HTML5
A vocabulary and associated APIs for HTML and XHTML
A vocabulary and associated APIs for HTML and XHTML
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;
referrerReturns 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.
lastModifiedReturns 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.
readyStateReturns "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.
headReturns 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.imagesReturns an HTMLCollection of the img elements in the Document.
embedspluginsReturn an HTMLCollection of the embed elements in the Document.
linksReturns an HTMLCollection of the a and area elements in the Document that have href attributes.
formsReturn an HTMLCollection of the form elements in the Document.
scriptsReturn 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.
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:[email protected]"/>
<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.
aabbraddressarea (if it is a descendant of a map element)articleasideaudiobbdibdoblockquotebrbuttoncanvascitecodedatadatalistdeldfndivdlemembedfieldsetfigurefooterformh1h2h3h4h5h6headerhriiframeimginputinskbdkeygenlabelmainmapmarkmathmeternavnoscriptobjectoloutputppreprogressqrubyssampscriptsectionselectsmallspanstrongsubsupsvgtabletemplatetextareatimeuulvarvideowbrSectioning 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.
aabbrarea (if it is a descendant of a map element)audiobbdibdobrbuttoncanvascitecodedatadatalistdeldfnemembediiframeimginputinskbdkeygenlabelmapmarkmathmeternoscriptobjectoutputprogressqrubyssampscriptselectsmallspanstrongsubsupsvgtemplatetextareatimeuvarvideowbrMost 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.
aaudio (if the controls attribute is present)buttonembediframeimg (if the usemap attribute is present)input (if the type attribute is not in the Hidden state)keygenlabelobject (if the usemap attribute is present)selecttextareavideo (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:
aabbraddressarticleasideaudio (if the controls attribute is present)bbdibdoblockquotebuttoncanvascitecodedatadfndivdl (if the element's children include at least one name-value group)emembedfieldsetfigurefooterformh1h2h3h4h5h6headeriiframeimginput (if the type attribute is not in the Hidden state)inskbdkeygenlabelmainmapmarkmathmeternavobjectol (if the element's children include at least one li element)outputppreprogressqrubyssampsectionselectsmallspanstrongsubsupsvgtabletextareatimeuul (if the element's children include at least one li element)varvideoScript-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):
accesskeyclasscontenteditabledirdraggabledropzonehiddenidlangspellcheckstyletabindextitletranslateThese 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:
onabortonblur*oncanceloncanplayoncanplaythroughonchangeonclickoncloseoncuechangeondblclickondragondragendondragenterondragexitondragleaveondragoverondragstartondropondurationchangeonemptiedonendedonerror*onfocus*oninputoninvalidonkeydownonkeypressonkeyuponload*onloadeddataonloadedmetadataonloadstartonmousedownonmouseenteronmouseleaveonmousemoveonmouseoutonmouseoveronmouseuponmousewheelonpauseonplayonplayingonprogressonratechangeonresetonresize*onscroll*onseekedonseekingonselectonshowonstalledonsubmitonsuspendontimeupdateontoggleonvolumechangeonwaitingThe 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.)
styleReturns 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.
datasetReturns 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"
|
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 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 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
|
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 |
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
|
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>