a
, b
, big
, code
,
em
, font
, i
, nobr
, s
,
small
, strike
, strong
, tt
, and
u
.
All other elements found while parsing an HTML document.
The stack of open elements is said to have an element target node in a specific scope consisting of a list of element types list when the following algorithm terminates in a match state:
Initialize node to be the current node (the bottommost node of the stack).
If node is the target node, terminate in a match state.
Otherwise, if node is one of the element types in list, terminate in a failure state.
Otherwise, set node to the previous entry in the stack of open
elements and return to step 2. (This will never fail, since the loop will always terminate
in the previous step if the top of the stack — an html
element — is
reached.)
The stack of open elements is said to have a particular element in scope when it has that element in the specific scope consisting of the following element types:
applet
in the HTML namespacecaption
in the HTML namespacehtml
in the HTML namespacetable
in the HTML namespacetd
in the HTML namespaceth
in the HTML namespacemarquee
in the HTML namespaceobject
in the HTML namespacetemplate
in the HTML namespacemi
in the MathML namespacemo
in the MathML namespacemn
in the MathML namespacems
in the MathML namespacemtext
in the MathML namespaceannotation-xml
in the MathML namespaceforeignObject
in the SVG namespacedesc
in the SVG namespacetitle
in the SVG namespaceThe stack of open elements is said to have a particular element in list item scope when it has that element in the specific scope consisting of the following element types:
ol
in the HTML namespaceul
in the HTML namespaceThe stack of open elements is said to have a particular element in button scope when it has that element in the specific scope consisting of the following element types:
button
in the HTML namespaceThe stack of open elements is said to have a particular element in table scope when it has that element in the specific scope consisting of the following element types:
html
in the HTML namespacetable
in the HTML namespacetemplate
in the HTML namespaceThe stack of open elements is said to have a particular element in select scope when it has that element in the specific scope consisting of all element types except the following:
optgroup
in the HTML namespaceoption
in the HTML namespaceNothing happens if at any time any of the elements in the stack of open elements
are moved to a new location in, or removed from, the Document
tree. In particular,
the stack is not changed in this situation. This can cause, amongst other strange effects, content
to be appended to nodes that are no longer in the DOM.
In some cases (namely, when closing misnested formatting elements), the stack is manipulated in a random-access fashion.
Initially, the list of active formatting elements is empty. It is used to handle mis-nested formatting element tags.
The list contains elements in the formatting category, and scope markers. The
scope markers are inserted when entering applet
elements, buttons,
object
elements, marquees, table cells, and table captions, and are used to prevent
formatting from "leaking" into applet
elements, buttons, object
elements, marquees, and tables.
The scope markers are unrelated to the concept of an element being in scope.
In addition, each element in the list of active formatting elements is associated with the token for which it was created, so that further elements can be created for that token if necessary.
When the steps below require the UA to push onto the list of active formatting elements an element element, the UA must perform the following steps:
If there are already three elements in the list of active formatting elements after the last list marker, if any, or anywhere in the list if there are no list markers, that have the same tag name, namespace, and attributes as element, then remove the earliest such element from the list of active formatting elements. For these purposes, the attributes must be compared as they were when the elements were created by the parser; two elements have the same attributes if all their parsed attributes can be paired such that the two attributes in each pair have identical names, namespaces, and values (the order of the attributes does not matter).
This is the Noah's Ark clause. But with three per family instead of two.
Add element to the list of active formatting elements.
When the steps below require the UA to reconstruct the active formatting elements, the UA must perform the following steps:
If there are no entries in the list of active formatting elements, then there is nothing to reconstruct; stop this algorithm.
If the last (most recently added) entry in the list of active formatting elements is a marker, or if it is an element that is in the stack of open elements, then there is nothing to reconstruct; stop this algorithm.
Let entry be the last (most recently added) element in the list of active formatting elements.
Rewind: If there are no entries before entry in the list of active formatting elements, then jump to the step labeled create.
Let entry be the entry one earlier than entry in the list of active formatting elements.
If entry is neither a marker nor an element that is also in the stack of open elements, go to the step labeled rewind.
Advance: Let entry be the element one later than entry in the list of active formatting elements.
Create: Insert an HTML element for the token for which the element entry was created, to obtain new element.
Replace the entry for entry in the list with an entry for new element.
If the entry for new element in the list of active formatting elements is not the last entry in the list, return to the step labeled advance.
This has the effect of reopening all the formatting elements that were opened in the current body, cell, or caption (whichever is youngest) that haven't been explicitly closed.
The way this specification is written, the list of active formatting elements always consists of elements in chronological order with the least recently added element first and the most recently added element last (except for while steps 8 to 11 of the above algorithm are being executed, of course).
When the steps below require the UA to clear the list of active formatting elements up to the last marker, the UA must perform the following steps:
Let entry be the last (most recently added) entry in the list of active formatting elements.
Remove entry from the list of active formatting elements.
If entry was a marker, then stop the algorithm at this point. The list has been cleared up to the last marker.
Go to step 1.
Initially, the head
element pointer and the form
element pointer are both null.
Once a head
element has been parsed (whether implicitly or explicitly) the
head
element pointer gets set to point to this node.
The form
element pointer points to the last
form
element that was opened and whose end tag has not yet been seen. It is used to
make form controls associate with forms in the face of dramatically bad markup, for historical
reasons. It is ignored inside template
elements.
The scripting flag is set to "enabled" if scripting
was enabled for the Document
with which the parser is associated when the
parser was created, and "disabled" otherwise.
The scripting flag can be enabled even when the parser was originally
created for the HTML fragment parsing algorithm, even though script
elements don't execute in that case.
The frameset-ok flag is set to "ok" when the parser is created. It is set to "not ok" after certain tokens are seen.
Implementations must act as if they used the following state machine to tokenize HTML. The state machine must start in the data state. Most states consume a single character, which may have various side-effects, and either switches the state machine to a new state to reconsume the same character, or switches it to a new state to consume the next character, or stays in the same state to consume the next character. Some states have more complicated behavior and can consume several characters before switching to another state. In some cases, the tokenizer state is also changed by the tree construction stage.
The exact behavior of certain states depends on the insertion mode and the stack of open elements. Certain states also use a temporary buffer to track progress.
The output of the tokenization step is a series of zero or more of the following tokens: DOCTYPE, start tag, end tag, comment, character, end-of-file. DOCTYPE tokens have a name, a public identifier, a system identifier, and a force-quirks flag. When a DOCTYPE token is created, its name, public identifier, and system identifier must be marked as missing (which is a distinct state from the empty string), and the force-quirks flag must be set to off (its other state is on). Start and end tag tokens have a tag name, a self-closing flag, and a list of attributes, each of which has a name and a value. When a start or end tag token is created, its self-closing flag must be unset (its other state is that it be set), and its attributes list must be empty. Comment and character tokens have data.
When a token is emitted, it must immediately be handled by the tree construction
stage. The tree construction stage can affect the state of the tokenization stage, and can insert
additional characters into the stream. (For example, the script
element can result in
scripts executing and using the dynamic markup insertion APIs to insert characters
into the stream being tokenized.)
Creating a token and emitting it are distinct actions. It is possible for a token to be created but implicitly abandoned (never emitted), e.g. if the file ends unexpectedly while processing the characters that are being parsed into a start tag token.
When a start tag token is emitted with its self-closing flag set, if the flag is not acknowledged when it is processed by the tree construction stage, that is a parse error.
When an end tag token is emitted with attributes, that is a parse error.
When an end tag token is emitted with its self-closing flag set, that is a parse error.
An appropriate end tag token is an end tag token whose tag name matches the tag name of the last start tag to have been emitted from this tokenizer, if any. If no start tag has been emitted from this tokenizer, then no end tag token is appropriate.
Before each step of the tokenizer, the user agent must first check the parser pause flag. If it is true, then the tokenizer must abort the processing of any nested invocations of the tokenizer, yielding control back to the caller.
The tokenizer state machine consists of the states defined in the following subsections.
Consume the next input character:
Switch to the data state.
Attempt to consume a character reference, with no additional allowed character.
If nothing is returned, emit a U+0026 AMPERSAND character (&) token.
Otherwise, emit the character tokens that were returned.
Consume the next input character:
Switch to the RCDATA state.
Attempt to consume a character reference, with no additional allowed character.
If nothing is returned, emit a U+0026 AMPERSAND character (&) token.
Otherwise, emit the character tokens that were returned.
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
script
", then switch
to the script data double escaped state. Otherwise, switch to the script data
escaped state. Emit the current input character as a character token.Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
script
", then switch
to the script data escaped state. Otherwise, switch to the script data double
escaped state. Emit the current input character as a character token.Consume the next input character:
Consume the next input character:
When the user agent leaves the attribute name state (and before emitting the tag token, if appropriate), the complete attribute's name must be compared to the other attributes on the same token; if there is already an attribute on the token with the exact same name, then this is a parse error and the new attribute must be removed from the token.
If an attribute is so removed from a token, it, along with the value that gets associated with it, if any, are never subsequently used by the parser, and are therefore effectively discarded. Removing the attribute in this way does not change its status as the "current attribute" for the purposes of the tokenizer, however.
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Attempt to consume a character reference.
If nothing is returned, append a U+0026 AMPERSAND character (&) to the current attribute's value.
Otherwise, append the returned character tokens to the current attribute's value.
Finally, switch back to the attribute value state that switched into this state.
Consume the next input character:
Consume the next input character:
Consume every character up to and including the first ">" (U+003E) character
or the end of the file (EOF), whichever comes first. Emit a comment token whose data is the
concatenation of all the characters starting from and including the character that caused the
state machine to switch into the bogus comment state, up to and including the character
immediately before the last consumed character (i.e. up to the character just before the U+003E or
EOF character), but with any U+0000 NULL characters replaced by U+FFFD REPLACEMENT CHARACTER
characters. (If the comment was started by the end of the file (EOF), the token is empty.
Similarly, the token is empty if it was generated by the string "<!>
".)
Switch to the data state.
If the end of the file was reached, reconsume the EOF character.
If the next two characters are both "-" (U+002D) characters, consume those two characters, create a comment token whose data is the empty string, and switch to the comment start state.
Otherwise, if the next seven characters are an ASCII case-insensitive match for the word "DOCTYPE", then consume those characters and switch to the DOCTYPE state.
Otherwise, if there is an adjusted current node and it is not an element in the HTML namespace and the next seven characters are a case-sensitive match for the string "[CDATA[" (the five uppercase letters "CDATA" with a U+005B LEFT SQUARE BRACKET character before and after), then consume those characters and switch to the CDATA section state.
Otherwise, this is a parse error. Switch to the bogus comment state. The next character that is consumed, if any, is the first character that will be in the comment.
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
If the six characters starting from the current input character are an ASCII case-insensitive match for the word "PUBLIC", then consume those characters and switch to the after DOCTYPE public keyword state.
Otherwise, if the six characters starting from the current input character are an ASCII case-insensitive match for the word "SYSTEM", then consume those characters and switch to the after DOCTYPE system keyword state.
Otherwise, this is a parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Consume the next input character:
Switch to the data state.
Consume every character up to the next occurrence of the three character sequence U+005D RIGHT
SQUARE BRACKET U+005D RIGHT SQUARE BRACKET U+003E GREATER-THAN SIGN (]]>
),
or the end of the file (EOF), whichever comes first. Emit a series of character tokens consisting
of all the characters consumed except the matching three character sequence at the end (if one was
found before the end of the file).
If the end of the file was reached, reconsume the EOF character.
This section defines how to consume a character reference, optionally with an additional allowed character, which, if specified where the algorithm is invoked, adds a character to the list of characters that cause there to not be a character reference.
This definition is used when parsing character references in text and in attributes.
The behavior depends on the identity of the next character (the one immediately after the U+0026 AMPERSAND character), as follows:
Consume the U+0023 NUMBER SIGN.
The behavior further depends on the character after the U+0023 NUMBER SIGN:
Consume the X.
Follow the steps below, but using ASCII hex digits.
When it comes to interpreting the number, interpret it as a hexadecimal number.
Follow the steps below, but using ASCII digits.
When it comes to interpreting the number, interpret it as a decimal number.
Consume as many characters as match the range of characters given above (ASCII hex digits or ASCII digits).
If no characters match the range, then don't consume any characters (and unconsume the U+0023 NUMBER SIGN character and, if appropriate, the X character). This is a parse error; nothing is returned.
Otherwise, if the next character is a U+003B SEMICOLON, consume that too. If it isn't, there is a parse error.
If one or more characters match the range, then take them all and interpret the string of characters as a number (either hexadecimal or decimal as appropriate).
If that number is one of the numbers in the first column of the following table, then this is a parse error. Find the row with that number in the first column, and return a character token for the Unicode character given in the second column of that row.
Number | Unicode character | |
---|---|---|
0x00 | U+FFFD | REPLACEMENT CHARACTER |
0x80 | U+20AC | EURO SIGN (€) |
0x82 | U+201A | SINGLE LOW-9 QUOTATION MARK (‚) |
0x83 | U+0192 | LATIN SMALL LETTER F WITH HOOK (ƒ) |
0x84 | U+201E | DOUBLE LOW-9 QUOTATION MARK („) |
0x85 | U+2026 | HORIZONTAL ELLIPSIS (…) |
0x86 | U+2020 | DAGGER (†) |
0x87 | U+2021 | DOUBLE DAGGER (‡) |
0x88 | U+02C6 | MODIFIER LETTER CIRCUMFLEX ACCENT (ˆ) |
0x89 | U+2030 | PER MILLE SIGN (‰) |
0x8A | U+0160 | LATIN CAPITAL LETTER S WITH CARON (Š) |
0x8B | U+2039 | SINGLE LEFT-POINTING ANGLE QUOTATION MARK (‹) |
0x8C | U+0152 | LATIN CAPITAL LIGATURE OE (Œ) |
0x8E | U+017D | LATIN CAPITAL LETTER Z WITH CARON (Ž) |
0x91 | U+2018 | LEFT SINGLE QUOTATION MARK (‘) |
0x92 | U+2019 | RIGHT SINGLE QUOTATION MARK (’) |
0x93 | U+201C | LEFT DOUBLE QUOTATION MARK (“) |
0x94 | U+201D | RIGHT DOUBLE QUOTATION MARK (”) |
0x95 | U+2022 | BULLET (•) |
0x96 | U+2013 | EN DASH (–) |
0x97 | U+2014 | EM DASH (—) |
0x98 | U+02DC | SMALL TILDE (˜) |
0x99 | U+2122 | TRADE MARK SIGN (™) |
0x9A | U+0161 | LATIN SMALL LETTER S WITH CARON (š) |
0x9B | U+203A | SINGLE RIGHT-POINTING ANGLE QUOTATION MARK (›) |
0x9C | U+0153 | LATIN SMALL LIGATURE OE (œ) |
0x9E | U+017E | LATIN SMALL LETTER Z WITH CARON (ž) |
0x9F | U+0178 | LATIN CAPITAL LETTER Y WITH DIAERESIS (Ÿ) |
Otherwise, if the number is in the range 0xD800 to 0xDFFF or is greater than 0x10FFFF, then this is a parse error. Return a U+FFFD REPLACEMENT CHARACTER character token.
Otherwise, return a character token for the Unicode character whose code point is that number. Additionally, if the number is in the range 0x0001 to 0x0008, 0x000D to 0x001F, 0x007F to 0x009F, 0xFDD0 to 0xFDEF, or is one of 0x000B, 0xFFFE, 0xFFFF, 0x1FFFE, 0x1FFFF, 0x2FFFE, 0x2FFFF, 0x3FFFE, 0x3FFFF, 0x4FFFE, 0x4FFFF, 0x5FFFE, 0x5FFFF, 0x6FFFE, 0x6FFFF, 0x7FFFE, 0x7FFFF, 0x8FFFE, 0x8FFFF, 0x9FFFE, 0x9FFFF, 0xAFFFE, 0xAFFFF, 0xBFFFE, 0xBFFFF, 0xCFFFE, 0xCFFFF, 0xDFFFE, 0xDFFFF, 0xEFFFE, 0xEFFFF, 0xFFFFE, 0xFFFFF, 0x10FFFE, or 0x10FFFF, then this is a parse error.
Consume the maximum number of characters possible, with the consumed characters matching one of the identifiers in the first column of the named character references table (in a case-sensitive manner).
If no match can be made, then no characters are consumed, and nothing is returned. In this case, if the characters after the U+0026 AMPERSAND character (&) consist of a sequence of one or more alphanumeric ASCII characters followed by a U+003B SEMICOLON character (;), then this is a parse error.
If the character reference is being consumed as part of an attribute, and the last character matched is not a ";" (U+003B) character, and the next character is either a "=" (U+003D) character or an alphanumeric ASCII character, then, for historical reasons, all the characters that were matched after the U+0026 AMPERSAND character (&) must be unconsumed, and nothing is returned. However, if this next character is in fact a "=" (U+003D) character, then this is a parse error, because some legacy user agents will misinterpret the markup in those cases.
Otherwise, a character reference is parsed. If the last character matched is not a ";" (U+003B) character, there is a parse error.
Return one or two character tokens for the character(s) corresponding to the character reference name (as given by the second column of the named character references table).
If the markup contains (not in an attribute) the string I'm ¬it; I
tell you
, the character reference is parsed as "not", as in, I'm ¬it;
I tell you
(and this is a parse error). But if the markup was I'm
∉ I tell you
, the character reference would be parsed as "notin;", resulting
in I'm ∉ I tell you
(and no parse error).
The input to the tree construction stage is a sequence of tokens from the
tokenization stage. The tree construction stage is associated with a DOM
Document
object when a parser is created. The "output" of this stage consists of
dynamically modifying or extending that document's DOM tree.
This specification does not define when an interactive user agent has to render the
Document
so that it is available to the user, or when it has to begin accepting user
input.
As each token is emitted from the tokenizer, the user agent must follow the appropriate steps from the following list, known as the tree construction dispatcher:
annotation-xml
element in the MathML namespace and the token is a start tag whose tag name is "svg"The next token is the token that is about to be processed by the tree construction dispatcher (even if the token is subsequently just ignored).
A node is a MathML text integration point if it is one of the following elements:
mi
element in the MathML namespacemo
element in the MathML namespacemn
element in the MathML namespacems
element in the MathML namespacemtext
element in the MathML namespaceA node is an HTML integration point if it is one of the following elements:
annotation-xml
element in the MathML namespace whose
start tag token had an attribute with the name "encoding" whose value was an ASCII
case-insensitive match for the string "text/html
"annotation-xml
element in the MathML namespace whose
start tag token had an attribute with the name "encoding" whose value was an ASCII
case-insensitive match for the string "application/xhtml+xml
"foreignObject
element in the SVG namespacedesc
element in the SVG namespacetitle
element in the SVG namespaceNot all of the tag names mentioned below are conformant tag names in this specification; many are included to handle legacy content. They still form part of the algorithm that implementations are required to implement to claim conformance.
The algorithm described below places no limit on the depth of the DOM tree
generated, or on the length of tag names, attribute names, attribute values, Text
nodes, etc. While implementors are encouraged to avoid arbitrary limits, it is recognized that practical concerns will likely force user agents to impose nesting
depth constraints.
While the parser is processing a token, it can enable or disable foster parenting. This affects the following algorithm.
The appropriate place for inserting a node, optionally using a particular override target, is the position in an element returned by running the following steps:
If there was an override target specified, then let target be the override target.
Otherwise, let target be the current node.
Determine the adjusted insertion location using the first matching steps from the following list:
table
, tbody
, tfoot
,
thead
, or tr
elementFoster parenting happens when content is misnested in tables.
Run these substeps:
Let last template be the last template
element in the
stack of open elements, if any.
Let last table be the last table
element in the
stack of open elements, if any.
If there is a last template and either there is no last table, or there is one, but last template is lower (more recently added) than last table in the stack of open elements, then: let adjusted insertion location be inside last template's template contents, after its last child (if any), and abort these substeps.
If there is no last table, then let adjusted insertion
location be inside the first element in the stack of open elements (the
html
element), after its last child (if any), and abort these substeps.
(fragment case)
If last table has a parent element, then let adjusted insertion location be inside last table's parent element, immediately before last table, and abort these substeps.
Let previous element be the element immediately above last table in the stack of open elements.
Let adjusted insertion location be inside previous element, after its last child (if any).
These steps are involved in part because it's possible for elements, the
table
element in this case in particular, to have been moved by a script around
in the DOM, or indeed removed from the DOM entirely, after the element was inserted by the
parser.
Let adjusted insertion location be inside target, after its last child (if any).
If the adjusted insertion location is inside a template
element, let it instead be inside the template
element's template
contents, after its last child (if any).
Return the adjusted insertion location.
When the steps below require the UA to create an element for a token in a particular given namespace and with a particular intended parent, the UA must run the following steps:
Create a node implementing the interface appropriate for the element type corresponding to
the tag name of the token in given namespace (as given in the specification
that defines that element, e.g. for an a
element in the HTML
namespace, this specification defines it to be the HTMLAnchorElement
interface), with the tag name being the name of that element, with the node being in the given
namespace, and with the attributes on the node being those given in the given token.
The interface appropriate for an element in the HTML namespace that is not
defined in this specification (or other applicable specifications) is
HTMLUnknownElement
. Elements in other namespaces whose interface is not defined by
that namespace's specification must use the interface Element
.
The ownerDocument
of the newly created element
must be the same as that of the intended parent.
If the newly created element has an xmlns
attribute in the
XMLNS namespace whose value is not exactly the same as the element's namespace,
that is a parse error. Similarly, if the newly created element has an xmlns:xlink
attribute in the XMLNS namespace whose value is not the
XLink Namespace, that is a parse error.
If the newly created element is a resettable element, invoke its reset algorithm. (This initializes the element's value and checkedness based on the element's attributes.)
If the element is a form-associated element, and the form
element pointer is not null, and there is no template
element on the stack of open elements, and the newly created element is either not
reassociateable or doesn't have a form
attribute, and the intended parent is in
the same home subtree as the element pointed to by the form
element pointer, associate the newly created element with the
form
element pointed to by the form
element
pointer, and suppress the running of the reset the form owner algorithm when
the parser subsequently attempts to insert the element.
Return the newly created element.
When the steps below require the user agent to insert a foreign element for a token in a given namespace, the user agent must run these steps:
Let the adjusted insertion location be the appropriate place for inserting a node.
Create an element for the token in the given namespace, with the intended parent being the element in which the adjusted insertion location finds itself.
If it is possible to insert an element at the adjusted insertion location, then insert the newly created element at the adjusted insertion location.
If the adjusted insertion location cannot accept more
elements, e.g. because it's a Document
that already has an element child, then the
newly created element is dropped on the floor.
Push the element onto the stack of open elements so that it is the new current node.
Return the newly created element.
When the steps below require the user agent to insert an HTML element for a token, the user agent must insert a foreign element for the token, in the HTML namespace.
When the steps below require the user agent to adjust MathML attributes for a token,
then, if the token has an attribute named definitionurl
, change its name to
definitionURL
(note the case difference).
When the steps below require the user agent to adjust SVG attributes for a token, then, for each attribute on the token whose attribute name is one of the ones in the first column of the following table, change the attribute's name to the name given in the corresponding cell in the second column. (This fixes the case of SVG attributes that are not all lowercase.)
Attribute name on token | Attribute name on element |
---|---|
attributename | attributeName
|
attributetype | attributeType
|
basefrequency | baseFrequency
|
baseprofile | baseProfile
|
calcmode | calcMode
|
clippathunits | clipPathUnits
|
contentscripttype | contentScriptType
|
contentstyletype | contentStyleType
|
diffuseconstant | diffuseConstant
|
edgemode | edgeMode
|
externalresourcesrequired | externalResourcesRequired
|
filterres | filterRes
|
filterunits | filterUnits
|
glyphref | glyphRef
|
gradienttransform | gradientTransform
|
gradientunits | gradientUnits
|
kernelmatrix | kernelMatrix
|
kernelunitlength | kernelUnitLength
|
keypoints | keyPoints
|
keysplines | keySplines
|
keytimes | keyTimes
|
lengthadjust | lengthAdjust
|
limitingconeangle | limitingConeAngle
|
markerheight | markerHeight
|
markerunits | markerUnits
|
markerwidth | markerWidth
|
maskcontentunits | maskContentUnits
|
maskunits | maskUnits
|
numoctaves | numOctaves
|
pathlength | pathLength
|
patterncontentunits | patternContentUnits
|
patterntransform | patternTransform
|
patternunits | patternUnits
|
pointsatx | pointsAtX
|
pointsaty | pointsAtY
|
pointsatz | pointsAtZ
|
preservealpha | preserveAlpha
|
preserveaspectratio | preserveAspectRatio
|
primitiveunits | primitiveUnits
|
refx | refX
|
refy | refY
|
repeatcount | repeatCount
|
repeatdur | repeatDur
|
requiredextensions | requiredExtensions
|
requiredfeatures | requiredFeatures
|
specularconstant | specularConstant
|
specularexponent | specularExponent
|
spreadmethod | spreadMethod
|
startoffset | startOffset
|
stddeviation | stdDeviation
|
stitchtiles | stitchTiles
|
surfacescale | surfaceScale
|
systemlanguage | systemLanguage
|
tablevalues | tableValues
|
targetx | targetX
|
targety | targetY
|
textlength | textLength
|
viewbox | viewBox
|
viewtarget | viewTarget
|
xchannelselector | xChannelSelector
|
ychannelselector | yChannelSelector
|
zoomandpan | zoomAndPan
|
When the steps below require the user agent to adjust foreign attributes for a
token, then, if any of the attributes on the token match the strings given in the first column of
the following table, let the attribute be a namespaced attribute, with the prefix being the string
given in the corresponding cell in the second column, the local name being the string given in the
corresponding cell in the third column, and the namespace being the namespace given in the
corresponding cell in the fourth column. (This fixes the use of namespaced attributes, in
particular lang
attributes in the XML
namespace.)
Attribute name | Prefix | Local name | Namespace |
---|---|---|---|
xlink:actuate | xlink | actuate | XLink namespace |
xlink:arcrole | xlink | arcrole | XLink namespace |
xlink:href | xlink | href | XLink namespace |
xlink:role | xlink | role | XLink namespace |
xlink:show | xlink | show | XLink namespace |
xlink:title | xlink | title | XLink namespace |
xlink:type | xlink | type | XLink namespace |
xml:base | xml | base | XML namespace |
xml:lang | xml | lang | XML namespace |
xml:space | xml | space | XML namespace |
xmlns | (none) | xmlns | XMLNS namespace |
xmlns:xlink | xmlns | xlink | XMLNS namespace |
When the steps below require the user agent to insert a character while processing a token, the user agent must run the following steps:
Let data be the characters passed to the algorithm, or, if no characters were explicitly specified, the character of the character token being processed.
Let the adjusted insertion location be the appropriate place for inserting a node.
If the adjusted insertion location is in a Document
node,
then abort these steps.
The DOM will not let Document
nodes have Text
node
children, so they are dropped on the floor.
If there is a Text
node immediately before the adjusted insertion
location, then append data to that Text
node's data.
Otherwise, create a new Text
node whose data is data and
whose ownerDocument
is the same as that of the
element in which the adjusted insertion location finds itself, and insert
the newly created node at the adjusted insertion location.
Here are some sample inputs to the parser and the corresponding number of Text
nodes that they result in, assuming a user agent that executes scripts.
Input | Number of Text nodes
|
---|---|
A<script> var script = document.getElementsByTagName('script')[0]; document.body.removeChild(script); </script>B | One Text node in the document, containing "AB".
|
A<script> var text = document.createTextNode('B'); document.body.appendChild(text); </script>C | Three Text nodes; "A" before the script, the script's contents, and "BC" after the script (the parser appends to the Text node created by the script).
|
A<script> var text = document.getElementsByTagName('script')[0].firstChild; text.data = 'B'; document.body.appendChild(text); </script>C | Two adjacent Text nodes in the document, containing "A" and "BC".
|
A<table>B<tr>C</tr>D</table> | One Text node before the table, containing "ABCD". (This is caused by foster parenting.)
|
A<table><tr> B</tr> C</table> | One Text node before the table, containing "A B C" (A-space-B-space-C). (This is caused by foster parenting.)
|
A<table><tr> B</tr> </em>C</table> | One Text node before the table, containing "A BC" (A-space-B-C), and one Text node inside the table (as a child of a tbody ) with a single space character. (Space characters separated from non-space characters by non-character tokens are not affected by foster parenting, even if those other tokens then get ignored.)
|
When the steps below require the user agent to insert a comment while processing a comment token, optionally with an explicitly insertion position position, the user agent must run the following steps:
Let data be the data given in the comment token being processed.
If position was specified, then let the adjusted insertion location be position. Otherwise, let adjusted insertion location be the appropriate place for inserting a node.
Create a Comment
node whose data
attribute is set to
data and whose ownerDocument
is
the same as that of the node in which the adjusted insertion location finds
itself.
Insert the newly created node at the adjusted insertion location.
DOM mutation events must not fire for changes caused by the UA
parsing the document. This includes the parsing of any content inserted using document.write()
and document.writeln()
calls. [DOMEVENTS]
However, mutation observers do fire, as required by the DOM specification.
The generic raw text element parsing algorithm and the generic RCDATA element parsing algorithm consist of the following steps. These algorithms are always invoked in response to a start tag token.
Insert an HTML element for the token.
If the algorithm that was invoked is the generic raw text element parsing algorithm, switch the tokenizer to the RAWTEXT state; otherwise the algorithm invoked was the generic RCDATA element parsing algorithm, switch the tokenizer to the RCDATA state.
Let the original insertion mode be the current insertion mode.
Then, switch the insertion mode to "text".
When the steps below require the UA to generate implied end
tags, then, while the current node is a
dd
element, a dt
element, an
li
element, an option
element, an
optgroup
element, a p
element, an
rb
element, an rp
element, an rt
element, or an rtc
element, the UA must
pop the current node off the stack of open
elements.
If a step requires the UA to generate implied end tags but lists an element to exclude from the process, then the UA must perform the above steps as if that element was not in the above list.
When the user agent is to apply the rules for the "initial" insertion mode, the user agent must handle the token as follows:
Ignore the token.
Insert a comment as the last child of the Document
object.
If the DOCTYPE token's name is not a case-sensitive match for the string "html
", or the token's public identifier is not missing, or the token's system
identifier is neither missing nor a case-sensitive match for the string
"about:legacy-compat
", and none of the sets of conditions in the following list are
matched, then there is a parse error.
html
", the token's public identifier is the case-sensitive string
"-//W3C//DTD HTML 4.0//EN
", and the token's system identifier
is either missing or the case-sensitive string "http://www.w3.org/TR/REC-html40/strict.dtd
".html
", the token's public identifier is the case-sensitive string
"-//W3C//DTD HTML 4.01//EN
", and the token's system identifier
is either missing or the case-sensitive string "http://www.w3.org/TR/html4/strict.dtd
".html
", the token's public identifier is the case-sensitive string
"-//W3C//DTD XHTML 1.0 Strict//EN
", and the token's system
identifier is the case-sensitive string "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd
".html
", the token's public identifier is the case-sensitive string
"-//W3C//DTD XHTML 1.1//EN
", and the token's system identifier
is the case-sensitive string "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd
".Conformance checkers may, based on the values (including presence or lack thereof) of the DOCTYPE token's name, public identifier, or system identifier, switch to a conformance checking mode for another language (e.g. based on the DOCTYPE token a conformance checker could recognize that the document is an HTML4-era document, and defer to an HTML4 conformance checker.)
Append a DocumentType
node to the Document
node, with the name
attribute set to the name given in the DOCTYPE token, or the empty string
if the name was missing; the publicId
attribute set to the public
identifier given in the DOCTYPE token, or the empty string if the public identifier was missing;
the systemId
attribute set to the system identifier given in the DOCTYPE
token, or the empty string if the system identifier was missing; and the other attributes
specific to DocumentType
objects set to null and empty lists as appropriate.
Associate the DocumentType
node with the Document
object so that it is
returned as the value of the doctype
attribute of the
Document
object.
Then, if the document is not an iframe
srcdoc
document, and the DOCTYPE token matches
one of the conditions in the following list, then set the Document
to quirks
mode:
html
" (compared case-sensitively). +//Silmaril//dtd html Pro v0r11 19970101//
" -//AdvaSoft Ltd//DTD HTML 3.0 asWedit + extensions//
" -//AS//DTD HTML 3.0 asWedit + extensions//
" -//IETF//DTD HTML 2.0 Level 1//
" -//IETF//DTD HTML 2.0 Level 2//
" -//IETF//DTD HTML 2.0 Strict Level 1//
" -//IETF//DTD HTML 2.0 Strict Level 2//
" -//IETF//DTD HTML 2.0 Strict//
" -//IETF//DTD HTML 2.0//
" -//IETF//DTD HTML 2.1E//
" -//IETF//DTD HTML 3.0//
" -//IETF//DTD HTML 3.2 Final//
" -//IETF//DTD HTML 3.2//
" -//IETF//DTD HTML 3//
" -//IETF//DTD HTML Level 0//
" -//IETF//DTD HTML Level 1//
" -//IETF//DTD HTML Level 2//
" -//IETF//DTD HTML Level 3//
" -//IETF//DTD HTML Strict Level 0//
" -//IETF//DTD HTML Strict Level 1//
" -//IETF//DTD HTML Strict Level 2//
" -//IETF//DTD HTML Strict Level 3//
" -//IETF//DTD HTML Strict//
" -//IETF//DTD HTML//
" -//Metrius//DTD Metrius Presentational//
" -//Microsoft//DTD Internet Explorer 2.0 HTML Strict//
" -//Microsoft//DTD Internet Explorer 2.0 HTML//
" -//Microsoft//DTD Internet Explorer 2.0 Tables//
" -//Microsoft//DTD Internet Explorer 3.0 HTML Strict//
" -//Microsoft//DTD Internet Explorer 3.0 HTML//
" -//Microsoft//DTD Internet Explorer 3.0 Tables//
" -//Netscape Comm. Corp.//DTD HTML//
" -//Netscape Comm. Corp.//DTD Strict HTML//
" -//O'Reilly and Associates//DTD HTML 2.0//
" -//O'Reilly and Associates//DTD HTML Extended 1.0//
" -//O'Reilly and Associates//DTD HTML Extended Relaxed 1.0//
" -//SoftQuad Software//DTD HoTMetaL PRO 6.0::19990601::extensions to HTML 4.0//
" -//SoftQuad//DTD HoTMetaL PRO 4.0::19971010::extensions to HTML 4.0//
" -//Spyglass//DTD HTML 2.0 Extended//
" -//SQ//DTD HTML 2.0 HoTMetaL + extensions//
" -//Sun Microsystems Corp.//DTD HotJava HTML//
" -//Sun Microsystems Corp.//DTD HotJava Strict HTML//
" -//W3C//DTD HTML 3 1995-03-24//
" -//W3C//DTD HTML 3.2 Draft//
" -//W3C//DTD HTML 3.2 Final//
" -//W3C//DTD HTML 3.2//
" -//W3C//DTD HTML 3.2S Draft//
" -//W3C//DTD HTML 4.0 Frameset//
" -//W3C//DTD HTML 4.0 Transitional//
" -//W3C//DTD HTML Experimental 19960712//
" -//W3C//DTD HTML Experimental 970421//
" -//W3C//DTD W3 HTML//
" -//W3O//DTD W3 HTML 3.0//
" -//W3O//DTD W3 HTML Strict 3.0//EN//
" -//WebTechs//DTD Mozilla HTML 2.0//
" -//WebTechs//DTD Mozilla HTML//
" -/W3C/DTD HTML 4.0 Transitional/EN
" HTML
" http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd
" -//W3C//DTD HTML 4.01 Frameset//
" -//W3C//DTD HTML 4.01 Transitional//
" Otherwise, if the document is not an iframe
srcdoc
document, and the DOCTYPE token matches one of
the conditions in the following list, then set the Document
to limited-quirks
mode:
-//W3C//DTD XHTML 1.0 Frameset//
" -//W3C//DTD XHTML 1.0 Transitional//
" -//W3C//DTD HTML 4.01 Frameset//
" -//W3C//DTD HTML 4.01 Transitional//
" The system identifier and public identifier strings must be compared to the values given in the lists above in an ASCII case-insensitive manner. A system identifier whose value is the empty string is not considered missing for the purposes of the conditions above.
Then, switch the insertion mode to "before html".
If the document is not an iframe
srcdoc
document, then this is a parse
error; set the Document
to quirks mode.
In any case, switch the insertion mode to "before html", then reprocess the token.
When the user agent is to apply the rules for the "before html" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Insert a comment as the last child of the Document
object.
Ignore the token.
Create an element for the token in the HTML namespace, with the
Document
as the intended parent. Append it to the Document
object. Put
this element in the stack of open elements.
If the Document
is being loaded as part of navigation of a browsing context, then: if the newly
created element has a manifest
attribute whose value is
not the empty string, then resolve the value of that
attribute to an absolute URL, relative to the newly created element, and if that is
successful, run the application cache selection
algorithm with the result of applying the URL
serializer algorithm to the resulting parsed URL with the exclude
fragment flag set; otherwise, if there is no such attribute, or its value is the empty
string, or resolving its value fails, run the application
cache selection algorithm with no manifest. The algorithm must be passed the
Document
object.
Switch the insertion mode to "before head".
Act as described in the "anything else" entry below.
Parse error. Ignore the token.
Create an html
element whose ownerDocument
is the Document
object. Append
it to the Document
object. Put this element in the stack of open
elements.
If the Document
is being loaded as part of navigation of a browsing context, then: run the application cache selection algorithm with no manifest,
passing it the Document
object.
Switch the insertion mode to "before head", then reprocess the token.
The root element can end up being removed from the Document
object, e.g. by
scripts; nothing in particular happens in such cases, content continues being appended to the
nodes as described in the next section.
When the user agent is to apply the rules for the "before head" insertion mode, the user agent must handle the token as follows:
Ignore the token.
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Insert an HTML element for the token.
Set the head
element pointer to the newly created
head
element.
Switch the insertion mode to "in head".
Act as described in the "anything else" entry below.
Parse error. Ignore the token.
Insert an HTML element for a "head" start tag token with no attributes.
Set the head
element pointer to the newly created
head
element.
Switch the insertion mode to "in head".
Reprocess the current token.
When the user agent is to apply the rules for the "in head" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
If the element has a charset
attribute, and getting an encoding from
its value results in a supported ASCII-compatible character encoding or a
UTF-16 encoding, and the confidence is
currently tentative, then change the encoding to the resulting encoding.
Otherwise, if the element has an http-equiv
attribute whose value is an ASCII case-insensitive match for the string "Content-Type
", and the element has a content
attribute, and applying the algorithm for
extracting a character encoding from a meta
element to that attribute's
value returns a supported ASCII-compatible character encoding or a UTF-16
encoding, and the confidence is
currently tentative, then change the encoding to the extracted encoding.
Follow the generic RCDATA element parsing algorithm.
Follow the generic raw text element parsing algorithm.
Insert an HTML element for the token.
Switch the insertion mode to "in head noscript".
Run these steps:
Let the adjusted insertion location be the appropriate place for inserting a node.
Create an element for the token in the HTML namespace, with the intended parent being the element in which the adjusted insertion location finds itself.
Mark the element as being "parser-inserted" and unset the element's "force-async" flag.
This ensures that, if the script is external, any document.write()
calls in the script will execute in-line,
instead of blowing the document away, as would happen in most other cases. It also prevents
the script from executing until the end tag is seen.
If the parser was originally created for the HTML fragment parsing
algorithm, then mark the script
element as "already started".
(fragment case)
Insert the newly created element at the adjusted insertion location.
Push the element onto the stack of open elements so that it is the new current node.
Switch the tokenizer to the script data state.
Let the original insertion mode be the current insertion mode.
Switch the insertion mode to "text".
Pop the current node (which will be the head
element) off the
stack of open elements.
Switch the insertion mode to "after head".
Act as described in the "anything else" entry below.
Insert an HTML element for the token.
Insert a marker at the end of the list of active formatting elements.
Set the frameset-ok flag to "not ok".
Switch the insertion mode to "in template".
Push "in template" onto the stack of template insertion modes so that it is the new current template insertion mode.
If there is no template
element on the stack of open elements, then
this is a parse error; ignore the token.
Otherwise, run these steps:
If the current node is not a template
element, then this is a
parse error.
Pop elements from the stack of open elements until a template
element has been popped from the stack.
Pop the current template insertion mode off the stack of template insertion modes.
Parse error. Ignore the token.
Pop the current node (which will be the head
element) off the
stack of open elements.
Switch the insertion mode to "after head".
Reprocess the token.
When the user agent is to apply the rules for the "in head noscript" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Pop the current node (which will be a noscript
element) from the
stack of open elements; the new current node will be a
head
element.
Switch the insertion mode to "in head".
Process the token using the rules for the "in head" insertion mode.
Act as described in the "anything else" entry below.
Parse error. Ignore the token.
Pop the current node (which will be a noscript
element) from the
stack of open elements; the new current node will be a
head
element.
Switch the insertion mode to "in head".
Reprocess the token.
When the user agent is to apply the rules for the "after head" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Insert an HTML element for the token.
Set the frameset-ok flag to "not ok".
Switch the insertion mode to "in body".
Insert an HTML element for the token.
Switch the insertion mode to "in frameset".
Push the node pointed to by the head
element pointer onto
the stack of open elements.
Process the token using the rules for the "in head" insertion mode.
Remove the node pointed to by the head
element pointer
from the stack of open elements. (It might not be the current node at
this point.)
The head
element pointer cannot be null at
this point.
Process the token using the rules for the "in head" insertion mode.
Act as described in the "anything else" entry below.
Parse error. Ignore the token.
Insert an HTML element for a "body" start tag token with no attributes.
Switch the insertion mode to "in body".
Reprocess the current token.
When the user agent is to apply the rules for the "in body" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Reconstruct the active formatting elements, if any.
Set the frameset-ok flag to "not ok".
Parse error. Ignore the token.
If there is a template
element on the stack of open elements, then
ignore the token.
Otherwise, for each attribute on the token, check to see if the attribute is already present on the top element of the stack of open elements. If it is not, add the attribute and its corresponding value to that element.
Process the token using the rules for the "in head" insertion mode.
If the second element on the stack of open elements is not a body
element, if the stack of open elements has only one node on it, or if there is a
template
element on the stack of open elements, then ignore the token.
(fragment case)
Otherwise, set the frameset-ok flag to "not ok"; then, for each attribute on the
token, check to see if the attribute is already present on the body
element (the
second element) on the stack of open elements, and if it is not, add the attribute
and its corresponding value to that element.
If the stack of open elements has only one node on it, or if the second element
on the stack of open elements is not a body
element, then ignore the
token. (fragment case)
If the frameset-ok flag is set to "not ok", ignore the token.
Otherwise, run the following steps:
Remove the second element on the stack of open elements from its parent node, if it has one.
Pop all the nodes from the bottom of the stack of open elements, from the
current node up to, but not including, the root html
element.
Insert an HTML element for the token.
Switch the insertion mode to "in frameset".
If there is a node in the stack of open elements that is not either a
dd
element, a dt
element, an li
element, a p
element, a tbody
element, a td
element, a tfoot
element,
a th
element, a thead
element, a tr
element, the
body
element, or the html
element, then this is a parse
error.
If the stack of template insertion modes is not empty, then process the token using the rules for the "in template" insertion mode.
Otherwise, stop parsing.
If the stack of open elements does not have a body
element in scope, this is a parse error;
ignore the token.
Otherwise, if there is a node in the stack of open elements that is not either a
dd
element, a dt
element, an li
element, an
optgroup
element, an option
element, a p
element, an
rb
element, an rp
element, an rt
element, an
rtc
element, a tbody
element, a td
element, a
tfoot
element, a th
element, a thead
element, a
tr
element, the body
element, or the html
element, then
this is a parse error.
Switch the insertion mode to "after body".
If the stack of open elements does not have a body
element in scope, this is a parse error;
ignore the token.
Otherwise, if there is a node in the stack of open elements that is not either a
dd
element, a dt
element, an li
element, an
optgroup
element, an option
element, a p
element, an
rb
element, an rp
element, an rt
element, an
rtc
element, a tbody
element, a td
element, a
tfoot
element, a th
element, a thead
element, a
tr
element, the body
element, or the html
element, then
this is a parse error.
Switch the insertion mode to "after body".
Reprocess the token.
If the stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for the token.
If the stack of open elements has a
p
element in button scope, then close a p
element.
If the current node is an HTML element whose tag name is one of "h1", "h2", "h3", "h4", "h5", or "h6", then this is a parse error; pop the current node off the stack of open elements.
Insert an HTML element for the token.
If the stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for the token.
If the next token is a "LF" (U+000A) character token, then ignore that
token and move on to the next one. (Newlines at the start of pre
blocks are ignored
as an authoring convenience.)
Set the frameset-ok flag to "not ok".
If the form
element pointer is not null, and there is no template
element on the stack of open elements, then this is
a parse error; ignore the token.
Otherwise:
If the stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for the token, and, if there is no template
element on the stack of open elements, set the form
element pointer to point to the element created.
Run these steps:
Set the frameset-ok flag to "not ok".
Initialize node to be the current node (the bottommost node of the stack).
Loop: If node is an li
element, then run these
substeps:
Generate implied end tags, except for li
elements.
If the current node is not an li
element, then this is a
parse error.
Pop elements from the stack of open elements until an li
element has been popped from the stack.
Jump to the step labeled done below.
If node is in the special category, but is not an
address
, div
, or p
element, then jump to the step
labeled done below.
Otherwise, set node to the previous entry in the stack of open elements and return to the step labeled loop.
Done: If the stack of open elements has a p
element in button scope, then close a
p
element.
Finally, insert an HTML element for the token.
Run these steps:
Set the frameset-ok flag to "not ok".
Initialize node to be the current node (the bottommost node of the stack).
Loop: If node is a dd
element, then run these
substeps:
Generate implied end tags, except for dd
elements.
If the current node is not a dd
element, then this is a
parse error.
Pop elements from the stack of open elements until a dd
element has been popped from the stack.
Jump to the step labeled done below.
If node is a dt
element, then run these substeps:
Generate implied end tags, except for dt
elements.
If the current node is not a dt
element, then this is a
parse error.
Pop elements from the stack of open elements until a dt
element has been popped from the stack.
Jump to the step labeled done below.
If node is in the special category, but is not an
address
, div
, or p
element, then jump to the step
labeled done below.
Otherwise, set node to the previous entry in the stack of open elements and return to the step labeled loop.
Done: If the stack of open elements has a p
element in button scope, then close a
p
element.
Finally, insert an HTML element for the token.
If the stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for the token.
Switch the tokenizer to the PLAINTEXT state.
Once a start tag with the tag name "plaintext" has been seen, that will be the last token ever seen other than character tokens (and the end-of-file token), because there is no way to switch out of the PLAINTEXT state.
If the stack of open elements has a
button
element in scope, then run these substeps:
Pop elements from the stack of open elements until a button
element has been popped from the stack.
Insert an HTML element for the token.
Set the frameset-ok flag to "not ok".
If the stack of open elements does not have an element in scope that is an HTML element and with the same tag name as that of the token, then this is a parse error; ignore the token.
Otherwise, run these steps:
If the current node is not an HTML element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an HTML element with the same tag name as the token has been popped from the stack.
If there is no template
element on the stack of open elements, then
run these substeps:
Let node be the element that the form
element pointer is set to, or null if it is not set to an element.
Set the form
element pointer to null. Otherwise, let
node be null.
If node is null or if the stack of open elements does not have node in scope, then this is a parse error; abort these steps and ignore the token.
If the current node is not node, then this is a parse error.
Remove node from the stack of open elements.
If there is a template
element on the stack of open
elements, then run these substeps instead:
If the stack of open elements does not have a form
element in scope, then this is a parse
error; abort these steps and ignore the token.
If the current node is not a form
element, then this is a
parse error.
Pop elements from the stack of open elements until a form
element has been popped from the stack.
If the stack of open elements does not have a p
element in button scope, then this is a parse
error; insert an HTML element for a "p" start tag token with no
attributes.
If the stack of open elements does not have an li
element in list item scope, then this is a parse
error; ignore the token.
Otherwise, run these steps:
Generate implied end tags, except for li
elements.
If the current node is not an li
element, then this is a
parse error.
Pop elements from the stack of open elements until an li
element has been popped from the stack.
If the stack of open elements does not have an element in scope that is an HTML element and with the same tag name as that of the token, then this is a parse error; ignore the token.
Otherwise, run these steps:
Generate implied end tags, except for HTML elements with the same tag name as the token.
If the current node is not an HTML element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an HTML element with the same tag name as the token has been popped from the stack.
If the stack of open elements does not have an element in scope that is an HTML element and whose tag name is one of "h1", "h2", "h3", "h4", "h5", or "h6", then this is a parse error; ignore the token.
Otherwise, run these steps:
If the current node is not an HTML element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an HTML element whose tag name is one of "h1", "h2", "h3", "h4", "h5", or "h6" has been popped from the stack.
Take a deep breath, then act as described in the "any other end tag" entry below.
If the list of active formatting elements contains an a
element
between the end of the list and the last marker on the list (or the start of the list if there
is no marker on the list), then this is a parse error; run the adoption
agency algorithm for the tag name "a", then remove that element from the list of
active formatting elements and the stack of open elements if the
adoption agency algorithm didn't already remove it (it might not have if the
element is not in table scope).
In the non-conforming stream
<a href="a">a<table><a href="b">b</table>x
, the first
a
element would be closed upon seeing the second one, and the "x" character would
be inside a link to "b", not to "a". This is despite the fact that the outer a
element is not in table scope (meaning that a regular </a>
end tag at the start
of the table wouldn't close the outer a
element). The result is that the two
a
elements are indirectly nested inside each other — non-conforming markup
will often result in non-conforming DOMs when parsed.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token. Push onto the list of active formatting elements that element.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token. Push onto the list of active formatting elements that element.
Reconstruct the active formatting elements, if any.
If the stack of open elements has a
nobr
element in scope, then this is a parse error; run the
adoption agency algorithm for the tag name "nobr", then once again
reconstruct the active formatting elements, if any.
Insert an HTML element for the token. Push onto the list of active formatting elements that element.
Run the adoption agency algorithm for the token's tag name.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token.
Insert a marker at the end of the list of active formatting elements.
Set the frameset-ok flag to "not ok".
If the stack of open elements does not have an element in scope that is an HTML element and with the same tag name as that of the token, then this is a parse error; ignore the token.
Otherwise, run these steps:
If the current node is not an HTML element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an HTML element with the same tag name as the token has been popped from the stack.
If the Document
is not set to quirks mode, and the
stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for the token.
Set the frameset-ok flag to "not ok".
Switch the insertion mode to "in table".
Parse error. Act as described in the next entry, as if this was a "br" start tag token, rather than an end tag token.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
Set the frameset-ok flag to "not ok".
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
If the token does not have an attribute with the name "type", or if it does, but that
attribute's value is not an ASCII case-insensitive match for the string "hidden
", then: set the frameset-ok flag to "not ok".
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
If the stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
Set the frameset-ok flag to "not ok".
Parse error. Change the token's tag name to "img" and reprocess it. (Don't ask.)
If there is no template
element on the stack of open elements and
the form
element pointer is not null, then ignore the
token.
Otherwise:
Acknowledge the token's self-closing flag, if it is set.
Set the frameset-ok flag to "not ok".
If the stack of open elements has a
p
element in button scope, then close a p
element.
Insert an HTML element for a "form" start tag token with no attributes, and, if there is no template
element on the stack of open elements, set
the form
element pointer to point to the element
created.
If the token has an attribute called "action", set the action
attribute on the resulting form
element to the
value of the "action" attribute of the token.
Insert an HTML element for an "hr" start tag token with no attributes. Immediately pop the current node off the stack of open elements.
Reconstruct the active formatting elements, if any.
Insert an HTML element for a "label" start tag token with no attributes.
Insert characters (see below for what they should say).
Insert an HTML element for an "input" start tag token with all the attributes
from the "isindex" token except "name", "action", and "prompt", and with an attribute named
"name" with the value "isindex". (This creates an input
element with the name
attribute set to the magic balue "isindex
".) Immediately pop the current node off
the stack of open elements.
Insert more characters (see below for what they should say).
Pop the current node (which will be the label
element created
earlier) off the stack of open elements.
Insert an HTML element for an "hr" start tag token with no attributes. Immediately pop the current node off the stack of open elements.
Pop the current node (which will be the form
element created
earlier) off the stack of open elements, and, if there is no template
element on the stack of open elements, set the form
element pointer back to null.
Prompt: If the token has an attribute
with the name "prompt", then the first stream of characters must be the same string as given in
that attribute, and the second stream of characters must be empty. Otherwise, the two streams of
character tokens together should, together with the input
element, express the
equivalent of "This is a searchable index. Enter search keywords: (input field)" in the user's
preferred language.
Run these steps:
Insert an HTML element for the token.
If the next token is a "LF" (U+000A) character token, then ignore
that token and move on to the next one. (Newlines at the start of textarea
elements are ignored as an authoring convenience.)
Switch the tokenizer to the RCDATA state.
Let the original insertion mode be the current insertion mode.
Set the frameset-ok flag to "not ok".
Switch the insertion mode to "text".
If the stack of open elements has a
p
element in button scope, then close a p
element.
Reconstruct the active formatting elements, if any.
Set the frameset-ok flag to "not ok".
Follow the generic raw text element parsing algorithm.
Set the frameset-ok flag to "not ok".
Follow the generic raw text element parsing algorithm.
Follow the generic raw text element parsing algorithm.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token.
Set the frameset-ok flag to "not ok".
If the insertion mode is one of "in table", "in caption", "in table body", "in row", or "in cell", then switch the insertion mode to "in select in table". Otherwise, switch the insertion mode to "in select".
If the current node is an option
element, then pop the
current node off the stack of open elements.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token.
If the stack of open elements has a
ruby
element in scope, then generate implied end tags. If the
current node is not then a ruby
element, this is a parse
error.
Insert an HTML element for the token.
If the stack of open elements has a
ruby
element in scope, then generate implied end tags, except
for rtc
elements. If the current node is not then a ruby
element, this is a parse error.
Insert an HTML element for the token.
Reconstruct the active formatting elements, if any.
Adjust MathML attributes for the token. (This fixes the case of MathML attributes that are not all lowercase.)
Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink.)
Insert a foreign element for the token, in the MathML namespace.
If the token has its self-closing flag set, pop the current node off the stack of open elements and acknowledge the token's self-closing flag.
Reconstruct the active formatting elements, if any.
Adjust SVG attributes for the token. (This fixes the case of SVG attributes that are not all lowercase.)
Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink in SVG.)
Insert a foreign element for the token, in the SVG namespace.
If the token has its self-closing flag set, pop the current node off the stack of open elements and acknowledge the token's self-closing flag.
Parse error. Ignore the token.
Reconstruct the active formatting elements, if any.
Insert an HTML element for the token.
This element will be an ordinary element.
Run these steps:
Initialize node to be the current node (the bottommost node of the stack).
Loop: If node is an HTML element with the same tag name as the token, then:
Generate implied end tags, except for HTML elements with the same tag name as the token.
If node is not the current node, then this is a parse error.
Pop all the nodes from the current node up to node, including node, then stop these steps.
Otherwise, if node is in the special category, then this is a parse error; ignore the token, and abort these steps.
Set node to the previous entry in the stack of open elements.
Return to the step labeled loop.
When the steps above say the user agent is to close a p
element, it
means that the user agent must run the following steps:
Generate implied end tags, except for p
elements.
If the current node is not a p
element, then this is a
parse error.
Pop elements from the stack of open elements until a p
element
has been popped from the stack.
The adoption agency algorithm, which takes as its only argument a tag name subject for which the algorithm is being run, consists of the following steps:
If the current node is an HTML element whose tag name is subject, then run these substeps:
Let element be the current node.
Pop element off the stack of open elements.
If element is also in the list of active formatting elements, remove the element from the list.
Abort the adoption agency algorithm.
Let outer loop counter be zero.
Outer loop: If outer loop counter is greater than or equal to eight, then abort these steps.
Increment outer loop counter by one.
Let formatting element be the last element in the list of active formatting elements that:
If there is no such element, then abort these steps and instead act as described in the "any other end tag" entry above.
If formatting element is not in the stack of open elements, then this is a parse error; remove the element from the list, and abort these steps.
If formatting element is in the stack of open elements, but the element is not in scope, then this is a parse error; abort these steps.
If formatting element is not the current node, this is a parse error. (But do not abort these steps.)
Let furthest block be the topmost node in the stack of open elements that is lower in the stack than formatting element, and is an element in the special category. There might not be one.
If there is no furthest block, then the UA must first pop all the nodes from the bottom of the stack of open elements, from the current node up to and including formatting element, then remove formatting element from the list of active formatting elements, and finally abort these steps.
Let common ancestor be the element immediately above formatting element in the stack of open elements.
Let a bookmark note the position of formatting element in the list of active formatting elements relative to the elements on either side of it in the list.
Let node and last node be furthest block. Follow these steps:
Let inner loop counter be zero.
Inner loop: Increment inner loop counter by one.
Let node be the element immediately above node in the stack of open elements, or if node is no longer in the stack of open elements (e.g. because it got removed by this algorithm), the element that was immediately above node in the stack of open elements before node was removed.
If node is formatting element, then go to the next step in the overall algorithm.
If inner loop counter is greater than three and node is in the list of active formatting elements, then remove node from the list of active formatting elements.
If node is not in the list of active formatting elements, then remove node from the stack of open elements and then go back to the step labeled inner loop.
Create an element for the token for which the element node was created, in the HTML namespace, with common ancestor as the intended parent; replace the entry for node in the list of active formatting elements with an entry for the new element, replace the entry for node in the stack of open elements with an entry for the new element, and let node be the new element.
If last node is furthest block, then move the aforementioned bookmark to be immediately after the new node in the list of active formatting elements.
Insert last node into node, first removing it from its previous parent node if any.
Let last node be node.
Return to the step labeled inner loop.
Insert whatever last node ended up being in the previous step at the appropriate place for inserting a node, but using common ancestor as the override target.
Create an element for the token for which formatting element was created, in the HTML namespace, with furthest block as the intended parent.
Take all of the child nodes of furthest block and append them to the element created in the last step.
Append that new element to furthest block.
Remove formatting element from the list of active formatting elements, and insert the new element into the list of active formatting elements at the position of the aforementioned bookmark.
Remove formatting element from the stack of open elements, and insert the new element into the stack of open elements immediately below the position of furthest block in that stack.
Jump back to the step labeled outer loop.
This algorithm's name, the "adoption agency algorithm", comes from the way it causes elements to change parents, and is in contrast with other possible algorithms for dealing with misnested content, which included the "incest algorithm", the "secret affair algorithm", and the "Heisenberg algorithm".
When the user agent is to apply the rules for the "text" insertion mode, the user agent must handle the token as follows:
This can never be a U+0000 NULL character; the tokenizer converts those to U+FFFD REPLACEMENT CHARACTER characters.
If the current node is a script
element, mark the
script
element as "already started".
Pop the current node off the stack of open elements.
Switch the insertion mode to the original insertion mode and reprocess the token.
Perform a microtask checkpoint.
Let script be the current node (which will be a
script
element).
Pop the current node off the stack of open elements.
Switch the insertion mode to the original insertion mode.
Let the old insertion point have the same value as the current insertion point. Let the insertion point be just before the next input character.
Increment the parser's script nesting level by one.
Prepare the script. This might cause some script to execute, which might cause new characters to be inserted into the tokenizer, and might cause the tokenizer to output more tokens, resulting in a reentrant invocation of the parser.
Decrement the parser's script nesting level by one. If the parser's script nesting level is zero, then set the parser pause flag to false.
Let the insertion point have the value of the old insertion point. (In other words, restore the insertion point to its previous value. This value might be the "undefined" value.)
At this stage, if there is a pending parsing-blocking script, then:
Set the parser pause flag to true, and abort the processing of any nested invocations of the tokenizer, yielding control back to the caller. (Tokenization will resume when the caller returns to the "outer" tree construction stage.)
The tree construction stage of this particular parser is being called reentrantly, say from a call to document.write()
.
Run these steps:
Let the script be the pending parsing-blocking script. There is no longer a pending parsing-blocking script.
Block the tokenizer for this instance of the HTML parser, such that the event loop will not run tasks that invoke the tokenizer.
If the parser's Document
has a style sheet that is blocking
scripts or the script's "ready to be parser-executed"
flag is not set: spin the event loop until the parser's Document
has no style sheet that is blocking scripts and the script's
"ready to be parser-executed" flag is set.
If this parser has been aborted in the meantime, abort these steps.
This could happen if, e.g., while the spin the event loop
algorithm is running, the browsing context gets closed, or the document.open()
method gets invoked on the
Document
.
Unblock the tokenizer for this instance of the HTML parser, such that tasks that invoke the tokenizer can again be run.
Let the insertion point be just before the next input character.
Increment the parser's script nesting level by one (it should be zero before this step, so this sets it to one).
Execute the script.
Decrement the parser's script nesting level by one. If the parser's script nesting level is zero (which it always should be at this point), then set the parser pause flag to false.
Let the insertion point be undefined again.
If there is once again a pending parsing-blocking script, then repeat these steps from step 1.
Pop the current node off the stack of open elements.
Switch the insertion mode to the original insertion mode.
When the user agent is to apply the rules for the "in table" insertion mode, the user agent must handle the token as follows:
table
, tbody
, tfoot
, thead
, or tr
elementLet the pending table character tokens be an empty list of tokens.
Let the original insertion mode be the current insertion mode.
Switch the insertion mode to "in table text" and reprocess the token.
Parse error. Ignore the token.
Clear the stack back to a table context. (See below.)
Insert a marker at the end of the list of active formatting elements.
Insert an HTML element for the token, then switch the insertion mode to "in caption".
Clear the stack back to a table context. (See below.)
Insert an HTML element for the token, then switch the insertion mode to "in column group".
Clear the stack back to a table context. (See below.)
Insert an HTML element for a "colgroup" start tag token with no attributes, then switch the insertion mode to "in column group".
Reprocess the current token.
Clear the stack back to a table context. (See below.)
Insert an HTML element for the token, then switch the insertion mode to "in table body".
Clear the stack back to a table context. (See below.)
Insert an HTML element for a "tbody" start tag token with no attributes, then switch the insertion mode to "in table body".
Reprocess the current token.
If the stack of open elements does not have a table
element in table scope, ignore the token.
Otherwise:
Pop elements from this stack until a table
element has been popped from the
stack.
Reset the insertion mode appropriately.
Reprocess the token.
If the stack of open elements does not have a table
element in table scope, this is a parse
error; ignore the token.
Otherwise:
Pop elements from this stack until a table
element has been popped from the
stack.
Parse error. Ignore the token.
Process the token using the rules for the "in head" insertion mode.
If the token does not have an attribute with the name "type", or if it does, but that
attribute's value is not an ASCII case-insensitive match for the string "hidden
", then: act as described in the "anything else" entry below.
Otherwise:
Insert an HTML element for the token.
Pop that input
element off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
If there is a template
element on the stack of open elements, or if
the form
element pointer is not null, ignore the
token.
Otherwise:
Insert an HTML element for the token, and set the form
element pointer to point to the element created.
Pop that form
element off the stack of open elements.
Process the token using the rules for the "in body" insertion mode.
Parse error. Enable foster parenting, process the token using the rules for the "in body" insertion mode, and then disable foster parenting.
When the steps above require the UA to clear the stack back to a table context, it
means that the UA must, while the current node is not a table
,
template
, or html
element, pop elements from the stack of open
elements.
The current node being an html
element after this
process is a fragment case.
When the user agent is to apply the rules for the "in table text" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Append the character token to the pending table character tokens list.
If any of the tokens in the pending table character tokens list are character tokens that are not space characters, then reprocess the character tokens in the pending table character tokens list using the rules given in the "anything else" entry in the "in table" insertion mode.
Otherwise, insert the characters given by the pending table character tokens list.
Switch the insertion mode to the original insertion mode and reprocess the token.
When the user agent is to apply the rules for the "in caption" insertion mode, the user agent must handle the token as follows:
If the stack of open elements does not have a caption
element in table scope, this is a parse
error; ignore the token. (fragment case)
Otherwise:
Now, if the current node is not a caption
element, then this is a
parse error.
Pop elements from this stack until a caption
element has been popped from the
stack.
Clear the list of active formatting elements up to the last marker.
Switch the insertion mode to "in table".
If the stack of open elements does not have a caption
element in table scope, ignore the token.
(fragment case)
Otherwise:
Pop elements from this stack until a caption
element has been popped from the
stack.
Clear the list of active formatting elements up to the last marker.
Switch the insertion mode to "in table".
Reprocess the token.
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
When the user agent is to apply the rules for the "in column group" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
If the current node is not a colgroup
element, then this is a
parse error; ignore the token.
Otherwise, pop the current node from the stack of open elements. Switch the insertion mode to "in table".
Parse error. Ignore the token.
Process the token using the rules for the "in head" insertion mode.
Process the token using the rules for the "in body" insertion mode.
If the current node is not a colgroup
element, then this is a
parse error; ignore the token.
Otherwise, pop the current node from the stack of open elements.
Switch the insertion mode to "in table".
Reprocess the token.
When the user agent is to apply the rules for the "in table body" insertion mode, the user agent must handle the token as follows:
Clear the stack back to a table body context. (See below.)
Insert an HTML element for the token, then switch the insertion mode to "in row".
Clear the stack back to a table body context. (See below.)
Insert an HTML element for a "tr" start tag token with no attributes, then switch the insertion mode to "in row".
Reprocess the current token.
If the stack of open elements does not have an element in table scope that is an HTML element and with the same tag name as the token, this is a parse error; ignore the token.
Otherwise:
Clear the stack back to a table body context. (See below.)
Pop the current node from the stack of open elements. Switch the insertion mode to "in table".
If the stack of open elements does not have a tbody
, thead
, or tfoot
element in table
scope, this is a parse error; ignore the token.
Otherwise:
Clear the stack back to a table body context. (See below.)
Pop the current node from the stack of open elements. Switch the insertion mode to "in table".
Reprocess the token.
Parse error. Ignore the token.
Process the token using the rules for the "in table" insertion mode.
When the steps above require the UA to clear the stack back to a table body context,
it means that the UA must, while the current node is not a tbody
,
tfoot
, thead
, template
, or html
element, pop
elements from the stack of open elements.
The current node being an html
element after this
process is a fragment case.
When the user agent is to apply the rules for the "in row" insertion mode, the user agent must handle the token as follows:
Clear the stack back to a table row context. (See below.)
Insert an HTML element for the token, then switch the insertion mode to "in cell".
Insert a marker at the end of the list of active formatting elements.
If the stack of open elements does not have a tr
element in table scope, this is a parse error;
ignore the token.
Otherwise:
Clear the stack back to a table row context. (See below.)
Pop the current node (which will be a tr
element) from the
stack of open elements. Switch the insertion mode to "in table body".
If the stack of open elements does not have a tr
element in table scope, this is a parse error;
ignore the token.
Otherwise:
Clear the stack back to a table row context. (See below.)
Pop the current node (which will be a tr
element) from the
stack of open elements. Switch the insertion mode to "in table body".
Reprocess the token.
If the stack of open elements does not have an element in table scope that is an HTML element and with the same tag name as the token, this is a parse error; ignore the token.
If the stack of open elements does not have a tr
element in table scope, ignore the token.
Otherwise:
Clear the stack back to a table row context. (See below.)
Pop the current node (which will be a tr
element) from the
stack of open elements. Switch the insertion mode to "in table body".
Reprocess the token.
Parse error. Ignore the token.
Process the token using the rules for the "in table" insertion mode.
When the steps above require the UA to clear the stack back to a table row context,
it means that the UA must, while the current node is not a tr
,
template
, or html
element, pop elements from the stack of open
elements.
The current node being an html
element after this
process is a fragment case.
When the user agent is to apply the rules for the "in cell" insertion mode, the user agent must handle the token as follows:
If the stack of open elements does not have an element in table scope that is an HTML element and with the same tag name as that of the token, then this is a parse error; ignore the token.
Otherwise:
Now, if the current node is not an HTML element with the same tag name as the token, then this is a parse error.
Pop elements from the stack of open elements stack until an HTML element with the same tag name as the token has been popped from the stack.
Clear the list of active formatting elements up to the last marker.
Switch the insertion mode to "in row".
If the stack of open elements does not have a td
or th
element in table scope, then this
is a parse error; ignore the token. (fragment case)
Otherwise, close the cell (see below) and reprocess the token.
Parse error. Ignore the token.
If the stack of open elements does not have an element in table scope that is an HTML element and with the same tag name as that of the token, then this is a parse error; ignore the token.
Otherwise, close the cell (see below) and reprocess the token.
Process the token using the rules for the "in body" insertion mode.
Where the steps above say to close the cell, they mean to run the following algorithm:
If the current node is not now a td
element or a th
element, then this is a parse error.
Pop elements from the stack of open elements stack until a td
element or a th
element has been popped from the stack.
Clear the list of active formatting elements up to the last marker.
Switch the insertion mode to "in row".
The stack of open elements cannot have both a td
and a
th
element in table scope at the
same time, nor can it have neither when the close the cell algorithm is invoked.
When the user agent is to apply the rules for the "in select" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
If the current node is an option
element, pop that node from the
stack of open elements.
Insert an HTML element for the token.
If the current node is an option
element, pop that node from the
stack of open elements.
If the current node is an optgroup
element, pop that node from the
stack of open elements.
Insert an HTML element for the token.
First, if the current node is an option
element, and the node
immediately before it in the stack of open elements is an optgroup
element, then pop the current node from the stack of open
elements.
If the current node is an optgroup
element, then pop that node from
the stack of open elements. Otherwise, this is a parse error; ignore
the token.
If the current node is an option
element, then pop that node from
the stack of open elements. Otherwise, this is a parse error; ignore
the token.
If the stack of open elements does not have a select
element in select scope, this is a parse
error; ignore the token. (fragment case)
Otherwise:
Pop elements from the stack of open elements until a select
element
has been popped from the stack.
Pop elements from the stack of open elements until a select
element
has been popped from the stack.
Reset the insertion mode appropriately.
It just gets treated like an end tag.
If the stack of open elements does not have a select
element in select scope, ignore the token.
(fragment case)
Pop elements from the stack of open elements until a select
element
has been popped from the stack.
Reset the insertion mode appropriately.
Reprocess the token.
Process the token using the rules for the "in head" insertion mode.
Process the token using the rules for the "in body" insertion mode.
Parse error. Ignore the token.
When the user agent is to apply the rules for the "in select in table" insertion mode, the user agent must handle the token as follows:
Pop elements from the stack of open elements until a select
element
has been popped from the stack.
Reset the insertion mode appropriately.
Reprocess the token.
If the stack of open elements does not have an element in table scope that is an HTML element and with the same tag name as that of the token, then ignore the token.
Otherwise:
Pop elements from the stack of open elements until a select
element
has been popped from the stack.
Reset the insertion mode appropriately.
Reprocess the token.
Process the token using the rules for the "in select" insertion mode.
When the user agent is to apply the rules for the "in template" insertion mode, the user agent must handle the token as follows:
Process the token using the rules for the "in body" insertion mode.
Process the token using the rules for the "in head" insertion mode.
Pop the current template insertion mode off the stack of template insertion modes.
Push "in table" onto the stack of template insertion modes so that it is the new current template insertion mode.
Switch the insertion mode to "in table", and reprocess the token.
Pop the current template insertion mode off the stack of template insertion modes.
Push "in column group" onto the stack of template insertion modes so that it is the new current template insertion mode.
Switch the insertion mode to "in column group", and reprocess the token.
Pop the current template insertion mode off the stack of template insertion modes.
Push "in table body" onto the stack of template insertion modes so that it is the new current template insertion mode.
Switch the insertion mode to "in table body", and reprocess the token.
Pop the current template insertion mode off the stack of template insertion modes.
Push "in row" onto the stack of template insertion modes so that it is the new current template insertion mode.
Switch the insertion mode to "in row", and reprocess the token.
Pop the current template insertion mode off the stack of template insertion modes.
Push "in body" onto the stack of template insertion modes so that it is the new current template insertion mode.
Switch the insertion mode to "in body", and reprocess the token.
Parse error. Ignore the token.
If there is no template
element on the stack of open elements, then
stop parsing. (fragment case)
Otherwise, this is a parse error.
Pop elements from the stack of open elements until a template
element has been popped from the stack.
Clear the list of active formatting elements up to the last marker.
Pop the current template insertion mode off the stack of template insertion modes.
Reset the insertion mode appropriately.
Reprocess the token.
When the user agent is to apply the rules for the "after body" insertion mode, the user agent must handle the token as follows:
Process the token using the rules for the "in body" insertion mode.
Insert a comment as the last child of the first element in the stack of
open elements (the html
element).
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
If the parser was originally created as part of the HTML fragment parsing algorithm, this is a parse error; ignore the token. (fragment case)
Otherwise, switch the insertion mode to "after after body".
Parse error. Switch the insertion mode to "in body" and reprocess the token.
When the user agent is to apply the rules for the "in frameset" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Insert an HTML element for the token.
If the current node is the root html
element, then this is a
parse error; ignore the token. (fragment case)
Otherwise, pop the current node from the stack of open elements.
If the parser was not originally created as part of the HTML fragment parsing
algorithm (fragment case), and the current node is no longer a
frameset
element, then switch the insertion mode to "after frameset".
Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.
Acknowledge the token's self-closing flag, if it is set.
Process the token using the rules for the "in head" insertion mode.
If the current node is not the root html
element, then this is a
parse error.
The current node can only be the root
html
element in the fragment case.
Parse error. Ignore the token.
When the user agent is to apply the rules for the "after frameset" insertion mode, the user agent must handle the token as follows:
Parse error. Ignore the token.
Process the token using the rules for the "in body" insertion mode.
Switch the insertion mode to "after after frameset".
Process the token using the rules for the "in head" insertion mode.
Parse error. Ignore the token.
When the user agent is to apply the rules for the "after after body" insertion mode, the user agent must handle the token as follows:
Insert a comment as the last child of the Document
object.
Process the token using the rules for the "in body" insertion mode.
Parse error. Switch the insertion mode to "in body" and reprocess the token.
When the user agent is to apply the rules for the "after after frameset" insertion mode, the user agent must handle the token as follows:
Insert a comment as the last child of the Document
object.
Process the token using the rules for the "in body" insertion mode.
Process the token using the rules for the "in head" insertion mode.
Parse error. Ignore the token.
When the user agent is to apply the rules for parsing tokens in foreign content, the user agent must handle the token as follows:
Parse error. Insert a U+FFFD REPLACEMENT CHARACTER character.
Set the frameset-ok flag to "not ok".
Parse error. Ignore the token.
If the parser was originally created for the HTML fragment parsing algorithm, then act as described in the "any other start tag" entry below. (fragment case)
Otherwise:
Pop an element from the stack of open elements, and then keep popping more elements from the stack of open elements until the current node is a MathML text integration point, an HTML integration point, or an element in the HTML namespace.
Then, reprocess the token.
If the adjusted current node is an element in the MathML namespace, adjust MathML attributes for the token. (This fixes the case of MathML attributes that are not all lowercase.)
If the adjusted current node is an element in the SVG namespace, and the token's tag name is one of the ones in the first column of the following table, change the tag name to the name given in the corresponding cell in the second column. (This fixes the case of SVG elements that are not all lowercase.)
Tag name | Element name |
---|---|
altglyph | altGlyph
|
altglyphdef | altGlyphDef
|
altglyphitem | altGlyphItem
|
animatecolor | animateColor
|
animatemotion | animateMotion
|
animatetransform | animateTransform
|
clippath | clipPath
|
feblend | feBlend
|
fecolormatrix | feColorMatrix
|
fecomponenttransfer | feComponentTransfer
|
fecomposite | feComposite
|
feconvolvematrix | feConvolveMatrix
|
fediffuselighting | feDiffuseLighting
|
fedisplacementmap | feDisplacementMap
|
fedistantlight | feDistantLight
|
feflood | feFlood
|
fefunca | feFuncA
|
fefuncb | feFuncB
|
fefuncg | feFuncG
|
fefuncr | feFuncR
|
fegaussianblur | feGaussianBlur
|
feimage | feImage
|
femerge | feMerge
|
femergenode | feMergeNode
|
femorphology | feMorphology
|
feoffset | feOffset
|
fepointlight | fePointLight
|
fespecularlighting | feSpecularLighting
|
fespotlight | feSpotLight
|
fetile | feTile
|
feturbulence | feTurbulence
|
foreignobject | foreignObject
|
glyphref | glyphRef
|
lineargradient | linearGradient
|
radialgradient | radialGradient
|
textpath | textPath
|
If the adjusted current node is an element in the SVG namespace, adjust SVG attributes for the token. (This fixes the case of SVG attributes that are not all lowercase.)
Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink in SVG.)
Insert a foreign element for the token, in the same namespace as the adjusted current node.
If the token has its self-closing flag set, then run the appropriate steps from the following list:
Acknowledge the token's self-closing flag, and then act as described in the steps for a "script" end tag below.
Pop the current node off the stack of open elements and acknowledge the token's self-closing flag.
script
element in the SVG namespacePop the current node off the stack of open elements.
Let the old insertion point have the same value as the current insertion point. Let the insertion point be just before the next input character.
Increment the parser's script nesting level by one. Set the parser pause flag to true.
Process the
script
element according to the SVG rules, if the user agent supports
SVG. [SVG]
Even if this causes new characters to be inserted into the tokenizer, the parser will not be executed reentrantly, since the parser pause flag is true.
Decrement the parser's script nesting level by one. If the parser's script nesting level is zero, then set the parser pause flag to false.
Let the insertion point have the value of the old insertion point. (In other words, restore the insertion point to its previous value. This value might be the "undefined" value.)
Run these steps:
Initialize node to be the current node (the bottommost node of the stack).
If node's tag name, converted to ASCII lowercase, is not the same as the tag name of the token, then this is a parse error.
Loop: If node is the topmost element in the stack of open elements, abort these steps. (fragment case)
If node's tag name, converted to ASCII lowercase, is the same as the tag name of the token, pop elements from the stack of open elements until node has been popped from the stack, and then abort these steps.
Set node to the previous entry in the stack of open elements.
If node is not an element in the HTML namespace, return to the step labeled loop.
Otherwise, process the token according to the rules given in the section corresponding to the current insertion mode in HTML content.
Once the user agent stops parsing the document, the user agent must run the following steps:
Set the current document readiness to "interactive
"
and the insertion point to
undefined.
Pop all the nodes off the stack of open elements.
If the list of scripts that will execute when the document has finished parsing is not empty, run these substeps:
Spin the event loop until the first script
in the list
of scripts that will execute when the document has finished parsing has its "ready
to be parser-executed" flag set and the parser's Document
has no style sheet that is blocking scripts.
Execute the first script
in
the list of scripts that will execute when the document has finished
parsing.
Remove the first script
element from the list of scripts that will
execute when the document has finished parsing (i.e. shift out the first entry in the
list).
If the list of scripts that will execute when the document has finished parsing is still not empty, repeat these substeps again from substep 1.
Queue a task to fire a simple event that bubbles named DOMContentLoaded
at the Document
.
Spin the event loop until the set of scripts that will execute as soon as possible and the list of scripts that will execute in order as soon as possible are empty.
Spin the event loop until there is nothing that delays the load event in the Document
.
Queue a task to run the following substeps:
Set the current document readiness to "complete
".
If the Document
is in a browsing context, create a trusted event named load
that does not bubble and is not cancelable and which uses the
Event
interface, and dispatch it at
the Document
's Window
object, with target override set to the
Document
object.
If the Document
is in a browsing context, then queue a
task to run the following substeps:
If the Document
's page showing flag is true, then abort this
task (i.e. don't fire the event below).
Set the Document
's page showing flag to true.
Fire a trusted event with the name pageshow
at the Window
object of the
Document
, but with its target
set to the
Document
object (and the currentTarget
set to the Window
object),
using the PageTransitionEvent
interface, with the persisted
attribute initialized to false. This
event must not bubble, must not be cancelable, and has no default action.
If the Document
has any pending application cache download process
tasks, then queue each such task in the order they were added to the list of pending
application cache download process tasks, and then empty the list of pending
application cache download process tasks. The task source for these tasks is the networking task source.
If the Document
's print when loaded flag is set, then run the
printing steps.
The Document
is now ready for post-load tasks.
Queue a task to mark the Document
as completely
loaded.
When the user agent is to abort a parser, it must run the following steps:
Throw away any pending content in the input stream, and discard any future content that would have been added to it.
Set the current document readiness to "interactive
".
Pop all the nodes off the stack of open elements.
Set the current document readiness to "complete
".
Except where otherwise specified, the task source for the tasks mentioned in this section is the DOM manipulation task source.
When an application uses an HTML parser in conjunction with an XML pipeline, it is
possible that the constructed DOM is not compatible with the XML tool chain in certain subtle
ways. For example, an XML toolchain might not be able to represent attributes with the name xmlns
, since they conflict with the Namespaces in XML syntax. There is also some
data that the HTML parser generates that isn't included in the DOM itself. This
section specifies some rules for handling these issues.
If the XML API being used doesn't support DOCTYPEs, the tool may drop DOCTYPEs altogether.
If the XML API doesn't support attributes in no namespace that are named "xmlns
", attributes whose names start with "xmlns:
", or
attributes in the XMLNS namespace, then the tool may drop such attributes.
The tool may annotate the output with any namespace declarations required for proper operation.
If the XML API being used restricts the allowable characters in the local names of elements and attributes, then the tool may map all element and attribute local names that the API wouldn't support to a set of names that are allowed, by replacing any character that isn't supported with the uppercase letter U and the six digits of the character's Unicode code point when expressed in hexadecimal, using digits 0-9 and capital letters A-F as the symbols, in increasing numeric order.
For example, the element name foo<bar
, which can be
output by the HTML parser, though it is neither a legal HTML element name nor a
well-formed XML element name, would be converted into fooU00003Cbar
, which
is a well-formed XML element name (though it's still not legal in HTML by any means).
As another example, consider the attribute xlink:href
. Used on a
MathML element, it becomes, after being adjusted,
an attribute with a prefix "xlink
" and a local name "href
". However, used on an HTML element, it becomes an attribute with no prefix
and the local name "xlink:href
", which is not a valid NCName, and thus might
not be accepted by an XML API. It could thus get converted, becoming "xlinkU00003Ahref
".
The resulting names from this conversion conveniently can't clash with any attribute generated by the HTML parser, since those are all either lowercase or those listed in the adjust foreign attributes algorithm's table.
If the XML API restricts comments from having two consecutive U+002D HYPHEN-MINUS characters (--), the tool may insert a single U+0020 SPACE character between any such offending characters.
If the XML API restricts comments from ending in a "-" (U+002D) character, the tool may insert a single U+0020 SPACE character at the end of such comments.
If the XML API restricts allowed characters in character data, attribute values, or comments, the tool may replace any "FF" (U+000C) character with a U+0020 SPACE character, and any other literal non-XML character with a U+FFFD REPLACEMENT CHARACTER.
If the tool has no way to convey out-of-band information, then the tool may drop the following information:
form
element ancestor (use of the form
element pointer in the parser)template
elements.The mutations allowed by this section apply after the HTML
parser's rules have been applied. For example, a <a::>
start tag
will be closed by a </a::>
end tag, and never by a </aU00003AU00003A>
end tag, even if the user agent is using the rules above to
then generate an actual element in the DOM with the name aU00003AU00003A
for
that start tag.
This section is non-normative.
This section examines some erroneous markup and discusses how the HTML parser handles these cases.
This section is non-normative.
The most-often discussed example of erroneous markup is as follows:
<p>1<b>2<i>3</b>4</i>5</p>
The parsing of this markup is straightforward up to the "3". At this point, the DOM looks like this:
Here, the stack of open elements has five elements on it: html
,
body
, p
, b
, and i
. The list of active
formatting elements just has two: b
and i
. The insertion
mode is "in body".
Upon receiving the end tag token with the tag name "b", the "adoption
agency algorithm" is invoked. This is a simple case, in that the formatting
element is the b
element, and there is no furthest block.
Thus, the stack of open elements ends up with just three elements: html
,
body
, and p
, while the list of active formatting elements
has just one: i
. The DOM tree is unmodified at this point.
The next token is a character ("4"), triggers the reconstruction of the active formatting elements, in this case just
the i
element. A new i
element is thus created for the "4"
Text
node. After the end tag token for the "i" is also received, and the "5"
Text
node is inserted, the DOM looks as follows:
This section is non-normative.
A case similar to the previous one is the following:
<b>1<p>2</b>3</p>
Up to the "2" the parsing here is straightforward:
The interesting part is when the end tag token with the tag name "b" is parsed.
Before that token is seen, the stack of open elements has four elements on it:
html
, body
, b
, and p
. The list of active
formatting elements just has the one: b
. The insertion mode is
"in body".
Upon receiving the end tag token with the tag name "b", the "adoption
agency algorithm" is invoked, as in the previous example. However, in this case, there
is a furthest block, namely the p
element. Thus, this
time the adoption agency algorithm isn't skipped over.
The common ancestor is the body
element. A conceptual
"bookmark" marks the position of the b
in the list of active formatting
elements, but since that list has only one element in it, the bookmark won't have much
effect.
As the algorithm progresses, node ends up set to the formatting element
(b
), and last node ends up set to the furthest
block (p
).
The last node gets appended (moved) to the common ancestor, so that the DOM looks like:
A new b
element is created, and the children of the p
element are
moved to it:
Finally, the new b
element is appended to the p
element, so that the
DOM looks like:
The b
element is removed from the list of active formatting elements
and the stack of open elements, so that when the "3" is parsed, it is appended to the
p
element:
This section is non-normative.
Error handling in tables is, for historical reasons, especially strange. For example, consider the following markup:
<table><b><tr><td>aaa</td></tr>bbb</table>ccc
The highlighted b
element start tag is not allowed directly inside a table like
that, and the parser handles this case by placing the element before the table. (This is
called foster parenting.) This can be seen by examining the DOM tree
as it stands just after the table
element's start tag has been seen:
...and then immediately after the b
element start tag has been seen:
At this point, the stack of open elements has on it the elements
html
, body
, table
, and b
(in that order,
despite the resulting DOM tree); the list of active formatting elements just has the
b
element in it; and the insertion mode is "in table".
The tr
start tag causes the b
element to be popped off the stack and
a tbody
start tag to be implied; the tbody
and tr
elements
are then handled in a rather straight-forward manner, taking the parser through the "in table body" and "in row" insertion modes, after which the DOM looks as follows:
Here, the stack of open elements has on it the elements html
,
body
, table
, tbody
, and tr
; the list of
active formatting elements still has the b
element in it; and the
insertion mode is "in row".
The td
element start tag token, after putting a td
element on the
tree, puts a marker on the list of active formatting elements (it also switches to
the "in cell" insertion mode).
The marker means that when the "aaa" character tokens are seen, no b
element is
created to hold the resulting Text
node:
The end tags are handled in a straight-forward manner; after handling them, the stack of
open elements has on it the elements html
, body
,
table
, and tbody
; the list of active formatting elements
still has the b
element in it (the marker having been removed by the "td" end tag
token); and the insertion mode is "in
table body".
Thus it is that the "bbb" character tokens are found. These trigger the "in table text" insertion mode to be used (with the original
insertion mode set to "in table body").
The character tokens are collected, and when the next token (the table
element end
tag) is seen, they are processed as a group. Since they are not all spaces, they are handled as
per the "anything else" rules in the "in table"
insertion mode, which defer to the "in body"
insertion mode but with foster parenting.
When the active formatting elements
are reconstructed, a b
element is created and foster parented, and then the "bbb" Text
node is appended to it:
The stack of open elements has on it the elements html
,
body
, table
, tbody
, and the new b
(again, note
that this doesn't match the resulting tree!); the list of active formatting elements
has the new b
element in it; and the insertion mode is still "in table body".
Had the character tokens been only space characters
instead of "bbb", then those space characters would just be
appended to the tbody
element.
Finally, the table
is closed by a "table" end tag. This pops all the nodes from
the stack of open elements up to and including the table
element, but it
doesn't affect the list of active formatting elements, so the "ccc" character tokens
after the table result in yet another b
element being created, this time after the
table:
This section is non-normative.
Consider the following markup, which for this example we will assume is the document with
URL http://example.com/inner
, being rendered as the content of
an iframe
in another document with the URL http://example.com/outer
:
<div id=a> <script> var div = document.getElementById('a'); parent.document.body.appendChild(div); </script> <script> alert(document.URL); </script> </div> <script> alert(document.URL); </script>
Up to the first "script" end tag, before the script is parsed, the result is relatively straightforward:
After the script is parsed, though, the div
element and its child
script
element are gone:
They are, at this point, in the Document
of the aforementioned outer
browsing context. However, the stack of open elements still contains
the div
element.
Thus, when the second script
element is parsed, it is inserted into the outer
Document
object.
Those parsed into different Document
s than the one the parser was created for do
not execute, so the first alert does not show.
Once the div
element's end tag is parsed, the div
element is popped
off the stack, and so the next script
element is in the inner
Document
:
This script does execute, resulting in an alert that says "http://example.com/inner".
This section is non-normative.
Elaborating on the example in the previous section, consider the case where the second
script
element is an external script (i.e. one with a src
attribute). Since the element was not in the parser's
Document
when it was created, that external script is not even downloaded.
In a case where a script
element with a src
attribute is parsed normally into its parser's Document
, but while the external
script is being downloaded, the element is moved to another document, the script continues to
download, but does not execute.
In general, moving script
elements between Document
s is
considered a bad practice.
This section is non-normative.
The following markup shows how nested formatting elements (such as b
) get
collected and continue to be applied even as the elements they are contained in are closed, but
that excessive duplicates are thrown away.
<!DOCTYPE html> <p><b class=x><b class=x><b><b class=x><b class=x><b>X <p>X <p><b><b class=x><b>X <p></b></b></b></b></b></b>X
The resulting DOM tree is as follows:
Note how the second p
element in the markup has no explicit b
elements, but in the resulting DOM, up to three of each kind of formatting element (in this case
three b
elements with the class attribute, and two unadorned b
elements)
get reconstructed before the element's "X".
Also note how this means that in the final paragraph only six b
end tags are
needed to completely clear the list of formatting elements, even though nine b
start
tags have been seen up to this point.
The following steps form the HTML fragment serialization algorithm. The algorithm
takes as input a DOM Element
, Document
, or DocumentFragment
referred to as the node, and either returns a string or throws an
exception.
This algorithm serializes the children of the node being serialized, not the node itself.
Let s be a string, and initialize it to the empty string.
If the node is a template
element, then let the node instead be the template
element's template
contents (a DocumentFragment
node).
For each child node of the node, in tree order, run the following steps:
Let current node be the child node being processed.
Append the appropriate string from the following list to s:
Element
If current node is an element in the HTML namespace, the MathML namespace, or the SVG namespace, then let tagname be current node's local name. Otherwise, let tagname be current node's qualified name.
Append a "<" (U+003C) character, followed by tagname.
For HTML elements created by the HTML parser or
Document.createElement()
, tagname will be
lowercase.
For each attribute that the element has, append a U+0020 SPACE character, the attribute's serialized name as described below, a "=" (U+003D) character, a U+0022 QUOTATION MARK character ("), the attribute's value, escaped as described below in attribute mode, and a second U+0022 QUOTATION MARK character (").
An attribute's serialized name for the purposes of the previous paragraph must be determined as follows:
The attribute's serialized name is the attribute's local name.
For attributes on HTML elements set by the HTML
parser or by Element.setAttribute()
, the local name will be
lowercase.
The attribute's serialized name is the string "xml:
" followed
by the attribute's local name.
xmlns
The attribute's serialized name is the string "xmlns
".
xmlns
The attribute's serialized name is the string "xmlns:
" followed by the attribute's local
name.
The attribute's serialized name is the string "xlink:
"
followed by the attribute's local name.
The attribute's serialized name is the attribute's qualified name.
While the exact order of attributes is UA-defined, and may depend on factors such as the order that the attributes were given in the original markup, the sort order must be stable, such that consecutive invocations of this algorithm serialize an element's attributes in the same order.
Append a ">" (U+003E) character.
If current node is an area
, base
,
basefont
, bgsound
, br
, col
,
embed
, frame
, hr
, img
,
input
, keygen
, link
,
meta
, param
, source
, track
or
wbr
element, then continue on to the next child node at this point.
If current node is a pre
, textarea
, or
listing
element, and the first child node of the element, if any, is a
Text
node whose character data has as its first character a "LF" (U+000A) character, then append a "LF" (U+000A) character.
Append the value of running the HTML fragment serialization algorithm on the current node element (thus recursing into this algorithm for that element), followed by a "<" (U+003C) character, a U+002F SOLIDUS character (/), tagname again, and finally a U+003E GREATER-THAN SIGN character (>).
Text
nodeIf the parent of current node is a style
,
script
, xmp
, iframe
, noembed
,
noframes
, or plaintext
element, or if the parent of current node is a noscript
element and scripting is enabled for the node, then append the value of
current node's data
IDL attribute literally.
Otherwise, append the value of current node's data
IDL attribute, escaped as described
below.
Comment
Append the literal string <!--
(U+003C LESS-THAN SIGN, U+0021 EXCLAMATION
MARK, U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS), followed by the value of current node's data
IDL attribute, followed by the
literal string -->
(U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS, U+003E
GREATER-THAN SIGN).
ProcessingInstruction
Append the literal string <?
(U+003C LESS-THAN SIGN, U+003F QUESTION
MARK), followed by the value of current node's target
IDL attribute, followed by a single U+0020 SPACE character, followed
by the value of current node's data
IDL attribute,
followed by a single ">" (U+003E) character.
DocumentType
Append the literal string <!DOCTYPE
(U+003C LESS-THAN SIGN, U+0021
EXCLAMATION MARK, U+0044 LATIN CAPITAL LETTER D, U+004F LATIN CAPITAL LETTER O, U+0043 LATIN
CAPITAL LETTER C, U+0054 LATIN CAPITAL LETTER T, U+0059 LATIN CAPITAL LETTER Y, U+0050 LATIN
CAPITAL LETTER P, U+0045 LATIN CAPITAL LETTER E), followed by a space (U+0020 SPACE),
followed by the value of current node's name
IDL
attribute, followed by the literal string >
(U+003E GREATER-THAN SIGN).
The result of the algorithm is the string s.
It is possible that the output of this algorithm, if parsed with an HTML parser, will not return the original tree structure.
For instance, if a textarea
element to which a Comment
node
has been appended is serialized and the output is then reparsed, the comment will end up being
displayed in the text field. Similarly, if, as a result of DOM manipulation, an element contains
a comment that contains the literal string "-->
", then when the result
of serializing the element is parsed, the comment will be truncated at that point and the rest of
the comment will be interpreted as markup. More examples would be making a script
element contain a Text
node with the text string "</script>
", or
having a p
element that contains a ul
element (as the ul
element's start tag would imply the end tag for the
p
).
This can enable cross-site scripting attacks. An example of this would be a page that lets the
user enter some font family names that are then inserted into a CSS style
block via
the DOM and which then uses the innerHTML
IDL attribute to get
the HTML serialization of that style
element: if the user enters
"</style><script>attack</script>
" as a font family name, innerHTML
will return markup that, if parsed in a different context,
would contain a script
node, even though no script
node existed in the
original DOM.
Escaping a string (for the purposes of the algorithm above) consists of running the following steps:
Replace any occurrence of the "&
" character by the string "&
".
Replace any occurrences of the U+00A0 NO-BREAK SPACE character by the string "
".
If the algorithm was invoked in the attribute mode, replace any occurrences of the
""
" character by the string ""
".
If the algorithm was not invoked in the attribute mode, replace any
occurrences of the "<
" character by the string "<
", and any occurrences of the ">
" character by
the string ">
".
The following steps form the HTML fragment parsing algorithm. The algorithm
optionally takes as input an Element
node, referred to as the context element, which gives the context for
the parser, as well as input, a string to parse, and returns a list of zero or
more nodes.
Parts marked fragment case in algorithms in the parser section are parts that only occur if the parser was created for the purposes of this algorithm (and with a context element). The algorithms have been annotated with such markings for informational purposes only; such markings have no normative weight. If it is possible for a condition described as a fragment case to occur even when the parser wasn't created for the purposes of handling this algorithm, then that is an error in the specification.
Create a new Document
node, and mark it as being an HTML document.
If there is a context element, and the
Document
of the context element is in
quirks mode, then let the Document
be in quirks mode.
Otherwise, if there is a context element, and the
Document
of the context element is in
limited-quirks mode, then let the Document
be in limited-quirks
mode. Otherwise, leave the Document
in no-quirks mode.
Create a new HTML parser, and associate it with the just created
Document
node.
If there is a context element, run these substeps:
Set the state of the HTML parser's tokenization stage as follows:
title
or textarea
elementstyle
, xmp
, iframe
,
noembed
, or noframes
elementscript
elementnoscript
elementplaintext
elementFor performance reasons, an implementation that does not report errors and that uses the actual state machine described in this specification directly could use the PLAINTEXT state instead of the RAWTEXT and script data states where those are mentioned in the list above. Except for rules regarding parse errors, they are equivalent, since there is no appropriate end tag token in the fragment case, yet they involve far fewer state transitions.
Let root be a new html
element with no attributes.
Append the element root to the Document
node created
above.
Set up the parser's stack of open elements so that it contains just the single element root.
If the context element is a
template
element, push "in
template" onto the stack of template insertion modes so that it is the new
current template insertion mode.
Reset the parser's insertion mode appropriately.
The parser will reference the context element as part of that algorithm.
Set the parser's
form
element pointer to the nearest node to the context element that is a form
element
(going straight up the ancestor chain, and including the element itself, if it is a
form
element), if any. (If there is no such form
element, the form
element pointer keeps its initial value, null.)
Place into the input stream for the HTML parser just created the input. The encoding confidence is irrelevant.
Start the parser and let it run until it has consumed all the characters just inserted into the input stream.
If there is a context element, return the child nodes of root, in tree order.
Otherwise, return the children of the Document
object, in tree
order.
This table lists the character reference names that are supported by HTML, and the code points to which they refer. It is referenced by the previous sections.
Name | Character(s) | Glyph |
---|---|---|
Aacute; | U+000C1 | Á |
Aacute | U+000C1 | Á |
aacute; | U+000E1 | á |
aacute | U+000E1 | á |
Abreve; | U+00102 | Ă |
abreve; | U+00103 | ă |
ac; | U+0223E | ∾ |
acd; | U+0223F | ∿ |
acE; | U+0223E U+00333 | ∾̳ |
Acirc; | U+000C2 | Â |
Acirc | U+000C2 | Â |
acirc; | U+000E2 | â |
acirc | U+000E2 | â |
acute; | U+000B4 | ´ |
acute | U+000B4 | ´ |
Acy; | U+00410 | А |
acy; | U+00430 | а |
AElig; | U+000C6 | Æ |
AElig | U+000C6 | Æ |
aelig; | U+000E6 | æ |
aelig | U+000E6 | æ |
af; | U+02061 | |
Afr; | U+1D504 | 프 |
afr; | U+1D51E | 픞 |
Agrave; | U+000C0 | À |
Agrave | U+000C0 | À |
agrave; | U+000E0 | à |
agrave | U+000E0 | à |
alefsym; | U+02135 | ℵ |
aleph; | U+02135 | ℵ |
Alpha; | U+00391 | Α |
alpha; | U+003B1 | α |
Amacr; | U+00100 | Ā |
amacr; | U+00101 | ā |
amalg; | U+02A3F | ⨿ |
AMP; | U+00026 | & |
AMP | U+00026 | & |
amp; | U+00026 | & |
amp | U+00026 | & |
And; | U+02A53 | ⩓ |
and; | U+02227 | ∧ |
andand; | U+02A55 | ⩕ |
andd; | U+02A5C | ⩜ |
andslope; | U+02A58 | ⩘ |
andv; | U+02A5A | ⩚ |
ang; | U+02220 | ∠ |
ange; | U+029A4 | ⦤ |
angle; | U+02220 | ∠ |
angmsd; | U+02221 | ∡ |
angmsdaa; | U+029A8 | ⦨ |
angmsdab; | U+029A9 | ⦩ |
angmsdac; | U+029AA | ⦪ |
angmsdad; | U+029AB | ⦫ |
angmsdae; | U+029AC | ⦬ |
angmsdaf; | U+029AD | ⦭ |
angmsdag; | U+029AE | ⦮ |
angmsdah; | U+029AF | ⦯ |
angrt; | U+0221F | ∟ |
angrtvb; | U+022BE | ⊾ |
angrtvbd; | U+0299D | ⦝ |
angsph; | U+02222 | ∢ |
angst; | U+000C5 | Å |
angzarr; | U+0237C | ⍼ |
Aogon; | U+00104 | Ą |
aogon; | U+00105 | ą |
Aopf; | U+1D538 | 픸 |
aopf; | U+1D552 | 핒 |
ap; | U+02248 | ≈ |
apacir; | U+02A6F | ⩯ |
apE; | U+02A70 | ⩰ |
ape; | U+0224A | ≊ |
apid; | U+0224B | ≋ |
apos; | U+00027 | ' |
ApplyFunction; | U+02061 | |
approx; | U+02248 | ≈ |
approxeq; | U+0224A | ≊ |
Aring; | U+000C5 | Å |
Aring | U+000C5 | Å |
aring; | U+000E5 | å |
aring | U+000E5 | å |
Ascr; | U+1D49C | 풜 |
ascr; | U+1D4B6 | 풶 |
Assign; | U+02254 | ≔ |
ast; | U+0002A | * |
asymp; | U+02248 | ≈ |
asympeq; | U+0224D | ≍ |
Atilde; | U+000C3 | Ã |
Atilde | U+000C3 | Ã |
atilde; | U+000E3 | ã |
atilde | U+000E3 | ã |
Auml; | U+000C4 | Ä |
Auml | U+000C4 | Ä |
auml; | U+000E4 | ä |
auml | U+000E4 | ä |
awconint; | U+02233 | ∳ |
awint; | U+02A11 | ⨑ |
backcong; | U+0224C | ≌ |
backepsilon; | U+003F6 | ϶ |
backprime; | U+02035 | ‵ |
backsim; | U+0223D | ∽ |
backsimeq; | U+022CD | ⋍ |
Backslash; | U+02216 | ∖ |
Barv; | U+02AE7 | ⫧ |
barvee; | U+022BD | ⊽ |
Barwed; | U+02306 | ⌆ |
barwed; | U+02305 | ⌅ |
barwedge; | U+02305 | ⌅ |
bbrk; | U+023B5 | ⎵ |
bbrktbrk; | U+023B6 | ⎶ |
bcong; | U+0224C | ≌ |
Bcy; | U+00411 | Б |
bcy; | U+00431 | б |
bdquo; | U+0201E | „ |
becaus; | U+02235 | ∵ |
Because; | U+02235 | ∵ |
because; | U+02235 | ∵ |
bemptyv; | U+029B0 | ⦰ |
bepsi; | U+003F6 | ϶ |
bernou; | U+0212C | ℬ |
Bernoullis; | U+0212C | ℬ |
Beta; | U+00392 | Β |
beta; | U+003B2 | β |
beth; | U+02136 | ℶ |
between; | U+0226C | ≬ |
Bfr; | U+1D505 | 픅 |
bfr; | U+1D51F | 픟 |
bigcap; | U+022C2 | ⋂ |
bigcirc; | U+025EF | ◯ |
bigcup; | U+022C3 | ⋃ |
bigodot; | U+02A00 | ⨀ |
bigoplus; | U+02A01 | ⨁ |
bigotimes; | U+02A02 | ⨂ |
bigsqcup; | U+02A06 | ⨆ |
bigstar; | U+02605 | ★ |
bigtriangledown; | U+025BD | ▽ |
bigtriangleup; | U+025B3 | △ |
biguplus; | U+02A04 | ⨄ |
bigvee; | U+022C1 | ⋁ |
bigwedge; | U+022C0 | ⋀ |
bkarow; | U+0290D | ⤍ |
blacklozenge; | U+029EB | ⧫ |
blacksquare; | U+025AA | ▪ |
blacktriangle; | U+025B4 | ▴ |
blacktriangledown; | U+025BE | ▾ |
blacktriangleleft; | U+025C2 | ◂ |
blacktriangleright; | U+025B8 | ▸ |
blank; | U+02423 | ␣ |
blk12; | U+02592 | ▒ |
blk14; | U+02591 | ░ |
blk34; | U+02593 | ▓ |
block; | U+02588 | █ |
bne; | U+0003D U+020E5 | =⃥ |
bnequiv; | U+02261 U+020E5 | ≡⃥ |
bNot; | U+02AED | ⫭ |
bnot; | U+02310 | ⌐ |
Bopf; | U+1D539 | 픹 |
bopf; | U+1D553 | 핓 |
bot; | U+022A5 | ⊥ |
bottom; | U+022A5 | ⊥ |
bowtie; | U+022C8 | ⋈ |
boxbox; | U+029C9 | ⧉ |
boxDL; | U+02557 | ╗ |
boxDl; | U+02556 | ╖ |
boxdL; | U+02555 | ╕ |
boxdl; | U+02510 | ┐ |
boxDR; | U+02554 | ╔ |
boxDr; | U+02553 | ╓ |
boxdR; | U+02552 | ╒ |
boxdr; | U+0250C | ┌ |
boxH; | U+02550 | ═ |
boxh; | U+02500 | ─ |
boxHD; | U+02566 | ╦ |
boxHd; | U+02564 | ╤ |
boxhD; | U+02565 | ╥ |
boxhd; | U+0252C | ┬ |
boxHU; | U+02569 | ╩ |
boxHu; | U+02567 | ╧ |
boxhU; | U+02568 | ╨ |
boxhu; | U+02534 | ┴ |
boxminus; | U+0229F | ⊟ |
boxplus; | U+0229E | ⊞ |
boxtimes; | U+022A0 | ⊠ |
boxUL; | U+0255D | ╝ |
boxUl; | U+0255C | ╜ |
boxuL; | U+0255B | ╛ |
boxul; | U+02518 | ┘ |
boxUR; | U+0255A | ╚ |
boxUr; | U+02559 | ╙ |
boxuR; | U+02558 | ╘ |
boxur; | U+02514 | └ |
boxV; | U+02551 | ║ |
boxv; | U+02502 | │ |
boxVH; | U+0256C | ╬ |
boxVh; | U+0256B | ╫ |
boxvH; | U+0256A | ╪ |
boxvh; | U+0253C | ┼ |
boxVL; | U+02563 | ╣ |
boxVl; | U+02562 | ╢ |
boxvL; | U+02561 | ╡ |
boxvl; | U+02524 | ┤ |
boxVR; | U+02560 | ╠ |
boxVr; | U+0255F | ╟ |
boxvR; | U+0255E | ╞ |
boxvr; | U+0251C | ├ |
bprime; | U+02035 | ‵ |
Breve; | U+002D8 | ˘ |
breve; | U+002D8 | ˘ |
brvbar; | U+000A6 | ¦ |
brvbar | U+000A6 | ¦ |
Bscr; | U+0212C | ℬ |
bscr; | U+1D4B7 | 풷 |
bsemi; | U+0204F | ⁏ |
bsim; | U+0223D | ∽ |
bsime; | U+022CD | ⋍ |
bsol; | U+0005C | \ |
bsolb; | U+029C5 | ⧅ |
bsolhsub; | U+027C8 | ⟈ |
bull; | U+02022 | • |
bullet; | U+02022 | • |
bump; | U+0224E | ≎ |
bumpE; | U+02AAE | ⪮ |
bumpe; | U+0224F | ≏ |
Bumpeq; | U+0224E | ≎ |
bumpeq; | U+0224F | ≏ |
Cacute; | U+00106 | Ć |
cacute; | U+00107 | ć |
Cap; | U+022D2 | ⋒ |
cap; | U+02229 | ∩ |
capand; | U+02A44 | ⩄ |
capbrcup; | U+02A49 | ⩉ |
capcap; | U+02A4B | ⩋ |
capcup; | U+02A47 | ⩇ |
capdot; | U+02A40 | ⩀ |
CapitalDifferentialD; | U+02145 | ⅅ |
caps; | U+02229 U+0FE00 | ∩︀ |
caret; | U+02041 | ⁁ |
caron; | U+002C7 | ˇ |
Cayleys; | U+0212D | ℭ |
ccaps; | U+02A4D | ⩍ |
Ccaron; | U+0010C | Č |
ccaron; | U+0010D | č |
Ccedil; | U+000C7 | Ç |
Ccedil | U+000C7 | Ç |
ccedil; | U+000E7 | ç |
ccedil | U+000E7 | ç |
Ccirc; | U+00108 | Ĉ |
ccirc; | U+00109 | ĉ |
Cconint; | U+02230 | ∰ |
ccups; | U+02A4C | ⩌ |
ccupssm; | U+02A50 | ⩐ |
Cdot; | U+0010A | Ċ |
cdot; | U+0010B | ċ |
cedil; | U+000B8 | ¸ |
cedil | U+000B8 | ¸ |
Cedilla; | U+000B8 | ¸ |
cemptyv; | U+029B2 | ⦲ |
cent; | U+000A2 | ¢ |
cent | U+000A2 | ¢ |
CenterDot; | U+000B7 | · |
centerdot; | U+000B7 | · |
Cfr; | U+0212D | ℭ |
cfr; | U+1D520 | 픠 |
CHcy; | U+00427 | Ч |
chcy; | U+00447 | ч |
check; | U+02713 | ✓ |
checkmark; | U+02713 | ✓ |
Chi; | U+003A7 | Χ |
chi; | U+003C7 | χ |
cir; | U+025CB | ○ |
circ; | U+002C6 | ˆ |
circeq; | U+02257 | ≗ |
circlearrowleft; | U+021BA | ↺ |
circlearrowright; | U+021BB | ↻ |
circledast; | U+0229B | ⊛ |
circledcirc; | U+0229A | ⊚ |
circleddash; | U+0229D | ⊝ |
CircleDot; | U+02299 | ⊙ |
circledR; | U+000AE | ® |
circledS; | U+024C8 | Ⓢ |
CircleMinus; | U+02296 | ⊖ |
CirclePlus; | U+02295 | ⊕ |
CircleTimes; | U+02297 | ⊗ |
cirE; | U+029C3 | ⧃ |
cire; | U+02257 | ≗ |
cirfnint; | U+02A10 | ⨐ |
cirmid; | U+02AEF | ⫯ |
cirscir; | U+029C2 | ⧂ |
ClockwiseContourIntegral; | U+02232 | ∲ |
CloseCurlyDoubleQuote; | U+0201D | ” |
CloseCurlyQuote; | U+02019 | ’ |
clubs; | U+02663 | ♣ |
clubsuit; | U+02663 | ♣ |
Colon; | U+02237 | ∷ |
colon; | U+0003A | : |
Colone; | U+02A74 | ⩴ |
colone; | U+02254 | ≔ |
coloneq; | U+02254 | ≔ |
comma; | U+0002C | , |
commat; | U+00040 | @ |
comp; | U+02201 | ∁ |
compfn; | U+02218 | ∘ |
complement; | U+02201 | ∁ |
complexes; | U+02102 | ℂ |
cong; | U+02245 | ≅ |
congdot; | U+02A6D | ⩭ |
Congruent; | U+02261 | ≡ |
Conint; | U+0222F | ∯ |
conint; | U+0222E | ∮ |
ContourIntegral; | U+0222E | ∮ |
Copf; | U+02102 | ℂ |
copf; | U+1D554 | 핔 |
coprod; | U+02210 | ∐ |
Coproduct; | U+02210 | ∐ |
COPY; | U+000A9 | © |
COPY | U+000A9 | © |
copy; | U+000A9 | © |
copy | U+000A9 | © |
copysr; | U+02117 | ℗ |
CounterClockwiseContourIntegral; | U+02233 | ∳ |
crarr; | U+021B5 | ↵ |
Cross; | U+02A2F | ⨯ |
cross; | U+02717 | ✗ |
Cscr; | U+1D49E | 풞 |
cscr; | U+1D4B8 | 풸 |
csub; | U+02ACF | ⫏ |
csube; | U+02AD1 | ⫑ |
csup; | U+02AD0 | ⫐ |
csupe; | U+02AD2 | ⫒ |
ctdot; | U+022EF | ⋯ |
cudarrl; | U+02938 | ⤸ |
cudarrr; | U+02935 | ⤵ |
cuepr; | U+022DE | ⋞ |
cuesc; | U+022DF | ⋟ |
cularr; | U+021B6 | ↶ |
cularrp; | U+0293D | ⤽ |
Cup; | U+022D3 | ⋓ |
cup; | U+0222A | ∪ |
cupbrcap; | U+02A48 | ⩈ |
CupCap; | U+0224D | ≍ |
cupcap; | U+02A46 | ⩆ |
cupcup; | U+02A4A | ⩊ |
cupdot; | U+0228D | ⊍ |
cupor; | U+02A45 | ⩅ |
cups; | U+0222A U+0FE00 | ∪︀ |
curarr; | U+021B7 | ↷ |
curarrm; | U+0293C | ⤼ |
curlyeqprec; | U+022DE | ⋞ |
curlyeqsucc; | U+022DF | ⋟ |
curlyvee; | U+022CE | ⋎ |
curlywedge; | U+022CF | ⋏ |
curren; | U+000A4 | ¤ |
curren | U+000A4 | ¤ |
curvearrowleft; | U+021B6 | ↶ |
curvearrowright; | U+021B7 | ↷ |
cuvee; | U+022CE | ⋎ |
cuwed; | U+022CF | ⋏ |
cwconint; | U+02232 | ∲ |
cwint; | U+02231 | ∱ |
cylcty; | U+0232D | ⌭ |
Dagger; | U+02021 | ‡ |
dagger; | U+02020 | † |
daleth; | U+02138 | ℸ |
Darr; | U+021A1 | ↡ |
dArr; | U+021D3 | ⇓ |
darr; | U+02193 | ↓ |
dash; | U+02010 | ‐ |
Dashv; | U+02AE4 | ⫤ |
dashv; | U+022A3 | ⊣ |
dbkarow; | U+0290F | ⤏ |
dblac; | U+002DD | ˝ |
Dcaron; | U+0010E | Ď |
dcaron; | U+0010F | ď |
Dcy; | U+00414 | Д |
dcy; | U+00434 | д |
DD; | U+02145 | ⅅ |
dd; | U+02146 | ⅆ |
ddagger; | U+02021 | ‡ |
ddarr; | U+021CA | ⇊ |
DDotrahd; | U+02911 | ⤑ |
ddotseq; | U+02A77 | ⩷ |
deg; | U+000B0 | ° |
deg | U+000B0 | ° |
Del; | U+02207 | ∇ |
Delta; | U+00394 | Δ |
delta; | U+003B4 | δ |
demptyv; | U+029B1 | ⦱ |
dfisht; | U+0297F | ⥿ |
Dfr; | U+1D507 | 픇 |
dfr; | U+1D521 | 픡 |
dHar; | U+02965 | ⥥ |
dharl; | U+021C3 | ⇃ |
dharr; | U+021C2 | ⇂ |
DiacriticalAcute; | U+000B4 | ´ |
DiacriticalDot; | U+002D9 | ˙ |
DiacriticalDoubleAcute; | U+002DD | ˝ |
DiacriticalGrave; | U+00060 | ` |
DiacriticalTilde; | U+002DC | ˜ |
diam; | U+022C4 | ⋄ |
Diamond; | U+022C4 | ⋄ |
diamond; | U+022C4 | ⋄ |
diamondsuit; | U+02666 | ♦ |
diams; | U+02666 | ♦ |
die; | U+000A8 | ¨ |
DifferentialD; | U+02146 | ⅆ |
digamma; | U+003DD | ϝ |
disin; | U+022F2 | ⋲ |
div; | U+000F7 | ÷ |
divide; | U+000F7 | ÷ |
divide | U+000F7 | ÷ |
divideontimes; | U+022C7 | ⋇ |
divonx; | U+022C7 | ⋇ |
DJcy; | U+00402 | Ђ |
djcy; | U+00452 | ђ |
dlcorn; | U+0231E | ⌞ |
dlcrop; | U+0230D | ⌍ |
dollar; | U+00024 | $ |
Dopf; | U+1D53B | 픻 |
dopf; | U+1D555 | 핕 |
Dot; | U+000A8 | ¨ |
dot; | U+002D9 | ˙ |
DotDot; | U+020DC | ◌⃜ |
doteq; | U+02250 | ≐ |
doteqdot; | U+02251 | ≑ |
DotEqual; | U+02250 | ≐ |
dotminus; | U+02238 | ∸ |
dotplus; | U+02214 | ∔ |
dotsquare; | U+022A1 | ⊡ |
doublebarwedge; | U+02306 | ⌆ |
DoubleContourIntegral; | U+0222F | ∯ |
DoubleDot; | U+000A8 | ¨ |
DoubleDownArrow; | U+021D3 | ⇓ |
DoubleLeftArrow; | U+021D0 | ⇐ |
DoubleLeftRightArrow; | U+021D4 | ⇔ |
DoubleLeftTee; | U+02AE4 | ⫤ |
DoubleLongLeftArrow; | U+027F8 | ⟸ |
DoubleLongLeftRightArrow; | U+027FA | ⟺ |
DoubleLongRightArrow; | U+027F9 | ⟹ |
DoubleRightArrow; | U+021D2 | ⇒ |
DoubleRightTee; | U+022A8 | ⊨ |
DoubleUpArrow; | U+021D1 | ⇑ |
DoubleUpDownArrow; | U+021D5 | ⇕ |
DoubleVerticalBar; | U+02225 | ∥ |
DownArrow; | U+02193 | ↓ |
Downarrow; | U+021D3 | ⇓ |
downarrow; | U+02193 | ↓ |
DownArrowBar; | U+02913 | ⤓ |
DownArrowUpArrow; | U+021F5 | ⇵ |
DownBreve; | U+00311 | ◌̑ |
downdownarrows; | U+021CA | ⇊ |
downharpoonleft; | U+021C3 | ⇃ |
downharpoonright; | U+021C2 | ⇂ |
DownLeftRightVector; | U+02950 | ⥐ |
DownLeftTeeVector; | U+0295E | ⥞ |
DownLeftVector; | U+021BD | ↽ |
DownLeftVectorBar; | U+02956 | ⥖ |
DownRightTeeVector; | U+0295F | ⥟ |
DownRightVector; | U+021C1 | ⇁ |
DownRightVectorBar; | U+02957 | ⥗ |
DownTee; | U+022A4 | ⊤ |
DownTeeArrow; | U+021A7 | ↧ |
drbkarow; | U+02910 | ⤐ |
drcorn; | U+0231F | ⌟ |
drcrop; | U+0230C | ⌌ |
Dscr; | U+1D49F | 풟 |
dscr; | U+1D4B9 | 풹 |
DScy; | U+00405 | Ѕ |
dscy; | U+00455 | ѕ |
dsol; | U+029F6 | ⧶ |
Dstrok; | U+00110 | Đ |
dstrok; | U+00111 | đ |
dtdot; | U+022F1 | ⋱ |
dtri; | U+025BF | ▿ |
dtrif; | U+025BE | ▾ |
duarr; | U+021F5 | ⇵ |
duhar; | U+0296F | ⥯ |
dwangle; | U+029A6 | ⦦ |
DZcy; | U+0040F | Џ |
dzcy; | U+0045F | џ |
dzigrarr; | U+027FF | ⟿ |
Eacute; | U+000C9 | É |
Eacute | U+000C9 | É |
eacute; | U+000E9 | é |
eacute | U+000E9 | é |
easter; | U+02A6E | ⩮ |
Ecaron; | U+0011A | Ě |
ecaron; | U+0011B | ě |
ecir; | U+02256 | ≖ |
Ecirc; | U+000CA | Ê |
Ecirc | U+000CA | Ê |
ecirc; | U+000EA | ê |
ecirc | U+000EA | ê |
ecolon; | U+02255 | ≕ |
Ecy; | U+0042D | Э |
ecy; | U+0044D | э |
eDDot; | U+02A77 | ⩷ |
Edot; | U+00116 | Ė |
eDot; | U+02251 | ≑ |
edot; | U+00117 | ė |
ee; | U+02147 | ⅇ |
efDot; | U+02252 | ≒ |
Efr; | U+1D508 | 픈 |
efr; | U+1D522 | 픢 |
eg; | U+02A9A | ⪚ |
Egrave; | U+000C8 | È |
Egrave | U+000C8 | È |
egrave; | U+000E8 | è |
egrave | U+000E8 | è |
egs; | U+02A96 | ⪖ |
egsdot; | U+02A98 | ⪘ |
el; | U+02A99 | ⪙ |
Element; | U+02208 | ∈ |
elinters; | U+023E7 | ⏧ |
ell; | U+02113 | ℓ |
els; | U+02A95 | ⪕ |
elsdot; | U+02A97 | ⪗ |
Emacr; | U+00112 | Ē |
emacr; | U+00113 | ē |
empty; | U+02205 | ∅ |
emptyset; | U+02205 | ∅ |
EmptySmallSquare; | U+025FB | ◻ |
emptyv; | U+02205 | ∅ |
EmptyVerySmallSquare; | U+025AB | ▫ |
emsp; | U+02003 | |
emsp13; | U+02004 | |
emsp14; | U+02005 | |
ENG; | U+0014A | Ŋ |
eng; | U+0014B | ŋ |
ensp; | U+02002 | |
Eogon; | U+00118 | Ę |
eogon; | U+00119 | ę |
Eopf; | U+1D53C | 피 |
eopf; | U+1D556 | 핖 |
epar; | U+022D5 | ⋕ |
eparsl; | U+029E3 | ⧣ |
eplus; | U+02A71 | ⩱ |
epsi; | U+003B5 | ε |
Epsilon; | U+00395 | Ε |
epsilon; | U+003B5 | ε |
epsiv; | U+003F5 | ϵ |
eqcirc; | U+02256 | ≖ |
eqcolon; | U+02255 | ≕ |
eqsim; | U+02242 | ≂ |
eqslantgtr; | U+02A96 | ⪖ |
eqslantless; | U+02A95 | ⪕ |
Equal; | U+02A75 | ⩵ |
equals; | U+0003D | = |
EqualTilde; | U+02242 | ≂ |
equest; | U+0225F | ≟ |
Equilibrium; | U+021CC | ⇌ |
equiv; | U+02261 | ≡ |
equivDD; | U+02A78 | ⩸ |
eqvparsl; | U+029E5 | ⧥ |
erarr; | U+02971 | ⥱ |
erDot; | U+02253 | ≓ |
Escr; | U+02130 | ℰ |
escr; | U+0212F | ℯ |
esdot; | U+02250 | ≐ |
Esim; | U+02A73 | ⩳ |
esim; | U+02242 | ≂ |
Eta; | U+00397 | Η |
eta; | U+003B7 | η |
ETH; | U+000D0 | Ð |
ETH | U+000D0 | Ð |
eth; | U+000F0 | ð |
eth | U+000F0 | ð |
Euml; | U+000CB | Ë |
Euml | U+000CB | Ë |
euml; | U+000EB | ë |
euml | U+000EB | ë |
euro; | U+020AC | € |
excl; | U+00021 | ! |
exist; | U+02203 | ∃ |
Exists; | U+02203 | ∃ |
expectation; | U+02130 | ℰ |
ExponentialE; | U+02147 | ⅇ |
exponentiale; | U+02147 | ⅇ |
fallingdotseq; | U+02252 | ≒ |
Fcy; | U+00424 | Ф |
fcy; | U+00444 | ф |
female; | U+02640 | ♀ |
ffilig; | U+0FB03 | ffi |
fflig; | U+0FB00 | ff |
ffllig; | U+0FB04 | ffl |
Ffr; | U+1D509 | 픉 |
ffr; | U+1D523 | 픣 |
filig; | U+0FB01 | fi |
FilledSmallSquare; | U+025FC | ◼ |
FilledVerySmallSquare; | U+025AA | ▪ |
fjlig; | U+00066 U+0006A | fj |
flat; | U+0266D | ♭ |
fllig; | U+0FB02 | fl |
fltns; | U+025B1 | ▱ |
fnof; | U+00192 | ƒ |
Fopf; | U+1D53D | 픽 |
fopf; | U+1D557 | 핗 |
ForAll; | U+02200 | ∀ |
forall; | U+02200 | ∀ |
fork; | U+022D4 | ⋔ |
forkv; | U+02AD9 | ⫙ |
Fouriertrf; | U+02131 | ℱ |
fpartint; | U+02A0D | ⨍ |
frac12; | U+000BD | ½ |
frac12 | U+000BD | ½ |
frac13; | U+02153 | ⅓ |
frac14; | U+000BC | ¼ |
frac14 | U+000BC | ¼ |
frac15; | U+02155 | ⅕ |
frac16; | U+02159 | ⅙ |
frac18; | U+0215B | ⅛ |
frac23; | U+02154 | ⅔ |
frac25; | U+02156 | ⅖ |
frac34; | U+000BE | ¾ |
frac34 | U+000BE | ¾ |
frac35; | U+02157 | ⅗ |
frac38; | U+0215C | ⅜ |
frac45; | U+02158 | ⅘ |
frac56; | U+0215A | ⅚ |
frac58; | U+0215D | ⅝ |
frac78; | U+0215E | ⅞ |
frasl; | U+02044 | ⁄ |
frown; | U+02322 | ⌢ |
Fscr; | U+02131 | ℱ |
fscr; | U+1D4BB | 풻 |
gacute; | U+001F5 | ǵ |
Gamma; | U+00393 | Γ |
gamma; | U+003B3 | γ |
Gammad; | U+003DC | Ϝ |
gammad; | U+003DD | ϝ |
gap; | U+02A86 | ⪆ |
Gbreve; | U+0011E | Ğ |
gbreve; | U+0011F | ğ |
Gcedil; | U+00122 | Ģ |
Gcirc; | U+0011C | Ĝ |
gcirc; | U+0011D | ĝ |
Gcy; | U+00413 | Г |
gcy; | U+00433 | г |
Gdot; | U+00120 | Ġ |
gdot; | U+00121 | ġ |
gE; | U+02267 | ≧ |
ge; | U+02265 | ≥ |
gEl; | U+02A8C | ⪌ |
gel; | U+022DB | ⋛ |
geq; | U+02265 | ≥ |
geqq; | U+02267 | ≧ |
geqslant; | U+02A7E | ⩾ |
ges; | U+02A7E | ⩾ |
gescc; | U+02AA9 | ⪩ |
gesdot; | U+02A80 | ⪀ |
gesdoto; | U+02A82 | ⪂ |
gesdotol; | U+02A84 | ⪄ |
gesl; | U+022DB U+0FE00 | ⋛︀ |
gesles; | U+02A94 | ⪔ |
Gfr; | U+1D50A | 픊 |
gfr; | U+1D524 | 픤 |
Gg; | U+022D9 | ⋙ |
gg; | U+0226B | ≫ |
ggg; | U+022D9 | ⋙ |
gimel; | U+02137 | ℷ |
GJcy; | U+00403 | Ѓ |
gjcy; | U+00453 | ѓ |
gl; | U+02277 | ≷ |
gla; | U+02AA5 | ⪥ |
glE; | U+02A92 | ⪒ |
glj; | U+02AA4 | ⪤ |
gnap; | U+02A8A | ⪊ |
gnapprox; | U+02A8A | ⪊ |
gnE; | U+02269 | ≩ |
gne; | U+02A88 | ⪈ |
gneq; | U+02A88 | ⪈ |
gneqq; | U+02269 | ≩ |
gnsim; | U+022E7 | ⋧ |
Gopf; | U+1D53E | 픾 |
gopf; | U+1D558 | 하 |
grave; | U+00060 | ` |
GreaterEqual; | U+02265 | ≥ |
GreaterEqualLess; | U+022DB | ⋛ |
GreaterFullEqual; | U+02267 | ≧ |
GreaterGreater; | U+02AA2 | ⪢ |
GreaterLess; | U+02277 | ≷ |
GreaterSlantEqual; | U+02A7E | ⩾ |
GreaterTilde; | U+02273 | ≳ |
Gscr; | U+1D4A2 | 풢 |
gscr; | U+0210A | ℊ |
gsim; | U+02273 | ≳ |
gsime; | U+02A8E | ⪎ |
gsiml; | U+02A90 | ⪐ |
GT; | U+0003E | > |
GT | U+0003E | > |
Gt; | U+0226B | ≫ |
gt; | U+0003E | > |
gt | U+0003E | > |
gtcc; | U+02AA7 | ⪧ |
gtcir; | U+02A7A | ⩺ |
gtdot; | U+022D7 | ⋗ |
gtlPar; | U+02995 | ⦕ |
gtquest; | U+02A7C | ⩼ |
gtrapprox; | U+02A86 | ⪆ |
gtrarr; | U+02978 | ⥸ |
gtrdot; | U+022D7 | ⋗ |
gtreqless; | U+022DB | ⋛ |
gtreqqless; | U+02A8C | ⪌ |
gtrless; | U+02277 | ≷ |
gtrsim; | U+02273 | ≳ |
gvertneqq; | U+02269 U+0FE00 | ≩︀ |
gvnE; | U+02269 U+0FE00 | ≩︀ |
Hacek; | U+002C7 | ˇ |
hairsp; | U+0200A | |
half; | U+000BD | ½ |
hamilt; | U+0210B | ℋ |
HARDcy; | U+0042A | Ъ |
hardcy; | U+0044A | ъ |
hArr; | U+021D4 | ⇔ |
harr; | U+02194 | ↔ |
harrcir; | U+02948 | ⥈ |
harrw; | U+021AD | ↭ |
Hat; | U+0005E | ^ |
hbar; | U+0210F | ℏ |
Hcirc; | U+00124 | Ĥ |
hcirc; | U+00125 | ĥ |
hearts; | U+02665 | ♥ |
heartsuit; | U+02665 | ♥ |
hellip; | U+02026 | … |
hercon; | U+022B9 | ⊹ |
Hfr; | U+0210C | ℌ |
hfr; | U+1D525 | 픥 |
HilbertSpace; | U+0210B | ℋ |
hksearow; | U+02925 | ⤥ |
hkswarow; | U+02926 | ⤦ |
hoarr; | U+021FF | ⇿ |
homtht; | U+0223B | ∻ |
hookleftarrow; | U+021A9 | ↩ |
hookrightarrow; | U+021AA | ↪ |
Hopf; | U+0210D | ℍ |
hopf; | U+1D559 | 학 |
horbar; | U+02015 | ― |
HorizontalLine; | U+02500 | ─ |
Hscr; | U+0210B | ℋ |
hscr; | U+1D4BD | 풽 |
hslash; | U+0210F | ℏ |
Hstrok; | U+00126 | Ħ |
hstrok; | U+00127 | ħ |
HumpDownHump; | U+0224E | ≎ |
HumpEqual; | U+0224F | ≏ |
hybull; | U+02043 | ⁃ |
hyphen; | U+02010 | ‐ |
Iacute; | U+000CD | Í |
Iacute | U+000CD | Í |
iacute; | U+000ED | í |
iacute | U+000ED | í |
ic; | U+02063 | |
Icirc; | U+000CE | Î |
Icirc | U+000CE | Î |
icirc; | U+000EE | î |
icirc | U+000EE | î |
Icy; | U+00418 | И |
icy; | U+00438 | и |
Idot; | U+00130 | İ |
IEcy; | U+00415 | Е |
iecy; | U+00435 | е |
iexcl; | U+000A1 | ¡ |
iexcl | U+000A1 | ¡ |
iff; | U+021D4 | ⇔ |
Ifr; | U+02111 | ℑ |
ifr; | U+1D526 | 픦 |
Igrave; | U+000CC | Ì |
Igrave | U+000CC | Ì |
igrave; | U+000EC | ì |
igrave | U+000EC | ì |
ii; | U+02148 | ⅈ |
iiiint; | U+02A0C | ⨌ |
iiint; | U+0222D | ∭ |
iinfin; | U+029DC | ⧜ |
iiota; | U+02129 | ℩ |
IJlig; | U+00132 | IJ |
ijlig; | U+00133 | ij |
Im; | U+02111 | ℑ |
Imacr; | U+0012A | Ī |
imacr; | U+0012B | ī |
image; | U+02111 | ℑ |
ImaginaryI; | U+02148 | ⅈ |
imagline; | U+02110 | ℐ |
imagpart; | U+02111 | ℑ |
imath; | U+00131 | ı |
imof; | U+022B7 | ⊷ |
imped; | U+001B5 | Ƶ |
Implies; | U+021D2 | ⇒ |
in; | U+02208 | ∈ |
incare; | U+02105 | ℅ |
infin; | U+0221E | ∞ |
infintie; | U+029DD | ⧝ |
inodot; | U+00131 | ı |
Int; | U+0222C | ∬ |
int; | U+0222B | ∫ |
intcal; | U+022BA | ⊺ |
integers; | U+02124 | ℤ |
Integral; | U+0222B | ∫ |
intercal; | U+022BA | ⊺ |
Intersection; | U+022C2 | ⋂ |
intlarhk; | U+02A17 | ⨗ |
intprod; | U+02A3C | ⨼ |
InvisibleComma; | U+02063 | |
InvisibleTimes; | U+02062 | |
IOcy; | U+00401 | Ё |
iocy; | U+00451 | ё |
Iogon; | U+0012E | Į |
iogon; | U+0012F | į |
Iopf; | U+1D540 | 핀 |
iopf; | U+1D55A | 핚 |
Iota; | U+00399 | Ι |
iota; | U+003B9 | ι |
iprod; | U+02A3C | ⨼ |
iquest; | U+000BF | ¿ |
iquest | U+000BF | ¿ |
Iscr; | U+02110 | ℐ |
iscr; | U+1D4BE | 풾 |
isin; | U+02208 | ∈ |
isindot; | U+022F5 | ⋵ |
isinE; | U+022F9 | ⋹ |
isins; | U+022F4 | ⋴ |
isinsv; | U+022F3 | ⋳ |
isinv; | U+02208 | ∈ |
it; | U+02062 | |
Itilde; | U+00128 | Ĩ |
itilde; | U+00129 | ĩ |
Iukcy; | U+00406 | І |
iukcy; | U+00456 | і |
Iuml; | U+000CF | Ï |
Iuml | U+000CF | Ï |
iuml; | U+000EF | ï |
iuml | U+000EF | ï |
Jcirc; | U+00134 | Ĵ |
jcirc; | U+00135 | ĵ |
Jcy; | U+00419 | Й |
jcy; | U+00439 | й |
Jfr; | U+1D50D | 픍 |
jfr; | U+1D527 | 픧 |
jmath; | U+00237 | ȷ |
Jopf; | U+1D541 | 핁 |
jopf; | U+1D55B | 핛 |
Jscr; | U+1D4A5 | 풥 |
jscr; | U+1D4BF | 풿 |
Jsercy; | U+00408 | Ј |
jsercy; | U+00458 | ј |
Jukcy; | U+00404 | Є |
jukcy; | U+00454 | є |
Kappa; | U+0039A | Κ |
kappa; | U+003BA | κ |
kappav; | U+003F0 | ϰ |
Kcedil; | U+00136 | Ķ |
kcedil; | U+00137 | ķ |
Kcy; | U+0041A | К |
kcy; | U+0043A | к |
Kfr; | U+1D50E | 픎 |
kfr; | U+1D528 | 픨 |
kgreen; | U+00138 | ĸ |
KHcy; | U+00425 | Х |
khcy; | U+00445 | х |
KJcy; | U+0040C | Ќ |
kjcy; | U+0045C | ќ |
Kopf; | U+1D542 | 핂 |
kopf; | U+1D55C | 한 |
Kscr; | U+1D4A6 | 풦 |
kscr; | U+1D4C0 | 퓀 |
lAarr; | U+021DA | ⇚ |
Lacute; | U+00139 | Ĺ |
lacute; | U+0013A | ĺ |
laemptyv; | U+029B4 | ⦴ |
lagran; | U+02112 | ℒ |
Lambda; | U+0039B | Λ |
lambda; | U+003BB | λ |
Lang; | U+027EA | ⟪ |
lang; | U+027E8 | ⟨ |
langd; | U+02991 | ⦑ |
langle; | U+027E8 | 〈 |
lap; | U+02A85 | ⪅ |
Laplacetrf; | U+02112 | ℒ |
laquo; | U+000AB | « |
laquo | U+000AB | « |
Larr; | U+0219E | ↞ |
lArr; | U+021D0 | ⇐ |
larr; | U+02190 | ← |
larrb; | U+021E4 | ⇤ |
larrbfs; | U+0291F | ⤟ |
larrfs; | U+0291D | ⤝ |
larrhk; | U+021A9 | ↩ |
larrlp; | U+021AB | ↫ |
larrpl; | U+02939 | ⤹ |
larrsim; | U+02973 | ⥳ |
larrtl; | U+021A2 | ↢ |
lat; | U+02AAB | ⪫ |
lAtail; | U+0291B | ⤛ |
latail; | U+02919 | ⤙ |
late; | U+02AAD | ⪭ |
lates; | U+02AAD U+0FE00 | ⪭︀ |
lBarr; | U+0290E | ⤎ |
lbarr; | U+0290C | ⤌ |
lbbrk; | U+02772 | ❲ |
lbrace; | U+0007B | { |
lbrack; | U+0005B | [ |
lbrke; | U+0298B | ⦋ |
lbrksld; | U+0298F | ⦏ |
lbrkslu; | U+0298D | ⦍ |
Lcaron; | U+0013D | Ľ |
lcaron; | U+0013E | ľ |
Lcedil; | U+0013B | Ļ |
lcedil; | U+0013C | ļ |
lceil; | U+02308 | ⌈ |
lcub; | U+0007B | { |
Lcy; | U+0041B | Л |
lcy; | U+0043B | л |
ldca; | U+02936 | ⤶ |
ldquo; | U+0201C | “ |
ldquor; | U+0201E | „ |
ldrdhar; | U+02967 | ⥧ |
ldrushar; | U+0294B | ⥋ |
ldsh; | U+021B2 | ↲ |
lE; | U+02266 | ≦ |
le; | U+02264 | ≤ |
LeftAngleBracket; | U+027E8 | 〈 |
LeftArrow; | U+02190 | ← |
Leftarrow; | U+021D0 | ⇐ |
leftarrow; | U+02190 | ← |
LeftArrowBar; | U+021E4 | ⇤ |
LeftArrowRightArrow; | U+021C6 | ⇆ |
leftarrowtail; | U+021A2 | ↢ |
LeftCeiling; | U+02308 | ⌈ |
LeftDoubleBracket; | U+027E6 | ⟦ |
LeftDownTeeVector; | U+02961 | ⥡ |
LeftDownVector; | U+021C3 | ⇃ |
LeftDownVectorBar; | U+02959 | ⥙ |
LeftFloor; | U+0230A | ⌊ |
leftharpoondown; | U+021BD | ↽ |
leftharpoonup; | U+021BC | ↼ |
leftleftarrows; | U+021C7 | ⇇ |
LeftRightArrow; | U+02194 | ↔ |
Leftrightarrow; | U+021D4 | ⇔ |
leftrightarrow; | U+02194 | ↔ |
leftrightarrows; | U+021C6 | ⇆ |
leftrightharpoons; | U+021CB | ⇋ |
leftrightsquigarrow; | U+021AD | ↭ |
LeftRightVector; | U+0294E | ⥎ |
LeftTee; | U+022A3 | ⊣ |
LeftTeeArrow; | U+021A4 | ↤ |
LeftTeeVector; | U+0295A | ⥚ |
leftthreetimes; | U+022CB | ⋋ |
LeftTriangle; | U+022B2 | ⊲ |
LeftTriangleBar; | U+029CF | ⧏ |
LeftTriangleEqual; | U+022B4 | ⊴ |
LeftUpDownVector; | U+02951 | ⥑ |
LeftUpTeeVector; | U+02960 | ⥠ |
LeftUpVector; | U+021BF | ↿ |
LeftUpVectorBar; | U+02958 | ⥘ |
LeftVector; | U+021BC | ↼ |
LeftVectorBar; | U+02952 | ⥒ |
lEg; | U+02A8B | ⪋ |
leg; | U+022DA | ⋚ |
leq; | U+02264 | ≤ |
leqq; | U+02266 | ≦ |
leqslant; | U+02A7D | ⩽ |
les; | U+02A7D | ⩽ |
lescc; | U+02AA8 | ⪨ |
lesdot; | U+02A7F | ⩿ |
lesdoto; | U+02A81 | ⪁ |
lesdotor; | U+02A83 | ⪃ |
lesg; | U+022DA U+0FE00 | ⋚︀ |
lesges; | U+02A93 | ⪓ |
lessapprox; | U+02A85 | ⪅ |
lessdot; | U+022D6 | ⋖ |
lesseqgtr; | U+022DA | ⋚ |
lesseqqgtr; | U+02A8B | ⪋ |
LessEqualGreater; | U+022DA | ⋚ |
LessFullEqual; | U+02266 | ≦ |
LessGreater; | U+02276 | ≶ |
lessgtr; | U+02276 | ≶ |
LessLess; | U+02AA1 | ⪡ |
lesssim; | U+02272 | ≲ |
LessSlantEqual; | U+02A7D | ⩽ |
LessTilde; | U+02272 | ≲ |
lfisht; | U+0297C | ⥼ |
lfloor; | U+0230A | ⌊ |
Lfr; | U+1D50F | 픏 |
lfr; | U+1D529 | 픩 |
lg; | U+02276 | ≶ |
lgE; | U+02A91 | ⪑ |
lHar; | U+02962 | ⥢ |
lhard; | U+021BD | ↽ |
lharu; | U+021BC | ↼ |
lharul; | U+0296A | ⥪ |
lhblk; | U+02584 | ▄ |
LJcy; | U+00409 | Љ |
ljcy; | U+00459 | љ |
Ll; | U+022D8 | ⋘ |
ll; | U+0226A | ≪ |
llarr; | U+021C7 | ⇇ |
llcorner; | U+0231E | ⌞ |
Lleftarrow; | U+021DA | ⇚ |
llhard; | U+0296B | ⥫ |
lltri; | U+025FA | ◺ |
Lmidot; | U+0013F | Ŀ |
lmidot; | U+00140 | ŀ |
lmoust; | U+023B0 | ⎰ |
lmoustache; | U+023B0 | ⎰ |
lnap; | U+02A89 | ⪉ |
lnapprox; | U+02A89 | ⪉ |
lnE; | U+02268 | ≨ |
lne; | U+02A87 | ⪇ |
lneq; | U+02A87 | ⪇ |
lneqq; | U+02268 | ≨ |
lnsim; | U+022E6 | ⋦ |
loang; | U+027EC | ⟬ |
loarr; | U+021FD | ⇽ |
lobrk; | U+027E6 | ⟦ |
LongLeftArrow; | U+027F5 | ⟵ |
Longleftarrow; | U+027F8 | ⟸ |
longleftarrow; | U+027F5 | ⟵ |
LongLeftRightArrow; | U+027F7 | ⟷ |
Longleftrightarrow; | U+027FA | ⟺ |
longleftrightarrow; | U+027F7 | ⟷ |
longmapsto; | U+027FC | ⟼ |
LongRightArrow; | U+027F6 | ⟶ |
Longrightarrow; | U+027F9 | ⟹ |
longrightarrow; | U+027F6 | ⟶ |
looparrowleft; | U+021AB | ↫ |
looparrowright; | U+021AC | ↬ |
lopar; | U+02985 | ⦅ |
Lopf; | U+1D543 | 핃 |
lopf; | U+1D55D | 핝 |
loplus; | U+02A2D | ⨭ |
lotimes; | U+02A34 | ⨴ |
lowast; | U+02217 | ∗ |
lowbar; | U+0005F | _ |
LowerLeftArrow; | U+02199 | ↙ |
LowerRightArrow; | U+02198 | ↘ |
loz; | U+025CA | ◊ |
lozenge; | U+025CA | ◊ |
lozf; | U+029EB | ⧫ |
lpar; | U+00028 | ( |
lparlt; | U+02993 | ⦓ |
lrarr; | U+021C6 | ⇆ |
lrcorner; | U+0231F | ⌟ |
lrhar; | U+021CB | ⇋ |
lrhard; | U+0296D | ⥭ |
lrm; | U+0200E | |
lrtri; | U+022BF | ⊿ |
lsaquo; | U+02039 | ‹ |
Lscr; | U+02112 | ℒ |
lscr; | U+1D4C1 | 퓁 |
Lsh; | U+021B0 | ↰ |
lsh; | U+021B0 | ↰ |
lsim; | U+02272 | ≲ |
lsime; | U+02A8D | ⪍ |
lsimg; | U+02A8F | ⪏ |
lsqb; | U+0005B | [ |
lsquo; | U+02018 | ‘ |
lsquor; | U+0201A | ‚ |
Lstrok; | U+00141 | Ł |
lstrok; | U+00142 | ł |
LT; | U+0003C | < |
LT | U+0003C | < |
Lt; | U+0226A | ≪ |
lt; | U+0003C | < |
lt | U+0003C | < |
ltcc; | U+02AA6 | ⪦ |
ltcir; | U+02A79 | ⩹ |
ltdot; | U+022D6 | ⋖ |
lthree; | U+022CB | ⋋ |
ltimes; | U+022C9 | ⋉ |
ltlarr; | U+02976 | ⥶ |
ltquest; | U+02A7B | ⩻ |
ltri; | U+025C3 | ◃ |
ltrie; | U+022B4 | ⊴ |
ltrif; | U+025C2 | ◂ |
ltrPar; | U+02996 | ⦖ |
lurdshar; | U+0294A | ⥊ |
luruhar; | U+02966 | ⥦ |
lvertneqq; | U+02268 U+0FE00 | ≨︀ |
lvnE; | U+02268 U+0FE00 | ≨︀ |
macr; | U+000AF | ¯ |
macr | U+000AF | ¯ |
male; | U+02642 | ♂ |
malt; | U+02720 | ✠ |
maltese; | U+02720 | ✠ |
Map; | U+02905 | ⤅ |
map; | U+021A6 | ↦ |
mapsto; | U+021A6 | ↦ |
mapstodown; | U+021A7 | ↧ |
mapstoleft; | U+021A4 | ↤ |
mapstoup; | U+021A5 | ↥ |
marker; | U+025AE | ▮ |
mcomma; | U+02A29 | ⨩ |
Mcy; | U+0041C | М |
mcy; | U+0043C | м |
mdash; | U+02014 | — |
mDDot; | U+0223A | ∺ |
measuredangle; | U+02221 | ∡ |
MediumSpace; | U+0205F | |
Mellintrf; | U+02133 | ℳ |
Mfr; | U+1D510 | 픐 |
mfr; | U+1D52A | 픪 |
mho; | U+02127 | ℧ |
micro; | U+000B5 | µ |
micro | U+000B5 | µ |
mid; | U+02223 | ∣ |
midast; | U+0002A | * |
midcir; | U+02AF0 | ⫰ |
middot; | U+000B7 | · |
middot | U+000B7 | · |
minus; | U+02212 | − |
minusb; | U+0229F | ⊟ |
minusd; | U+02238 | ∸ |
minusdu; | U+02A2A | ⨪ |
MinusPlus; | U+02213 | ∓ |
mlcp; | U+02ADB | ⫛ |
mldr; | U+02026 | … |
mnplus; | U+02213 | ∓ |
models; | U+022A7 | ⊧ |
Mopf; | U+1D544 | 필 |
mopf; | U+1D55E | 핞 |
mp; | U+02213 | ∓ |
Mscr; | U+02133 | ℳ |
mscr; | U+1D4C2 | 퓂 |
mstpos; | U+0223E | ∾ |
Mu; | U+0039C | Μ |
mu; | U+003BC | μ |
multimap; | U+022B8 | ⊸ |
mumap; | U+022B8 | ⊸ |
nabla; | U+02207 | ∇ |
Nacute; | U+00143 | Ń |
nacute; | U+00144 | ń |
nang; | U+02220 U+020D2 | ∠⃒ |
nap; | U+02249 | ≉ |
napE; | U+02A70 U+00338 | ⩰̸ |
napid; | U+0224B U+00338 | ≋̸ |
napos; | U+00149 | ʼn |
napprox; | U+02249 | ≉ |
natur; | U+0266E | ♮ |
natural; | U+0266E | ♮ |
naturals; | U+02115 | ℕ |
nbsp; | U+000A0 | |
nbsp | U+000A0 | |
nbump; | U+0224E U+00338 | ≎̸ |
nbumpe; | U+0224F U+00338 | ≏̸ |
ncap; | U+02A43 | ⩃ |
Ncaron; | U+00147 | Ň |
ncaron; | U+00148 | ň |
Ncedil; | U+00145 | Ņ |
ncedil; | U+00146 | ņ |
ncong; | U+02247 | ≇ |
ncongdot; | U+02A6D U+00338 | ⩭̸ |
ncup; | U+02A42 | ⩂ |
Ncy; | U+0041D | Н |
ncy; | U+0043D | н |
ndash; | U+02013 | – |
ne; | U+02260 | ≠ |
nearhk; | U+02924 | ⤤ |
neArr; | U+021D7 | ⇗ |
nearr; | U+02197 | ↗ |
nearrow; | U+02197 | ↗ |
nedot; | U+02250 U+00338 | ≐̸ |
NegativeMediumSpace; | U+0200B | |
NegativeThickSpace; | U+0200B | |
NegativeThinSpace; | U+0200B | |
NegativeVeryThinSpace; | U+0200B | |
nequiv; | U+02262 | ≢ |
nesear; | U+02928 | ⤨ |
nesim; | U+02242 U+00338 | ≂̸ |
NestedGreaterGreater; | U+0226B | ≫ |
NestedLessLess; | U+0226A | ≪ |
NewLine; | U+0000A | ␊ |
nexist; | U+02204 | ∄ |
nexists; | U+02204 | ∄ |
Nfr; | U+1D511 | 픑 |
nfr; | U+1D52B | 픫 |
ngE; | U+02267 U+00338 | ≧̸ |
nge; | U+02271 | ≱ |
ngeq; | U+02271 | ≱ |
ngeqq; | U+02267 U+00338 | ≧̸ |
ngeqslant; | U+02A7E U+00338 | ⩾̸ |
nges; | U+02A7E U+00338 | ⩾̸ |
nGg; | U+022D9 U+00338 | ⋙̸ |
ngsim; | U+02275 | ≵ |
nGt; | U+0226B U+020D2 | ≫⃒ |
ngt; | U+0226F | ≯ |
ngtr; | U+0226F | ≯ |
nGtv; | U+0226B U+00338 | ≫̸ |
nhArr; | U+021CE | ⇎ |
nharr; | U+021AE | ↮ |
nhpar; | U+02AF2 | ⫲ |
ni; | U+0220B | ∋ |
nis; | U+022FC | ⋼ |
nisd; | U+022FA | ⋺ |
niv; | U+0220B | ∋ |
NJcy; | U+0040A | Њ |
njcy; | U+0045A | њ |
nlArr; | U+021CD | ⇍ |
nlarr; | U+0219A | ↚ |
nldr; | U+02025 | ‥ |
nlE; | U+02266 U+00338 | ≦̸ |
nle; | U+02270 | ≰ |
nLeftarrow; | U+021CD | ⇍ |
nleftarrow; | U+0219A | ↚ |
nLeftrightarrow; | U+021CE | ⇎ |
nleftrightarrow; | U+021AE | ↮ |
nleq; | U+02270 | ≰ |
nleqq; | U+02266 U+00338 | ≦̸ |
nleqslant; | U+02A7D U+00338 | ⩽̸ |
nles; | U+02A7D U+00338 | ⩽̸ |
nless; | U+0226E | ≮ |
nLl; | U+022D8 U+00338 | ⋘̸ |
nlsim; | U+02274 | ≴ |
nLt; | U+0226A U+020D2 | ≪⃒ |
nlt; | U+0226E | ≮ |
nltri; | U+022EA | ⋪ |
nltrie; | U+022EC | ⋬ |
nLtv; | U+0226A U+00338 | ≪̸ |
nmid; | U+02224 | ∤ |
NoBreak; | U+02060 | |
NonBreakingSpace; | U+000A0 | |
Nopf; | U+02115 | ℕ |
nopf; | U+1D55F | 핟 |
Not; | U+02AEC | ⫬ |
not; | U+000AC | ¬ |
not | U+000AC | ¬ |
NotCongruent; | U+02262 | ≢ |
NotCupCap; | U+0226D | ≭ |
NotDoubleVerticalBar; | U+02226 | ∦ |
NotElement; | U+02209 | ∉ |
NotEqual; | U+02260 | ≠ |
NotEqualTilde; | U+02242 U+00338 | ≂̸ |
NotExists; | U+02204 | ∄ |
NotGreater; | U+0226F | ≯ |
NotGreaterEqual; | U+02271 | ≱ |
NotGreaterFullEqual; | U+02267 U+00338 | ≧̸ |
NotGreaterGreater; | U+0226B U+00338 | ≫̸ |
NotGreaterLess; | U+02279 | ≹ |
NotGreaterSlantEqual; | U+02A7E U+00338 | ⩾̸ |
NotGreaterTilde; | U+02275 | ≵ |
NotHumpDownHump; | U+0224E U+00338 | ≎̸ |
NotHumpEqual; | U+0224F U+00338 | ≏̸ |
notin; | U+02209 | ∉ |
notindot; | U+022F5 U+00338 | ⋵̸ |
notinE; | U+022F9 U+00338 | ⋹̸ |
notinva; | U+02209 | ∉ |
notinvb; | U+022F7 | ⋷ |
notinvc; | U+022F6 | ⋶ |
NotLeftTriangle; | U+022EA | ⋪ |
NotLeftTriangleBar; | U+029CF U+00338 | ⧏̸ |
NotLeftTriangleEqual; | U+022EC | ⋬ |
NotLess; | U+0226E | ≮ |
NotLessEqual; | U+02270 | ≰ |
NotLessGreater; | U+02278 | ≸ |
NotLessLess; | U+0226A U+00338 | ≪̸ |
NotLessSlantEqual; | U+02A7D U+00338 | ⩽̸ |
NotLessTilde; | U+02274 | ≴ |
NotNestedGreaterGreater; | U+02AA2 U+00338 | ⪢̸ |
NotNestedLessLess; | U+02AA1 U+00338 | ⪡̸ |
notni; | U+0220C | ∌ |
notniva; | U+0220C | ∌ |
notnivb; | U+022FE | ⋾ |
notnivc; | U+022FD | ⋽ |
NotPrecedes; | U+02280 | ⊀ |
NotPrecedesEqual; | U+02AAF U+00338 | ⪯̸ |
NotPrecedesSlantEqual; | U+022E0 | ⋠ |
NotReverseElement; | U+0220C | ∌ |
NotRightTriangle; | U+022EB | ⋫ |
NotRightTriangleBar; | U+029D0 U+00338 | ⧐̸ |
NotRightTriangleEqual; | U+022ED | ⋭ |
NotSquareSubset; | U+0228F U+00338 | ⊏̸ |
NotSquareSubsetEqual; | U+022E2 | ⋢ |
NotSquareSuperset; | U+02290 U+00338 | ⊐̸ |
NotSquareSupersetEqual; | U+022E3 | ⋣ |
NotSubset; | U+02282 U+020D2 | ⊂⃒ |
NotSubsetEqual; | U+02288 | ⊈ |
NotSucceeds; | U+02281 | ⊁ |
NotSucceedsEqual; | U+02AB0 U+00338 | ⪰̸ |
NotSucceedsSlantEqual; | U+022E1 | ⋡ |
NotSucceedsTilde; | U+0227F U+00338 | ≿̸ |
NotSuperset; | U+02283 U+020D2 | ⊃⃒ |
NotSupersetEqual; | U+02289 | ⊉ |
NotTilde; | U+02241 | ≁ |
NotTildeEqual; | U+02244 | ≄ |
NotTildeFullEqual; | U+02247 | ≇ |
NotTildeTilde; | U+02249 | ≉ |
NotVerticalBar; | U+02224 | ∤ |
npar; | U+02226 | ∦ |
nparallel; | U+02226 | ∦ |
nparsl; | U+02AFD U+020E5 | ⫽⃥ |
npart; | U+02202 U+00338 | ∂̸ |
npolint; | U+02A14 | ⨔ |
npr; | U+02280 | ⊀ |
nprcue; | U+022E0 | ⋠ |
npre; | U+02AAF U+00338 | ⪯̸ |
nprec; | U+02280 | ⊀ |
npreceq; | U+02AAF U+00338 | ⪯̸ |
nrArr; | U+021CF | ⇏ |
nrarr; | U+0219B | ↛ |
nrarrc; | U+02933 U+00338 | ⤳̸ |
nrarrw; | U+0219D U+00338 | ↝̸ |
nRightarrow; | U+021CF | ⇏ |
nrightarrow; | U+0219B | ↛ |
nrtri; | U+022EB | ⋫ |
nrtrie; | U+022ED | ⋭ |
nsc; | U+02281 | ⊁ |
nsccue; | U+022E1 | ⋡ |
nsce; | U+02AB0 U+00338 | ⪰̸ |
Nscr; | U+1D4A9 | 풩 |
nscr; | U+1D4C3 | 퓃 |
nshortmid; | U+02224 | ∤ |
nshortparallel; | U+02226 | ∦ |
nsim; | U+02241 | ≁ |
nsime; | U+02244 | ≄ |
nsimeq; | U+02244 | ≄ |
nsmid; | U+02224 | ∤ |
nspar; | U+02226 | ∦ |
nsqsube; | U+022E2 | ⋢ |
nsqsupe; | U+022E3 | ⋣ |
nsub; | U+02284 | ⊄ |
nsubE; | U+02AC5 U+00338 | ⫅̸ |
nsube; | U+02288 | ⊈ |
nsubset; | U+02282 U+020D2 | ⊂⃒ |
nsubseteq; | U+02288 | ⊈ |
nsubseteqq; | U+02AC5 U+00338 | ⫅̸ |
nsucc; | U+02281 | ⊁ |
nsucceq; | U+02AB0 U+00338 | ⪰̸ |
nsup; | U+02285 | ⊅ |
nsupE; | U+02AC6 U+00338 | ⫆̸ |
nsupe; | U+02289 | ⊉ |
nsupset; | U+02283 U+020D2 | ⊃⃒ |
nsupseteq; | U+02289 | ⊉ |
nsupseteqq; | U+02AC6 U+00338 | ⫆̸ |
ntgl; | U+02279 | ≹ |
Ntilde; | U+000D1 | Ñ |
Ntilde | U+000D1 | Ñ |
ntilde; | U+000F1 | ñ |
ntilde | U+000F1 | ñ |
ntlg; | U+02278 | ≸ |
ntriangleleft; | U+022EA | ⋪ |
ntrianglelefteq; | U+022EC | ⋬ |
ntriangleright; | U+022EB | ⋫ |
ntrianglerighteq; | U+022ED | ⋭ |
Nu; | U+0039D | Ν |
nu; | U+003BD | ν |
num; | U+00023 | # |
numero; | U+02116 | № |
numsp; | U+02007 | |
nvap; | U+0224D U+020D2 | ≍⃒ |
nVDash; | U+022AF | ⊯ |
nVdash; | U+022AE | ⊮ |
nvDash; | U+022AD | ⊭ |
nvdash; | U+022AC | ⊬ |
nvge; | U+02265 U+020D2 | ≥⃒ |
nvgt; | U+0003E U+020D2 | >⃒ |
nvHarr; | U+02904 | ⤄ |
nvinfin; | U+029DE | ⧞ |
nvlArr; | U+02902 | ⤂ |
nvle; | U+02264 U+020D2 | ≤⃒ |
nvlt; | U+0003C U+020D2 | <⃒ |
nvltrie; | U+022B4 U+020D2 | ⊴⃒ |
nvrArr; | U+02903 | ⤃ |
nvrtrie; | U+022B5 U+020D2 | ⊵⃒ |
nvsim; | U+0223C U+020D2 | ∼⃒ |
nwarhk; | U+02923 | ⤣ |
nwArr; | U+021D6 | ⇖ |
nwarr; | U+02196 | ↖ |
nwarrow; | U+02196 | ↖ |
nwnear; | U+02927 | ⤧ |
Oacute; | U+000D3 | Ó |
Oacute | U+000D3 | Ó |
oacute; | U+000F3 | ó |
oacute | U+000F3 | ó |
oast; | U+0229B | ⊛ |
ocir; | U+0229A | ⊚ |
Ocirc; | U+000D4 | Ô |
Ocirc | U+000D4 | Ô |
ocirc; | U+000F4 | ô |
ocirc | U+000F4 | ô |
Ocy; | U+0041E | О |
ocy; | U+0043E | о |
odash; | U+0229D | ⊝ |
Odblac; | U+00150 | Ő |
odblac; | U+00151 | ő |
odiv; | U+02A38 | ⨸ |
odot; | U+02299 | ⊙ |
odsold; | U+029BC | ⦼ |
OElig; | U+00152 | Œ |
oelig; | U+00153 | œ |
ofcir; | U+029BF | ⦿ |
Ofr; | U+1D512 | 픒 |
ofr; | U+1D52C | 픬 |
ogon; | U+002DB | ˛ |
Ograve; | U+000D2 | Ò |
Ograve | U+000D2 | Ò |
ograve; | U+000F2 | ò |
ograve | U+000F2 | ò |
ogt; | U+029C1 | ⧁ |
ohbar; | U+029B5 | ⦵ |
ohm; | U+003A9 | Ω |
oint; | U+0222E | ∮ |
olarr; | U+021BA | ↺ |
olcir; | U+029BE | ⦾ |
olcross; | U+029BB | ⦻ |
oline; | U+0203E | ‾ |
olt; | U+029C0 | ⧀ |
Omacr; | U+0014C | Ō |
omacr; | U+0014D | ō |
Omega; | U+003A9 | Ω |
omega; | U+003C9 | ω |
Omicron; | U+0039F | Ο |
omicron; | U+003BF | ο |
omid; | U+029B6 | ⦶ |
ominus; | U+02296 | ⊖ |
Oopf; | U+1D546 | 핆 |
oopf; | U+1D560 | 할 |
opar; | U+029B7 | ⦷ |
OpenCurlyDoubleQuote; | U+0201C | “ |
OpenCurlyQuote; | U+02018 | ‘ |
operp; | U+029B9 | ⦹ |
oplus; | U+02295 | ⊕ |
Or; | U+02A54 | ⩔ |
or; | U+02228 | ∨ |
orarr; | U+021BB | ↻ |
ord; | U+02A5D | ⩝ |
order; | U+02134 | ℴ |
orderof; | U+02134 | ℴ |
ordf; | U+000AA | ª |
ordf | U+000AA | ª |
ordm; | U+000BA | º |
ordm | U+000BA | º |
origof; | U+022B6 | ⊶ |
oror; | U+02A56 | ⩖ |
orslope; | U+02A57 | ⩗ |
orv; | U+02A5B | ⩛ |
oS; | U+024C8 | Ⓢ |
Oscr; | U+1D4AA | 풪 |
oscr; | U+02134 | ℴ |
Oslash; | U+000D8 | Ø |
Oslash | U+000D8 | Ø |
oslash; | U+000F8 | ø |
oslash | U+000F8 | ø |
osol; | U+02298 | ⊘ |
Otilde; | U+000D5 | Õ |
Otilde | U+000D5 | Õ |
otilde; | U+000F5 | õ |
otilde | U+000F5 | õ |
Otimes; | U+02A37 | ⨷ |
otimes; | U+02297 | ⊗ |
otimesas; | U+02A36 | ⨶ |
Ouml; | U+000D6 | Ö |
Ouml | U+000D6 | Ö |
ouml; | U+000F6 | ö |
ouml | U+000F6 | ö |
ovbar; | U+0233D | ⌽ |
OverBar; | U+0203E | ‾ |
OverBrace; | U+023DE | ⏞ |
OverBracket; | U+023B4 | ⎴ |
OverParenthesis; | U+023DC | ⏜ |
par; | U+02225 | ∥ |
para; | U+000B6 | ¶ |
para | U+000B6 | ¶ |
parallel; | U+02225 | ∥ |
parsim; | U+02AF3 | ⫳ |
parsl; | U+02AFD | ⫽ |
part; | U+02202 | ∂ |
PartialD; | U+02202 | ∂ |
Pcy; | U+0041F | П |
pcy; | U+0043F | п |
percnt; | U+00025 | % |
period; | U+0002E | . |
permil; | U+02030 | ‰ |
perp; | U+022A5 | ⊥ |
pertenk; | U+02031 | ‱ |
Pfr; | U+1D513 | 픓 |
pfr; | U+1D52D | 픭 |
Phi; | U+003A6 | Φ |
phi; | U+003C6 | φ |
phiv; | U+003D5 | ϕ |
phmmat; | U+02133 | ℳ |
phone; | U+0260E | ☎ |
Pi; | U+003A0 | Π |
pi; | U+003C0 | π |
pitchfork; | U+022D4 | ⋔ |
piv; | U+003D6 | ϖ |
planck; | U+0210F | ℏ |
planckh; | U+0210E | ℎ |
plankv; | U+0210F | ℏ |
plus; | U+0002B | + |
plusacir; | U+02A23 | ⨣ |
plusb; | U+0229E | ⊞ |
pluscir; | U+02A22 | ⨢ |
plusdo; | U+02214 | ∔ |
plusdu; | U+02A25 | ⨥ |
pluse; | U+02A72 | ⩲ |
PlusMinus; | U+000B1 | ± |
plusmn; | U+000B1 | ± |
plusmn | U+000B1 | ± |
plussim; | U+02A26 | ⨦ |
plustwo; | U+02A27 | ⨧ |
pm; | U+000B1 | ± |
Poincareplane; | U+0210C | ℌ |
pointint; | U+02A15 | ⨕ |
Popf; | U+02119 | ℙ |
popf; | U+1D561 | 핡 |
pound; | U+000A3 | £ |
pound | U+000A3 | £ |
Pr; | U+02ABB | ⪻ |
pr; | U+0227A | ≺ |
prap; | U+02AB7 | ⪷ |
prcue; | U+0227C | ≼ |
prE; | U+02AB3 | ⪳ |
pre; | U+02AAF | ⪯ |
prec; | U+0227A | ≺ |
precapprox; | U+02AB7 | ⪷ |
preccurlyeq; | U+0227C | ≼ |
Precedes; | U+0227A | ≺ |
PrecedesEqual; | U+02AAF | ⪯ |
PrecedesSlantEqual; | U+0227C | ≼ |
PrecedesTilde; | U+0227E | ≾ |
preceq; | U+02AAF | ⪯ |
precnapprox; | U+02AB9 | ⪹ |
precneqq; | U+02AB5 | ⪵ |
precnsim; | U+022E8 | ⋨ |
precsim; | U+0227E | ≾ |
Prime; | U+02033 | ″ |
prime; | U+02032 | ′ |
primes; | U+02119 | ℙ |
prnap; | U+02AB9 | ⪹ |
prnE; | U+02AB5 | ⪵ |
prnsim; | U+022E8 | ⋨ |
prod; | U+0220F | ∏ |
Product; | U+0220F | ∏ |
profalar; | U+0232E | ⌮ |
profline; | U+02312 | ⌒ |
profsurf; | U+02313 | ⌓ |
prop; | U+0221D | ∝ |
Proportion; | U+02237 | ∷ |
Proportional; | U+0221D | ∝ |
propto; | U+0221D | ∝ |
prsim; | U+0227E | ≾ |
prurel; | U+022B0 | ⊰ |
Pscr; | U+1D4AB | 풫 |
pscr; | U+1D4C5 | 퓅 |
Psi; | U+003A8 | Ψ |
psi; | U+003C8 | ψ |
puncsp; | U+02008 | |
Qfr; | U+1D514 | 픔 |
qfr; | U+1D52E | 픮 |
qint; | U+02A0C | ⨌ |
Qopf; | U+0211A | ℚ |
qopf; | U+1D562 | 핢 |
qprime; | U+02057 | ⁗ |
Qscr; | U+1D4AC | 풬 |
qscr; | U+1D4C6 | 퓆 |
quaternions; | U+0210D | ℍ |
quatint; | U+02A16 | ⨖ |
quest; | U+0003F | ? |
questeq; | U+0225F | ≟ |
QUOT; | U+00022 | " |
QUOT | U+00022 | " |
quot; | U+00022 | " |
quot | U+00022 | " |
rAarr; | U+021DB | ⇛ |
race; | U+0223D U+00331 | ∽̱ |
Racute; | U+00154 | Ŕ |
racute; | U+00155 | ŕ |
radic; | U+0221A | √ |
raemptyv; | U+029B3 | ⦳ |
Rang; | U+027EB | ⟫ |
rang; | U+027E9 | ⟩ |
rangd; | U+02992 | ⦒ |
range; | U+029A5 | ⦥ |
rangle; | U+027E9 | 〉 |
raquo; | U+000BB | » |
raquo | U+000BB | » |
Rarr; | U+021A0 | ↠ |
rArr; | U+021D2 | ⇒ |
rarr; | U+02192 | → |
rarrap; | U+02975 | ⥵ |
rarrb; | U+021E5 | ⇥ |
rarrbfs; | U+02920 | ⤠ |
rarrc; | U+02933 | ⤳ |
rarrfs; | U+0291E | ⤞ |
rarrhk; | U+021AA | ↪ |
rarrlp; | U+021AC | ↬ |
rarrpl; | U+02945 | ⥅ |
rarrsim; | U+02974 | ⥴ |
Rarrtl; | U+02916 | ⤖ |
rarrtl; | U+021A3 | ↣ |
rarrw; | U+0219D | ↝ |
rAtail; | U+0291C | ⤜ |
ratail; | U+0291A | ⤚ |
ratio; | U+02236 | ∶ |
rationals; | U+0211A | ℚ |
RBarr; | U+02910 | ⤐ |
rBarr; | U+0290F | ⤏ |
rbarr; | U+0290D | ⤍ |
rbbrk; | U+02773 | ❳ |
rbrace; | U+0007D | } |
rbrack; | U+0005D | ] |
rbrke; | U+0298C | ⦌ |
rbrksld; | U+0298E | ⦎ |
rbrkslu; | U+02990 | ⦐ |
Rcaron; | U+00158 | Ř |
rcaron; | U+00159 | ř |
Rcedil; | U+00156 | Ŗ |
rcedil; | U+00157 | ŗ |
rceil; | U+02309 | ⌉ |
rcub; | U+0007D | } |
Rcy; | U+00420 | Р |
rcy; | U+00440 | р |
rdca; | U+02937 | ⤷ |
rdldhar; | U+02969 | ⥩ |
rdquo; | U+0201D | ” |
rdquor; | U+0201D | ” |
rdsh; | U+021B3 | ↳ |
Re; | U+0211C | ℜ |
real; | U+0211C | ℜ |
realine; | U+0211B | ℛ |
realpart; | U+0211C | ℜ |
reals; | U+0211D | ℝ |
rect; | U+025AD | ▭ |
REG; | U+000AE | ® |
REG | U+000AE | ® |
reg; | U+000AE | ® |
reg | U+000AE | ® |
ReverseElement; | U+0220B | ∋ |
ReverseEquilibrium; | U+021CB | ⇋ |
ReverseUpEquilibrium; | U+0296F | ⥯ |
rfisht; | U+0297D | ⥽ |
rfloor; | U+0230B | ⌋ |
Rfr; | U+0211C | ℜ |
rfr; | U+1D52F | 픯 |
rHar; | U+02964 | ⥤ |
rhard; | U+021C1 | ⇁ |
rharu; | U+021C0 | ⇀ |
rharul; | U+0296C | ⥬ |
Rho; | U+003A1 | Ρ |
rho; | U+003C1 | ρ |
rhov; | U+003F1 | ϱ |
RightAngleBracket; | U+027E9 | 〉 |
RightArrow; | U+02192 | → |
Rightarrow; | U+021D2 | ⇒ |
rightarrow; | U+02192 | → |
RightArrowBar; | U+021E5 | ⇥ |
RightArrowLeftArrow; | U+021C4 | ⇄ |
rightarrowtail; | U+021A3 | ↣ |
RightCeiling; | U+02309 | ⌉ |
RightDoubleBracket; | U+027E7 | ⟧ |
RightDownTeeVector; | U+0295D | ⥝ |
RightDownVector; | U+021C2 | ⇂ |
RightDownVectorBar; | U+02955 | ⥕ |
RightFloor; | U+0230B | ⌋ |
rightharpoondown; | U+021C1 | ⇁ |
rightharpoonup; | U+021C0 | ⇀ |
rightleftarrows; | U+021C4 | ⇄ |
rightleftharpoons; | U+021CC | ⇌ |
rightrightarrows; | U+021C9 | ⇉ |
rightsquigarrow; | U+0219D | ↝ |
RightTee; | U+022A2 | ⊢ |
RightTeeArrow; | U+021A6 | ↦ |
RightTeeVector; | U+0295B | ⥛ |
rightthreetimes; | U+022CC | ⋌ |
RightTriangle; | U+022B3 | ⊳ |
RightTriangleBar; | U+029D0 | ⧐ |
RightTriangleEqual; | U+022B5 | ⊵ |
RightUpDownVector; | U+0294F | ⥏ |
RightUpTeeVector; | U+0295C | ⥜ |
RightUpVector; | U+021BE | ↾ |
RightUpVectorBar; | U+02954 | ⥔ |
RightVector; | U+021C0 | ⇀ |
RightVectorBar; | U+02953 | ⥓ |
ring; | U+002DA | ˚ |
risingdotseq; | U+02253 | ≓ |
rlarr; | U+021C4 | ⇄ |
rlhar; | U+021CC | ⇌ |
rlm; | U+0200F | |
rmoust; | U+023B1 | ⎱ |
rmoustache; | U+023B1 | ⎱ |
rnmid; | U+02AEE | ⫮ |
roang; | U+027ED | ⟭ |
roarr; | U+021FE | ⇾ |
robrk; | U+027E7 | ⟧ |
ropar; | U+02986 | ⦆ |
Ropf; | U+0211D | ℝ |
ropf; | U+1D563 | 핣 |
roplus; | U+02A2E | ⨮ |
rotimes; | U+02A35 | ⨵ |
RoundImplies; | U+02970 | ⥰ |
rpar; | U+00029 | ) |
rpargt; | U+02994 | ⦔ |
rppolint; | U+02A12 | ⨒ |
rrarr; | U+021C9 | ⇉ |
Rrightarrow; | U+021DB | ⇛ |
rsaquo; | U+0203A | › |
Rscr; | U+0211B | ℛ |
rscr; | U+1D4C7 | 퓇 |
Rsh; | U+021B1 | ↱ |
rsh; | U+021B1 | ↱ |
rsqb; | U+0005D | ] |
rsquo; | U+02019 | ’ |
rsquor; | U+02019 | ’ |
rthree; | U+022CC | ⋌ |
rtimes; | U+022CA | ⋊ |
rtri; | U+025B9 | ▹ |
rtrie; | U+022B5 | ⊵ |
rtrif; | U+025B8 | ▸ |
rtriltri; | U+029CE | ⧎ |
RuleDelayed; | U+029F4 | ⧴ |
ruluhar; | U+02968 | ⥨ |
rx; | U+0211E | ℞ |
Sacute; | U+0015A | Ś |
sacute; | U+0015B | ś |
sbquo; | U+0201A | ‚ |
Sc; | U+02ABC | ⪼ |
sc; | U+0227B | ≻ |
scap; | U+02AB8 | ⪸ |
Scaron; | U+00160 | Š |
scaron; | U+00161 | š |
sccue; | U+0227D | ≽ |
scE; | U+02AB4 | ⪴ |
sce; | U+02AB0 | ⪰ |
Scedil; | U+0015E | Ş |
scedil; | U+0015F | ş |
Scirc; | U+0015C | Ŝ |
scirc; | U+0015D | ŝ |
scnap; | U+02ABA | ⪺ |
scnE; | U+02AB6 | ⪶ |
scnsim; | U+022E9 | ⋩ |
scpolint; | U+02A13 | ⨓ |
scsim; | U+0227F | ≿ |
Scy; | U+00421 | С |
scy; | U+00441 | с |
sdot; | U+022C5 | ⋅ |
sdotb; | U+022A1 | ⊡ |
sdote; | U+02A66 | ⩦ |
searhk; | U+02925 | ⤥ |
seArr; | U+021D8 | ⇘ |
searr; | U+02198 | ↘ |
searrow; | U+02198 | ↘ |
sect; | U+000A7 | § |
sect | U+000A7 | § |
semi; | U+0003B | ; |
seswar; | U+02929 | ⤩ |
setminus; | U+02216 | ∖ |
setmn; | U+02216 | ∖ |
sext; | U+02736 | ✶ |
Sfr; | U+1D516 | 픖 |
sfr; | U+1D530 | 픰 |
sfrown; | U+02322 | ⌢ |
sharp; | U+0266F | ♯ |
SHCHcy; | U+00429 | Щ |
shchcy; | U+00449 | щ |
SHcy; | U+00428 | Ш |
shcy; | U+00448 | ш |
ShortDownArrow; | U+02193 | ↓ |
ShortLeftArrow; | U+02190 | ← |
shortmid; | U+02223 | ∣ |
shortparallel; | U+02225 | ∥ |
ShortRightArrow; | U+02192 | → |
ShortUpArrow; | U+02191 | ↑ |
shy; | U+000AD | |
shy | U+000AD | |
Sigma; | U+003A3 | Σ |
sigma; | U+003C3 | σ |
sigmaf; | U+003C2 | ς |
sigmav; | U+003C2 | ς |
sim; | U+0223C | ∼ |
simdot; | U+02A6A | ⩪ |
sime; | U+02243 | ≃ |
simeq; | U+02243 | ≃ |
simg; | U+02A9E | ⪞ |
simgE; | U+02AA0 | ⪠ |
siml; | U+02A9D | ⪝ |
simlE; | U+02A9F | ⪟ |
simne; | U+02246 | ≆ |
simplus; | U+02A24 | ⨤ |
simrarr; | U+02972 | ⥲ |
slarr; | U+02190 | ← |
SmallCircle; | U+02218 | ∘ |
smallsetminus; | U+02216 | ∖ |
smashp; | U+02A33 | ⨳ |
smeparsl; | U+029E4 | ⧤ |
smid; | U+02223 | ∣ |
smile; | U+02323 | ⌣ |
smt; | U+02AAA | ⪪ |
smte; | U+02AAC | ⪬ |
smtes; | U+02AAC U+0FE00 | ⪬︀ |
SOFTcy; | U+0042C | Ь |
softcy; | U+0044C | ь |
sol; | U+0002F | / |
solb; | U+029C4 | ⧄ |
solbar; | U+0233F | ⌿ |
Sopf; | U+1D54A | 핊 |
sopf; | U+1D564 | 핤 |
spades; | U+02660 | ♠ |
spadesuit; | U+02660 | ♠ |
spar; | U+02225 | ∥ |
sqcap; | U+02293 | ⊓ |
sqcaps; | U+02293 U+0FE00 | ⊓︀ |
sqcup; | U+02294 | ⊔ |
sqcups; | U+02294 U+0FE00 | ⊔︀ |
Sqrt; | U+0221A | √ |
sqsub; | U+0228F | ⊏ |
sqsube; | U+02291 | ⊑ |
sqsubset; | U+0228F | ⊏ |
sqsubseteq; | U+02291 | ⊑ |
sqsup; | U+02290 | ⊐ |
sqsupe; | U+02292 | ⊒ |
sqsupset; | U+02290 | ⊐ |
sqsupseteq; | U+02292 | ⊒ |
squ; | U+025A1 | □ |
Square; | U+025A1 | □ |
square; | U+025A1 | □ |
SquareIntersection; | U+02293 | ⊓ |
SquareSubset; | U+0228F | ⊏ |
SquareSubsetEqual; | U+02291 | ⊑ |
SquareSuperset; | U+02290 | ⊐ |
SquareSupersetEqual; | U+02292 | ⊒ |
SquareUnion; | U+02294 | ⊔ |
squarf; | U+025AA | ▪ |
squf; | U+025AA | ▪ |
srarr; | U+02192 | → |
Sscr; | U+1D4AE | 풮 |
sscr; | U+1D4C8 | 퓈 |
ssetmn; | U+02216 | ∖ |
ssmile; | U+02323 | ⌣ |
sstarf; | U+022C6 | ⋆ |
Star; | U+022C6 | ⋆ |
star; | U+02606 | ☆ |
starf; | U+02605 | ★ |
straightepsilon; | U+003F5 | ϵ |
straightphi; | U+003D5 | ϕ |
strns; | U+000AF | ¯ |
Sub; | U+022D0 | ⋐ |
sub; | U+02282 | ⊂ |
subdot; | U+02ABD | ⪽ |
subE; | U+02AC5 | ⫅ |
sube; | U+02286 | ⊆ |
subedot; | U+02AC3 | ⫃ |
submult; | U+02AC1 | ⫁ |
subnE; | U+02ACB | ⫋ |
subne; | U+0228A | ⊊ |
subplus; | U+02ABF | ⪿ |
subrarr; | U+02979 | ⥹ |
Subset; | U+022D0 | ⋐ |
subset; | U+02282 | ⊂ |
subseteq; | U+02286 | ⊆ |
subseteqq; | U+02AC5 | ⫅ |
SubsetEqual; | U+02286 | ⊆ |
subsetneq; | U+0228A | ⊊ |
subsetneqq; | U+02ACB | ⫋ |
subsim; | U+02AC7 | ⫇ |
subsub; | U+02AD5 | ⫕ |
subsup; | U+02AD3 | ⫓ |
succ; | U+0227B | ≻ |
succapprox; | U+02AB8 | ⪸ |
succcurlyeq; | U+0227D | ≽ |
Succeeds; | U+0227B | ≻ |
SucceedsEqual; | U+02AB0 | ⪰ |
SucceedsSlantEqual; | U+0227D | ≽ |
SucceedsTilde; | U+0227F | ≿ |
succeq; | U+02AB0 | ⪰ |
succnapprox; | U+02ABA | ⪺ |
succneqq; | U+02AB6 | ⪶ |
succnsim; | U+022E9 | ⋩ |
succsim; | U+0227F | ≿ |
SuchThat; | U+0220B | ∋ |
Sum; | U+02211 | ∑ |
sum; | U+02211 | ∑ |
sung; | U+0266A | ♪ |
Sup; | U+022D1 | ⋑ |
sup; | U+02283 | ⊃ |
sup1; | U+000B9 | ¹ |
sup1 | U+000B9 | ¹ |
sup2; | U+000B2 | ² |
sup2 | U+000B2 | ² |
sup3; | U+000B3 | ³ |
sup3 | U+000B3 | ³ |
supdot; | U+02ABE | ⪾ |
supdsub; | U+02AD8 | ⫘ |
supE; | U+02AC6 | ⫆ |
supe; | U+02287 | ⊇ |
supedot; | U+02AC4 | ⫄ |
Superset; | U+02283 | ⊃ |
SupersetEqual; | U+02287 | ⊇ |
suphsol; | U+027C9 | ⟉ |
suphsub; | U+02AD7 | ⫗ |
suplarr; | U+0297B | ⥻ |
supmult; | U+02AC2 | ⫂ |
supnE; | U+02ACC | ⫌ |
supne; | U+0228B | ⊋ |
supplus; | U+02AC0 | ⫀ |
Supset; | U+022D1 | ⋑ |
supset; | U+02283 | ⊃ |
supseteq; | U+02287 | ⊇ |
supseteqq; | U+02AC6 | ⫆ |
supsetneq; | U+0228B | ⊋ |
supsetneqq; | U+02ACC | ⫌ |
supsim; | U+02AC8 | ⫈ |
supsub; | U+02AD4 | ⫔ |
supsup; | U+02AD6 | ⫖ |
swarhk; | U+02926 | ⤦ |
swArr; | U+021D9 | ⇙ |
swarr; | U+02199 | ↙ |
swarrow; | U+02199 | ↙ |
swnwar; | U+0292A | ⤪ |
szlig; | U+000DF | ß |
szlig | U+000DF | ß |
Tab; | U+00009 | ␉ |
target; | U+02316 | ⌖ |
Tau; | U+003A4 | Τ |
tau; | U+003C4 | τ |
tbrk; | U+023B4 | ⎴ |
Tcaron; | U+00164 | Ť |
tcaron; | U+00165 | ť |
Tcedil; | U+00162 | Ţ |
tcedil; | U+00163 | ţ |
Tcy; | U+00422 | Т |
tcy; | U+00442 | т |
tdot; | U+020DB | ◌⃛ |
telrec; | U+02315 | ⌕ |
Tfr; | U+1D517 | 픗 |
tfr; | U+1D531 | 픱 |
there4; | U+02234 | ∴ |
Therefore; | U+02234 | ∴ |
therefore; | U+02234 | ∴ |
Theta; | U+00398 | Θ |
theta; | U+003B8 | θ |
thetasym; | U+003D1 | ϑ |
thetav; | U+003D1 | ϑ |
thickapprox; | U+02248 | ≈ |
thicksim; | U+0223C | ∼ |
ThickSpace; | U+0205F U+0200A | |
thinsp; | U+02009 | |
ThinSpace; | U+02009 | |
thkap; | U+02248 | ≈ |
thksim; | U+0223C | ∼ |
THORN; | U+000DE | Þ |
THORN | U+000DE | Þ |
thorn; | U+000FE | þ |
thorn | U+000FE | þ |
Tilde; | U+0223C | ∼ |
tilde; | U+002DC | ˜ |
TildeEqual; | U+02243 | ≃ |
TildeFullEqual; | U+02245 | ≅ |
TildeTilde; | U+02248 | ≈ |
times; | U+000D7 | × |
times | U+000D7 | × |
timesb; | U+022A0 | ⊠ |
timesbar; | U+02A31 | ⨱ |
timesd; | U+02A30 | ⨰ |
tint; | U+0222D | ∭ |
toea; | U+02928 | ⤨ |
top; | U+022A4 | ⊤ |
topbot; | U+02336 | ⌶ |
topcir; | U+02AF1 | ⫱ |
Topf; | U+1D54B | 핋 |
topf; | U+1D565 | 핥 |
topfork; | U+02ADA | ⫚ |
tosa; | U+02929 | ⤩ |
tprime; | U+02034 | ‴ |
TRADE; | U+02122 | ™ |
trade; | U+02122 | ™ |
triangle; | U+025B5 | ▵ |
triangledown; | U+025BF | ▿ |
triangleleft; | U+025C3 | ◃ |
trianglelefteq; | U+022B4 | ⊴ |
triangleq; | U+0225C | ≜ |
triangleright; | U+025B9 | ▹ |
trianglerighteq; | U+022B5 | ⊵ |
tridot; | U+025EC | ◬ |
trie; | U+0225C | ≜ |
triminus; | U+02A3A | ⨺ |
TripleDot; | U+020DB | ◌⃛ |
triplus; | U+02A39 | ⨹ |
trisb; | U+029CD | ⧍ |
tritime; | U+02A3B | ⨻ |
trpezium; | U+023E2 | ⏢ |
Tscr; | U+1D4AF | 풯 |
tscr; | U+1D4C9 | 퓉 |
TScy; | U+00426 | Ц |
tscy; | U+00446 | ц |
TSHcy; | U+0040B | Ћ |
tshcy; | U+0045B | ћ |
Tstrok; | U+00166 | Ŧ |
tstrok; | U+00167 | ŧ |
twixt; | U+0226C | ≬ |
twoheadleftarrow; | U+0219E | ↞ |
twoheadrightarrow; | U+021A0 | ↠ |
Uacute; | U+000DA | Ú |
Uacute | U+000DA | Ú |
uacute; | U+000FA | ú |
uacute | U+000FA | ú |
Uarr; | U+0219F | ↟ |
uArr; | U+021D1 | ⇑ |
uarr; | U+02191 | ↑ |
Uarrocir; | U+02949 | ⥉ |
Ubrcy; | U+0040E | Ў |
ubrcy; | U+0045E | ў |
Ubreve; | U+0016C | Ŭ |
ubreve; | U+0016D | ŭ |
Ucirc; | U+000DB | Û |
Ucirc | U+000DB | Û |
ucirc; | U+000FB | û |
ucirc | U+000FB | û |
Ucy; | U+00423 | У |
ucy; | U+00443 | у |
udarr; | U+021C5 | ⇅ |
Udblac; | U+00170 | Ű |
udblac; | U+00171 | ű |
udhar; | U+0296E | ⥮ |
ufisht; | U+0297E | ⥾ |
Ufr; | U+1D518 | 픘 |
ufr; | U+1D532 | 픲 |
Ugrave; | U+000D9 | Ù |
Ugrave | U+000D9 | Ù |
ugrave; | U+000F9 | ù |
ugrave | U+000F9 | ù |
uHar; | U+02963 | ⥣ |
uharl; | U+021BF | ↿ |
uharr; | U+021BE | ↾ |
uhblk; | U+02580 | ▀ |
ulcorn; | U+0231C | ⌜ |
ulcorner; | U+0231C | ⌜ |
ulcrop; | U+0230F | ⌏ |
ultri; | U+025F8 | ◸ |
Umacr; | U+0016A | Ū |
umacr; | U+0016B | ū |
uml; | U+000A8 | ¨ |
uml | U+000A8 | ¨ |
UnderBar; | U+0005F | _ |
UnderBrace; | U+023DF | ⏟ |
UnderBracket; | U+023B5 | ⎵ |
UnderParenthesis; | U+023DD | ⏝ |
Union; | U+022C3 | ⋃ |
UnionPlus; | U+0228E | ⊎ |
Uogon; | U+00172 | Ų |
uogon; | U+00173 | ų |
Uopf; | U+1D54C | 핌 |
uopf; | U+1D566 | 핦 |
UpArrow; | U+02191 | ↑ |
Uparrow; | U+021D1 | ⇑ |
uparrow; | U+02191 | ↑ |
UpArrowBar; | U+02912 | ⤒ |
UpArrowDownArrow; | U+021C5 | ⇅ |
UpDownArrow; | U+02195 | ↕ |
Updownarrow; | U+021D5 | ⇕ |
updownarrow; | U+02195 | ↕ |
UpEquilibrium; | U+0296E | ⥮ |
upharpoonleft; | U+021BF | ↿ |
upharpoonright; | U+021BE | ↾ |
uplus; | U+0228E | ⊎ |
UpperLeftArrow; | U+02196 | ↖ |
UpperRightArrow; | U+02197 | ↗ |
Upsi; | U+003D2 | ϒ |
upsi; | U+003C5 | υ |
upsih; | U+003D2 | ϒ |
Upsilon; | U+003A5 | Υ |
upsilon; | U+003C5 | υ |
UpTee; | U+022A5 | ⊥ |
UpTeeArrow; | U+021A5 | ↥ |
upuparrows; | U+021C8 | ⇈ |
urcorn; | U+0231D | ⌝ |
urcorner; | U+0231D | ⌝ |
urcrop; | U+0230E | ⌎ |
Uring; | U+0016E | Ů |
uring; | U+0016F | ů |
urtri; | U+025F9 | ◹ |
Uscr; | U+1D4B0 | 풰 |
uscr; | U+1D4CA | 퓊 |
utdot; | U+022F0 | ⋰ |
Utilde; | U+00168 | Ũ |
utilde; | U+00169 | ũ |
utri; | U+025B5 | ▵ |
utrif; | U+025B4 | ▴ |
uuarr; | U+021C8 | ⇈ |
Uuml; | U+000DC | Ü |
Uuml | U+000DC | Ü |
uuml; | U+000FC | ü |
uuml | U+000FC | ü |
uwangle; | U+029A7 | ⦧ |
vangrt; | U+0299C | ⦜ |
varepsilon; | U+003F5 | ϵ |
varkappa; | U+003F0 | ϰ |
varnothing; | U+02205 | ∅ |
varphi; | U+003D5 | ϕ |
varpi; | U+003D6 | ϖ |
varpropto; | U+0221D | ∝ |
vArr; | U+021D5 | ⇕ |
varr; | U+02195 | ↕ |
varrho; | U+003F1 | ϱ |
varsigma; | U+003C2 | ς |
varsubsetneq; | U+0228A U+0FE00 | ⊊︀ |
varsubsetneqq; | U+02ACB U+0FE00 | ⫋︀ |
varsupsetneq; | U+0228B U+0FE00 | ⊋︀ |
varsupsetneqq; | U+02ACC U+0FE00 | ⫌︀ |
vartheta; | U+003D1 | ϑ |
vartriangleleft; | U+022B2 | ⊲ |
vartriangleright; | U+022B3 | ⊳ |
Vbar; | U+02AEB | ⫫ |
vBar; | U+02AE8 | ⫨ |
vBarv; | U+02AE9 | ⫩ |
Vcy; | U+00412 | В |
vcy; | U+00432 | в |
VDash; | U+022AB | ⊫ |
Vdash; | U+022A9 | ⊩ |
vDash; | U+022A8 | ⊨ |
vdash; | U+022A2 | ⊢ |
Vdashl; | U+02AE6 | ⫦ |
Vee; | U+022C1 | ⋁ |
vee; | U+02228 | ∨ |
veebar; | U+022BB | ⊻ |
veeeq; | U+0225A | ≚ |
vellip; | U+022EE | ⋮ |
Verbar; | U+02016 | ‖ |
verbar; | U+0007C | | |
Vert; | U+02016 | ‖ |
vert; | U+0007C | | |
VerticalBar; | U+02223 | ∣ |
VerticalLine; | U+0007C | | |
VerticalSeparator; | U+02758 | ❘ |
VerticalTilde; | U+02240 | ≀ |
VeryThinSpace; | U+0200A | |
Vfr; | U+1D519 | 픙 |
vfr; | U+1D533 | 픳 |
vltri; | U+022B2 | ⊲ |
vnsub; | U+02282 U+020D2 | ⊂⃒ |
vnsup; | U+02283 U+020D2 | ⊃⃒ |
Vopf; | U+1D54D | 핍 |
vopf; | U+1D567 | 핧 |
vprop; | U+0221D | ∝ |
vrtri; | U+022B3 | ⊳ |
Vscr; | U+1D4B1 | 풱 |
vscr; | U+1D4CB | 퓋 |
vsubnE; | U+02ACB U+0FE00 | ⫋︀ |
vsubne; | U+0228A U+0FE00 | ⊊︀ |
vsupnE; | U+02ACC U+0FE00 | ⫌︀ |
vsupne; | U+0228B U+0FE00 | ⊋︀ |
Vvdash; | U+022AA | ⊪ |
vzigzag; | U+0299A | ⦚ |
Wcirc; | U+00174 | Ŵ |
wcirc; | U+00175 | ŵ |
wedbar; | U+02A5F | ⩟ |
Wedge; | U+022C0 | ⋀ |
wedge; | U+02227 | ∧ |
wedgeq; | U+02259 | ≙ |
weierp; | U+02118 | ℘ |
Wfr; | U+1D51A | 픚 |
wfr; | U+1D534 | 픴 |
Wopf; | U+1D54E | 핎 |
wopf; | U+1D568 | 함 |
wp; | U+02118 | ℘ |
wr; | U+02240 | ≀ |
wreath; | U+02240 | ≀ |
Wscr; | U+1D4B2 | 풲 |
wscr; | U+1D4CC | 퓌 |
xcap; | U+022C2 | ⋂ |
xcirc; | U+025EF | ◯ |
xcup; | U+022C3 | ⋃ |
xdtri; | U+025BD | ▽ |
Xfr; | U+1D51B | 픛 |
xfr; | U+1D535 | 픵 |
xhArr; | U+027FA | ⟺ |
xharr; | U+027F7 | ⟷ |
Xi; | U+0039E | Ξ |
xi; | U+003BE | ξ |
xlArr; | U+027F8 | ⟸ |
xlarr; | U+027F5 | ⟵ |
xmap; | U+027FC | ⟼ |
xnis; | U+022FB | ⋻ |
xodot; | U+02A00 | ⨀ |
Xopf; | U+1D54F | 핏 |
xopf; | U+1D569 | 합 |
xoplus; | U+02A01 | ⨁ |
xotime; | U+02A02 | ⨂ |
xrArr; | U+027F9 | ⟹ |
xrarr; | U+027F6 | ⟶ |
Xscr; | U+1D4B3 | 풳 |
xscr; | U+1D4CD | 퓍 |
xsqcup; | U+02A06 | ⨆ |
xuplus; | U+02A04 | ⨄ |
xutri; | U+025B3 | △ |
xvee; | U+022C1 | ⋁ |
xwedge; | U+022C0 | ⋀ |
Yacute; | U+000DD | Ý |
Yacute | U+000DD | Ý |
yacute; | U+000FD | ý |
yacute | U+000FD | ý |
YAcy; | U+0042F | Я |
yacy; | U+0044F | я |
Ycirc; | U+00176 | Ŷ |
ycirc; | U+00177 | ŷ |
Ycy; | U+0042B | Ы |
ycy; | U+0044B | ы |
yen; | U+000A5 | ¥ |
yen | U+000A5 | ¥ |
Yfr; | U+1D51C | 픜 |
yfr; | U+1D536 | 픶 |
YIcy; | U+00407 | Ї |
yicy; | U+00457 | ї |
Yopf; | U+1D550 | 핐 |
yopf; | U+1D56A | 핪 |
Yscr; | U+1D4B4 | 풴 |
yscr; | U+1D4CE | 퓎 |
YUcy; | U+0042E | Ю |
yucy; | U+0044E | ю |
Yuml; | U+00178 | Ÿ |
yuml; | U+000FF | ÿ |
yuml | U+000FF | ÿ |
Zacute; | U+00179 | Ź |
zacute; | U+0017A | ź |
Zcaron; | U+0017D | Ž |
zcaron; | U+0017E | ž |
Zcy; | U+00417 | З |
zcy; | U+00437 | з |
Zdot; | U+0017B | Ż |
zdot; | U+0017C | ż |
zeetrf; | U+02128 | ℨ |
ZeroWidthSpace; | U+0200B | |
Zeta; | U+00396 | Ζ |
zeta; | U+003B6 | ζ |
Zfr; | U+02128 | ℨ |
zfr; | U+1D537 | 픷 |
ZHcy; | U+00416 | Ж |
zhcy; | U+00436 | ж |
zigrarr; | U+021DD | ⇝ |
Zopf; | U+02124 | ℤ |
zopf; | U+1D56B | 핫 |
Zscr; | U+1D4B5 | 풵 |
zscr; | U+1D4CF | 퓏 |
zwj; | U+0200D | |
zwnj; | U+0200C | |
This data is also available as a JSON file.
The glyphs displayed above are non-normative. Refer to the Unicode specifications for formal definitions of the characters listed above.
This section only describes the rules for XML resources. Rules for
text/html
resources are discussed in the section above entitled "The HTML
syntax".
The syntax for using HTML with XML, whether in XHTML documents or embedded in other XML documents, is defined in the XML and Namespaces in XML specifications. [XML] [XMLNS]
This specification does not define any syntax-level requirements beyond those defined for XML proper.
XML documents may contain a DOCTYPE
if desired, but this is not required to
conform to this specification. This specification does not define a public or system identifier,
nor provide a formal DTD.
According to the XML specification, XML processors are not guaranteed to process
the external DTD subset referenced in the DOCTYPE. This means, for example, that using entity references for characters in XHTML documents
is unsafe if they are defined in an external file (except for <
,
>
, &
, "
and '
).
This section describes the relationship between XML and the DOM, with a particular emphasis on how this interacts with HTML.
An XML parser, for the purposes of this specification, is a construct that follows
the rules given in the XML specification to map a string of bytes or characters into a
Document
object.
At the time of writing, no such rules actually exist.
An XML parser is either associated with a Document
object when it is
created, or creates one implicitly.
This Document
must then be populated with DOM nodes that represent the tree
structure of the input passed to the parser, as defined by the XML specification, the Namespaces
in XML specification, and the DOM specification. DOM mutation events must not fire for the
operations that the XML parser performs on the Document
's tree, but the
user agent must act as if elements and attributes were individually appended and set respectively
so as to trigger rules in this specification regarding what happens when an element is inserted
into a document or has its attributes set, and the DOM specification's requirements regarding
mutation observers mean that mutation observers are fired (unlike mutation events). [XML] [XMLNS] [DOM] [DOMEVENTS]
Between the time an element's start tag is parsed and the time either the element's end tag is parsed or the parser detects a well-formedness error, the user agent must act as if the element was in a stack of open elements.
This is used by the object
element to avoid instantiating plugins
before the param
element children have been parsed.
This specification provides the following additional information that user agents should use when retrieving an external entity: the public identifiers given in the following list all correspond to the URL given by this link. (This URL is a DTD containing the entity declarations for the names listed in the named character references section.) [XML]
-//W3C//DTD XHTML 1.0 Transitional//EN
-//W3C//DTD XHTML 1.1//EN
-//W3C//DTD XHTML 1.0 Strict//EN
-//W3C//DTD XHTML 1.0 Frameset//EN
-//W3C//DTD XHTML Basic 1.0//EN
-//W3C//DTD XHTML 1.1 plus MathML 2.0//EN
-//W3C//DTD XHTML 1.1 plus MathML 2.0 plus SVG 1.1//EN
-//W3C//DTD MathML 2.0//EN
-//WAPFORUM//DTD XHTML Mobile 1.0//EN
Furthermore, user agents should attempt to retrieve the above external entity's content when one of the above public identifiers is used, and should not attempt to retrieve any other external entity's content.
This is not strictly a violation of the XML specification, but it does contradict the spirit of the XML specification's requirements. This is motivated by a desire for user agents to all handle entities in an interoperable fashion without requiring any network access for handling external subsets. [XML]
When an XML parser creates a script
element, it
must be marked as being "parser-inserted" and its "force-async" flag
must be unset. If the parser was originally created for the XML fragment parsing
algorithm, then the element must be marked as "already started" also. When the
element's end tag is parsed, the user agent must perform a microtask checkpoint,
provide a stable state, and then prepare the
script
element. If this causes there to be a pending parsing-blocking
script, then the user agent must run the following steps:
Block this instance of the XML parser, such that the event loop will not run tasks that invoke it.
Spin the event loop until the parser's Document
has no
style sheet that is blocking scripts and the pending parsing-blocking
script's "ready to be parser-executed" flag is set.
Unblock this instance of the XML parser, such that tasks that invoke it can again be run.
There is no longer a pending parsing-blocking script.
Since the document.write()
API is not
available for XML documents, much of the complexity in the HTML parser
is not needed in the XML parser.
When an XML parser would append a node to a
template
element, it must instead append it to the template
element's
template contents (a DocumentFragment
node).
This is a willful violation of the XML specification; unfortunately,
XML is not formally extensible in the manner that is needed for template
processing.
[XML]
When an XML parser creates a Node
object, its ownerDocument
must be set to the Document
of
the node into which the newly created node is to be inserted.
Certain algorithms in this specification spoon-feed the parser characters one string at a time. In such cases, the XML parser must act as it would have if faced with a single string consisting of the concatenation of all those characters.
When an XML parser reaches the end of its input, it must stop parsing, following the same rules as the HTML parser. An XML parser can also be aborted, which must again by done in the same way as for an HTML parser.
For the purposes of conformance checkers, if a resource is determined to be in the XHTML syntax, then it is an XML document.
The XML fragment serialization algorithm for a Document
or
Element
node either returns a fragment of XML that represents that node or throws an
exception.
For Document
s, the algorithm must return a string in the form of a document entity, if none of the error cases
below apply.
For Element
s, the algorithm must return a string in the form of an internal general parsed entity, if none of the
error cases below apply.
In both cases, the string returned must be XML namespace-well-formed and must be an isomorphic
serialization of all of that node's relevant child nodes, in tree order.
User agents may adjust prefixes and namespace declarations in the serialization (and indeed might
be forced to do so in some cases to obtain namespace-well-formed XML). User agents may use a
combination of regular text and character references to represent Text
nodes in the
DOM.
A node's relevant child nodes are those that apply given the following rules:
template
elementstemplate
element's template contents, if any.For Element
s, if any of the elements in the serialization are in no namespace, the
default namespace in scope for those elements must be explicitly declared as the empty string. (This doesn't apply in the Document
case.) [XML]
[XMLNS]
For the purposes of this section, an internal general parsed entity is considered XML namespace-well-formed if a document consisting of an element with no namespace declarations whose contents are the internal general parsed entity would itself be XML namespace-well-formed.
If any of the following error cases are found in the DOM subtree being serialized, then the
algorithm must throw an InvalidStateError
exception instead of returning a
string:
Document
node with no child element nodes.DocumentType
node that has an external subset public identifier that contains
characters that are not matched by the XML PubidChar
production. [XML]DocumentType
node that has an external subset system identifier that contains
both a """ (U+0022) and a "'" (U+0027) or that contains characters that are
not matched by the XML Char
production. [XML]Name
production. [XML]Attr
node with no namespace whose local name is the lowercase string "xmlns
". [XMLNS]Element
node with two or more attributes with the same local name and
namespace.Attr
node, Text
node, Comment
node, or
ProcessingInstruction
node whose data contains characters that are not matched by
the XML Char
production. [XML]Comment
node whose data contains two adjacent U+002D HYPHEN-MINUS characters
(-) or ends with such a character.ProcessingInstruction
node whose target name is an ASCII
case-insensitive match for the string "xml
".ProcessingInstruction
node whose target name contains a ":" (U+003A).ProcessingInstruction
node whose data contains the string "?>
".These are the only ways to make a DOM unserializable. The DOM enforces all the
other XML constraints; for example, trying to append two elements to a Document
node
will throw a HierarchyRequestError
exception.
When the algorithm must produce a serialization of a template
element, the string
returned must contain a serialization of the child nodes of the template element's content
DocumentFragment
, rather than the
template
element's children.
The XML fragment parsing algorithm either returns a Document
or throws
a SyntaxError
exception. Given a string input and an optional
context element context, the algorithm is as
follows:
Create a new XML parser.
If there is a context element, feed the parser just created the string corresponding to the start tag of that element, declaring all the namespace prefixes that are in scope on that element in the DOM, as well as declaring the default namespace (if any) that is in scope on that element in the DOM.
A namespace prefix is in scope if the DOM lookupNamespaceURI()
method
on the element would return a non-null value for that prefix.
The default namespace is the namespace for which the DOM isDefaultNamespace()
method on the element would return true.
If there is a context element, no
DOCTYPE
is passed to the parser, and therefore no external subset is
referenced, and therefore no entities will be recognized.
Feed the parser just created the string input.
If there is a context element, feed the parser just created the string corresponding to the end tag of that element.
If there is an XML well-formedness or XML namespace well-formedness error, then throw a
SyntaxError
exception and abort these steps.
If there is a context element, and the root
element of the resulting Document
has any sibling nodes, then throw a
SyntaxError
exception and abort these steps.
If there is a context element, then return the
child nodes of the root element of the resulting Document
, in tree
order.
Otherwise, return the children of the Document
object, in tree
order.
User agents are not required to present HTML documents in any particular way. However, this section provides a set of suggestions for rendering HTML documents that, if followed, are likely to lead to a user experience that closely resembles the experience intended by the documents' authors. So as to avoid confusion regarding the normativity of this section, RFC2119 terms have not been used. Instead, the term "expected" is used to indicate behavior that will lead to this experience. For the purposes of conformance for user agents designated as supporting the suggested default rendering, the term "expected" in this section has the same conformance implications as the RFC2119-defined term "must".
In general, user agents are expected to support CSS, and many of the suggestions in this section are expressed in CSS terms. User agents that use other presentation mechanisms can derive their expected behavior by translating from the CSS rules given in this section.
In the absence of style-layer rules to the contrary (e.g. author style sheets), user agents are expected to render an element so that it conveys to the user the meaning that the element represents, as described by this specification.
The suggestions in this section generally assume a visual output medium with a resolution of 96dpi or greater, but HTML is intended to apply to multiple media (it is a media-independent language). User agent implementors are encouraged to adapt the suggestions in this section to their target media.
An element is being rendered if it has any associated CSS layout boxes, SVG layout boxes, or some equivalent in other styling languages.
Just being off-screen does not mean the element is not being
rendered. The presence of the hidden
attribute normally
means the element is not being rendered, though this might be overridden by the style
sheets.
User agents that do not honor author-level CSS style sheets are nonetheless expected to act as if they applied the CSS rules given in these sections in a manner consistent with this specification and the relevant CSS and Unicode specifications. [CSS] [UNICODE] [BIDI]
This is especially important for issues relating to the 'display', 'unicode-bidi', and 'direction' properties.
The CSS rules given in these subsections are, except where otherwise specified, expected to be used as part of the user-agent level style sheet defaults for all documents that contain HTML elements.
Some rules are intended for the author-level zero-specificity presentational hints part of the CSS cascade; these are explicitly called out as presentational hints.
Some of the rules regarding left and right margins are given here as appropriate for elements whose 'direction' property is 'ltr', and are expected to be flipped around on elements whose 'direction' property is 'rtl'. These are marked "LTR-specific".
These markings only affect the handling of attribute values, not attribute names or element names.
When the text below says that an attribute attribute on an element element maps to the pixel length property (or properties) properties, it means that if element has an attribute attribute set, and parsing that attribute's value using the rules for parsing non-negative integers doesn't generate an error, then the user agent is expected to use the parsed value as a pixel length for a presentational hint for properties.
When the text below says that an attribute attribute on an element element maps to the dimension property (or properties) properties, it means that if element has an attribute attribute set, and parsing that attribute's value using the rules for parsing dimension values doesn't generate an error, then the user agent is expected to use the parsed dimension as the value for a presentational hint for properties, with the value given as a pixel length if the dimension was an integer, and with the value given as a percentage if the dimension was a percentage.
When a user agent is to align descendants of a node, the user agent is expected to
align only those descendants that have both their 'margin-left' and 'margin-right' properties
computing to a value other than 'auto', that are over-constrained and that have one of those two
margins with a used value forced to a greater value, and that do not themselves have an applicable
align
attribute. When multiple elements are to align a particular descendant, the most deeply nested such element is expected
to override the others. Aligned elements are expected to be aligned by having the used values of
their left and right margins be set accordingly.
@namespace url(http://www.w3.org/1999/xhtml);
, area, base, basefont, datalist, head, link,
meta, noembed, noframes, param, rp, script, source, style, template, track, title {
display: none;
}
embed[hidden] { display: inline; height: 0; width: 0; }The user agent is expected to force the 'display' property of noscript
elements
for whom scripting is enabled to compute to 'none',
irrespective of CSS rules.
The user agent is expected to force the 'display' property of input
elements whose
type
attribute is in the Hidden state to compute to 'none', irrespective of CSS
rules.
@namespace url(http://www.w3.org/1999/xhtml); html, body { display: block; }
For each property in the table below, given a body
element, the first attribute
that exists maps to the pixel length property on the body
element. If
none of the attributes for a property are found, or if the value of the attribute that was found
cannot be parsed successfully, then, if the body
element's Document
's
browsing context does not have its seamless browsing context flag set, a
default value of 8px is expected to be used for that property instead.
Property | Source |
---|---|
'margin-top' | body element's marginheight attribute
|
The body element's container frame element's marginheight attribute
| |
body element's topmargin attribute
| |
'margin-right' | body element's marginwidth attribute
|
The body element's container frame element's marginwidth attribute
| |
body element's rightmargin attribute
| |
'margin-bottom' | body element's marginheight attribute
|
The body element's container frame element's marginheight attribute
| |
body element's bottommargin attribute
| |
'margin-left' | body element's marginwidth attribute
|
The body element's container frame element's marginwidth attribute
| |
body element's leftmargin attribute
|
If the body
element's Document
's browsing context is a
nested browsing context, and the browsing context container of that
nested browsing context is a frame
or iframe
element, then
the container frame element of the body
element is that frame
or iframe
element. Otherwise, there is no container frame element.
The above requirements imply that a page can change the margins of another page
(including one from another origin) using, for example, an iframe
. This
is potentially a security risk, as it might in some cases allow an attack to contrive a situation
in which a page is rendered not as the author intended, possibly for the purposes of phishing or
otherwise misleading the user.
If the Document
has a root element, and the Document
's
browsing context is a nested browsing context, and the browsing
context container of that nested browsing context is a frame
or
iframe
element, and that element has a scrolling
attribute, then the user agent is expected to
compare the value of the attribute in an ASCII case-insensitive manner to the values
in the first column of the following table, and if one of them matches, then the user agent is
expected to treat that attribute as a presentational
hint for the aforementioned root element's 'overflow' property, setting it to the value
given in the corresponding cell on the same row in the second column:
Attribute value | 'overflow' value |
---|---|
on
| 'scroll' |
scroll
| 'scroll' |
yes
| 'scroll' |
off
| 'hidden' |
noscroll
| 'hidden' |
no
| 'hidden' |
auto
| 'auto' |
When a body
element has a background
attribute set to a non-empty value, the new value is expected to be resolved relative to the element, and if this is successful, the user agent is
expected to treat the attribute as a presentational hint
setting the element's 'background-image' property to the resulting absolute URL.
When a body
element has a bgcolor
attribute
set, the new value is expected to be parsed using the rules for parsing a legacy color
value, and if that does not return an error, the user agent is expected to treat the
attribute as a presentational hint setting the element's
'background-color' property to the resulting color.
When a body
element has a text
attribute, its
value is expected to be parsed using the rules for parsing a legacy color value, and
if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element's 'color' property to
the resulting color.
When a body
element has a link
attribute, its
value is expected to be parsed using the rules for parsing a legacy color value, and
if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the 'color' property of any
element in the Document
matching the ':link' pseudo-class to the resulting color.
When a body
element has a vlink
attribute,
its value is expected to be parsed using the rules for parsing a legacy color value,
and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the 'color' property of any
element in the Document
matching the ':visited' pseudo-class to the resulting
color.
When a body
element has an alink
attribute,
its value is expected to be parsed using the rules for parsing a legacy color value,
and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the 'color' property of any
element in the Document
matching the ':active' pseudo-class and either the ':link'
pseudo-class or the ':visited' pseudo-class to the resulting color.
@namespace url(http://www.w3.org/1999/xhtml); address, blockquote, center, div, figure, figcaption, footer, form, header, hr, legend, listing, p, plaintext, pre, summary, xmp { display: block; } blockquote, figure, listing, p, plaintext, pre, xmp { margin-top: 1em; margin-bottom: 1em; } blockquote, figure { margin-left: 40px; margin-right: 40px; } address { font-style: italic; } listing, plaintext, pre, xmp { font-family: monospace; white-space: pre; } dialog:not([open]) { display: none; } dialog { position: absolute; left: 0; right: 0; width: fit-content; height: fit-content; margin: auto; border: solid; padding: 1em; background: white; color: black; } dialog::backdrop { position: fixed; top: 0; right: 0; bottom: 0; left: 0; background: rgba(0,0,0,0.1); }
The following rules are also expected to apply, as presentational hints:
@namespace url(http://www.w3.org/1999/xhtml); pre[wrap] { white-space: pre-wrap; }
In quirks mode, the following rules are also expected to apply:
@namespace url(http://www.w3.org/1999/xhtml); form { margin-bottom: 1em; }
The center
element, and the div
element when it has an align
attribute whose value is an ASCII
case-insensitive match for either the string "center
" or the string
"middle
", are expected to center text within themselves, as if they had
their 'text-align' property set to 'center' in a presentational
hint, and to align descendants to the center.
The div
element, when it has an align
attribute
whose value is an ASCII case-insensitive match for the string "left
", is expected to left-align text within itself, as if it had its 'text-align'
property set to 'left' in a presentational hint, and to
align descendants to the left.
The div
element, when it has an align
attribute
whose value is an ASCII case-insensitive match for the string "right
", is expected to right-align text within itself, as if it had its
'text-align' property set to 'right' in a presentational
hint, and to align descendants to the right.
The div
element, when it has an align
attribute
whose value is an ASCII case-insensitive match for the string "justify
", is expected to full-justify text within itself, as if it had its
'text-align' property set to 'justify' in a presentational
hint, and to align descendants to the left.
@namespace url(http://www.w3.org/1999/xhtml);
cite, dfn, em, i, var { font-style: italic; }
b, strong { font-weight: bolder; }
code, kbd, samp, tt { font-family: monospace; }
big { font-size: larger; }
small { font-size: smaller; }
sub { vertical-align: sub; }
sup { vertical-align: super; }
sub, sup { line-height: normal; font-size: smaller; }
ruby { display: ruby; }
rb { display: ruby-base; white-space: nowrap; }
rt {
display: ruby-text;
white-space: nowrap;
font-size: 50%;
font-variant-east-asian: ruby;
text-emphasis: none;
}
rbc { display: ruby-base-container; }
rtc { display: ruby-text-container; }
ruby, rb, rt, rbc, rtc { unicode-bidi: isolate; }
:link { color: #0000EE; }
:visited { color: #551A8B; }
:link, :visited { text-decoration: underline; }
a:link[rel~=help], a:visited[rel~=help],
area:link[rel~=help], area:visited[rel~=help] { cursor: help; }
:focus { outline: auto; }
mark { background: yellow; color: black; } /* this color is just a suggestion and can be changed based on implementation feedback */
abbr[title], acronym[title] { text-decoration: dotted underline; }
ins, u { text-decoration: underline; }
del, s, strike { text-decoration: line-through; }
blink { text-decoration: blink; }
q::before { content: open-quote; }
q::after { content: close-quote; }
br { content: '\A'; white-space: pre; } /* this also has bidi implications */
nobr { white-space: nowrap; }
wbr { content: '\200B'; } /* this also has bidi implications */
nobr wbr { white-space: normal; }
The following rules are also expected to apply, as presentational hints:
@namespace url(http://www.w3.org/1999/xhtml); br[clear=left i] { clear: left; } br[clear=right i] { clear: right; } br[clear=all i], br[clear=both i] { clear: both; }
User agents that do not support correct ruby rendering are expected to render parentheses
around the text of rt
elements in the absence of rp
elements.
[CSSRUBY]
User agents are expected to support the 'clear' property on inline elements (in order to render
br
elements with clear
attributes) in the manner
described in the non-normative note to this effect in CSS2.1.
The initial value for the 'color' property is expected to be black. The initial value for the 'background-color' property is expected to be 'transparent'. The canvas' background is expected to be white.
When a font
element has a color
attribute,
its value is expected to be parsed using the rules for parsing a legacy color value,
and if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element's 'color' property to
the resulting color.
When a font
element has a face
attribute, the
user agent is expected to treat the attribute as a presentational hint setting the element's 'font-family' property to the attribute's
value.
When a font
element has a size
attribute, the
user agent is expected to use the following steps, known as the rules for parsing a legacy
font size, to treat the attribute as a presentational
hint setting the element's 'font-size' property:
Let input be the attribute's value.
Let position be a pointer into input, initially pointing at the start of the string.
If position is past the end of input, there is no presentational hint. Abort these steps.
If the character at position is a "+" (U+002B) character, then let mode be relative-plus, and advance position to the next character. Otherwise, if the character at position is a "-" (U+002D) character, then let mode be relative-minus, and advance position to the next character. Otherwise, let mode be absolute.
Collect a sequence of characters that are ASCII digits, and let the resulting sequence be digits.
If digits is the empty string, there is no presentational hint. Abort these steps.
Interpret digits as a base-ten integer. Let value be the resulting number.
If mode is relative-plus, then increment value by 3. If mode is relative-minus, then let value be the result of subtracting value from 3.
If value is greater than 7, let it be 7.
If value is less than 1, let it be 1.
Set 'font-size' to the keyword corresponding to the value of value according to the following table:
value | 'font-size' keyword | Notes |
---|---|---|
1 | x-small | |
2 | small | |
3 | medium | |
4 | large | |
5 | x-large | |
6 | xx-large | |
7 | xxx-large | see below |
The 'xxx-large' value is a non-CSS value used here to indicate a font size 50% larger than 'xx-large'.
@namespace url(http://www.w3.org/1999/xhtml); [dir]:dir(ltr), bdi:dir(ltr), input[type=tel]:dir(ltr) { direction: ltr; } [dir]:dir(rtl), bdi:dir(rtl) { direction: rtl; } address, blockquote, center, div, figure, figcaption, footer, form, header, hr, legend, listing, p, plaintext, pre, summary, xmp, article, aside, h1, h2, h3, h4, h5, h6, hgroup, main, nav, section, table, caption, colgroup, col, thead, tbody, tfoot, tr, td, th, dir, dd, dl, dt, ol, ul, li, bdi, output, [dir=ltr i], [dir=rtl i], [dir=auto i] { unicode-bidi: isolate; } bdo, bdo[dir] { unicode-bidi: isolate-override; } textarea[dir=auto i], input[type=text][dir=auto i], input[type=search][dir=auto i], input[type=tel][dir=auto i], input[type=url][dir=auto i], input[type=email][dir=auto i], pre[dir=auto i] { unicode-bidi: plaintext; } /* the rules setting the 'content' property onbr
andwbr
elements also has bidi implications */
Input fields (i.e. textarea
elements, and input
elements when their
type
attribute is in the Text, Search,
Telephone, URL,
or E-mail state) are expected to present an editing
user interface with a directionality that matches the element's 'direction' property.
This block is automatically generated from the Unicode Common Locale Data Repository. [CLDR]
User agents are expected to use either the block below (which will be regularly updated) or to
automatically generate their own copy directly from the source material. The language codes are
derived from the CLDR file names. The quotes are derived from the delimiter
blocks, with fallback handled as specified in the CLDR documentation.
@namespace url(http://www.w3.org/1999/xhtml); :root { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(af), :not(:lang(af)) > :lang(af) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(agq), :not(:lang(agq)) > :lang(agq) { quotes: '\201e' '\201d' '\201a' '\2019' } /* „ ” ‚ ’ */ :root:lang(ak), :not(:lang(ak)) > :lang(ak) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(am), :not(:lang(am)) > :lang(am) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(ar), :not(:lang(ar)) > :lang(ar) { quotes: '\201d' '\201c' '\2019' '\2018' } /* ” “ ’ ‘ */ :root:lang(asa), :not(:lang(asa)) > :lang(asa) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(az-Cyrl), :not(:lang(az-Cyrl)) > :lang(az-Cyrl) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(bas), :not(:lang(bas)) > :lang(bas) { quotes: '\00ab' '\00bb' '\201e' '\201c' } /* « » „ “ */ :root:lang(bem), :not(:lang(bem)) > :lang(bem) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(bez), :not(:lang(bez)) > :lang(bez) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(bg), :not(:lang(bg)) > :lang(bg) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(bm), :not(:lang(bm)) > :lang(bm) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(bn), :not(:lang(bn)) > :lang(bn) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(br), :not(:lang(br)) > :lang(br) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(brx), :not(:lang(brx)) > :lang(brx) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(bs-Cyrl), :not(:lang(bs-Cyrl)) > :lang(bs-Cyrl) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(ca), :not(:lang(ca)) > :lang(ca) { quotes: '\201c' '\201d' '\00ab' '\00bb' } /* “ ” « » */ :root:lang(cgg), :not(:lang(cgg)) > :lang(cgg) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(chr), :not(:lang(chr)) > :lang(chr) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(cs), :not(:lang(cs)) > :lang(cs) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(da), :not(:lang(da)) > :lang(da) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(dav), :not(:lang(dav)) > :lang(dav) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(de), :not(:lang(de)) > :lang(de) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(de-CH), :not(:lang(de-CH)) > :lang(de-CH) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(dje), :not(:lang(dje)) > :lang(dje) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(dua), :not(:lang(dua)) > :lang(dua) { quotes: '\00ab' '\00bb' '\2018' '\2019' } /* « » ‘ ’ */ :root:lang(dyo), :not(:lang(dyo)) > :lang(dyo) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(dz), :not(:lang(dz)) > :lang(dz) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ebu), :not(:lang(ebu)) > :lang(ebu) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ee), :not(:lang(ee)) > :lang(ee) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(el), :not(:lang(el)) > :lang(el) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(en), :not(:lang(en)) > :lang(en) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(es), :not(:lang(es)) > :lang(es) { quotes: '\201c' '\201d' '\00ab' '\00bb' } /* “ ” « » */ :root:lang(et), :not(:lang(et)) > :lang(et) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(eu), :not(:lang(eu)) > :lang(eu) { quotes: '\201c' '\201d' '\00ab' '\00bb' } /* “ ” « » */ :root:lang(ewo), :not(:lang(ewo)) > :lang(ewo) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(fa), :not(:lang(fa)) > :lang(fa) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(ff), :not(:lang(ff)) > :lang(ff) { quotes: '\201e' '\201d' '\201a' '\2019' } /* „ ” ‚ ’ */ :root:lang(fi), :not(:lang(fi)) > :lang(fi) { quotes: '\201d' '\201d' '\2019' '\2019' } /* ” ” ’ ’ */ :root:lang(fr), :not(:lang(fr)) > :lang(fr) { quotes: '\00ab' '\00bb' '\00ab' '\00bb' } /* « » « » */ :root:lang(fr-CA), :not(:lang(fr-CA)) > :lang(fr-CA) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(fr-CH), :not(:lang(fr-CH)) > :lang(fr-CH) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(gsw), :not(:lang(gsw)) > :lang(gsw) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(gu), :not(:lang(gu)) > :lang(gu) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(guz), :not(:lang(guz)) > :lang(guz) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ha), :not(:lang(ha)) > :lang(ha) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(he), :not(:lang(he)) > :lang(he) { quotes: '\0022' '\0022' '\0027' '\0027' } /* " " ' ' */ :root:lang(hi), :not(:lang(hi)) > :lang(hi) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(hr), :not(:lang(hr)) > :lang(hr) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(hu), :not(:lang(hu)) > :lang(hu) { quotes: '\201e' '\201d' '\00bb' '\00ab' } /* „ ” » « */ :root:lang(id), :not(:lang(id)) > :lang(id) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ig), :not(:lang(ig)) > :lang(ig) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(it), :not(:lang(it)) > :lang(it) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(ja), :not(:lang(ja)) > :lang(ja) { quotes: '\300c' '\300d' '\300e' '\300f' } /* 「 」 『 』 */ :root:lang(jgo), :not(:lang(jgo)) > :lang(jgo) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(jmc), :not(:lang(jmc)) > :lang(jmc) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(kab), :not(:lang(kab)) > :lang(kab) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(kam), :not(:lang(kam)) > :lang(kam) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(kde), :not(:lang(kde)) > :lang(kde) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(kea), :not(:lang(kea)) > :lang(kea) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(khq), :not(:lang(khq)) > :lang(khq) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ki), :not(:lang(ki)) > :lang(ki) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(kkj), :not(:lang(kkj)) > :lang(kkj) { quotes: '\00ab' '\00bb' '\2039' '\203a' } /* « » ‹ › */ :root:lang(kln), :not(:lang(kln)) > :lang(kln) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(km), :not(:lang(km)) > :lang(km) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(kn), :not(:lang(kn)) > :lang(kn) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ko), :not(:lang(ko)) > :lang(ko) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ksb), :not(:lang(ksb)) > :lang(ksb) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ksf), :not(:lang(ksf)) > :lang(ksf) { quotes: '\00ab' '\00bb' '\2018' '\2019' } /* « » ‘ ’ */ :root:lang(lag), :not(:lang(lag)) > :lang(lag) { quotes: '\201d' '\201d' '\2019' '\2019' } /* ” ” ’ ’ */ :root:lang(lg), :not(:lang(lg)) > :lang(lg) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ln), :not(:lang(ln)) > :lang(ln) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(lo), :not(:lang(lo)) > :lang(lo) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(lt), :not(:lang(lt)) > :lang(lt) { quotes: '\201e' '\201c' '\201e' '\201c' } /* „ “ „ “ */ :root:lang(lu), :not(:lang(lu)) > :lang(lu) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(luo), :not(:lang(luo)) > :lang(luo) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(luy), :not(:lang(luy)) > :lang(luy) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(lv), :not(:lang(lv)) > :lang(lv) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mas), :not(:lang(mas)) > :lang(mas) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mer), :not(:lang(mer)) > :lang(mer) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mfe), :not(:lang(mfe)) > :lang(mfe) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mg), :not(:lang(mg)) > :lang(mg) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(mgo), :not(:lang(mgo)) > :lang(mgo) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mk), :not(:lang(mk)) > :lang(mk) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(ml), :not(:lang(ml)) > :lang(ml) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mr), :not(:lang(mr)) > :lang(mr) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ms), :not(:lang(ms)) > :lang(ms) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(mua), :not(:lang(mua)) > :lang(mua) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(my), :not(:lang(my)) > :lang(my) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(naq), :not(:lang(naq)) > :lang(naq) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(nb), :not(:lang(nb)) > :lang(nb) { quotes: '\00ab' '\00bb' '\2018' '\2019' } /* « » ‘ ’ */ :root:lang(nd), :not(:lang(nd)) > :lang(nd) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(nl), :not(:lang(nl)) > :lang(nl) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(nmg), :not(:lang(nmg)) > :lang(nmg) { quotes: '\201e' '\201d' '\00ab' '\00bb' } /* „ ” « » */ :root:lang(nn), :not(:lang(nn)) > :lang(nn) { quotes: '\00ab' '\00bb' '\2018' '\2019' } /* « » ‘ ’ */ :root:lang(nnh), :not(:lang(nnh)) > :lang(nnh) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(nus), :not(:lang(nus)) > :lang(nus) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(nyn), :not(:lang(nyn)) > :lang(nyn) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(pl), :not(:lang(pl)) > :lang(pl) { quotes: '\201e' '\201d' '\00ab' '\00bb' } /* „ ” « » */ :root:lang(pt), :not(:lang(pt)) > :lang(pt) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(pt-PT), :not(:lang(pt-PT)) > :lang(pt-PT) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(rn), :not(:lang(rn)) > :lang(rn) { quotes: '\201d' '\201d' '\2019' '\2019' } /* ” ” ’ ’ */ :root:lang(ro), :not(:lang(ro)) > :lang(ro) { quotes: '\201e' '\201d' '\00ab' '\00bb' } /* „ ” « » */ :root:lang(rof), :not(:lang(rof)) > :lang(rof) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ru), :not(:lang(ru)) > :lang(ru) { quotes: '\00ab' '\00bb' '\201e' '\201c' } /* « » „ “ */ :root:lang(rw), :not(:lang(rw)) > :lang(rw) { quotes: '\00ab' '\00bb' '\2018' '\2019' } /* « » ‘ ’ */ :root:lang(rwk), :not(:lang(rwk)) > :lang(rwk) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(saq), :not(:lang(saq)) > :lang(saq) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(sbp), :not(:lang(sbp)) > :lang(sbp) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(seh), :not(:lang(seh)) > :lang(seh) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ses), :not(:lang(ses)) > :lang(ses) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(sg), :not(:lang(sg)) > :lang(sg) { quotes: '\00ab' '\00bb' '\201c' '\201d' } /* « » “ ” */ :root:lang(shi), :not(:lang(shi)) > :lang(shi) { quotes: '\00ab' '\00bb' '\201e' '\201d' } /* « » „ ” */ :root:lang(shi-Latn), :not(:lang(shi-Latn)) > :lang(shi-Latn) { quotes: '\00ab' '\00bb' '\201e' '\201d' } /* « » „ ” */ :root:lang(si), :not(:lang(si)) > :lang(si) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(sk), :not(:lang(sk)) > :lang(sk) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(sl), :not(:lang(sl)) > :lang(sl) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(sn), :not(:lang(sn)) > :lang(sn) { quotes: '\201d' '\201d' '\2019' '\2019' } /* ” ” ’ ’ */ :root:lang(so), :not(:lang(so)) > :lang(so) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(sq), :not(:lang(sq)) > :lang(sq) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(sr), :not(:lang(sr)) > :lang(sr) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(sr-Latn), :not(:lang(sr-Latn)) > :lang(sr-Latn) { quotes: '\201e' '\201c' '\201a' '\2018' } /* „ “ ‚ ‘ */ :root:lang(sv), :not(:lang(sv)) > :lang(sv) { quotes: '\201d' '\201d' '\2019' '\2019' } /* ” ” ’ ’ */ :root:lang(sw), :not(:lang(sw)) > :lang(sw) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(swc), :not(:lang(swc)) > :lang(swc) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ta), :not(:lang(ta)) > :lang(ta) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(te), :not(:lang(te)) > :lang(te) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(teo), :not(:lang(teo)) > :lang(teo) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(th), :not(:lang(th)) > :lang(th) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(ti-ER), :not(:lang(ti-ER)) > :lang(ti-ER) { quotes: '\2018' '\2019' '\201c' '\201d' } /* ‘ ’ “ ” */ :root:lang(to), :not(:lang(to)) > :lang(to) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(tr), :not(:lang(tr)) > :lang(tr) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(twq), :not(:lang(twq)) > :lang(twq) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(tzm), :not(:lang(tzm)) > :lang(tzm) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(uk), :not(:lang(uk)) > :lang(uk) { quotes: '\00ab' '\00bb' '\201e' '\201c' } /* « » „ “ */ :root:lang(ur), :not(:lang(ur)) > :lang(ur) { quotes: '\201d' '\201c' '\2019' '\2018' } /* ” “ ’ ‘ */ :root:lang(vai), :not(:lang(vai)) > :lang(vai) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(vai-Latn), :not(:lang(vai-Latn)) > :lang(vai-Latn) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(vi), :not(:lang(vi)) > :lang(vi) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(vun), :not(:lang(vun)) > :lang(vun) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(xh), :not(:lang(xh)) > :lang(xh) { quotes: '\2018' '\2019' '\201c' '\201d' } /* ‘ ’ “ ” */ :root:lang(xog), :not(:lang(xog)) > :lang(xog) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(yav), :not(:lang(yav)) > :lang(yav) { quotes: '\00ab' '\00bb' '\00ab' '\00bb' } /* « » « » */ :root:lang(yo), :not(:lang(yo)) > :lang(yo) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(zh), :not(:lang(zh)) > :lang(zh) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */ :root:lang(zh-Hant), :not(:lang(zh-Hant)) > :lang(zh-Hant) { quotes: '\300c' '\300d' '\300e' '\300f' } /* 「 」 『 』 */ :root:lang(zu), :not(:lang(zu)) > :lang(zu) { quotes: '\201c' '\201d' '\2018' '\2019' } /* “ ” ‘ ’ */
@namespace url(http://www.w3.org/1999/xhtml); article, aside, h1, h2, h3, h4, h5, h6, hgroup, nav, section { display: block; } h1 { margin-top: 0.67em; margin-bottom: 0.67em; font-size: 2.00em; font-weight: bold; } h2 { margin-top: 0.83em; margin-bottom: 0.83em; font-size: 1.50em; font-weight: bold; } h3 { margin-top: 1.00em; margin-bottom: 1.00em; font-size: 1.17em; font-weight: bold; } h4 { margin-top: 1.33em; margin-bottom: 1.33em; font-size: 1.00em; font-weight: bold; } h5 { margin-top: 1.67em; margin-bottom: 1.67em; font-size: 0.83em; font-weight: bold; } h6 { margin-top: 2.33em; margin-bottom: 2.33em; font-size: 0.67em; font-weight: bold; }
The article
, aside
, nav
, and section
elements are expected to affect the margins and font size of h1
elements, as well as
h2
–h5
elements that follow h1
elements in
hgroup
elements, based on the nesting depth. If x is a selector
that matches elements that are either article
, aside
, nav
,
or section
elements, then the following rules capture what is expected:
@namespace url(http://www.w3.org/1999/xhtml); x h1 { margin-top: 0.83em; margin-bottom: 0.83em; font-size: 1.50em; } x x h1 { margin-top: 1.00em; margin-bottom: 1.00em; font-size: 1.17em; } x x x h1 { margin-top: 1.33em; margin-bottom: 1.33em; font-size: 1.00em; } x x x x h1 { margin-top: 1.67em; margin-bottom: 1.67em; font-size: 0.83em; } x x x x x h1 { margin-top: 2.33em; margin-bottom: 2.33em; font-size: 0.67em; } x hgroup > h1 ~ h2 { margin-top: 1.00em; margin-bottom: 1.00em; font-size: 1.17em; } x x hgroup > h1 ~ h2 { margin-top: 1.33em; margin-bottom: 1.33em; font-size: 1.00em; } x x x hgroup > h1 ~ h2 { margin-top: 1.67em; margin-bottom: 1.67em; font-size: 0.83em; } x x x x hgroup > h1 ~ h2 { margin-top: 2.33em; margin-bottom: 2.33em; font-size: 0.67em; } x hgroup > h1 ~ h3 { margin-top: 1.33em; margin-bottom: 1.33em; font-size: 1.00em; } x x hgroup > h1 ~ h3 { margin-top: 1.67em; margin-bottom: 1.67em; font-size: 0.83em; } x x x hgroup > h1 ~ h3 { margin-top: 2.33em; margin-bottom: 2.33em; font-size: 0.67em; } x hgroup > h1 ~ h4 { margin-top: 1.67em; margin-bottom: 1.67em; font-size: 0.83em; } x x hgroup > h1 ~ h4 { margin-top: 2.33em; margin-bottom: 2.33em; font-size: 0.67em; } x hgroup > h1 ~ h5 { margin-top: 2.33em; margin-bottom: 2.33em; font-size: 0.67em; }
@namespace url(http://www.w3.org/1999/xhtml); dir, dd, dl, dt, ol, ul { display: block; } li { display: list-item; } dir, dl, ol, ul { margin-top: 1em; margin-bottom: 1em; } dir dir, dir dl, dir ol, dir ul, dl dir, dl dl, dl ol, dl ul, ol dir, ol dl, ol ol, ol ul, ul dir, ul dl, ul ol, ul ul { margin-top: 0; margin-bottom: 0; } dd { margin-left: 40px; } /* LTR-specific: use 'margin-right' for rtl elements */ dir, ol, ul { padding-left: 40px; } /* LTR-specific: use 'padding-right' for rtl elements */ ol { list-style-type: decimal; } dir, ul { list-style-type: disc; } dir dir, dir ul, ol dir, ol ul, ul dir, ul ul { list-style-type: circle; } dir dir dir, dir dir ul, dir ol dir, dir ol ul, dir ul dir, dir ul ul, ol dir dir, ol dir ul, ol ol dir, ol ol ul, ol ul dir, ol ul ul, ul dir dir, ul dir ul, ul ol dir, ul ol ul, ul ul dir, ul ul ul { list-style-type: square; }
The following rules are also expected to apply, as presentational hints:
@namespace url(http://www.w3.org/1999/xhtml); ol[type=1], li[type=1] { list-style-type: decimal; } ol[type=a], li[type=a] { list-style-type: lower-alpha; } ol[type=A], li[type=A] { list-style-type: upper-alpha; } ol[type=i], li[type=i] { list-style-type: lower-roman; } ol[type=I], li[type=I] { list-style-type: upper-roman; } ul[type=disc i], li[type=disc i] { list-style-type: disc; } ul[type=circle i], li[type=circle i] { list-style-type: circle; } ul[type=square i], li[type=square i] { list-style-type: square; }
When rendering li
elements, non-CSS user agents are expected to use the
ordinal value of the li
element to render the counter in the list item
marker.
This specification does not yet define the
CSS-specific rules for rendering li
elements, because CSS doesn't yet provide
sufficient hooks for this purpose.
@namespace url(http://www.w3.org/1999/xhtml); table { display: table; } caption { display: table-caption; } colgroup, colgroup[hidden] { display: table-column-group; } col, col[hidden] { display: table-column; } thead, thead[hidden] { display: table-header-group; } tbody, tbody[hidden] { display: table-row-group; } tfoot, tfoot[hidden] { display: table-footer-group; } tr, tr[hidden] { display: table-row; } td, th, td[hidden], th[hidden] { display: table-cell; } colgroup[hidden], col[hidden], thead[hidden], tbody[hidden], tfoot[hidden], tr[hidden], td[hidden], th[hidden] { visibility: collapse; } table { box-sizing: border-box; border-spacing: 2px; border-collapse: separate; text-indent: initial; } td, th { padding: 1px; } th { font-weight: bold; } thead, tbody, tfoot, table > tr { vertical-align: middle; } tr, td, th { vertical-align: inherit; } table, td, th { border-color: gray; } thead, tbody, tfoot, tr { border-color: inherit; } table[rules=none i], table[rules=groups i], table[rules=rows i], table[rules=cols i], table[rules=all i], table[frame=void i], table[frame=above i], table[frame=below i], table[frame=hsides i], table[frame=lhs i], table[frame=rhs i], table[frame=vsides i], table[frame=box i], table[frame=border i], table[rules=none i] > tr > td, table[rules=none i] > tr > th, table[rules=groups i] > tr > td, table[rules=groups i] > tr > th, table[rules=rows i] > tr > td, table[rules=rows i] > tr > th, table[rules=cols i] > tr > td, table[rules=cols i] > tr > th, table[rules=all i] > tr > td, table[rules=all i] > tr > th, table[rules=none i] > thead > tr > td, table[rules=none i] > thead > tr > th, table[rules=groups i] > thead > tr > td, table[rules=groups i] > thead > tr > th, table[rules=rows i] > thead > tr > td, table[rules=rows i] > thead > tr > th, table[rules=cols i] > thead > tr > td, table[rules=cols i] > thead > tr > th, table[rules=all i] > thead > tr > td, table[rules=all i] > thead > tr > th, table[rules=none i] > tbody > tr > td, table[rules=none i] > tbody > tr > th, table[rules=groups i] > tbody > tr > td, table[rules=groups i] > tbody > tr > th, table[rules=rows i] > tbody > tr > td, table[rules=rows i] > tbody > tr > th, table[rules=cols i] > tbody > tr > td, table[rules=cols i] > tbody > tr > th, table[rules=all i] > tbody > tr > td, table[rules=all i] > tbody > tr > th, table[rules=none i] > tfoot > tr > td, table[rules=none i] > tfoot > tr > th, table[rules=groups i] > tfoot > tr > td, table[rules=groups i] > tfoot > tr > th, table[rules=rows i] > tfoot > tr > td, table[rules=rows i] > tfoot > tr > th, table[rules=cols i] > tfoot > tr > td, table[rules=cols i] > tfoot > tr > th, table[rules=all i] > tfoot > tr > td, table[rules=all i] > tfoot > tr > th { border-color: black; }
The following rules are also expected to apply, as presentational hints:
@namespace url(http://www.w3.org/1999/xhtml); table[align=left i] { float: left; } table[align=right i] { float: right; } table[align=center i] { margin-left: auto; margin-right: auto; } thead[align=absmiddle i], tbody[align=absmiddle i], tfoot[align=absmiddle i], tr[align=absmiddle i], td[align=absmiddle i], th[align=absmiddle i] { text-align: center; } caption[align=bottom i] { caption-side: bottom; } p[align=left i], h1[align=left i], h2[align=left i], h3[align=left i], h4[align=left i], h5[align=left i], h6[align=left i] { text-align: left; } p[align=right i], h1[align=right i], h2[align=right i], h3[align=right i], h4[align=right i], h5[align=right i], h6[align=right i] { text-align: right; } p[align=center i], h1[align=center i], h2[align=center i], h3[align=center i], h4[align=center i], h5[align=center i], h6[align=center i] { text-align: center; } p[align=justify i], h1[align=justify i], h2[align=justify i], h3[align=justify i], h4[align=justify i], h5[align=justify i], h6[align=justify i] { text-align: justify; } thead[valign=top i], tbody[valign=top i], tfoot[valign=top i], tr[valign=top i], td[valign=top i], th[valign=top i] { vertical-align: top; } thead[valign=middle i], tbody[valign=middle i], tfoot[valign=middle i], tr[valign=middle i], td[valign=middle i], th[valign=middle i] { vertical-align: middle; } thead[valign=bottom i], tbody[valign=bottom i], tfoot[valign=bottom i], tr[valign=bottom i], td[valign=bottom i], th[valign=bottom i] { vertical-align: bottom; } thead[valign=baseline i], tbody[valign=baseline i], tfoot[valign=baseline i], tr[valign=baseline i], td[valign=baseline i], th[valign=baseline i] { vertical-align: baseline; } td[nowrap], th[nowrap] { white-space: nowrap; } table[rules=none i], table[rules=groups i], table[rules=rows i], table[rules=cols i], table[rules=all i] { border-style: hidden; border-collapse: collapse; } table[border] { border-style: outset; } /* only if border is not equivalent to zero */ table[frame=void i] { border-style: hidden; } table[frame=above i] { border-style: outset hidden hidden hidden; } table[frame=below i] { border-style: hidden hidden outset hidden; } table[frame=hsides i] { border-style: outset hidden outset hidden; } table[frame=lhs i] { border-style: hidden hidden hidden outset; } table[frame=rhs i] { border-style: hidden outset hidden hidden; } table[frame=vsides i] { border-style: hidden outset; } table[frame=box i], table[frame=border i] { border-style: outset; } table[border] > tr > td, table[border] > tr > th, table[border] > thead > tr > td, table[border] > thead > tr > th, table[border] > tbody > tr > td, table[border] > tbody > tr > th, table[border] > tfoot > tr > td, table[border] > tfoot > tr > th { /* only if border is not equivalent to zero */ border-width: 1px; border-style: inset; } table[rules=none i] > tr > td, table[rules=none i] > tr > th, table[rules=none i] > thead > tr > td, table[rules=none i] > thead > tr > th, table[rules=none i] > tbody > tr > td, table[rules=none i] > tbody > tr > th, table[rules=none i] > tfoot > tr > td, table[rules=none i] > tfoot > tr > th, table[rules=groups i] > tr > td, table[rules=groups i] > tr > th, table[rules=groups i] > thead > tr > td, table[rules=groups i] > thead > tr > th, table[rules=groups i] > tbody > tr > td, table[rules=groups i] > tbody > tr > th, table[rules=groups i] > tfoot > tr > td, table[rules=groups i] > tfoot > tr > th, table[rules=rows i] > tr > td, table[rules=rows i] > tr > th, table[rules=rows i] > thead > tr > td, table[rules=rows i] > thead > tr > th, table[rules=rows i] > tbody > tr > td, table[rules=rows i] > tbody > tr > th, table[rules=rows i] > tfoot > tr > td, table[rules=rows i] > tfoot > tr > th { border-width: 1px; border-style: none; } table[rules=cols i] > tr > td, table[rules=cols i] > tr > th, table[rules=cols i] > thead > tr > td, table[rules=cols i] > thead > tr > th, table[rules=cols i] > tbody > tr > td, table[rules=cols i] > tbody > tr > th, table[rules=cols i] > tfoot > tr > td, table[rules=cols i] > tfoot > tr > th { border-width: 1px; border-style: none solid; } table[rules=all i] > tr > td, table[rules=all i] > tr > th, table[rules=all i] > thead > tr > td, table[rules=all i] > thead > tr > th, table[rules=all i] > tbody > tr > td, table[rules=all i] > tbody > tr > th, table[rules=all i] > tfoot > tr > td, table[rules=all i] > tfoot > tr > th { border-width: 1px; border-style: solid; } table[rules=groups i] > colgroup { border-left-width: 1px; border-left-style: solid; border-right-width: 1px; border-right-style: solid; } table[rules=groups i] > thead, table[rules=groups i] > tbody, table[rules=groups i] > tfoot { border-top-width: 1px; border-top-style: solid; border-bottom-width: 1px; border-bottom-style: solid; } table[rules=rows i] > tr, table[rules=rows i] > thead > tr, table[rules=rows i] > tbody > tr, table[rules=rows i] > tfoot > tr { border-top-width: 1px; border-top-style: solid; border-bottom-width: 1px; border-bottom-style: solid; }
In quirks mode, the following rules are also expected to apply:
@namespace url(http://www.w3.org/1999/xhtml); table { font-weight: initial; font-style: initial; font-variant: initial; font-size: initial; line-height: initial; white-space: initial; text-align: initial; }
For the purposes of the CSS table model, the col
element is expected to be treated
as if it was present as many times as its span
attribute specifies.
For the purposes of the CSS table model, the colgroup
element, if it contains no
col
element, is expected to be treated as if it had as many such children as its
span
attribute specifies.
For the purposes of the CSS table model, the colspan
and
rowspan
attributes on td
and th
elements are expected to provide the
special knowledge regarding cells spanning rows and columns.
In HTML documents, the user agent is expected to force the 'display' property of
form
elements that are children of table
, thead
,
tbody
, tfoot
, or tr
elements to compute to 'none',
irrespective of CSS rules.
The table
element's cellspacing
attribute maps to the pixel length property 'border-spacing' on the element.
The table
element's cellpadding
attribute maps to the pixel length
properties 'padding-top', 'padding-right', 'padding-bottom', and 'padding-left' of any
td
and th
elements that have corresponding cells in the table corresponding to
the table
element.
The table
element's hspace
attribute maps to the dimension properties 'margin-left' and
'margin-right' on the table
element.
The table
element's vspace
attribute maps to the dimension properties 'margin-top' and
'margin-bottom' on the table
element.
The table
element's height
attribute
maps to the dimension property 'height' on the table
element.
The table
element's width
attribute
maps to the dimension property 'width' on the table
element.
The col
element's width
attribute maps
to the dimension property 'width' on the col
element.
The tr
element's height
attribute maps
to the dimension property 'height' on the tr
element.
The td
and th
elements' height
attributes map to the dimension property
'height' on the element.
The td
and th
elements' width
attributes map to the dimension property
'width' on the element.
The caption
element unless specified otherwise below, and the thead
,
tbody
, tfoot
, tr
, td
, and th
elements when they have an align
attribute whose value is an
ASCII case-insensitive match for either the string "center
" or
the string "middle
", are expected to center text within themselves, as if
they had their 'text-align' property set to 'center' in a presentational hint, and to align descendants to the center.
The caption
, thead
, tbody
, tfoot
,
tr
, td
, and th
elements, when they have an align
attribute whose value is an ASCII case-insensitive
match for the string "left
", are expected to left-align text within
themselves, as if they had their 'text-align' property set to 'left' in a presentational hint, and to align descendants to
the left.
The caption
, thead
, tbody
, tfoot
,
tr
, td
, and th
elements, when they have an align
attribute whose value is an ASCII case-insensitive
match for the string "right
", are expected to right-align text within
themselves, as if they had their 'text-align' property set to 'right' in a presentational hint, and to align descendants to
the right.
The caption
, thead
, tbody
, tfoot
,
tr
, td
, and th
elements, when they have an align
attribute whose value is an ASCII case-insensitive
match for the string "justify
", are expected to full-justify text within
themselves, as if they had their 'text-align' property set to 'justify' in a presentational hint, and to align descendants to
the left.
User agents are expected to have a rule in their user agent stylesheet that matches
th
elements that have a parent node whose computed value for the 'text-align'
property is its initial value, whose declaration block consists of just a single declaration that
sets the 'text-align' property to the value 'center'.
When a table
, thead
, tbody
, tfoot
,
tr
, td
, or th
element has a background
attribute set to a non-empty value, the new value is
expected to be resolved relative to the element, and if this is
successful, the user agent is expected to treat the attribute as a presentational hint setting the element's 'background-image' property to the
resulting absolute URL.
When a table
, thead
, tbody
, tfoot
,
tr
, td
, or th
element has a bgcolor
attribute set, the new value is expected to be parsed using the rules for parsing a legacy
color value, and if that does not return an error, the user agent is expected to treat the
attribute as a presentational hint setting the element's
'background-color' property to the resulting color.
When a table
element has a bordercolor
attribute, its value is expected to be parsed using the rules for parsing a legacy color
value, and if that does not return an error, the user agent is expected to treat the
attribute as a presentational hint setting the element's
'border-top-color', 'border-right-color', 'border-bottom-color', and 'border-right-color'
properties to the resulting color.
The table
element's border
attribute maps to the pixel length properties
'border-top-width', 'border-right-width', 'border-bottom-width', 'border-left-width' on the
element. If the attribute is present but parsing the attribute's value using the rules for
parsing non-negative integers generates an error, a default value of 1px is expected to be
used for that property instead.
Rules marked "only if border is not equivalent to zero"
in the CSS block above is expected to only be applied if the border
attribute mentioned in the selectors for the rule is not
only present but, when parsed using the rules for parsing non-negative integers, is
also found to have a value other than zero or to generate an error.
In quirks mode, a td
element or a th
element that has a
nowrap
attribute but also has a width
attribute whose value, when parsed using the rules for
parsing dimension values, is found to be a length (not an error or a number classified as a
percentage), is expected to have a presentational hint
setting the element's 'white-space' property to 'normal', overriding the rule in the CSS block
above that sets it to 'nowrap'.
A node is substantial if it is a text node that is not inter-element whitespace, or if it is an element node.
A node is blank if it is an element that contains no substantial nodes.
The elements with default margins
are the following elements: blockquote
, dir
, dl
,
h1
, h2
, h3
, h4
, h5
,
h6
, listing
, multicol
, ol
,
p
, plaintext
, pre
, ul
, xmp
In quirks mode, any element
with default margins that is the child of a body
, td
, or
th
element and has no substantial
previous siblings is expected to have a user-agent level style sheet rule that sets its
'margin-top' property to zero.
In quirks mode, any element
with default margins that is the child of a body
, td
, or
th
element, has no substantial
previous siblings, and is blank, is expected to have
a user-agent level style sheet rule that sets its 'margin-bottom' property to zero also.
In quirks mode, any element
with default margins that is the child of a td
or th
element, has
no substantial following siblings, and is blank, is expected to have a user-agent level style sheet
rule that sets its 'margin-top' property to zero.
In quirks mode, any p
element that is the child of a td
or th
element and has no substantial following siblings, is expected to have a
user-agent level style sheet rule that sets its 'margin-bottom' property to zero.
@namespace url(http://www.w3.org/1999/xhtml); input, select, option, optgroup, button, textarea, keygen { text-indent: initial; } textarea { white-space: pre-wrap; } input[type="radio"], input[type="checkbox"], input[type="reset"], input[type="button"], input[type="submit"], select, button { box-sizing: border-box; }
In quirks mode, the following rules are also expected to apply:
@namespace url(http://www.w3.org/1999/xhtml); input:not([type=image]), textarea { box-sizing: border-box; }
Each kind of form control is also given a specific default binding, as described in subsequent sections, which implements the look and feel of the control.
hr
element@namespace url(http://www.w3.org/1999/xhtml); hr { color: gray; border-style: inset; border-width: 1px; margin: 0.5em auto; }
The following rules are also expected to apply, as presentational hints:
@namespace url(http://www.w3.org/1999/xhtml); hr[align=left] { margin-left: 0; margin-right: auto; } hr[align=right] { margin-left: auto; margin-right: 0; } hr[align=center] { margin-left: auto; margin-right: auto; } hr[color], hr[noshade] { border-style: solid; }
If an hr
element has either a color
attribute
or a noshade
attribute, and furthermore also has a size
attribute, and parsing that attribute's value using the
rules for parsing non-negative integers doesn't generate an error, then the user
agent is expected to use the parsed value divided by two as a pixel length for
presentational hints for the properties 'border-top-width', 'border-right-width',
'border-bottom-width', and 'border-left-width' on the element.
Otherwise, if an hr
element has neither a color
attribute nor a noshade
attribute, but does have a size
attribute, and parsing that attribute's value using the
rules for parsing non-negative integers doesn't generate an error, then: if the
parsed value is one, then the user agent is expected to use the attribute as a presentational hint setting the element's
'border-bottom-width' to 0; otherwise, if the parsed value is greater than one, then the user
agent is expected to use the parsed value minus two as a pixel length for presentational
hints for the 'height' property on the element.
The width
attribute on an hr
element maps
to the dimension property 'width' on the element.
When an hr
element has a color
attribute, its
value is expected to be parsed using the rules for parsing a legacy color value, and
if that does not return an error, the user agent is expected to treat the attribute as a presentational hint setting the element's 'color' property to
the resulting color.
fieldset
and legend
elements@namespace url(http://www.w3.org/1999/xhtml); fieldset { margin-left: 2px; margin-right: 2px; border: groove 2px ThreeDFace; padding: 0.35em 0.625em 0.75em; } legend { padding-left: 2px; padding-right: 2px; }
The fieldset
element is expected to establish a new block formatting context.
If the fieldset
element has a child that matches the conditions in the list below,
then the first such child is the fieldset
element's rendered legend:
legend
element.A fieldset
element's rendered legend, if any, is expected to be
rendered over the top border edge of the fieldset
element as a 'block' box
(overriding any explicit 'display' value). In the absence of an explicit width, the box should
shrink-wrap. If the legend
element in question has an align
attribute, and its value is an ASCII
case-insensitive match for one of the strings in the first column of the following table,
then the legend
is expected to be rendered horizontally aligned over the border edge
in the position given in the corresponding cell on the same row in the second column. If the
attribute is absent or has a value that doesn't match any of the cases in the table, then the
position is expected to be on the right if the 'direction' property on this element has a computed
value of 'rtl', and on the left otherwise.
Attribute value | Alignment position |
---|---|
left
| On the left |
right
| On the right |
center
| In the middle |
The embed
, iframe
, and video
elements are expected to be
treated as replaced elements.
A canvas
element that represents embedded content is
expected to be treated as a replaced element; the contents of such elements are the element's
bitmap, if any, or else a transparent black bitmap with the same intrinsic dimensions as the
element. Other canvas
elements are expected to be treated as ordinary elements in the
rendering model.
An object
element that represents an image, plugin, or nested
browsing context is expected to be treated as a replaced element. Other object
elements are expected to be treated as ordinary elements in the rendering model.
An applet
element that represents a plugin is expected
to be treated as a replaced element. Other applet
elements are expected to be treated
as ordinary elements in the rendering model.
The audio
element, when it is exposing a user interface, is expected to be treated as a replaced element about one
line high, as wide as is necessary to expose the user agent's user interface features. When an
audio
element is not exposing a
user interface, the user agent is expected to force its 'display' property to compute to
'none', irrespective of CSS rules.
Whether a video
element is exposing a user interface is not expected to affect the size of the rendering;
controls are expected to be overlaid above the page content without causing any layout changes,
and are expected to disappear when the user does not need them.
When a video
element represents a poster frame or frame of video, the poster frame
or frame of video is expected to be rendered at the largest size that maintains the aspect ratio
of that poster frame or frame of video without being taller or wider than the video
element itself, and is expected to be centered in the video
element.
Any subtitles or captions are expected to be overlayed directly on top of their
video
element, as defined by the relevant rendering rules; for WebVTT,
those are the rules for updating the display of WebVTT text tracks. [WEBVTT]
When the user agent starts exposing a user
interface for a video
element, the user agent should run the rules for
updating the text track rendering of each of the text
tracks in the video
element's list of text tracks that are showing and whose text track kind is one of subtitles
or captions
(e.g., for text
tracks based on WebVTT, the rules for updating the display of WebVTT
text tracks). [WEBVTT]
Resizing video
and canvas
elements does not interrupt
video playback or clear the canvas.
The following CSS rules are expected to apply:
@namespace url(http://www.w3.org/1999/xhtml);
iframe:not([seamless]) { border: 2px inset; }
iframe[seamless] { display: block; }
video { object-fit: contain; }
User agents are expected to render img
elements and input
elements
whose type
attributes are in the Image Button state, according to the first applicable rules
from the following list:
alt
attribute, or
Document
is in quirks mode
input
elements, the element is expected to
appear button-like to indicate that the element is a button.img
element that represents some text and the
user agent does not expect this to changeimg
element that represents nothing and the
user agent does not expect this to changeinput
element that does not represent an image and the user agent does not expect this to changeThe icons mentioned above are expected to be relatively small so as not to disrupt most text but be easily clickable. In a visual environment, for instance, icons could be 16 pixels by 16 pixels square, or 1em by 1em if the images are scalable. In an audio environment, the icon could be a short bleep. The icons are intended to indicate to the user that they can be used to get to whatever options the UA provides for images, and, where appropriate, are expected to provide access to the context menu that would have come up if the user interacted with the actual image.
All animated images with the same absolute URL and the same image data are expected to be rendered synchronized to the same timeline as a group, with the timeline starting at the time of the most recent addition to the group.
In other words, the animation loop of an animated image is restarted each time another image with the same absolute URL and image data begins to animate, e.g. after being inserted into the document.
The following CSS rules are expected to apply when the Document
is in quirks
mode:
@namespace url(http://www.w3.org/1999/xhtml); img[align=left i] { margin-right: 3px; } img[align=right i] { margin-left: 3px; }
The following CSS rules are expected to apply as presentational hints:
@namespace url(http://www.w3.org/1999/xhtml); iframe[frameborder=0], iframe[frameborder=no i] { border: none; } applet[align=left i], embed[align=left i], iframe[align=left i], img[align=left i], input[type=image i][align=left i], object[align=left i] { float: left; } applet[align=right i], embed[align=right i], iframe[align=right i], img[align=right i], input[type=image i][align=right i], object[align=right i] { float: right; } applet[align=top i], embed[align=top i], iframe[align=top i], img[align=top i], input[type=image i][align=top i], object[align=top i] { vertical-align: top; } applet[align=baseline i], embed[align=baseline i], iframe[align=baseline i], img[align=baseline i], input[type=image i][align=baseline i], object[align=baseline i] { vertical-align: baseline; } applet[align=texttop i], embed[align=texttop i], iframe[align=texttop i], img[align=texttop i], input[type=image i][align=texttop i], object[align=texttop i] { vertical-align: text-top; } applet[align=absmiddle i], embed[align=absmiddle i], iframe[align=absmiddle i], img[align=absmiddle i], input[type=image i][align=absmiddle i], object[align=absmiddle i], applet[align=abscenter i], embed[align=abscenter i], iframe[align=abscenter i], img[align=abscenter i], input[type=image i][align=abscenter i], object[align=abscenter i] { vertical-align: middle; } applet[align=bottom i], embed[align=bottom i], iframe[align=bottom i], img[align=bottom i], input[type=image i][align=bottom i], object[align=bottom i] { vertical-align: bottom; }
When an applet
, embed
, iframe
, img
, or
object
element, or an input
element whose type
attribute is in the Image
Button state, has an align
attribute whose value is an
ASCII case-insensitive match for the string "center
" or the
string "middle
", the user agent is expected to act as if the element's
'vertical-align' property was set to a value that aligns the vertical middle of the element with
the parent element's baseline.
The hspace
attribute of applet
,
embed
, iframe
, img
, or object
elements, and
input
elements with a type
attribute in the
Image Button state, maps to the dimension properties 'margin-left' and 'margin-right' on the
element.
The vspace
attribute of applet
,
embed
, iframe
, img
, or object
elements, and
input
elements with a type
attribute in the
Image Button state, maps to the dimension properties 'margin-top' and 'margin-bottom' on the
element.
When an img
element, object
element, or input
element
with a type
attribute in the Image Button state has a border
attribute whose value, when parsed using the rules for
parsing non-negative integers, is found to be a number greater than zero, the user agent is
expected to use the parsed value for eight presentational hints: four setting the
parsed value as a pixel length for the element's 'border-top-width', 'border-right-width',
'border-bottom-width', and 'border-left-width' properties, and four setting the element's
'border-top-style', 'border-right-style', 'border-bottom-style', and 'border-left-style'
properties to the value 'solid'.
The width
and height
attributes on applet
, embed
,
iframe
, object
or video
elements, and input
elements with a type
attribute in the Image Button state and that either represents an image or
that the user expects will eventually represent an image, map to the dimension properties 'width' and 'height' on the element
respectively.
Shapes on an image map are expected to act, for the purpose of the CSS cascade, as
elements independent of the original area
element that happen to match the same style
rules but inherit from the img
or object
element.
For the purposes of the rendering, only the 'cursor' property is expected to have any effect on the shape.
Thus, for example, if an area
element has a style
attribute that sets the 'cursor' property to 'help', then when the
user designates that shape, the cursor would change to a Help cursor.
Similarly, if an area
element had a CSS rule that set its 'cursor'
property to 'inherit' (or if no rule setting the 'cursor' property matched the element at all),
the shape's cursor would be inherited from the img
or object
element of
the image map, not from the parent of the area
element.
A number of elements have their rendering defined in terms of the 'binding' property. [BECSS]
The CSS snippets below set the 'binding' property to a user-agent-defined value, represented
below by keywords like button
. The rules then described for
these bindings are only expected to apply if the element's 'binding' property has not been
overridden (e.g. by the author) to have another value.
Exactly how the bindings are implemented is not specified by this specification. User agents are encouraged to make their bindings set the 'appearance' CSS property appropriately to achieve platform-native appearances for widgets, and are expected to implement any relevant animations, etc, that are appropriate for the platform. [CSSUI]
button
element@namespace url(http://www.w3.org/1999/xhtml); button { binding: button; }
When the button binding applies to a button
element, the element
is expected to render as an 'inline-block' box rendered as a button whose contents are the
contents of the element.
details
element@namespace url(http://www.w3.org/1999/xhtml); details { binding: details; }
When the details binding applies to a details
element, the element
is expected to render as a 'block' box with its 'padding-left' property set to '40px' for
left-to-right elements (LTR-specific) and with its 'padding-right' property set to
'40px' for right-to-left elements. The element's shadow tree is expected to take the element's
first child summary
element, if any, and place it in a first 'block' box container,
and then take the element's remaining descendants, if any, and place them in a second 'block' box
container.
The first container is expected to contain at least one line box, and that line box is expected
to contain a disclosure widget (typically a triangle), horizontally positioned within the left
padding of the details
element. That widget is expected to allow the user to request
that the details be shown or hidden.
The second container is expected to have its 'overflow' property set to 'hidden'. When the
details
element does not have an open
attribute, this second container is expected to be removed from the rendering.
input
element as a text entry widget@namespace url(http://www.w3.org/1999/xhtml); input { binding: input-textfield; } input[type=password i] { binding: input-password; } /* later rules override this for other values of type="" */
When the input-textfield binding applies to an input
element whose
type
attribute is in the Text, Search,
Telephone, URL,
or E-mail state, the element is expected to render as
an 'inline-block' box rendered as a text field.
When the input-password binding applies, to an input
element whose
type
attribute is in the Password state, the element is expected to render as an
'inline-block' box rendered as a text field whose contents are obscured.
If an input
element whose type
attribute is
in one of the above states has a size
attribute, and parsing
that attribute's value using the rules for parsing non-negative integers doesn't
generate an error, then the user agent is expected to use the attribute as a presentational hint for the 'width' property on the element,
with the value obtained from applying the converting a character width to pixels
algorithm to the value of the attribute.
If an input
element whose type
attribute is
in one of the above states does not have a size
attribute, then the user agent is expected to act as if it had a user-agent-level style sheet rule
setting the 'width' property on the element to the value obtained from applying the
converting a character width to pixels algorithm to the number 20.
The converting a character width to pixels algorithm returns (size-1)×avg + max, where size is the character width to convert, avg is the average character width of the primary font for the element for which the algorithm is being run, in pixels, and max is the maximum character width of that same font, also in pixels. (The element's 'letter-spacing' property does not affect the result.)
input
element as domain-specific widgets@namespace url(http://www.w3.org/1999/xhtml); input[type=datetime i] { binding: input-datetime; } input[type=date i] { binding: input-date; } input[type=month i] { binding: input-month; } input[type=week i] { binding: input-week; } input[type=time i] { binding: input-time; } input[type=datetime-local i] { binding: input-datetime-local; } input[type=number i] { binding: input-number; }
When the input-datetime binding applies to an input
element whose
type
attribute is in the Date and Time state, the element is expected to render as
an 'inline-block' box depicting a Date and Time control.
When the input-date binding applies to an input
element whose
type
attribute is in the Date state, the element is expected to render as an
'inline-block' box depicting a Date control.
When the input-month binding applies to an input
element whose
type
attribute is in the Month state, the element is expected to render as an
'inline-block' box depicting a Month control.
When the input-week binding applies to an input
element whose
type
attribute is in the Week state, the element is expected to render as an
'inline-block' box depicting a Week control.
When the input-time binding applies to an input
element whose
type
attribute is in the Time state, the element is expected to render as an
'inline-block' box depicting a Time control.
When the input-datetime-local binding applies to an input
element
whose type
attribute is in the Local Date and Time state, the element is expected
to render as an 'inline-block' box depicting a Local Date and Time control.
When the input-number binding applies to an input
element whose
type
attribute is in the Number state, the element is expected to render as an
'inline-block' box depicting a Number control.
These controls are all expected to be about one line high, and about as wide as necessary to show the widest possible value.
input
element as a range control@namespace url(http://www.w3.org/1999/xhtml); input[type=range i] { binding: input-range; }
When the input-range binding applies to an input
element whose
type
attribute is in the Range state, the element is expected to render as an
'inline-block' box depicting a slider control.
When the control is wider than it is tall (or square), the control is expected to be a horizontal slider, with the lowest value on the right if the 'direction' property on this element has a computed value of 'rtl', and on the left otherwise. When the control is taller than it is wide, it is expected to be a vertical slider, with the lowest value on the bottom.
Predefined suggested values (provided by the list
attribute) are expected to be shown as tick marks on the slider, which the slider can snap to.
User agents are expected to use the used value of the 'direction' property on the element to determine the direction in which the slider operates. Typically, a left-to-right ('ltr') horizontal control would have the lowest value on the left and the highest value on the right, and vice versa.
input
element as a color well@namespace url(http://www.w3.org/1999/xhtml); input[type=color i] { binding: input-color; }
When the input-color binding applies to an input
element whose
type
attribute is in the Color state, the element is expected to render as an
'inline-block' box depicting a color well, which, when activated, provides the user with a color
picker (e.g. a color wheel or color palette) from which the color can be changed.
Predefined suggested values (provided by the list
attribute) are expected to be shown in the color picker interface, not on the color well
itself.
input
element as a checkbox and radio button widgets@namespace url(http://www.w3.org/1999/xhtml); input[type=checkbox i] { binding: input-checkbox; } input[type=radio i] { binding: input-radio; }
When the input-checkbox binding applies to an input
element whose
type
attribute is in the Checkbox state, the element is expected to render as an
'inline-block' box containing a single checkbox control, with no label.
When the input-radio binding applies to an input
element whose
type
attribute is in the Radio Button state, the element is expected to render as an
'inline-block' box containing a single radio button control, with no label.
input
element as a file upload control@namespace url(http://www.w3.org/1999/xhtml); input[type=file i] { binding: input-file; }
When the input-file binding applies to an input
element whose
type
attribute is in the File Upload state, the element is expected to render as an
'inline-block' box containing a span of text giving the file name(s) of the selected files, if any, followed by a button that,
when activated, provides the user with a file picker from which the selection can be changed.
input
element as a button@namespace url(http://www.w3.org/1999/xhtml); input[type=submit i], input[type=reset i], input[type=button i] { binding: input-button; }
When the input-button binding applies to an input
element whose
type
attribute is in the Submit Button, Reset
Button, or Button state, the element is
expected to render as an 'inline-block' box rendered as a button, about one line high, containing
the contents of the element's value
attribute, if any, or
text derived from the element's type
attribute in a
user-agent-defined (and probably locale-specific) fashion, if not.
marquee
element@namespace url(http://www.w3.org/1999/xhtml); marquee { binding: marquee; }
When the marquee binding applies to a marquee
element, while the
element is turned on, the element is expected to render in
an animated fashion according to its attributes as follows:
behavior
attribute is in the
scroll stateSlide the contents of the element in the direction described by the direction
attribute as defined below, such that it begins
off the start side of the marquee
, and ends flush with the inner end side.
For example, if the direction
attribute is left (the default), then the
contents would start such that their left edge are off the side of the right edge of the
marquee
's content area, and the contents would then slide up to the point where the
left edge of the contents are flush with the left inner edge of the marquee
's
content area.
Once the animation has ended, the user agent is expected to increment the marquee current loop index. If the element is still turned on after this, then the user agent is expected to restart the animation.
behavior
attribute is in the
slide stateSlide the contents of the element in the direction described by the direction
attribute as defined below, such that it begins
off the start side of the marquee
, and ends off the end side of the
marquee
.
For example, if the direction
attribute is left (the default), then the
contents would start such that their left edge are off the side of the right edge of the
marquee
's content area, and the contents would then slide up to the point where the
right edge of the contents are flush with the left inner edge of the
marquee
's content area.
Once the animation has ended, the user agent is expected to increment the marquee current loop index. If the element is still turned on after this, then the user agent is expected to restart the animation.
behavior
attribute is in the
alternate stateWhen the marquee current loop index is even (or zero), slide the contents of the
element in the direction described by the direction
attribute as defined below, such that it begins flush with the start side of the
marquee
, and ends flush with the end side of the marquee
.
When the marquee current loop index is odd, slide the contents of the element in
the opposite direction than that described by the direction
attribute as defined below, such that it begins
flush with the end side of the marquee
, and ends flush with the start side of the
marquee
.
For example, if the direction
attribute is left (the default), then the
contents would with their right edge flush with the right inner edge of the
marquee
's content area, and the contents would then slide up to the point where the
left edge of the contents are flush with the left inner edge of the
marquee
's content area.
Once the animation has ended, the user agent is expected to increment the marquee current loop index. If the element is still turned on after this, then the user agent is expected to continue the animation.
The direction
attribute has the meanings described
in the following table:
direction attribute state
| Direction of animation | Start edge | End edge | Opposite direction |
---|---|---|---|---|
left | ← Right to left | Right | Left | → Left to Right |
right | → Left to Right | Left | Right | ← Right to left |
up | ↑ Up (Bottom to Top) | Bottom | Top | ↓ Down (Top to Bottom) |
down | ↓ Down (Top to Bottom) | Top | Bottom | ↑ Up (Bottom to Top) |
In any case, the animation should proceed such that there is a delay given by the marquee scroll interval between each frame, and such that the content moves at most the distance given by the marquee scroll distance with each frame.
When a marquee
element has a bgcolor
attribute set, the value is expected to be parsed using the rules for parsing a legacy color
value, and if that does not return an error, the user agent is expected to treat the
attribute as a presentational hint setting the element's
'background-color' property to the resulting color.
The width
and height
attributes on a marquee
element map to the dimension properties 'width' and 'height'
on the element respectively.
The intrinsic height of a marquee
element with its direction
attribute in the up or down states is 200 CSS pixels.
The vspace
attribute of a marquee
element
maps to the dimension properties 'margin-top'
and 'margin-bottom' on the element. The hspace
attribute
of a marquee
element maps to the
dimension properties 'margin-left' and 'margin-right' on the element.
The 'overflow' property on the marquee
element is expected to be ignored; overflow
is expected to always be hidden.
meter
element@namespace url(http://www.w3.org/1999/xhtml); meter { binding: meter; }
When the meter binding applies to a meter
element, the element is
expected to render as an 'inline-block' box with a 'height' of '1em' and a 'width' of '5em', a
'vertical-align' of '-0.2em', and with its contents depicting a gauge.
When the element is wider than it is tall (or square), the depiction is expected to be of a horizontal gauge, with the minimum value on the right if the 'direction' property on this element has a computed value of 'rtl', and on the left otherwise. When the element is taller than it is wide, it is expected to depict a vertical gauge, with the minimum value on the bottom.
User agents are expected to use a presentation consistent with platform conventions for gauges, if any.
Requirements for what must be depicted in the gauge are included in the definition
of the meter
element.
progress
element@namespace url(http://www.w3.org/1999/xhtml); progress { binding: progress; }
When the progress binding applies to a progress
element, the
element is expected to render as an 'inline-block' box with a 'height' of '1em' and a 'width' of
'10em', and a 'vertical-align' of '-0.2em'.
When the
element is wider than it is tall, the element is expected to be depicted as a horizontal progress
bar, with the start on the right and the end on the left if the 'direction' property on this
element has a computed value of 'rtl', and with the start on the left and the end on the right
otherwise. When the element is taller than it is wide, it is expected to depicted as a vertical
progress bar, with the lowest value on the bottom. When the element is square, it is expected to
be depicted as a direction-independent progress widget (e.g. a circular progress ring).
User agents are expected to use a presentation consistent with platform conventions for progress bars. In particular, user agents are expected to use different presentations for determinate and indeterminate progress bars. User agents are also expected to vary the presentation based on the dimensions of the element.
For example, on some platforms for showing indeterminate progress there is an asynchronous progress indicator with square dimensions, which could be used when the element is square, and an indeterminate progress bar, which could be used when the element is wide.
Requirements for how to determine if the progress bar is determinate or
indeterminate, and what progress a determinate progress bar is to show, are included in the
definition of the progress
element.
select
element@namespace url(http://www.w3.org/1999/xhtml); select { binding: select; }
When the select binding applies to a select
element whose multiple
attribute is present, the element is expected to
render as a multi-select list box.
When the select binding applies to a select
element whose multiple
attribute is absent, and the element's display size is greater than 1, the element is expected to
render as a single-select list box.
When the element renders as a list box, it is expected to render as an 'inline-block' box whose
'height' is the height necessary to contain as many rows for items as given by the element's display size, or four rows if the attribute is absent, and
whose 'width' is the width of the select
's labels plus the width of a
scrollbar.
When the select binding applies to a select
element whose multiple
attribute is absent, and the element's display size is 1, the element is expected to render as a
one-line drop down box whose width is the width of the select
's
labels.
In either case (list box or drop-down box), the element's items are expected to be the
element's list of options, with the element's
optgroup
element children providing headers for groups of options where
applicable.
An optgroup
element is expected to be rendered by displaying the element's label
attribute.
An option
element is expected to be rendered by displaying the element's label, indented under its optgroup
element if it
has one.
The width of the select
's labels is the wider of the width necessary to
render the widest optgroup
, and the width necessary to render the widest
option
element in the element's list of
options (including its indent, if any).
If a select
element contains a placeholder label option, the user
agent is expected to render that option
in a manner that conveys that it is a label,
rather than a valid option of the control. This can include preventing the placeholder label
option from being explicitly selected by the user. When the placeholder label
option's selectedness is true, the control
is expected to be displayed in a fashion that indicates that no valid option is currently
selected.
User agents are expected to render the labels in a select
in such a manner that
any alignment remains consistent whether the label is being displayed as part of the page or in a
menu control.
textarea
element@namespace url(http://www.w3.org/1999/xhtml); textarea { binding: textarea; white-space: pre-wrap; }
When the textarea binding applies to a textarea
element, the
element is expected to render as an 'inline-block' box rendered as a multiline text field.
If the element has a cols
attribute, and parsing that
attribute's value using the rules for parsing non-negative integers doesn't generate
an error, then the user agent is expected to use the attribute as a presentational hint for the 'width' property on the element, with the value being
the textarea effective width (as defined below). Otherwise, the user agent is
expected to act as if it had a user-agent-level style sheet rule setting the 'width' property on
the element to the textarea effective width.
The textarea effective width of a textarea
element is size×avg + sbw, where size is the element's character width, avg is the average
character width of the primary font of the element, in CSS pixels, and sbw is
the width of a scroll bar, in CSS pixels. (The element's 'letter-spacing' property does not affect
the result.)
If the element has a rows
attribute, and parsing that
attribute's value using the rules for parsing non-negative integers doesn't generate
an error, then the user agent is expected to use the attribute as a presentational hint for the 'height' property on the element, with the value being
the textarea effective height (as defined below). Otherwise, the user agent is
expected to act as if it had a user-agent-level style sheet rule setting the 'height' property on
the element to the textarea effective height.
The textarea effective height of a textarea
element is the height in
CSS pixels of the number of lines specified the element's character height, plus the height of a scrollbar in CSS
pixels.
User agents are expected to apply the 'white-space' CSS property to textarea
elements. For historical reasons, if the element has a wrap
attribute whose value is an ASCII
case-insensitive match for the string "off
",
then the user agent is expected to treat the attribute as a presentational hint setting the element's 'white-space' property to 'pre'.
keygen
element@namespace url(http://www.w3.org/1999/xhtml); keygen { binding: keygen; }
When the keygen binding applies to a keygen
element, the element
is expected to render as an 'inline-block' box containing a user interface to configure the key
pair to be generated.
User agent are expected to render frameset
elements as a box with the height and
width of the viewport, with a surface rendered according to the following layout algorithm:
The cols and rows variables are lists of zero or more pairs consisting of a number and a unit, the unit being one of percentage, relative, and absolute.
Use the rules for parsing a list of dimensions to parse the value of the
element's cols
attribute, if there is one. Let cols be the result, or an empty list if there is no such attribute.
Use the rules for parsing a list of dimensions to parse the value of the
element's rows
attribute, if there is one. Let rows be the result, or an empty list if there is no such attribute.
For any of the entries in cols or rows that have the number zero and the unit relative, change the entry's number to one.
If cols has no entries, then add a single entry consisting of the value 1 and the unit relative to cols.
If rows has no entries, then add a single entry consisting of the value 1 and the unit relative to rows.
Invoke the algorithm defined below to convert a list of dimensions to a list of pixel
values using cols as the input list, and the width of the surface
that the frameset
is being rendered into, in CSS pixels, as the input dimension.
Let sized cols be the resulting list.
Invoke the algorithm defined below to convert a list of dimensions to a list of pixel
values using rows as the input list, and the height of the surface
that the frameset
is being rendered into, in CSS pixels, as the input dimension.
Let sized rows be the resulting list.
Split the surface into a grid of w×h rectangles, where w is the number of entries in sized cols and h is the number of entries in sized rows.
Size the columns so that each column in the grid is as many CSS pixels wide as the corresponding entry in the sized cols list.
Size the rows so that each row in the grid is as many CSS pixels high as the corresponding entry in the sized rows list.
Let children be the list of frame
and frameset
elements that are children of the frameset
element for which the algorithm was
invoked.
For each row of the grid of rectangles created in the previous step, from top to bottom, run these substeps:
For each rectangle in the row, from left to right, run these substeps:
If there are any elements left in children, take the first element in the list, and assign it to the rectangle.
If this is a frameset
element, then recurse the entire frameset
layout algorithm for that frameset
element, with the rectangle as the
surface.
Otherwise, it is a frame
element; create a nested browsing
context sized to fit the rectangle.
If there are any elements left in children, remove the first element from children.
If the frameset
element has a border, draw an outer set of borders
around the rectangles, using the element's frame border color.
For each rectangle, if there is an element assigned to that rectangle, and that element has a border, draw an inner set of borders around that rectangle, using the element's frame border color.
For each (visible) border that does not abut a rectangle that is assigned a
frame
element with a noresize
attribute
(including rectangles in further nested frameset
elements), the user agent is
expected to allow the user to move the border, resizing the rectangles within, keeping the
proportions of any nested frameset
grids.
A frameset
or frame
element has a border if the
following algorithm returns true:
If the element has a frameborder
attribute
whose value is not the empty string and whose first character is either a "1" (U+0031)
character, a "y" (U+0079) character, or a "Y" (U+0059) character, then return true.
Otherwise, if the element has a frameborder
attribute, return false.
Otherwise, if the element has a parent element that is a frameset
element,
then return true if that element has a border, and false if it does
not.
Otherwise, return true.
The frame border color of a frameset
or frame
element is
the color obtained from the following algorithm:
If the element has a bordercolor
attribute,
and applying the rules for parsing a legacy color value to that attribute's value
does not result in an error, then return the color so obtained.
Otherwise, if the element has a parent element that is a frameset
element,
then return the frame border color of that element.
Otherwise, return gray.
The algorithm to convert a list of dimensions to a list of pixel values consists of the following steps:
Let input list be the list of numbers and units passed to the algorithm.
Let output list be a list of numbers the same length as input list, all zero.
Entries in output list correspond to the entries in input list that have the same position.
Let input dimension be the size passed to the algorithm.
Let count percentage be the number of entries in input list whose unit is percentage.
Let total percentage be the sum of all the numbers in input list whose unit is percentage.
Let count relative be the number of entries in input list whose unit is relative.
Let total relative be the sum of all the numbers in input list whose unit is relative.
Let count absolute be the number of entries in input list whose unit is absolute.
Let total absolute be the sum of all the numbers in input list whose unit is absolute.
Let remaining space be the value of input dimension.
If total absolute is greater than remaining space, then for each entry in input list whose unit is absolute, set the corresponding value in output list to the number of the entry in input list multiplied by remaining space and divided by total absolute. Then, set remaining space to zero.
Otherwise, for each entry in input list whose unit is absolute, set the corresponding value in output list to the number of the entry in input list. Then, decrement remaining space by total absolute.
If total percentage multiplied by the input dimension and divided by 100 is greater than remaining space, then for each entry in input list whose unit is percentage, set the corresponding value in output list to the number of the entry in input list multiplied by remaining space and divided by total percentage. Then, set remaining space to zero.
Otherwise, for each entry in input list whose unit is percentage, set the corresponding value in output list to the number of the entry in input list multiplied by the input dimension and divided by 100. Then, decrement remaining space by total percentage multiplied by the input dimension and divided by 100.
For each entry in input list whose unit is relative, set the corresponding value in output list to the number of the entry in input list multiplied by remaining space and divided by total relative.
Return output list.
User agents working with integer values for frame widths (as opposed to user agents that can lay frames out with subpixel accuracy) are expected to distribute the remainder first to the last entry whose unit is relative, then equally (not proportionally) to each entry whose unit is percentage, then equally (not proportionally) to each entry whose unit is absolute, and finally, failing all else, to the last entry.
User agents are expected to allow the user to control aspects of hyperlink activation and form submission, such as which browsing context is to be used for the subsequent navigation.
User agents are expected to allow users to discover the destination of hyperlinks and of forms before triggering their navigation.
User agents may allow users to navigate browsing contexts to the resources indicated by
the cite
attributes on q
, blockquote
,
ins
, and del
elements.
User agents may surface hyperlinks created by link
elements in their user interface.
While link
elements that create hyperlinks will match the ':link' or ':visited' pseudo-classes, will
react to clicks if visible, and so forth, this does not extend to any browser interface constructs
that expose those same links. Activating a link through the browser's interface, rather than in
the page itself, does not trigger click
events and the like.
title
attributeUser agents are expected to expose the advisory information of elements upon user request, and to make the user aware of the presence of such information.
On interactive graphical systems where the user can use a pointing device, this could take the form of a tooltip. When the user is unable to use a pointing device, then the user agent is expected to make the content available in some other fashion, e.g. by making the element focusable and always displaying the advisory information of the currently focused element, or by showing the advisory information of the elements under the user's finger on a touch device as the user pans around the screen.
"LF" (U+000A) characters are expected to cause line breaks in the tooltip; "tab" (U+0009) characters are expected to render as a non-zero horizontal shift that lines up the next glyph with the next tab stop, with tab stops occurring at points that are multiples of 8 times the width of a U+0020 SPACE character.
For example, a visual user agent could make elements with a title
attribute focusable, and could make any focused element with a
title
attribute show its tooltip under the element while the
element has focus. This would allow a user to tab around the document to find all the advisory
text.
As another example, a screen reader could provide an audio cue when reading an element with a tooltip, with an associated key to read the last tooltip for which a cue was played.
The current text editing caret (i.e. the active range, if it is empty and in an editing host), if any, is expected to act like an inline replaced element with the vertical dimensions of the caret and with zero width for the purposes of the CSS rendering model.
This means that even an empty block can have the caret inside it, and that when the caret is in such an element, it prevents margins from collapsing through the element.
User agents are expected to honor the Unicode semantics of text that is exposed in user interfaces, for example supporting the bidirectional algorithm in text shown in dialogs, title bars, pop-up menus, and tooltips. Text from the contents of elements is expected to be rendered in a manner that honors the directionality of the element from which the text was obtained. Text from attributes is expected to be rendered in a manner that honours the directionality of the attribute.
Consider the following markup, which has Hebrew text asking for a programming language, the languages being text for which a left-to-right direction is important given the punctuation in some of their names:
<p dir="rtl" lang="he">
<label>
בחר שפת תכנות:
<select>
<option dir="ltr">C++</option>
<option dir="ltr">C#</option>
<option dir="ltr">FreePascal</option>
<option dir="ltr">F#</option>
</select>
</label>
</p>
If the select
element was rendered as a drop down box, a correct rendering would
ensure that the punctuation was the same both in the drop down, and in the box showing the
current selection.
The directionality of attributes depends on the attribute and on the element's dir
attribute, as the following example demonstrates. Consider this
markup:
<table> <tr> <th abbr="(א" dir=ltr>A <th abbr="(א" dir=rtl>A <th abbr="(א" dir=auto>A </table>
If the abbr
attributes are rendered, e.g. in a tooltip or
other user interface, the first will have a left parenthesis (because the direction is 'ltr'),
the second will have a right parenthesis (because the direction is 'rtl'), and the third will
have a right parenthesis (because the direction is determined from the attribute value
to be 'rtl').
However, if instead the attribute was not a directionality-capable attribute, the results would be different:
<table> <tr> <th data-abbr="(א" dir=ltr>A <th data-abbr="(א" dir=rtl>A <th data-abbr="(א" dir=auto>A </table>
In this case, if the user agent were to expose the data-abbr
attribute
in the user interface (e.g. in a debugging environment), the last case would be rendered with a
left parenthesis, because the direction would be determined from the element's
contents.
A string provided by a script (e.g. the argument to window.alert()
) is expected to be treated as an independent set of one or
more bidirectional algorithm paragraphs when displayed, as defined by the bidirectional algorithm,
including, for instance, supporting the paragraph-breaking behaviour of "LF" (U+000A)
characters. For the purposes of determining the paragraph level of such text in the bidirectional
algorithm, this specification does not provide a higher-level override of rules P2 and
P3. [BIDI]
When necessary, authors can enforce a particular direction for a given paragraph by starting it with the Unicode U+200E LEFT-TO-RIGHT MARK or U+200F RIGHT-TO-LEFT MARK characters.
Thus, the following script:
alert('\u05DC\u05DE\u05D3 HTML \u05D4\u05D9\u05D5\u05DD!')
...would always result in a message reading "למד LMTH היום!" (not "דמל HTML םויה!"), regardless of the language of the user agent interface or the direction of the page or any of its elements.
For a more complex example, consider the following script:
/* Warning: this script does not handle right-to-left scripts correctly */ var s; if (s = prompt('What is your name?')) { alert(s + '! Ok, Fred, ' + s + ', and Wilma will get the car.'); }
When the user enters "Kitty", the user agent would alert "Kitty! Ok, Fred, Kitty, and Wilma will get the car.". However, if the user enters "لا أفهم", then the bidirectional algorithm will determine that the direction of the paragraph is right-to-left, and so the output will be the following unintended mess: "لا أفهم! derF ,kO, لا أفهم, rac eht teg lliw amliW dna."
To force an alert that starts with user-provided text (or other text of unknown directionality) to render left-to-right, the string can be prefixed with a U+200E LEFT-TO-RIGHT MARK character:
var s; if (s = prompt('What is your name?')) { alert('\u200E' + s + '! Ok, Fred, ' + s + ', and Wilma will get the car.'); }
User agents are expected to allow the user to request the opportunity to obtain a physical
form (or a representation of a physical form) of a Document
. For example,
selecting the option to print a page or convert it to PDF format. [PDF]
When the user actually obtains a physical form (or
a representation of a physical form) of a Document
, the user agent is expected to
create a new rendering of the Document
for the print media.
HTML user agents may, in certain circumstances, find themselves rendering non-HTML documents that use vocabularies for which they lack any built-in knowledge. This section provides for a way for user agents to handle such documents in a somewhat useful manner.
While a Document
is an unstyled document, the user agent is expected
to render an unstyled document view.
A Document
is an unstyled document while it matches the following
conditions:
Document
has no author style sheets (whether referenced by HTTP headers, processing instructions, elements like link
, inline elements like style
, or any other mechanism).
Document
have any presentational hints.
Document
have any CSS styling attributes.
Document
are in any of the following namespaces: HTML namespace, SVG namespace, MathML namespace
Document
has no focusable elements (e.g. from XLink).
Document
has no hyperlinks (e.g. from XLink).
Document
as the responsible document.
Document
have any registered event listeners.
An unstyled document view is one where the DOM is not rendered according to CSS
(which would, since there are no applicable styles in this context, just result in a wall of
text), but is instead rendered in a manner that is useful for a developer. This could consist of
just showing the Document
object's source, maybe with syntax highlighting, or it
could consist of displaying just the DOM tree, or simply a message saying that the page is not a
styled document.
If a Document
stops being an unstyled document, then the
conditions above stop applying, and thus a user agent following these requirements will switch to
using the regular CSS rendering.
Features listed in this section will trigger warnings in conformance checkers.
Authors should not specify a border
attribute on an
img
element. If the attribute is present, its value must be the string "0
". CSS should be used instead.
Authors should not specify a language
attribute on a
script
element. If the attribute is present, its value must be an ASCII
case-insensitive match for the string "JavaScript
" and either the
type
attribute must be omitted or its value must be an
ASCII case-insensitive match for the string "text/javascript
".
The attribute should be entirely omitted instead (with the value "JavaScript
", it has no effect), or replaced with use of the type
attribute.
Authors should not specify the name
attribute on
a
elements. If the attribute is present, its value must not be the empty string and
must neither be equal to the value of any of the IDs in the
element's home subtree other than the element's own ID, if any, nor be equal to the value of any of the other name
attributes on a
elements in the element's home
subtree. If this attribute is present and the element has an ID, then the attribute's value must be equal to the element's ID. In earlier versions of the language, this attribute was intended as
a way to specify possible targets for fragment identifiers in URLs. The
id
attribute should be used instead.
Authors should not, but may despite requirements to the contrary elsewhere in this
specification, specify the maxlength
and size
attributes on input
elements whose type
attributes are in the Number state. One valid reason for using these attributes
regardless is to help legacy user agents that do not support input
elements with
type="number"
to still render the text field with a useful width.
In the HTML syntax, specifying a DOCTYPE that is an obsolete permitted DOCTYPE will also trigger a warning.
To ease the transition from HTML4 Transitional documents to the language defined in this specification, and to discourage certain features that are only allowed in very few circumstances, conformance checkers are required to warn the user when the following features are used in a document. These are generally old obsolete features that have no effect, and are allowed only to distinguish between likely mistakes (regular conformance errors) and mere vestigial markup or unusual and discouraged practices (these warnings).
The following features must be categorized as described above:
The presence of an obsolete permitted DOCTYPE in an HTML document.
The presence of a border
attribute on an
img
element if its value is the string "0
".
The presence of a language
attribute on a
script
element if its value is an ASCII case-insensitive match for the
string "JavaScript
" and if there is no type
attribute or there is and its value is an ASCII
case-insensitive match for the string "text/javascript
".
The presence of a name
attribute on an a
element, if its value is not the empty string.
The presence of a maxlength
attribute on an
input
element whose type
attribute is in the
Number state.
The presence of a size
attribute on an
input
element whose type
attribute is in the
Number state.
Conformance checkers must distinguish between pages that have no conformance errors and have none of these obsolete features, and pages that have no conformance errors but do have some of these obsolete features.
For example, a validator could report some pages as "Valid HTML" and others as "Valid HTML with warnings".
Elements in the following list are entirely obsolete, and must not be used by authors:
applet
acronym
Use abbr
instead.
bgsound
Use audio
instead.
dir
Use ul
instead.
frame
frameset
noframes
Either use iframe
and CSS instead, or use server-side includes to generate complete pages with the various invariant parts merged in.
hgroup
To mark up subheadings, consider putting the subheading into a p
element after the h1
-h6
element containing the main heading, or putting the subheading directly within the h1
-h6
element containing the main heading, but separated from the main heading by punctuation and/or within, for example, a span class="subheading"
element with differentiated styling.
Headings and subheadings, alternative titles, or taglines can be grouped using the header
or div
elements.
isindex
Use an explicit form
and text field combination instead.
listing
nextid
Use GUIDs instead.
noembed
plaintext
Use the "text/plain
" MIME type instead.
strike
Use del
instead if the element is marking an edit, otherwise use s
instead.
xmp
Use pre
and code
instead, and escape "<
" and "&
" characters as "<
" and "&
" respectively.
basefont
big
blink
center
font
marquee
multicol
nobr
spacer
tt
Use appropriate elements or CSS instead.
Where the tt
element would have been used for marking up keyboard input,
consider the kbd
element; for variables, consider the var
element; for
computer code, consider the code
element; and for computer output, consider the
samp
element.
Similarly, if the big
element is being used to denote a heading, consider using
the h1
element; if it is being used for marking up important passages, consider the
strong
element; and if it is being used for highlighting text for reference
purposes, consider the mark
element.
See also the text-level semantics usage summary for more suggestions with examples.
The following attributes are obsolete (though the elements are still part of the language), and must not be used by authors:
charset
on a
elementscharset
on link
elementsUse an HTTP Content-Type header on the linked resource instead.
coords
on a
elementsshape
on a
elementsmethods
on a
elementsmethods
on link
elementsUse the HTTP OPTIONS feature instead.
name
on a
elements (except as noted in the previous section)name
on embed
elementsname
on img
elementsname
on option
elementsUse the id
attribute instead.
rev
on a
elementsrev
on link
elementsUse the rel
attribute instead, with an opposite term. (For example, instead of
rev="made"
, use rel="author"
.)
urn
on a
elementsurn
on link
elementsSpecify the preferred persistent identifier using the href
attribute instead.
accept
on form
elementsUse the accept
attribute directly on the input
elements instead.
nohref
on area
elementsOmitting the href
attribute is sufficient; the nohref
attribute is
unnecessary. Omit it altogether.
profile
on head
elementsWhen used for declaring which meta
terms are
used in the document, unnecessary; omit it altogether, and register the names.
When used for triggering specific user agent behaviors: use
a link
element instead.
version
on html
elementsUnnecessary. Omit it altogether.
ismap
on input
elementsUnnecessary. Omit it altogether. All input
elements with a type
attribute in the Image
Button state are processed as server-side image maps.
usemap
on input
elementslowsrc
on img
elementsUse a progressive JPEG image (given in the src
attribute),
instead of using two separate images.
target
on link
elementsUnnecessary. Omit it altogether.
scheme
on meta
elementsUse only one scheme per field, or make the scheme declaration part of the value.
archive
on object
elementsclassid
on object
elementscode
on object
elementscodebase
on object
elementscodetype
on object
elementsUse the data
and type
attributes to invoke plugins. To set parameters with these names
in particular, the param
element can be used.
declare
on object
elementsRepeat the object
element completely each time the resource is to be reused.
standby
on object
elementsOptimize the linked resource so that it loads quickly or, at least, incrementally.
type
on param
elementsvaluetype
on param
elementsUse the name
and value
attributes without declaring
value types.
language
on script
elements (except as noted in the previous section)Use the type
attribute
instead.
event
on script
elementsfor
on script
elementsUse DOM Events mechanisms to register event listeners. [DOM]
datapagesize
on table
elementsUnnecessary. Omit it altogether.
summary
on table
elementsUse one of the techniques for describing
tables given in the table
section
instead.
axis
on td
and th
elementsscope
on td
elementsUse th
elements for heading cells.
datasrc
on a
, applet
, button
, div
, frame
, iframe
, img
, input
, label
, legend
, marquee
, object
, option
, select
, span
, table
, and textarea
elementsdatafld
on a
, applet
, button
, div
, fieldset
, frame
, iframe
, img
, input
, label
, legend
, marquee
, object
, param
, select
, span
, and textarea
elementsdataformatas
on button
, div
, input
, label
, legend
, marquee
, object
, option
, select
, span
, and table
elementsUse script and a mechanism such as XMLHttpRequest
to populate the page dynamically. [XHR]
alink
on body
elementsbgcolor
on body
elementslink
on body
elementsmarginbottom
on body
elementsmarginheight
on body
elementsmarginleft
on body
elementsmarginright
on body
elementsmargintop
on body
elementsmarginwidth
on body
elementstext
on body
elementsvlink
on body
elementsclear
on br
elementsalign
on caption
elementsalign
on col
elementschar
on col
elementscharoff
on col
elementsvalign
on col
elementswidth
on col
elementsalign
on div
elementscompact
on dl
elementsalign
on embed
elementshspace
on embed
elementsvspace
on embed
elementsalign
on hr
elementscolor
on hr
elementsnoshade
on hr
elementssize
on hr
elementswidth
on hr
elementsalign
on h1
—h6
elementsalign
on iframe
elementsallowtransparency
on iframe
elementsframeborder
on iframe
elementshspace
on iframe
elementsmarginheight
on iframe
elementsmarginwidth
on iframe
elementsscrolling
on iframe
elementsvspace
on iframe
elementsalign
on input
elementshspace
on input
elementsvspace
on input
elementsalign
on img
elementsborder
on img
elements (except as noted in the previous section)hspace
on img
elementsvspace
on img
elementsalign
on legend
elementstype
on li
elementsalign
on object
elementsborder
on object
elementshspace
on object
elementsvspace
on object
elementscompact
on ol
elementsalign
on p
elementswidth
on pre
elementsalign
on table
elementsbgcolor
on table
elementsbordercolor
on table
elementscellpadding
on table
elementscellspacing
on table
elementsframe
on table
elementsrules
on table
elementswidth
on table
elementsalign
on tbody
, thead
, and tfoot
elementschar
on tbody
, thead
, and tfoot
elementscharoff
on tbody
, thead
, and tfoot
elementsvalign
on tbody
, thead
, and tfoot
elementsalign
on td
and th
elementsbgcolor
on td
and th
elementschar
on td
and th
elementscharoff
on td
and th
elementsheight
on td
and th
elementsnowrap
on td
and th
elementsvalign
on td
and th
elementswidth
on td
and th
elementsalign
on tr
elementsbgcolor
on tr
elementschar
on tr
elementscharoff
on tr
elementsvalign
on tr
elementscompact
on ul
elementstype
on ul
elementsbackground
on body
, table
, thead
, tbody
, tfoot
, tr
, td
, and th
elementsUse CSS instead.
The border
attribute on
the table
element can be used to provide basic fallback
styling for the purpose of making tables legible in browsing
environments where CSS support is limited or absent, such as
text-based browsers, WYSIWYG editors, and in situations where CSS
support is disabled or the style sheet is lost. Only the empty
string and the value "1
" may be used as border
values for this purpose.
Other values are considered obsolete. To regulate the thickness of
such borders, authors should instead use CSS.
applet
elementThe applet
element is a Java-specific variant of the embed
element.
The applet
element is now obsoleted so that all extension frameworks (Java, .NET,
Flash, etc) are handled in a consistent manner.
When the element matches any of the following conditions, it represents its contents:
Document
.Document
is not fully active.Document
's active sandboxing flag
set has its sandboxed plugins browsing context flag set.object
element that is not showing its
fallback content.Otherwise, the user agent should instantiate a Java Language runtime plugin, and
should pass the names and values of all the attributes on the element, in the order they were
added to the element, with the attributes added by the parser being ordered in source order, and
then a parameter named "PARAM" whose value is null, and then all the names and values of parameters given by param
elements that are
children of the applet
element, in tree order, to the
plugin used. If the plugin supports a scriptable interface, the
HTMLAppletElement
object representing the element should expose that interface. The
applet
element represents the plugin.
The applet
element is unaffected by the CSS 'display' property. The
Java Language runtime is instantiated even if the element is hidden with a 'display:none' CSS
style.
The applet
element must implement the HTMLAppletElement
interface.
interface HTMLAppletElement : HTMLElement { attribute DOMString align; attribute DOMString alt; attribute DOMString archive; attribute DOMString code; attribute DOMString codeBase; attribute DOMString height; attribute unsigned long hspace; attribute DOMString name; attribute DOMString _object; // the underscore is not part of the identifier attribute unsigned long vspace; attribute DOMString width; };
The align
, alt
, archive
, code
, height
, hspace
, name
, object
, vspace
, and width
IDL attributes must reflect the
respective content attributes of the same name. For the purposes of reflection, the
applet
element's object
content attribute is
defined as containing a URL.
The codeBase
IDL attribute must
reflect the codebase
content attribute,
which for the purposes of reflection is defined as containing a URL.
marquee
elementThe marquee
element is a presentational element that animates content. CSS
transitions and animations are a more appropriate mechanism. [CSSANIMATIONS] [CSSTRANSITIONS]
The task source for tasks mentioned in this section is the DOM manipulation task source.
The marquee
element must implement the HTMLMarqueeElement
interface.
interface HTMLMarqueeElement : HTMLElement { attribute DOMString behavior; attribute DOMString bgColor; attribute DOMString direction; attribute DOMString height; attribute unsigned long hspace; attribute long loop; attribute unsigned long scrollAmount; attribute unsigned long scrollDelay; attribute boolean trueSpeed; attribute unsigned long vspace; attribute DOMString width; attribute EventHandler onbounce; attribute EventHandler onfinish; attribute EventHandler onstart; void start(); void stop(); };
A marquee
element can be turned on or turned off. When it is created, it is turned on.
When the start()
method is called, the
marquee
element must be turned on.
When the stop()
method is called, the
marquee
element must be turned off.
When a marquee
element is created, the user agent must queue a task
to fire a simple event named start
at the
element.
The behavior
content attribute on
marquee
elements is an enumerated attribute with the following keywords
(all non-conforming):
Keyword | State |
---|---|
scroll
| scroll |
slide
| slide |
alternate
| alternate |
The missing value default is the scroll state.
The direction
content attribute on
marquee
elements is an enumerated attribute with the following keywords
(all non-conforming):
Keyword | State |
---|---|
left
| left |
right
| right |
up
| up |
down
| down |
The missing value default is the left state.
The truespeed
content attribute on
marquee
elements is a boolean attribute.
A marquee
element has a marquee scroll interval, which is obtained as
follows:
If the element has a scrolldelay
attribute,
and parsing its value using the rules for parsing non-negative integers does not
return an error, then let delay be the parsed value. Otherwise, let delay be 85.
If the element does not have a truespeed
attribute, and the delay value is less than 60, then let delay be 60 instead.
The marquee scroll interval is delay, interpreted in milliseconds.
A marquee
element has a marquee scroll distance, which, if the element
has a scrollamount
attribute, and parsing its value
using the rules for parsing non-negative integers does not return an error, is the
parsed value interpreted in CSS pixels, and otherwise is 6 CSS pixels.
A marquee
element has a marquee loop count, which, if the element has a
loop
attribute, and parsing its value using the rules
for parsing integers does not return an error or a number less than 1, is the parsed value,
and otherwise is −1.
The loop
IDL attribute, on getting, must
return the element's marquee loop count; and on setting, if the new value is
different than the element's marquee loop count and either greater than zero or equal
to −1, must set the element's loop
content attribute
(adding it if necessary) to the valid integer that represents the new value. (Other
values are ignored.)
A marquee
element also has a marquee current loop index, which is zero
when the element is created.
The rendering layer will occasionally increment the marquee current loop index, which must cause the following steps to be run:
If the marquee loop count is −1, then abort these steps.
Increment the marquee current loop index by one.
If the marquee current loop index is now equal to or greater than the element's
marquee loop count, turn off the
marquee
element and queue a task to fire a simple event
named finish
at the marquee
element.
Otherwise, if the behavior
attribute is in the
alternate state, then queue a
task to fire a simple event named bounce
at the marquee
element.
Otherwise, queue a task to fire a simple event named start
at the marquee
element.
The following are the event handlers (and their corresponding event handler event types) that must be supported, as event handler content attributes and event handler IDL
attributes, by marquee
elements:
Event handler | Event handler event type |
---|---|
onbounce | bounce
|
onfinish | finish
|
onstart | start
|
The behavior
, direction
, height
, hspace
, vspace
, and width
IDL attributes must reflect the
respective content attributes of the same name.
The bgColor
IDL attribute must
reflect the bgcolor
content attribute.
The scrollAmount
IDL attribute must
reflect the scrollamount
content
attribute. The default value is 6.
The scrollDelay
IDL attribute must
reflect the scrolldelay
content
attribute. The default value is 85.
The trueSpeed
IDL attribute must
reflect the truespeed
content
attribute.
The frameset
element acts as the body element in documents
that use frames.
The frameset
element must implement the HTMLFrameSetElement
interface.
interface HTMLFrameSetElement : HTMLElement { attribute DOMString cols; attribute DOMString rows; }; HTMLFrameSetElement implements WindowEventHandlers;
The cols
and rows
IDL attributes of the frameset
element must reflect the respective content attributes of the same name.
The frameset
element exposes as event handler
content attributes a number of the event
handlers of the Window
object. It also mirrors
their event handler IDL attributes.
The onblur
, onerror
, onfocus
, onload
, onresize
,
and onscroll
event handlers of the
Window
object, exposed on the frameset
element, replace the generic
event handlers with the same names normally supported by HTML elements.
The frame
element defines a nested browsing context
similar to the iframe
element, but rendered within a frameset
element.
A frame
element is said to be an active frame
element when
it is in a Document
and its parent element, if any, is a
frameset
element.
When a frame
element is created as an active frame
element, or becomes an active frame
element after not having been
one, the user agent must create a nested browsing context, and then process the
frame
attributes for the first time.
When a frame
element stops being an active frame
element, the user agent must discard
the nested browsing context.
Whenever a frame
element with a nested browsing context has its src
attribute set, changed, or removed, the user agent must
process the frame
attributes.
When the user agent is to process the frame
attributes, it must run the
first appropriate steps from the following list:
src
attribute specified, and the
user agent is processing the frame
's attributes for the first timeQueue a task to fire a simple event named load
at the frame
element.
If the value of the src
attribute is the empty string,
let url be the string "about:blank
".
Otherwise, resolve the value of the src
attribute, relative to the frame
element.
If that is not successful, then let url be the string
"about:blank
". Otherwise, let url be the resulting
absolute URL.
Navigate the element's child browsing context to url.
Any navigation required of the user agent in the process
the frame
attributes algorithm must be completed as an explicit
self-navigation override and with the frame
element's document's
browsing context as the source browsing context.
Furthermore, if the active document of the element's child browsing context before such a navigation was not completely loaded at the time of the new navigation, then the navigation must be completed with replacement enabled.
Similarly, if the child browsing context's session history contained
only one Document
when the process the frame
attributes
algorithm was invoked, and that was the about:blank
Document
created
when the child browsing context was created, then any navigation required of the user agent in that algorithm must be completed
with replacement enabled.
When a Document
in a frame
is marked as completely
loaded, the user agent must queue a task to fire a simple event
named load
at the frame
element.
The task source for the tasks above is the DOM manipulation task source.
When there is an active parser in the frame
, and when anything in the
frame
is delaying the load event of the
frame
's browsing context's active document, the
frame
must delay the load event of its document.
When the browsing context is created, if a name
attribute
is present, the browsing context name must be set to the value of this attribute;
otherwise, the browsing context name must be set to the empty string.
Whenever the name
attribute is set, the nested
browsing context's name must be changed to
the new value. If the attribute is removed, the browsing context name must be set to
the empty string.
The frame
element must implement the HTMLFrameElement
interface.
interface HTMLFrameElement : HTMLElement { attribute DOMString name; attribute DOMString scrolling; attribute DOMString src; attribute DOMString frameBorder; attribute DOMString longDesc; attribute boolean noResize; readonly attribute Document? contentDocument; readonly attribute WindowProxy? contentWindow; [TreatNullAs=EmptyString] attribute DOMString marginHeight; [TreatNullAs=EmptyString] attribute DOMString marginWidth; };
The name
, scrolling
, and src
IDL attributes of the frame
element must
reflect the respective content attributes of the same name. For the purposes of
reflection, the frame
element's src
content
attribute is defined as containing a URL.
The frameBorder
IDL attribute of the
frame
element must reflect the element's frameborder
content attribute.
The longDesc
IDL attribute of the
frame
element must reflect the element's longdesc
content attribute, which for the purposes of
reflection is defined as containing a URL.
The noResize
IDL attribute of the
frame
element must reflect the element's noresize
content attribute.
The contentDocument
IDL attribute of
the frame
element must return the Document
object of the active
document of the frame
element's nested browsing context, if any
and if its effective script origin is the same origin as the
effective script origin specified by the incumbent settings object, or
null otherwise.
The contentWindow
IDL attribute must
return the WindowProxy
object of the frame
element's nested
browsing context.
The marginHeight
IDL attribute of the
frame
element must reflect the element's marginheight
content attribute.
The marginWidth
IDL attribute of the
frame
element must reflect the element's marginwidth
content attribute.
User agents must treat acronym
elements in a manner
equivalent to abbr
elements in terms of semantics and
for purposes of rendering.
partial interface HTMLAnchorElement { attribute DOMString coords; attribute DOMString charset; attribute DOMString name; attribute DOMString rev; attribute DOMString shape; };
The coords
, charset
, name
, rev
, and shape
IDL attributes of the
a
element must reflect the respective
content attributes of the same name.
partial interface HTMLAreaElement { attribute boolean noHref; };
The noHref
IDL attribute of the
area
element must reflect the element's nohref
content attribute.
partial interface HTMLBodyElement { [TreatNullAs=EmptyString] attribute DOMString text; [TreatNullAs=EmptyString] attribute DOMString link; [TreatNullAs=EmptyString] attribute DOMString vLink; [TreatNullAs=EmptyString] attribute DOMString aLink; [TreatNullAs=EmptyString] attribute DOMString bgColor; attribute DOMString background; };
The text
IDL attribute of the body
element must reflect the element's text
content
attribute.
The link
IDL attribute of the body
element must reflect the element's link
content
attribute.
The aLink
IDL attribute of the body
element must reflect the element's alink
content
attribute.
The vLink
IDL attribute of the body
element must reflect the element's vlink
content
attribute.
The bgColor
IDL attribute of the
body
element must reflect the element's bgcolor
content attribute.
The background
IDL attribute of the
body
element must reflect the element's background
content attribute. (The background
content is not defined to contain a
URL, despite rules regarding its handling in the rendering section above.)
partial interface HTMLBRElement { attribute DOMString clear; };
The clear
IDL attribute of the br
element must reflect the content attribute of the same name.
partial interface HTMLTableCaptionElement { attribute DOMString align; };
The align
IDL attribute of the
caption
element must reflect the content attribute of the same name.
partial interface HTMLTableColElement { attribute DOMString align; attribute DOMString ch; attribute DOMString chOff; attribute DOMString vAlign; attribute DOMString width; };
The align
and width
IDL attributes of the col
element must
reflect the respective content attributes of the same name.
The ch
IDL attribute of the col
element
must reflect the element's char
content
attribute.
The chOff
IDL attribute of the col
element must reflect the element's charoff
content attribute.
The vAlign
IDL attribute of the col
element must reflect the element's valign
content attribute.
User agents must treat dir
elements in a manner equivalent to ul
elements in terms of semantics and for purposes of rendering.
The dir
element must implement the HTMLDirectoryElement
interface.
interface HTMLDirectoryElement : HTMLElement { attribute boolean compact; };
The compact
IDL attribute of the
dir
element must reflect the content attribute of the same name.
partial interface HTMLDivElement { attribute DOMString align; };
The align
IDL attribute of the div
element must reflect the content attribute of the same name.
partial interface HTMLDListElement { attribute boolean compact; };
The compact
IDL attribute of the dl
element must reflect the content attribute of the same name.
partial interface HTMLEmbedElement { attribute DOMString align; attribute DOMString name; };
The name
and align
IDL attributes of the embed
element
must reflect the respective content attributes of the same name.
The font
element must implement the HTMLFontElement
interface.
interface HTMLFontElement : HTMLElement { [TreatNullAs=EmptyString] attribute DOMString color; attribute DOMString face; attribute DOMString size; };
The color
, face
, and size
IDL attributes of the font
element must
reflect the respective content attributes of the same name.
partial interface HTMLHeadingElement { attribute DOMString align; };
The align
IDL attribute of the
h1
–h6
elements must reflect the content attribute of
the same name.
The profile
IDL attribute on
head
elements (with the HTMLHeadElement
interface) is intentionally
omitted. Unless so required by another applicable
specification, implementations would therefore not support this attribute. (It is mentioned
here as it was defined in a previous version of the DOM specifications.)
partial interface HTMLHRElement { attribute DOMString align; attribute DOMString color; attribute boolean noShade; attribute DOMString size; attribute DOMString width; };
The align
, color
, size
,
and width
IDL attributes of the hr
element must reflect the respective content attributes of the same name.
The noShade
IDL attribute of the hr
element must reflect the element's noshade
content attribute.
partial interface HTMLHtmlElement { attribute DOMString version; };
The version
IDL attribute of the
html
element must reflect the content attribute of the same name.
partial interface HTMLIFrameElement { attribute DOMString align; attribute DOMString scrolling; attribute DOMString frameBorder; attribute DOMString longDesc; [TreatNullAs=EmptyString] attribute DOMString marginHeight; [TreatNullAs=EmptyString] attribute DOMString marginWidth; };
The align
and scrolling
IDL attributes of the
iframe
element must reflect the respective content attributes of the
same name.
The frameBorder
IDL attribute of the
iframe
element must reflect the element's frameborder
content attribute.
The longDesc
IDL attribute of the
iframe
element must reflect the element's longdesc
content attribute, which for the purposes of
reflection is defined as containing a URL.
The marginHeight
IDL attribute of the
iframe
element must reflect the element's marginheight
content attribute.
The marginWidth
IDL attribute of the
iframe
element must reflect the element's marginwidth
content attribute.
partial interface HTMLImageElement { attribute DOMString name; attribute DOMString lowsrc; attribute DOMString align; attribute unsigned long hspace; attribute unsigned long vspace; attribute DOMString longDesc; [TreatNullAs=EmptyString] attribute DOMString border; };
The name
, align
, border
, hspace
, and vspace
IDL attributes of the img
element
must reflect the respective content attributes of the same name.
The longDesc
IDL attribute of the
img
element must reflect the element's longdesc
content attribute, which for the purposes of reflection
is defined as containing a URL.
The lowsrc
IDL attribute of the img
element must reflect the element's lowsrc
content attribute, which for the purposes of reflection is defined as containing a
URL.
partial interface HTMLInputElement { attribute DOMString align; attribute DOMString useMap; };
The align
IDL attribute of the
input
element must reflect the content attribute of the same name.
The useMap
IDL attribute of the
input
element must reflect the element's usemap
content attribute.
partial interface HTMLLegendElement { attribute DOMString align; };
The align
IDL attribute of the
legend
element must reflect the content attribute of the same name.
partial interface HTMLLIElement { attribute DOMString type; };
The type
IDL attribute of the li
element must reflect the content attribute of the same name.
partial interface HTMLLinkElement { attribute DOMString charset; attribute DOMString rev; attribute DOMString target; };
The charset
, rev
, and target
IDL attributes of the link
element
must reflect the respective content attributes of the same name.
User agents must treat listing
elements in a manner equivalent to pre
elements in terms of semantics and for purposes of rendering.
partial interface HTMLMetaElement { attribute DOMString scheme; };
User agents may treat the scheme
content attribute on the
meta
element as an extension of the element's name
content attribute when processing a meta
element
with a name
attribute whose value is one that the user agent
recognizes as supporting the scheme
attribute.
User agents are encouraged to ignore the scheme
attribute
and instead process the value given to the metadata name as if it had been specified for each
expected value of the scheme
attribute.
For example, if the user agent acts on meta
elements with name
attributes having the value "eGMS.subject.keyword", and knows
that the scheme
attribute is used with this metadata name,
then it could take the scheme
attribute into account,
acting as if it was an extension of the name
attribute. Thus
the following two meta
elements could be treated as two elements giving values for
two different metadata names, one consisting of a combination of "eGMS.subject.keyword" and
"LGCL", and the other consisting of a combination of "eGMS.subject.keyword" and "ORLY":
<!-- this markup is invalid --> <meta name="eGMS.subject.keyword" scheme="LGCL" content="Abandoned vehicles"> <meta name="eGMS.subject.keyword" scheme="ORLY" content="Mah car: kthxbye">
The suggested processing of this markup, however, would be equivalent to the following:
<meta name="eGMS.subject.keyword" content="Abandoned vehicles"> <meta name="eGMS.subject.keyword" content="Mah car: kthxbye">
The scheme
IDL attribute of the
meta
element must reflect the content attribute of the same name.
partial interface HTMLObjectElement { attribute DOMString align; attribute DOMString archive; attribute DOMString code; attribute boolean declare; attribute unsigned long hspace; attribute DOMString standby; attribute unsigned long vspace; attribute DOMString codeBase; attribute DOMString codeType; [TreatNullAs=EmptyString] attribute DOMString border; };
The align
, archive
, border
, code
, declare
, hspace
, standby
, and vspace
IDL attributes of the object
element must reflect the respective content attributes of the same name.
The codeBase
IDL attribute of the
object
element must reflect the element's codebase
content attribute, which for the purposes of
reflection is defined as containing a URL.
The codeType
IDL attribute of the
object
element must reflect the element's codetype
content attribute.
partial interface HTMLOListElement { attribute boolean compact; };
The compact
IDL attribute of the ol
element must reflect the content attribute of the same name.
partial interface HTMLParagraphElement { attribute DOMString align; };
The align
IDL attribute of the p
element must reflect the content attribute of the same name.
partial interface HTMLParamElement { attribute DOMString type; attribute DOMString valueType; };
The type
IDL
attribute of the param
element must
reflect the content attribute of the same name.
The valueType
IDL attribute of the param
element must
reflect the element's valuetype
content attribute.
User agents must treat plaintext
elements in a manner equivalent to
pre
elements in terms of semantics and for purposes of rendering. (The parser has
special behavior for this element, though.)
partial interface HTMLPreElement { attribute long width; };
The width
IDL
attribute of the pre
element must reflect
the content attribute of the same name.
partial interface HTMLScriptElement { attribute DOMString event; attribute DOMString htmlFor; };
The event
and htmlFor
IDL attributes of the script
element must return the empty string on getting, and do nothing on setting.
partial interface HTMLTableElement { attribute DOMString align; attribute DOMString frame; attribute DOMString rules; attribute DOMString summary; attribute DOMString width; [TreatNullAs=EmptyString] attribute DOMString bgColor; [TreatNullAs=EmptyString] attribute DOMString cellPadding; [TreatNullAs=EmptyString] attribute DOMString cellSpacing; };
The align
, border
, frame
, summary
, rules
, and width
, IDL attributes of the table
element
must reflect the respective content attributes of the same name.
The bgColor
IDL attribute of the
table
element must reflect the element's bgcolor
content attribute.
The cellPadding
IDL attribute of the
table
element must reflect the element's cellpadding
content attribute.
The cellSpacing
IDL attribute of the
table
element must reflect the element's cellspacing
content attribute.
partial interface HTMLTableSectionElement { attribute DOMString align; attribute DOMString ch; attribute DOMString chOff; attribute DOMString vAlign; };
The align
IDL attribute of the
tbody
, thead
, and tfoot
elements must reflect
the content attribute of the same name.
The ch
IDL attribute of the tbody
,
thead
, and tfoot
elements must reflect the elements' char
content attributes.
The chOff
IDL attribute of the
tbody
, thead
, and tfoot
elements must reflect
the elements' charoff
content attributes.
The vAlign
IDL attribute of the
tbody
, thead
, and tfoot
element must reflect
the elements' valign
content attributes.
partial interface HTMLTableCellElement { attribute DOMString align; attribute DOMString axis; attribute DOMString height; attribute DOMString width; attribute DOMString ch; attribute DOMString chOff; attribute boolean noWrap; attribute DOMString vAlign; [TreatNullAs=EmptyString] attribute DOMString bgColor; };
The align
, axis
, height
, and width
IDL attributes of the td
and
th
elements must reflect the respective content attributes of the same
name.
The ch
IDL attribute of the td
and
th
elements must reflect the elements' char
content attributes.
The chOff
IDL attribute of the td
and th
elements must reflect the elements' charoff
content attributes.
The noWrap
IDL attribute of the td
and th
elements must reflect the elements' nowrap
content attributes.
The vAlign
IDL attribute of the td
and th
element must reflect the elements' valign
content attributes.
The bgColor
IDL attribute of the
td
and th
elements must reflect the elements' bgcolor
content attributes.
partial interface HTMLTableDataCellElement { attribute DOMString abbr; };
The abbr
IDL attribute of the td
element must reflect the respective content attributes of the same name.
partial interface HTMLTableRowElement { attribute DOMString align; attribute DOMString ch; attribute DOMString chOff; attribute DOMString vAlign; [TreatNullAs=EmptyString] attribute DOMString bgColor; };
The align
IDL attribute of the tr
element must reflect the content attribute of the same name.
The ch
IDL attribute of the tr
element
must reflect the element's char
content
attribute.
The chOff
IDL attribute of the tr
element must reflect the element's charoff
content attribute.
The vAlign
IDL attribute of the tr
element must reflect the element's valign
content
attribute.
The bgColor
IDL attribute of the tr
element must reflect the element's bgcolor
content attribute.
partial interface HTMLUListElement { attribute boolean compact; attribute DOMString type; };
The compact
and type
IDL attributes of the ul
element must
reflect the respective content attributes of the same name.
User agents must treat xmp
elements in a manner equivalent to pre
elements in terms of semantics and for purposes of rendering. (The parser has special behavior for
this element though.)
The blink
, bgsound
, isindex
, multicol
,
nextid
, and
spacer
elements must use the HTMLUnknownElement
interface.
partial interface Document { [TreatNullAs=EmptyString] attribute DOMString fgColor; [TreatNullAs=EmptyString] attribute DOMString linkColor; [TreatNullAs=EmptyString] attribute DOMString vlinkColor; [TreatNullAs=EmptyString] attribute DOMString alinkColor; [TreatNullAs=EmptyString] attribute DOMString bgColor; readonly attribute HTMLCollection anchors; readonly attribute HTMLCollection applets; void clear(); void captureEvents(long dummy); void releaseEvents(long dummy); readonly attribute HTMLAllCollection all; };
The attributes of the Document
object listed in the first column of the following
table must reflect the content attribute on the body element with the
name given in the corresponding cell in the second column on the same row, if the body
element is a body
element (as opposed to a frameset
element).
When there is no body element or if it is a
frameset
element, the attributes must instead return the empty string on getting and
do nothing on setting.
IDL attribute | Content attribute |
---|---|
fgColor
| text
|
linkColor
| link
|
vlinkColor
| vlink
|
alinkColor
| alink
|
bgColor
| bgcolor
|
The anchors
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
a
elements with name
attributes.
The applets
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
applet
elements.
The clear()
, captureEvents()
, and releaseEvents()
methods must do nothing.
The all
attribute must return an
HTMLAllCollection
rooted at the Document
node, whose filter matches all
elements.
The object returned for all
has several unusual
behaviors:
The user agent must act as if the ToBoolean() operator in JavaScript converts the object
returned for all
to the false value.
The user agent must act as if, for the purposes of the ==
and !=
operators in JavaScript, the object returned for all
compares as equal to the undefined
and
null
values. (Comparisons using the ===
operator, and
comparisons to other values such as strings or objects, are unaffected.)
The user agent must act such that the typeof
operator in JavaScript
returns the string undefined
when applied to the object returned for all
.
These requirements are a willful violation of the JavaScript
specification current at the time of writing (ECMAScript edition 5). The JavaScript specification
requires that the ToBoolean() operator convert all objects to the true value, and does not have
provisions for objects acting as if they were undefined
for the purposes of
certain operators. This violation is motivated by a desire for compatibility with two classes of
legacy content: one that uses the presence of document.all
as a way to detect legacy user agents, and one that only supports those legacy user agents and
uses the document.all
object without testing for its
presence first. [ECMA262]
partial interface Window { void captureEvents(long dummy); void releaseEvents(long dummy); };
The captureEvents()
and releaseEvents()
methods must do nothing.
The hgroup
element does not have strong native semantics
or default implicit ARIA semantics. User agents must not implement
accessibility layer semantics for the hgroup
element that obfuscates
or modifies the semantics of its children.
text/html
This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
charset
The charset
parameter may be provided to definitively specify the
document's character encoding, overriding any character encoding declarations in the document. The parameter's value
must be one of the labels of the character encoding used to serialize the file. [ENCODING]
Entire novels have been written about the security considerations that apply to HTML documents. Many are listed in this document, to which the reader is referred for more details. Some general concerns bear mentioning here, however:
HTML is scripted language, and has a large number of APIs (some of which are described in this document). Script can expose the user to potential risks of information leakage, credential leakage, cross-site scripting attacks, cross-site request forgeries, and a host of other problems. While the designs in this specification are intended to be safe if implemented correctly, a full implementation is a massive undertaking and, as with any software, user agents are likely to have security bugs.
Even without scripting, there are specific features in HTML which, for historical reasons,
are required for broad compatibility with legacy content but that expose the user to unfortunate
security problems. In particular, the img
element can be used in conjunction with
some other features as a way to effect a port scan from the user's location on the Internet.
This can expose local network topologies that the attacker would otherwise not be able to
determine.
HTML relies on a compartmentalization scheme sometimes known as the same-origin policy. An origin in most cases consists of all the pages served from the same host, on the same port, using the same protocol.
It is critical, therefore, to ensure that any untrusted content that forms part of a site be hosted on a different origin than any sensitive content on that site. Untrusted content can easily spoof any other page on the same origin, read data from that origin, cause scripts in that origin to execute, submit forms to and from that origin even if they are protected from cross-site request forgery attacks by unique tokens, and make use of any third-party resources exposed to or rights granted to that origin.
html
" and "htm
"
are commonly, but certainly not exclusively, used as the
extension for HTML documents.TEXT
Fragment identifiers used with text/html
resources either refer to the
indicated part of the document or provide state information for in-page scripts.
multipart/x-mixed-replace
This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
boundary
(defined in RFC2046) [RFC2046]
multipart/x-mixed-replace
resource can be of any type, including types with non-trivial
security implications such as text/html
.
multipart/mixed
. [RFC2046]
multipart/x-mixed-replace
resource.Fragment identifiers used with multipart/x-mixed-replace
resources apply to each
body part as defined by the type used by that body part.
application/xhtml+xml
This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
application/xml
[RFC3023]application/xml
[RFC3023]application/xml
[RFC3023]application/xml
[RFC3023]application/xml
[RFC3023]application/xhtml+xml
type asserts that the resource is an XML document that likely has
a root element from the HTML namespace. Thus, the
relevant specifications are the XML specification, the Namespaces
in XML specification, and this specification. [XML] [XMLNS]
application/xml
[RFC3023]application/xml
[RFC3023]xhtml
" and "xht
"
are sometimes used as extensions for XML resources that have a
root element from the HTML namespace.TEXT
Fragment identifiers used with application/xhtml+xml
resources have the same
semantics as with any XML MIME type. [RFC3023]
application/x-www-form-urlencoded
This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
In isolation, an application/x-www-form-urlencoded
payload poses no security risks. However, as this type is usually
used as part of a form submission, all the risks that apply to
HTML forms need to be considered in the context of this type.
application/x-www-form-urlencoded
payloads are
defined in this specification.
application/x-www-form-urlencoded
payloads.Fragment identifiers have no meaning with the application/x-www-form-urlencoded
type.
text/cache-manifest
This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.
charset
The charset
parameter may be provided. The parameter's value must be
"utf-8
". This parameter serves no purpose; it is only allowed for
compatibility with legacy servers.
Cache manifests themselves pose no immediate risk unless sensitive information is included within the manifest. Implementations, however, are required to follow specific rules when populating a cache based on a cache manifest, to ensure that certain origin-based restrictions are honored. Failure to correctly implement these rules can result in information leakage, cross-site scripting attacks, and the like.
CACHE
MANIFEST
", followed by either a U+0020 SPACE character, a
"tab" (U+0009) character, a "LF" (U+000A) character, or a "CR" (U+000D) character.appcache
"Fragment identifiers have no meaning with text/cache-manifest
resources.
web+
scheme prefixThis section describes a convention for use with the IANA URI scheme registry. It does not itself register a specific scheme. [RFC4395]
web+
" followed by one or more letters in the range
a
-z
.
web+
" schemes should use UTF-8 encodings where relevant.web+
" schemes. As
such, these schemes must not be used for features intended to be core platform features (e.g.
network transfer protocols like HTTP or FTP). Similarly, such schemes must not store
confidential information in their URLs, such as usernames, passwords, personal information, or
confidential project names.
The following sections only cover conforming elements and features.
This section is non-normative.
An asterisk (*) in a cell indicates that the actual rules are more complicated than indicated in the table above.
† Categories in the "Parents" column refer to parents that list the given categories in
their content model, not to elements that themselves are in those categories. For example, the
a
element's "Parents" column says "phrasing", so any element whose content model
contains the "phrasing" category could be a parent of an a
element. Since the "flow"
category includes all the "phrasing" elements, that means the th
element could be a
parent to an a
element.
This section is non-normative.
This section is non-normative.
Attribute | Element(s) | Description | Value |
---|---|---|---|
abbr
| th
| Alternative label to use for the header cell when referencing the cell in other contexts | Text* |
accept
| input
| Hint for expected file type in file upload controls | Set of comma-separated tokens* consisting of valid MIME types with no parameters or audio/* , video/* , or image/*
|
accept-charset
| form
| Character encodings to use for form submission | Ordered set of unique space-separated tokens, ASCII case-insensitive, consisting of labels of ASCII-compatible character encodings* |
accesskey
| HTML elements | Keyboard shortcut to activate or focus element | Ordered set of unique space-separated tokens, case-sensitive, consisting of one Unicode code point in length |
action
| form
| URL to use for form submission | Valid non-empty URL potentially surrounded by spaces |
alt
| area ;
img ;
input
| Replacement text for use when images are not available | Text* |
async
| script
| Execute script asynchronously | Boolean attribute |
autocomplete
| form
| Default setting for autofill feature for controls in the form | "on "; "off "
|
autocomplete
| input ;
select ;
textarea
| Hint for form autofill feature | Autofill field name and related tokens* |
autofocus
| button ;
input ;
keygen ;
select ;
textarea
| Automatically focus the form control when the page is loaded | Boolean attribute |
autoplay
| audio ;
video
| Hint that the media resource can be started automatically when the page is loaded | Boolean attribute |
border
| table
| Explicit indication that the table element is not being used for layout purposes
| The empty string, or "1 "
|
challenge
| keygen
| String to package with the generated and signed public key | Text |
charset
| meta
| Character encoding declaration | Encoding label* |
charset
| script
| Character encoding of the external script resource | Encoding label* |
checked
| input
| Whether the control is checked | Boolean attribute |
cite
| blockquote ;
del ;
ins ;
q
| Link to the source of the quotation or more information about the edit | Valid URL potentially surrounded by spaces |
class
| HTML elements | Classes to which the element belongs | Set of space-separated tokens |
cols
| textarea
| Maximum number of characters per line | Valid non-negative integer greater than zero |
colspan
| td ;
th
| Number of columns that the cell is to span | Valid non-negative integer greater than zero |
content
| meta
| Value of the element | Text* |
contenteditable
| HTML elements | Whether the element is editable | "true "; "false "
|
controls
| audio ;
video
| Show user agent controls | Boolean attribute |
coords
| area
| Coordinates for the shape to be created in an image map | Valid list of integers* |
crossorigin
| audio ;
img ;
link ;
script ;
video
| How the element handles crossorigin requests | "anonymous "; "use-credentials "
|
data
| object
| Address of the resource | Valid non-empty URL potentially surrounded by spaces |
datetime
| del ;
ins
| Date and (optionally) time of the change | Valid date string with optional time |
datetime
| time
| Machine-readable value | Valid month string, valid date string, valid yearless date string, valid time string, valid local date and time string, valid time-zone offset string, valid global date and time string, valid week string, valid non-negative integer, or valid duration string |
default
| track
| Enable the track if no other text track is more suitable | Boolean attribute |
defer
| script
| Defer script execution | Boolean attribute |
dir
| HTML elements | The text directionality of the element | "ltr "; "rtl "; "auto "
|
dir
| bdo
| The text directionality of the element | "ltr "; "rtl "
|
dirname
| input ;
textarea
| Name of form field to use for sending the element's directionality in form submission | Text* |
disabled
| button ;
fieldset ;
input ;
keygen ;
optgroup ;
option ;
select ;
textarea
| Whether the form control is disabled | Boolean attribute |
download
| a ;
area
| Whether to download the resource instead of navigating to it, and its file name if so | Text |
draggable
| HTML elements | Whether the element is draggable | "true "; "false "
|
dropzone
| HTML elements | Accepted item types for drag-and-drop | Unordered set of unique space-separated tokens, ASCII case-insensitive, consisting of accepted types and drag feedback* |
enctype
| form
| Form data set encoding type to use for form submission | "application/x-www-form-urlencoded "; "multipart/form-data "; "text/plain "
|
for
| label
| Associate the label with form control | ID* |
for
| output
| Specifies controls from which the output was calculated | Unordered set of unique space-separated tokens, case-sensitive, consisting of IDs* |
form
| button ;
fieldset ;
input ;
keygen ;
label ;
object ;
output ;
select ;
textarea
| Associates the control with a form element
| ID* |
formaction
| button ;
input
| URL to use for form submission | Valid non-empty URL potentially surrounded by spaces |
formenctype
| button ;
input
| Form data set encoding type to use for form submission | "application/x-www-form-urlencoded "; "multipart/form-data "; "text/plain "
|
formmethod
| button ;
input
| HTTP method to use for form submission | "GET "; "POST "
|
formnovalidate
| button ;
input
| Bypass form control validation for form submission | Boolean attribute |
formtarget
| button ;
input
| Browsing context for form submission | Valid browsing context name or keyword |
headers
| td ;
th
| The header cells for this cell | Unordered set of unique space-separated tokens, case-sensitive, consisting of IDs* |
height
| canvas ;
embed ;
iframe ;
img ;
input ;
object ;
video
| Vertical dimension | Valid non-negative integer |
hidden
| HTML elements | Whether the element is relevant | Boolean attribute |
high
| meter
| Low limit of high range | Valid floating-point number* |
href
| a ;
area
| Address of the hyperlink | Valid URL potentially surrounded by spaces |
href
| link
| Address of the hyperlink | Valid non-empty URL potentially surrounded by spaces |
href
| base
| Document base URL | Valid URL potentially surrounded by spaces |
hreflang
| a ;
area ;
link
| Language of the linked resource | Valid BCP 47 language tag |
http-equiv
| meta
| Pragma directive | Text* |
id
| HTML elements | The element's ID | Text* |
ismap
| img
| Whether the image is a server-side image map | Boolean attribute |
keytype
| keygen
| The type of cryptographic key to generate | Text* |
kind
| track
| The type of text track | "subtitles ";
"captions ";
"descriptions ";
"chapters ";
"metadata "
|
label
| optgroup ;
option ;
track
| User-visible label | Text |
lang
| HTML elements | Language of the element | Valid BCP 47 language tag or the empty string |
list
| input
| List of autocomplete options | ID* |
loop
| audio ;
video
| Whether to loop the media resource | Boolean attribute |
low
| meter
| High limit of low range | Valid floating-point number* |
manifest
| html
| Application cache manifest | Valid non-empty URL potentially surrounded by spaces |
max
| input
| Maximum value | Varies* |
max
| meter ;
progress
| Upper bound of range | Valid floating-point number* |
maxlength
| input ;
textarea
| Maximum length of value | Valid non-negative integer |
media
| link ;
source ;
style
| Applicable media | Valid media query |
mediagroup
| audio ;
video
| Groups media elements together with an implicit MediaController
| Text |
method
| form
| HTTP method to use for form submission | "GET ";
"POST ";
|
min
| input
| Minimum value | Varies* |
min
| meter
| Lower bound of range | Valid floating-point number* |
minlength
| input ;
textarea
| Minimum length of value | Valid non-negative integer |
multiple
| input ;
select
| Whether to allow multiple values | Boolean attribute |
muted
| audio ;
video
| Whether to mute the media resource by default | Boolean attribute |
name
| button ;
fieldset ;
input ;
keygen ;
output ;
select ;
textarea
| Name of form control to use for form submission and in the form.elements API
| Text* |
name
| form
| Name of form to use in the document.forms API
| Text* |
name
| iframe ;
object
| Name of nested browsing context | Valid browsing context name or keyword |
name
| map
| Name of image map to reference from the usemap attribute
| Text* |
name
| meta
| Metadata name | Text* |
name
| param
| Name of parameter | Text |
novalidate
| form
| Bypass form control validation for form submission | Boolean attribute |
open
| details
| Whether the details are visible | Boolean attribute |
open
| dialog
| Whether the dialog box is showing | Boolean attribute |
optimum
| meter
| Optimum value in gauge | Valid floating-point number* |
pattern
| input
| Pattern to be matched by the form control's value | Regular expression matching the JavaScript Pattern production |
placeholder
| input ;
textarea
| User-visible label to be placed within the form control | Text* |
poster
| video
| Poster frame to show prior to video playback | Valid non-empty URL potentially surrounded by spaces |
preload
| audio ;
video
| Hints how much buffering the media resource will likely need | "none ";
"metadata ";
"auto "
|
readonly
| input ;
textarea
| Whether to allow the value to be edited by the user | Boolean attribute |
rel
| a ;
area ;
link
| Relationship between the document containing the hyperlink and the destination resource | Set of space-separated tokens* |
required
| input ;
select ;
textarea
| Whether the control is required for form submission | Boolean attribute |
reversed
| ol
| Number the list backwards | Boolean attribute |
rows
| textarea
| Number of lines to show | Valid non-negative integer greater than zero |
rowspan
| td ;
th
| Number of rows that the cell is to span | Valid non-negative integer |
sandbox
| iframe
| Security rules for nested content | Unordered set of unique space-separated tokens, ASCII case-insensitive, consisting of
"allow-forms ",
"allow-pointer-lock ",
"allow-popups ",
"allow-same-origin ",
"allow-scripts and
"allow-top-navigation "
|
spellcheck
| HTML elements | Whether the element is to have its spelling and grammar checked | "true "; "false "
|
scope
| th
| Specifies which cells the header cell applies to | "row ";
"col ";
"rowgroup ";
"colgroup "
|
scoped
| style
| Whether the styles apply to the entire document or just the parent subtree | Boolean attribute |
seamless
| iframe
| Whether to apply the document's styles to the nested content | Boolean attribute |
selected
| option
| Whether the option is selected by default | Boolean attribute |
shape
| area
| The kind of shape to be created in an image map | "circle ";
"default ";
"poly ";
"rect "
|
size
| input ;
select
| Size of the control | Valid non-negative integer greater than zero |
sizes
| link
| Sizes of the icons (for rel ="icon ")
| Unordered set of unique space-separated tokens, ASCII case-insensitive, consisting of sizes* |
span
| col ;
colgroup
| Number of columns spanned by the element | Valid non-negative integer greater than zero |
src
| audio ;
embed ;
iframe ;
img ;
input ;
script ;
source ;
track ;
video
| Address of the resource | Valid non-empty URL potentially surrounded by spaces |
srcdoc
| iframe
| A document to render in the iframe
| The source of an iframe srcdoc document*
|
srclang
| track
| Language of the text track | Valid BCP 47 language tag |
start
| ol
| Ordinal value of the first item | Valid integer |
step
| input
| Granularity to be matched by the form control's value | Valid floating-point number greater than zero, or "any "
|
style
| HTML elements | Presentational and formatting instructions | CSS declarations* |
tabindex
| HTML elements | Whether the element is focusable, and the relative order of the element for the purposes of sequential focus navigation | Valid integer |
target
| a ;
area
| Browsing context for hyperlink navigation | Valid browsing context name or keyword |
target
| base
| Default browsing context for hyperlink navigation and form submission | Valid browsing context name or keyword |
target
| form
| Browsing context for form submission | Valid browsing context name or keyword |
title
| HTML elements | Advisory information for the element | Text |
title
| abbr ;
dfn
| Full term or expansion of abbreviation | Text |
title
| input
| Description of pattern (when used with pattern attribute)
| Text |
title
| link
| Title of the link | Text |
title
| link ;
style
| Alternative style sheet set name | Text |
translate
| HTML elements | Whether the element is to be translated when the page is localized | "yes "; "no "
|
type
| a ;
area ;
link
| Hint for the type of the referenced resource | Valid MIME type |
type
| button
| Type of button | "submit ";
"reset ";
"button "
|
type
| embed ;
object ;
script ;
source ;
style
| Type of embedded resource | Valid MIME type |
type
| input
| Type of form control | input type keyword
|
type
| ol
| Kind of list marker | "1 ";
"a ";
"A ";
"i ";
"I "
|
typemustmatch
| object
| Whether the type attribute and the Content-Type value need to match for the resource to be used
| Boolean attribute |
usemap
| img ;
object
| Name of image map to use | Valid hash-name reference* |
value
| button ;
option
| Value to be used for form submission | Text |
value
| data
| Machine-readable value | Text* |
value
| input
| Value of the form control | Varies* |
value
| li
| Ordinal value of the list item | Valid integer |
value
| meter ;
progress
| Current value of the element | Valid floating-point number |
value
| param
| Value of parameter | Text |
width
| canvas ;
embed ;
iframe ;
img ;
input ;
object ;
video
| Horizontal dimension | Valid non-negative integer |
wrap
| textarea
| How the value of the form control is to be wrapped for form submission | "soft ";
"hard "
|
An asterisk (*) in a cell indicates that the actual rules are more complicated than indicated in the table above.
This section is non-normative.
This section is non-normative.
This section is non-normative.
Event | Interface | Description |
---|---|---|
abort
| Event
| Fired at the Window when the download was aborted by the user
|
afterprint
| Event
| Fired at the Window after printing
|
beforeprint
| Event
| Fired at the Window before printing
|
beforeunload
| BeforeUnloadEvent
| Fired at the Window when the page is about to be unloaded, in case the page would like to show a warning prompt
|
blur
| Event
| Fired at nodes losing focus |
change
| Event
| Fired at controls when the user commits a value change |
click
| Event
| Fired at an element before its activation behavior is run |
DOMContentLoaded
| Event
| Fired at the Document once the parser has finished
|
error
| Event
| Fired at elements when network and script errors occur |
focus
| Event
| Fired at nodes gaining focus |
hashchange
| HashChangeEvent
| Fired at the Window when the fragment identifier part of the document's address changes
|
input
| Event
| Fired at controls when the user changes the value |
invalid
| Event
| Fired at controls during form validation if they do not satisfy their constraints |
load
| Event
| Fired at the Window when the document has finished loading; fired at an element containing a resource (e.g. img , embed ) when its resource has finished loading
|
message
| MessageEvent
| Fired at an object when the object receives a message |
offline
| Event
| Fired at the Window when the network connections fails
|
online
| Event
| Fired at the Window when the network connections returns
|
pagehide
| PageTransitionEvent
| Fired at the Window when the page's entry in the session history stops being the current entry
|
pageshow
| PageTransitionEvent
| Fired at the Window when the page's entry in the session history becomes the current entry
|
popstate
| PopStateEvent
| Fired at the Window when the user navigates the session history
|
readystatechange
| Event
| Fired at the Document when it finishes parsing and again when all its subresources have finished loading
|
reset
| Event
| Fired at a form element when it is reset
|
submit
| Event
| Fired at a form element when it is submitted
|
unload
| Event
| Fired at the Window object when the page is going away
|
See also media element events, application cache events, and drag-and-drop events.
All references are normative unless marked "Non-normative".
XMLHttpRequest
, A. van Kesteren. WHATWG.Thanks to Tim Berners-Lee for inventing HTML, without which none of this would exist.
Thanks to Aankhen, Aaron Boodman, Aaron Leventhal, Adam Barth, Adam de Boor, Adam Hepton, Adam Klein, Adam Roben, Addison Phillips, Adele Peterson, Adrian Bateman, Adrian Sutton, Agustín Fernández, Aharon (Vladimir) Lanin, Ajai Tirumali, Akatsuki Kitamura, Alan Plum, Alastair Campbell, Alejandro G. Castro, Alex Bishop, Alex Nicolaou, Alex Rousskov, Alexander Farkas, Alexander J. Vincent, Alexandre Morgaut, Alexey Feldgendler, Алексей Проскуряков (Alexey Proskuryakov), Alexis Deveria, Allan Clements, Ami Fischman, Amos Jeffries, Anders Carlsson, André E. Veltstra, Andrea Rendine, Andreas, Andreas Kling, Andrei Popescu, Andres Gomez, Andrew Barfield, Andrew Clover, Andrew Gove, Andrew Grieve, Andrew Oakley, Andrew Sidwell, Andrew Simons, Andrew Smith, Andrew W. Hagen, Andrey V. Lukyanov, Andry Rendy, Andy Earnshaw, Andy Heydon, Andy Palay, Anne van Kesteren, Anthony Boyd, Anthony Bryan, Anthony Hickson, Anthony Ricaud, Antti Koivisto, Arne Thomassen, Aron Spohr, Arphen Lin, Arthur Stolyar, Arun Patole, Aryeh Gregor, Asbjørn Ulsberg, Ashley Gullen, Ashley Sheridan, Atsushi Takayama, Aurelien Levy, Ave Wrigley, Axel Dahmen, Ben Boyle, Ben Godfrey, Ben Lerner, Ben Leslie, Ben Meadowcroft, Ben Millard, Benjamin Carl Wiley Sittler, Benjamin Hawkes-Lewis, Benoit Ren, Bert Bos, Bijan Parsia, Bil Corry, Bill Mason, Bill McCoy, Billy Wong, Bjartur Thorlacius, Björn Höhrmann, Blake Frantz, Bob Lund, Bob Owen, Boris Zbarsky, Brad Fults, Brad Neuberg, Brad Spencer, Brady Eidson, Brendan Eich, Brenton Simpson, Brett Wilson, Brett Zamir, Brian Blakely, Brian Campbell, Brian Korver, Brian Kuhn, Brian M. Dube, Brian Ryner, Brian Smith, Brian Wilson, Bryan Sullivan, Bruce Bailey, Bruce D'Arcus, Bruce Lawson, Bruce Miller, C. Williams, Cameron McCormack, Cameron Zemek, Cao Yipeng, Carlos Amengual, Carlos Gabriel Cardona, Carlos Perelló Marín, Chao Cai, 윤석찬 (Channy Yun), Charl van Niekerk, Charles Iliya Krempeaux, Charles McCathieNevile, Chris Apers, Chris Cressman, Chris Evans, Chris Morris, Chris Pearce, Chris Peterson, Chris Weber, Christian Biesinger, Christian Johansen, Christian Schmidt, Christoph Päper, Christophe Dumez, Christopher Aillon, Christopher Ferris, Chriswa, Clark Buehler, Cole Robison, Colin Fine, Collin Jackson, Corprew Reed, Craig Cockburn, Csaba Gabor, Csaba Marton, Cynthia Shelly, Dan Yoder, Daniel Barclay, Daniel Bratell, Daniel Brooks, Daniel Brumbaugh Keeney, Daniel Cheng, Daniel Davis, Daniel Glazman, Daniel Peng, Daniel Schattenkirchner, Daniel Spång, Daniel Steinberg, Daniel Trebbien, Danny Sullivan, Darin Adler, Darin Fisher, Darxus, Dave Camp, Dave Hodder, Dave Lampton, Dave Singer, Dave Townsend, David Baron, David Bloom, David Bruant, David Carlisle, David E. Cleary, David Egan Evans, David Fink, David Flanagan, David Gerard, David Håsäther, David Hyatt, David I. Lehn, David John Burrowes, David Kendal, David MacDonald, David Matja, David Remahl, David Smith, David Woolley, DeWitt Clinton, Dean Edridge, Dean Edwards, Debi Orton, Derek Featherstone, Devarshi Pant, Devdatta, Dimitri Glazkov, Dimitry Golubovsky, Dirk Pranke, Dirk Schulze, Dirkjan Ochtman, Divya Manian, Dmitry Titov, dolphinling, Domenic Denicola, Dominique Hazaël-Massieux, Don Brutzman, Doron Rosenberg, Doug Kramer, Doug Simpkinson, Drew Wilson, Edmund Lai, Eduard Pascual, Eduardo Vela, Edward O'Connor, Edward Welbourne, Edward Z. Yang, Ehsan Akhgari, Eira Monstad, Eitan Adler, Eliot Graff, Elisabeth Robson, Elizabeth Castro, Elliott Sprehn, Elliotte Harold, Eric Carlson, Eric Lawrence, Eric Rescorla, Eric Semling, Erik Arvidsson, Erik Rose, Evan Martin, Evan Prodromou, Evert, fantasai, Felix Sasaki, Francesco Schwarz, Francis Brosnan Blazquez, Franck 'Shift' Quélain, Frank Barchard, 鵜飼文敏 (Fumitoshi Ukai), Futomi Hatano, Gavin Carothers, Gavin Kistner, Gareth Rees, Garrett Smith, Geoff Richards, Geoffrey Garen, Geoffrey Sneddon, Gez Lemon, George Lund, Gianmarco Armellin, Giovanni Campagna, Giuseppe Pascale, Glenn Adams, Glenn Maynard, Graham Klyne, Greg Botten, Greg Houston, Greg Wilkins, Gregg Tavares, Gregory J. Rosmaita, Grey, Guilherme Johansson Tramontina, Gytis Jakutonis, Håkon Wium Lie, Hallvord Reiar Michaelsen Steen, Hans S. Tømmerhalt, Hans Stimer, Harald Alvestrand, Henri Sivonen, Henrik Lied, Henry Mason, Heydon Pickering, Hugh Guiney, Hugh Winkler, Ian Bicking, Ian Clelland, Ian Davis, Ian Fette, Ido Green, Ignacio Javier, Ivan Enderlin, Ivo Emanuel Gonçalves, J. King, Jacob Davies, Jacques Distler, Jake Verbaten, Jakub Łopuszański, James Craig, James Graham, James Greene, James Justin Harrell, James Kozianski, James M Snell, James Perrett, James Robinson, Jamie Lokier, Janusz Majnert, Jan-Klaas Kollhof, Jared Jacobs, Jason Duell, Jason Kersey, Jason Lustig, Jason White, Jasper Bryant-Greene, Jasper St. Pierre, Jatinder Mann, Jed Hartman, Jeff Balogh, Jeff Cutsinger, Jeff Schiller, Jeff Walden, Jeffrey Zeldman, 胡慧鋒 (Jennifer Braithwaite), Jens Bannmann, Jens Fendler, Jens Lindström, Jens Meiert, Jeremey Hustman, Jeremy Keith, Jeremy Orlow, Jeroen van der Meer, Jian Li, Jim Jewett, Jim Ley, Jim Meehan, Jim Michaels, Jirka Kosek, Jjgod Jiang, João Eiras, Joe Clark, Joe Gregorio, Joel Spolsky, Joel Verhagen, Johan Herland, John Boyer, John Bussjaeger, John Carpenter, John Daggett, John Fallows, John Foliot, John Harding, John Keiser, John Snyders, John Stockton, John-Mark Bell, Johnny Stenback, Jon Ferraiolo, Jon Gibbins, Jon Perlow, Jonas Sicking, Jonathan Cook, Jonathan Rees, Jonathan Watt, Jonathan Worent, Jonny Axelsson, Jordan Tucker, Jorgen Horstink, Jorunn Danielsen Newth, Joseph Kesselman, Joseph Mansfield, Joseph Pecoraro, Josh Aas, Josh Hart, Josh Levenberg, Joshua Bell, Joshua Randall, Jukka K. Korpela, Jules Clément-Ripoche, Julian Reschke, Jürgen Jeka, Justin Lebar, Justin Novosad, Justin Schuh, Justin Sinclair, Ka-Sing Chou, Kai Hendry, 呂康豪 (KangHao Lu), Kartikaya Gupta, Kathy Walton, Kelly Ford, Kelly Norton, Kevin Benson, Kevin Gadd, Kevin Cole, Kornél Pál, Kornel Lesinski, Kris Northfield, Kristof Zelechovski, Krzysztof Maczyński, 黒澤剛志 (Kurosawa Takeshi), Kyle Barnhart, Kyle Hofmann, Kyle Huey, Léonard Bouchet, Léonie Watson, Lachlan Hunt, Larry Masinter, Larry Page, Lars Gunther, Lars Solberg, Laura Carlson, Laura Granka, Laura L. Carlson, Laura Wisewell, Laurens Holst, Lawrence Forooghian, Lee Kowalkowski, Leif Halvard Silli, Lenny Domnitser, Leonard Rosenthol, Leonie Watson, Leons Petrazickis, Lobotom Dysmon, Logan, Loune, Luke Kenneth Casson Leighton, Maciej Stachowiak, Magnus Kristiansen, Maik Merten, Malcolm Rowe, Manish Tripathi, Marc Hoyois, Marcus Bointon, Mark Birbeck, Mark Davis, Mark Miller, Mark Nottingham, Mark Pilgrim, Mark Rowe, Mark Schenk, Mark Vickers, Mark Wilton-Jones, Martijn Wargers, Martin Atkins, Martin Dürst, Martin Honnen, Martin Janecke, Martin Kutschker, Martin Nilsson, Martin Thomson, Masataka Yakura, Matt May, Mathias Bynens, Mathieu Henri, Matias Larsson, Matt Falkenhagen, Matt Schmidt, Matt Wright, Matthew Gregan, Matthew Mastracci, Matthew Raymond, Matthew Thomas, Mattias Waldau, Max Romantschuk, Menachem Salomon, Menno van Slooten, Micah Dubinko, Michael 'Ratt' Iannarelli, Michael A. Nachbaur, Michael A. Puls II, Michael Carter, Michael Daskalov, Michael Day, Michael Dyck, Michael Enright, Michael Gratton, Michael Nordman, Michael Powers, Michael Rakowski, Michael(tm) Smith, Michael Walmsley, Michal Zalewski, Michel Fortin, Michelangelo De Simone, Michiel van der Blonk, Mihai Şucan, Mihai Parparita, Mike Brown, Mike Dierken, Mike Dixon, Mike Hearn, Mike Schinkel, Mike Shaver, Mikko Rantalainen, Mohamed Zergaoui, Mohammad Al Houssami, Mounir Lamouri, Ms2ger, Nadia Heninger, NARUSE Yui, Neil Deakin, Neil Rashbrook, Neil Soiffer, Nicholas Shanks, Nicholas Stimpson, Nicholas Zakas, Nickolay Ponomarev, Nicolas Gallagher, Noah Mendelsohn, Noah Slater, Noel Gordon, Nolan Waite, NoozNooz42, Norbert Lindenberg, Ojan Vafai, Olaf Hoffmann, Olav Junker Kjær, Oldřich Vetešník, Oli Studholme, Oliver Hunt, Oliver Rigby, Olivier Gendrin, Olli Pettay, oSand, Pablo Flouret, Patrick Garies, Patrick H. Lauke, Patrik Persson, Paul Adenot, Paul Norman, Per-Erik Brodin, Perry Smith, Peter Beverloo, Peter Karlsson, Peter Kasting, Peter Moulder, Peter Occil, Peter Stark, Peter Van der Beken, Peter-Paul Koch, Phil Pickering, Philip Jägenstedt, Philip Taylor, Philip TAYLOR, Philippe De Ryck, Prateek Rungta, Pravir Gupta, 李普君 (Pujun Li), Rachid Finge, Rafael Weinstein, Rafał Miłecki, Raj Doshi, Rajas Moonka, Ralf Stoltze, Ralph Giles, Raphael Champeimont, Remci Mizkur, Remco, Remy Sharp, Rene Saarsoo, Rene Stach, Ric Hardacre, Rich Clark, Rich Doughty, Richard Ishida, Rigo Wenning, Rikkert Koppes, Rimantas Liubertas, Riona Macnamara, Rob Ennals, Rob Jellinghaus, Rob S, Robert Blaut, Robert Collins, Robert Kieffer, Robert Millan, Robert O'Callahan, Robert Sayre, Robin Berjon, Robin Schaufler, Rodger Combs, Roland Steiner, Roma Matusevich, Roman Ivanov, Roy Fielding, Ruud Steltenpool, Ryan King, Ryosuke Niwa, S. Mike Dierken, Salvatore Loreto, Sam Dutton, Sam Kuper, Sam Ruby, Sam Weinig, Samuel Bronson, Samy Kamkar, Sander van Lambalgen, Sarven Capadisli, Scott González, Scott Hess, Sean Fraser, Sean Hayes, Sean Hogan, Sean Knapp, Sebastian Markbåge, Sebastian Schnitzenbaumer, Seth Call, Seth Dillingham, Shanti Rao, Shaun Inman, Shiki Okasaka, Sierk Bornemann, Sigbjørn Finne, Sigbjørn Vik, Silver Ghost, Silvia Pfeiffer, Šime Vidas, Simon Montagu, Simon Pieters, Simon Spiegel, skeww, Smylers, Stanton McCandlish, Stefan Håkansson, Stefan Haustein, Stefan Santesson, Stefan Weiss, Steffen Meschkat, Stephen Ma, Stephen White, Steve Comstock, Steve Faulkner, Steve Runyon, Steven Bennett, Steven Garrity, Steven Tate, Stewart Brodie, Stuart Ballard, Stuart Langridge, Stuart Parmenter, Subramanian Peruvemba, Sunava Dutta, Susan Borgrink, Susan Lesch, Sylvain Pasche, T. J. Crowder, Tab Atkins, Takeshi Yoshino, Tantek Çelik, 田村健人 (TAMURA Kent), Ted Mielczarek, Terrence Wood, Thijs van der Vossen, Thomas Broyer, Thomas Koetter, Thomas O'Connor, Tim Altman, Tim Johansson, TJ VanToll, Toby Inkster, Todd Moody, Tom Baker, Tom Pike, Tommy Thorsen, Tony Ross, Travis Leithead, Tyler Close, Victor Carbune, Vipul Snehadeep Chawathe, Vitya Muhachev, Vladimir Katardjiev, Vladimir Vukićević, voracity, Wakaba, Wayne Carr, Wayne Pollock, Wellington Fernando de Macedo, Weston Ruter, Wilhelm Joys Andersen, Will Levine, William Chen, William Swanson, Wladimir Palant, Wojciech Mach, Wolfram Kriesing, Xan Gregg, Yang Chen, Ye-Kui Wang, Yehuda Katz, Yi-An Huang, Yngve Nysaeter Pettersen, Yonathan Randolph, Yuzo Fujishima, Zhenbin Xu, Zoltan Herczeg, and Øistein E. Andersen, for their useful comments, both large and small, that have led to changes to this specification over the years.
Thanks also to everyone who has ever posted about HTML to their blogs, public mailing lists, or forums, including all the contributors to the various W3C HTML WG lists and the various WHATWG lists.
Special thanks to Richard Williamson for creating the first implementation of
canvas
in Safari, from which the canvas feature was designed.
Special thanks also to the Microsoft employees who first implemented the event-based
drag-and-drop mechanism, contenteditable
, and other
features first widely deployed by the Windows Internet Explorer browser.
Thanks to the participants of the microdata usability study for allowing us to use their mistakes as a guide for designing the microdata feature.
Special thanks and $10,000 to David Hyatt who came up with a broken implementation of the adoption agency algorithm that the editor had to reverse engineer and fix before using it in the parsing section.
Thanks to the many sources that provided inspiration for the examples used in the specification.
The image of two cute kittens in a basket used in the context menu example is based on a photo by Alex G. (CC BY 2.0)
The Blue Robot Player sprite used in the canvas demo is based on a work by JohnColburn. (CC BY-SA 3.0)
Thanks also to the Microsoft blogging community for some ideas, to the attendees of the W3C Workshop on Web Applications and Compound Documents for inspiration, to the #mrt crew, the #mrt.no crew, and the #whatwg crew, and to Pillar and Hedral for their ideas and support.