Every XML and HTML document in an HTML UA is represented by a Document
object. [DOM]
The document's
address is the URL associated with a Document
(as defined in the DOM
standard). It is initially set when the Document
is created, but that can change
during the lifetime of the Document
; for example, it changes when the user navigates to a fragment identifier
on the page and when the pushState()
method is called
with a new URL. [DOM]
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 new response whose body 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; [SameObject] readonly attribute HTMLCollection images; [SameObject] readonly attribute HTMLCollection embeds; [SameObject] readonly attribute HTMLCollection plugins; [SameObject] readonly attribute HTMLCollection links; [SameObject] readonly attribute HTMLCollection forms; [SameObject] readonly attribute HTMLCollection scripts; NodeList getElementsByName(DOMString elementName); NodeList getItems(optional DOMString typeNames = ""); // microdata [SameObject] readonly attribute DOMElementMap cssElementMap; readonly attribute HTMLScriptElement? currentScript; // 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); readonly attribute HTMLCollection commands; // special event handler IDL attributes that only apply to Document objects [LenientThis] attribute EventHandler onreadystatechange; // also has obsolete members }; Document implements GlobalEventHandlers;
referrer
Returns the address of the Document
from which the user navigated to this one, unless it was blocked or there was no such document,
in which case it returns the empty string.
The noreferrer
link type can be used to block the
referrer.
The referrer
attribute must return
the document's referrer.
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] [ENCODING]
Since the cookie
attribute is accessible
across frames, the path restrictions on cookies are only a tool to help manage which cookies are
sent to which parts of the site, and are not in any way a security feature.
lastModified
Returns the date of the last modification to the document, as reported by the server, in the
form "MM/DD/YYYY hh:mm:ss
", in the user's local time zone.
If the last modification date is not known, the current time is returned instead.
The lastModified
attribute, on
getting, must return the date and time of the Document
's source file's last
modification, in the user's local time zone, in the following format:
All the numeric components above, other than the year, must be given as two ASCII digits representing the number in base ten, zero-padded if necessary. The year must be given as the shortest possible string of four or more ASCII digits representing the number in base ten, zero-padded if necessary.
The Document
's source file's last modification date and time must be derived from
relevant features of the networking protocols used, e.g. from the value of the HTTP `Last-Modified
` header of the document, or from metadata in the
file system for local files. If the last modification date and time are not known, the attribute
must return the current date and time in the above format.
readyState
Returns "loading
" while the Document
is loading, "interactive
" once it is finished parsing but still loading sub-resources, and
"complete
" once it has loaded.
The readystatechange
event fires on the
Document
object when this value changes.
Each document has a current document readiness. When a Document
object
is created, it must have its current document readiness set to the string "loading
" if the document is associated with an HTML parser, an
XML parser, or an XSLT processor, and to the string "complete
"
otherwise. Various algorithms during page loading affect this value. When the value is set, the
user agent must fire a simple event named readystatechange
at the Document
object.
A Document
is said to have an active parser if it is associated with an
HTML parser or an XML parser that has not yet been stopped or aborted.
The readyState
IDL attribute must, on
getting, return the current document readiness.
The html
element of a document is the document's root element, if there
is one and it's an html
element, or null otherwise.
head
Returns the head
element.
The head
element of a document is the first head
element
that is a child of the html
element, if there is one, or null
otherwise.
The head
attribute, on getting, must return
the head
element of the document (a head
element or
null).
title
[ = value ]Returns the document's title, as given by the title
element for
HTML and as given by the SVG title
element for SVG.
Can be set, to update the document's title. If there is no appropriate element to update, the new value is ignored.
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 SVG
namespace, then let value be a concatenation of the data of all the
child Text
nodes of the first title
element in the SVG
namespace that is a child of the root element. [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 steps corresponding to the first matching condition in the following list must be run:
svg
element in the SVG
namespace [SVG]Let element be the first title
element in
the SVG namespace that is a child of the root element, if any. If
there isn't one, create a title
element in the SVG
namespace, append it to the root element, and let element be that element. [SVG]
Act as if the textContent
IDL attribute of element was
set to the new value being assigned.
If the title
element is null and the head
element is null, then abort these steps.
If the title
element is null, then create a new
title
element and append it to the
head
element, and let element be the newly created
element; otherwise, let element be the title
element.
Act as if the textContent
IDL attribute of element was
set to the new value being assigned.
Do nothing.
body
[ = value ]Returns the body element.
Can be set, to replace the body element.
If the new value is not a body
or frameset
element, this will throw
a HierarchyRequestError
exception.
The body element of a document is the first child of the html
element that is either a body
element or a frameset
element. If
there is no such element, it is null.
The body
attribute, on getting, must return
the body element of the document (either a body
element, a
frameset
element, or null). On setting, the following algorithm must be run:
body
or frameset
element, then throw a
HierarchyRequestError
exception and abort these steps.replaceChild()
method had
been called with the new value and the incumbent body
element as its two arguments respectively, then abort these steps.HierarchyRequestError
exception
and abort these steps.images
Returns an HTMLCollection
of the img
elements in the Document
.
embeds
plugins
Return an HTMLCollection
of the embed
elements in the Document
.
links
Returns an HTMLCollection
of the a
and area
elements
in the Document
that have href
attributes.
forms
Return an HTMLCollection
of the form
elements in the Document
.
scripts
Return an HTMLCollection
of the script
elements in the Document
.
The images
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
img
elements.
The embeds
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
embed
elements.
The plugins
attribute must return the
same object as that returned by the embeds
attribute.
The links
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
a
elements with href
attributes and
area
elements with href
attributes.
The forms
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
form
elements.
The scripts
attribute must return an
HTMLCollection
rooted at the Document
node, whose filter matches only
script
elements.
getElementsByName
(name)Returns a NodeList
of elements in the Document
that have a name
attribute with the value name.
The getElementsByName(name)
method takes a string name, and must
return a live NodeList
containing all the HTML elements in
that document that have a name
attribute whose value is equal to the name argument (in a case-sensitive manner), in tree
order. When the method is invoked on a Document
object again with the same
argument, the user agent may return the same as the object returned by the earlier call. In other
cases, a new NodeList
object must be returned.
cssElementMap
Returns a DOMElementMap
object for the Document
representing the
current CSS element reference
identifiers.
The cssElementMap
IDL attribute
allows authors to define CSS element reference
identifiers, which are used in certain CSS features to override the normal ID-based mapping. [CSSIMAGES]
When a Document
is created, it must be associated with an initially-empty CSS
ID overrides list, which consists of a list of mappings each of which consists of a string
name mapped to an Element
node.
Each entry in the CSS ID overrides list, while it is in the list and is either
in the Document
or is an img
,
video
, or canvas
element, defines a CSS element reference
identifier mapping the given name to the given Element
. [CSSIMAGES]
On getting, the cssElementMap
IDL attribute
must return a DOMElementMap
object, associated with the following algorithms, which
expose the current mappings:
Return the Document
's CSS ID overrides list, maintaining the order
in which the entries were originally added to the list.
Let name be the name passed to the algorithm and element be the Element
passed to the algorithm.
If element is null, run the algorithm for deleting mappings by name, passing it name.
Otherwise, if there is an entry in the Document
's CSS ID overrides
list whose name is name, replace its current value with element.
Otherwise, add a mapping to the Document
's CSS ID overrides list
whose name is name and whose element is element.
If there is an entry in the Document
's CSS ID overrides list whose
name is the name passed to this algorithm, remove it. This also undefines the CSS element
reference identifier for that name. [CSSIMAGES]
currentScript
Returns the script
element that is currently executing. In the case of reentrant
script
execution, returns the one that most recently started executing amongst
those that have not yet finished executing.
Returns null if the Document
is not currently executing a script
element (e.g. because the running script is an event handler, or a timeout).
The currentScript
attribute, on
getting, must return the value to which it was most recently initialised. When the
Document
is created, the currentScript
must be initialised to null.
The Document
interface supports named properties. The supported property names at
any moment consist of the values of the name
content attributes of
all the
applet
,
exposed embed
,
form
,
iframe
,
img
, and
exposed object
elements in the Document
that have non-empty name
content
attributes, and the values of the id
content attributes of all the
applet
and
exposed object
elements in the Document
that have non-empty id
content
attributes, and the values of the id
content attributes of all the
img
elements in the Document
that have both non-empty name
content
attributes and non-empty id
content attributes. The supported
property names must be in tree order, ignoring later duplicates, with values
from id
attributes coming before values from name
attributes when the same element contributes both.
To determine the value of a named property name when the Document
object is indexed for property
retrieval, the user agent must return the value obtained using the following steps:
Let elements be the list of named elements with the name name in the Document
.
There will be at least one such element, by definition.
If elements has only one element, and that element is an
iframe
element, then return the WindowProxy
object of the nested
browsing context represented by that iframe
element, and abort these
steps.
Otherwise, if elements has only one element, return that element and abort these steps.
Otherwise return an HTMLCollection
rooted at the Document
node,
whose filter matches only named elements with
the name name.
Named elements with the name name, for the purposes of the above algorithm, are those that are either:
applet
, exposed embed
, form
,
iframe
, img
, or exposed object
elements that
have a name
content attribute whose value is name, orapplet
or exposed object
elements that have an id
content attribute whose value is name, orimg
elements that have an id
content attribute
whose value is name, and that have a non-empty name
content attribute present also.An embed
or object
element is said to be exposed if it has
no exposed object
ancestor, and, for object
elements, is
additionally either not showing its fallback content or has no object
or
embed
descendants.
The dir
attribute on the
Document
interface is defined along with the dir
content attribute.
partial interface XMLDocument { boolean load(DOMString url); };
The load(url)
method
must run the following steps:
Let document be the XMLDocument
object on which the
method was invoked.
Resolve the method's first argument, relative to the
API base URL specified by the entry settings object. If this is not
successful, throw a SyntaxError
exception and abort these steps. Otherwise, let url be the resulting absolute URL.
If the origin of url is not the same as the
origin of document, throw a SecurityError
exception
and abort these steps.
Remove all child nodes of document, without firing any mutation events.
Set the current document readiness of document to "loading
".
Run the remainder of these steps in parallel, and return true from the method.
Let result be a Document
object.
Let success be false.
Let request be a new request whose
url is url, client is entry settings object, destination is "subresource
",
synchronous flag is set, mode is "same-origin
", credentials
mode is "same-origin
", and whose use-URL-credentials
flag is set.
Let response be the result of fetching request.
If response's Content-Type metadata is an XML MIME type, then run these substeps:
Create a new XML parser associated with the result document.
Pass this parser response's body.
If there is an XML well-formedness or XML namespace well-formedness error, then remove all child nodes from result. Otherwise let success be true.
Queue a task to run the following steps.
Set the current document readiness of document to
"complete
".
Replace all the children of document by the children of result (even if it has no children), firing mutation events as if a
DocumentFragment
containing the new children had been inserted.
Fire a simple event named load
at document.
Elements, attributes, and attribute values in HTML are defined (by this specification) to have
certain meanings (semantics). For example, the ol
element represents an ordered list,
and the lang
attribute represents the language of the content.
These definitions allow HTML processors, such as Web browsers or search engines, to present and use documents and applications in a wide variety of contexts that the author might not have considered.
As a simple example, consider a Web page written by an author who only considered desktop computer Web browsers:
<!DOCTYPE HTML> <html> <head> <title>My Page</title> </head> <body> <h1>Welcome to my page</h1> <p>I like cars and lorries and have a big Jeep!</p> <h2>Where I live</h2> <p>I live in a small hut on a mountain!</p> </body> </html>
Because HTML conveys meaning, rather than presentation, the same page can also be used by a small browser on a mobile phone, without any change to the page. Instead of headings being in large letters as on the desktop, for example, the browser on the mobile phone might use the same size text for the whole the page, but with the headings in bold.
But it goes further than just differences in screen size: the same page could equally be used by a blind user using a browser based around speech synthesis, which instead of displaying the page on a screen, reads the page to the user, e.g. using headphones. Instead of large text for the headings, the speech browser might use a different volume or a slower voice.
That's not all, either. Since the browsers know which parts of the page are the headings, they can create a document outline that the user can use to quickly navigate around the document, using keys for "jump to next heading" or "jump to previous heading". Such features are especially common with speech browsers, where users would otherwise find quickly navigating a page quite difficult.
Even beyond browsers, software can make use of this information. Search engines can use the headings to more effectively index a page, or to provide quick links to subsections of the page from their results. Tools can use the headings to create a table of contents (that is in fact how this very specification's table of contents is generated).
This example has focused on headings, but the same principle applies to all of the semantics in HTML.
Authors must not use elements, attributes, or attribute values for purposes other than their appropriate intended semantic purpose, as doing so prevents software from correctly processing the page.
The document in this next example is similarly non-conforming, despite
being syntactically correct, because the data placed in the cells is clearly
not tabular data, and the cite
element mis-used:
<!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>
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; [SameObject] readonly attribute DOMStringMap dataset; // microdata attribute boolean itemScope; [PutForwards=value] readonly attribute DOMSettableTokenList itemType; attribute DOMString itemId; [PutForwards=value] readonly attribute DOMSettableTokenList itemRef; [PutForwards=value] readonly attribute DOMSettableTokenList itemProp; readonly attribute HTMLPropertiesCollection properties; attribute any itemValue; // acts as DOMString on setting // 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 HTMLMenuElement? contextMenu; attribute boolean spellcheck; void forceSpellCheck(); // command API readonly attribute DOMString? commandType; readonly attribute DOMString? commandLabel; readonly attribute DOMString? commandIcon; readonly attribute boolean? commandHidden; readonly attribute boolean? commandDisabled; readonly attribute boolean? commandChecked; }; HTMLElement implements GlobalEventHandlers; HTMLElement implements ElementContentEditable; 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'), };
When an element's content model is nothing, the
element must contain no Text
nodes (other than inter-element whitespace)
and no element nodes.
Most HTML elements whose content model is "nothing" are also, for convenience, void elements (elements that have no end tag in the HTML syntax). However, these are entirely separate concepts.
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 behaviour 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 serialisation, one can use RDF, like this:
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:r="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <head> <title>Hedral's Home Page</title> <r:RDF> <Person xmlns="http://www.w3.org/2000/10/swap/pim/contact#" r:about="http://hedral.example.com/#"> <fullName>Cat Hedral</fullName> <mailbox r:resource="mailto:hedral@damowmow.com"/> <personalTitle>Sir</personalTitle> </Person> </r:RDF> </head> <body> <h1>My home page</h1> <p>I like playing with string, I guess. Sister says squirrels are fun too so sometimes I follow her to play with them.</p> </body> </html>
This isn't possible in the HTML serialisation, however.
Most elements that are used in the body of documents and applications are categorised as flow content.
a
abbr
address
area
(if it is a descendant of a map
element)article
aside
audio
b
bdi
bdo
blockquote
br
button
canvas
cite
code
data
datalist
del
details
dfn
dialog
div
dl
em
embed
fieldset
figure
footer
form
h1
h2
h3
h4
h5
h6
header
hr
i
iframe
img
input
ins
kbd
keygen
label
link
(if the itemprop
attribute is present)main
map
mark
math
menu
meta
(if the itemprop
attribute is present)meter
nav
noscript
object
ol
output
p
picture
pre
progress
q
ruby
s
samp
script
section
select
small
span
strong
style
(if the scoped
attribute is present)sub
sup
svg
table
template
textarea
time
u
ul
var
video
wbr
Sectioning content is content that defines the scope of headings and footers.
Each sectioning content element potentially has a heading and an outline. See the section on headings and sections for further details.
There are also certain elements that are sectioning roots. These are distinct from sectioning content, but they can also have an outline.
Heading content defines the header of a section (whether explicitly marked up using sectioning content elements, or implied by the heading content itself).
Phrasing content is the text of the document, as well as elements that mark up that text at the intra-paragraph level. Runs of phrasing content form paragraphs.
a
abbr
area
(if it is a descendant of a map
element)audio
b
bdi
bdo
br
button
canvas
cite
code
data
datalist
del
dfn
em
embed
i
iframe
img
input
ins
kbd
keygen
label
link
(if the itemprop
attribute is present)map
mark
math
meta
(if the itemprop
attribute is present)meter
noscript
object
output
picture
progress
q
ruby
s
samp
script
select
small
span
strong
sub
sup
svg
template
textarea
time
u
var
video
wbr
Most elements that are categorised as phrasing content can only contain elements that are themselves categorised as phrasing content, not any flow content.
Text, in the context of content models, means either nothing,
or Text
nodes. Text is sometimes used as a content
model on its own, but is also phrasing content, and can be inter-element
whitespace (if the Text
nodes are empty or contain just space characters).
Text
nodes and attribute values must consist of Unicode characters, must not contain U+0000 characters, must not contain
permanently undefined Unicode characters (noncharacters), and must not contain control characters
other than space characters.
This specification includes extra constraints on the exact value of Text
nodes and
attribute values depending on their precise context.
Embedded content is content that imports another resource into the document, or content from another vocabulary that is inserted into the document.
Elements that are from namespaces other than the HTML namespace and that convey content but not metadata, are embedded content for the purposes of the content models defined in this specification. (For example, MathML, or SVG.)
Some embedded content elements can have fallback content: content that is to be used when the external resource cannot be used (e.g. because it is of an unsupported format). The element definitions state what the fallback is, if any.
Interactive content is content that is specifically intended for user interaction.
a
audio
(if the controls
attribute is present)button
details
embed
iframe
img
(if the usemap
attribute is present)input
(if the type
attribute is not in the state)keygen
label
object
(if the usemap
attribute is present)select
textarea
th
elementsvideo
(if the controls
attribute is present)The tabindex
attribute can also make any element into
interactive content.
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 attribute specified.
Palpable content makes an element non-empty by providing either
some descendant non-empty text, or else something users can
hear (audio
elements) or view (video
or img
or
canvas
elements) or otherwise interact with (for example, interactive form
controls).
This requirement is not a hard requirement, however, as there are many cases where an element can be empty legitimately, for example when it is used as a placeholder which will later be filled in by a script, or when the element is part of a template and would on most pages be filled in but on some pages is not relevant.
Conformance checkers are encouraged to provide a mechanism for authors to find elements that fail to fulfill this requirement, as an authoring aid.
The following elements are palpable content:
a
abbr
address
article
aside
audio
(if the controls
attribute is present)b
bdi
bdo
blockquote
button
canvas
cite
code
data
details
dfn
div
dl
(if the element's children include at least one name-value group)em
embed
fieldset
figure
footer
form
h1
h2
h3
h4
h5
h6
header
i
iframe
img
input
(if the type
attribute is not in the state)ins
kbd
keygen
label
main
map
mark
math
menu
(if the type
attribute is in the toolbar state)meter
nav
object
ol
(if the element's children include at least one li
element)output
p
pre
progress
q
ruby
s
samp
section
select
small
span
strong
sub
sup
svg
table
textarea
time
u
ul
(if the element's children include at least one li
element)var
video
Script-supporting elements are those that do not represent anything themselves (i.e. they are not rendered), but are used to support scripts, e.g. to provide functionality for the user.
The following elements are script-supporting elements:
Some elements are described as transparent; they have "transparent" in the description of their content model. The content model of a transparent element is derived from the content model of its parent element: the elements required in the part of the content model that is "transparent" are the same elements as required in the part of the content model of the parent of the transparent element in which the transparent element finds itself.
For instance, an ins
element inside a ruby
element cannot contain an
rt
element, because the part of the ruby
element's content model that
allows ins
elements is the part that allows phrasing content, and the
rt
element is not phrasing content.
In some cases, where transparent elements are nested in each other, the process has to be applied iteratively.
Consider the following markup fragment:
<p><object><param><ins><map><a href="/">Apples</a></map></ins></object></p>
To check whether "Apples" is allowed inside the a
element, the content models are
examined. The a
element's content model is transparent, as is the map
element's, as is the ins
element's, as is the part of the object
element's in which the ins
element is found. The object
element is
found in the p
element, whose content model is phrasing content. Thus,
"Apples" is allowed, as text is phrasing content.
When a transparent element has no parent, then the part of its content model that is "transparent" must instead be treated as accepting any flow content.
The term paragraph as defined in this section is used for more than
just the definition of the p
element. The paragraph concept defined here
is used to describe how to interpret documents. The p
element is merely one of
several ways of marking up a paragraph.
A paragraph is typically a run of phrasing content that forms a block of text with one or more sentences that discuss a particular topic, as in typography, but can also be used for more general thematic grouping. For instance, an address is also a paragraph, as is a part of a form, a byline, or a stanza in a poem.
In the following example, there are two paragraphs in a section. There is also a heading, which contains phrasing content that is not a paragraph. Note how the comments and inter-element whitespace do not form paragraphs.
<section> <h1>Example of paragraphs</h1> This is the <em>first</em> paragraph in this example. <p>This is the second.</p> <!-- This is not a paragraph. --> </section>
Paragraphs in flow content are defined relative to what the document looks like
without the a
, ins
, del
, and map
elements
complicating matters, since those elements, with their hybrid content models, can straddle
paragraph boundaries, as shown in the first two examples below.
Generally, having elements straddle paragraph boundaries is best avoided. Maintaining such markup can be difficult.
The following example takes the markup from the earlier example and puts ins
and
del
elements around some of the markup to show that the text was changed (though in
this case, the changes admittedly don't make much sense). Notice how this example has exactly the
same paragraphs as the previous one, despite the ins
and del
elements
— the ins
element straddles the heading and the first paragraph, and the
del
element straddles the boundary between the two paragraphs.
<section> <ins><h1>Example of paragraphs</h1> This is the <em>first</em> paragraph in</ins> this example<del>. <p>This is the second.</p></del> <!-- This is not a paragraph. --> </section>
Let view be a view of the DOM that replaces all a
,
ins
, del
, and map
elements in the document with their contents. Then, in view, for each run
of sibling phrasing content nodes uninterrupted by other types of content, in an
element that accepts content other than phrasing content as well as phrasing
content, let first be the first node of the run, and let last be the last node of the run. For each such run that consists of at least one
node that is neither embedded content nor inter-element whitespace, a
paragraph exists in the original DOM from immediately before first to
immediately after last. (Paragraphs can thus span across a
,
ins
, del
, and map
elements.)
Conformance checkers may warn authors of cases where they have paragraphs that overlap each
other (this can happen with object
, video
, audio
, and
canvas
elements, and indirectly through elements in other namespaces that allow HTML
to be further embedded therein, like svg
or math
).
A paragraph is also formed explicitly by p
elements.
The p
element can be used to wrap individual paragraphs when there
would otherwise not be any content other than phrasing content to separate the paragraphs from
each other.
In the following example, the link spans half of the first paragraph, all of the heading separating the two paragraphs, and half of the second paragraph. It straddles the paragraphs and the heading.
<header> Welcome! <a href="about.html"> This is home of... <h1>The Falcons!</h1> The Lockheed Martin multirole jet fighter aircraft! </a> This page discusses the F-16 Fighting Falcon's innermost secrets. </header>
Here is another way of marking this up, this time showing the paragraphs explicitly, and splitting the one link element into three:
<header> <p>Welcome! <a href="about.html">This is home of...</a></p> <h1><a href="about.html">The Falcons!</a></h1> <p><a href="about.html">The Lockheed Martin multirole jet fighter aircraft!</a> This page discusses the F-16 Fighting Falcon's innermost secrets.</p> </header>
It is possible for paragraphs to overlap when using certain elements that define fallback content. For example, in the following section:
<section> <h1>My Cats</h1> You can play with my cat simulator. <object data="cats.sim"> To see the cat simulator, use one of the following links: <ul> <li><a href="cats.sim">Download simulator file</a> <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a> </ul> Alternatively, upgrade to the Mellblom Browser. </object> I'm quite proud of it. </section>
There are five paragraphs:
object
element.The first paragraph is overlapped by the other four. A user agent that supports the "cats.sim" resource will only show the first one, but a user agent that shows the fallback will confusingly show the first sentence of the first paragraph as if it was in the same paragraph as the second one, and will show the last paragraph as if it was at the start of the second sentence of the first paragraph.
To avoid this confusion, explicit p
elements can be used. For example:
<section> <h1>My Cats</h1> <p>You can play with my cat simulator.</p> <object data="cats.sim"> <p>To see the cat simulator, use one of the following links:</p> <ul> <li><a href="cats.sim">Download simulator file</a> <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a> </ul> <p>Alternatively, upgrade to the Mellblom Browser.</p> </object> <p>I'm quite proud of it.</p> </section>
The following attributes are common to and may be specified on all HTML elements (even those not defined in this specification):
accesskey
class
contenteditable
contextmenu
dir
draggable
dropzone
id
itemid
itemprop
itemref
itemscope
itemtype
lang
spellcheck
style
tabindex
title
translate
These attributes are only defined by this specification as attributes for HTML elements. When this specification refers to elements having these attributes, elements from namespaces that are not defined as having these attributes must not be considered as being elements with these attributes.
For example, in the following XML fragment, the "bogus
" element does not
have a dir
attribute as defined in this specification, despite
having an attribute with the literal name "dir
". Thus, the
directionality of the inner-most span
element is 'rtl', inherited from the div
element indirectly through
the "bogus
" element.
<div xmlns="http://www.w3.org/1999/xhtml" dir="rtl"> <bogus xmlns="http://example.net/ns" dir="ltr"> <span xmlns="http://www.w3.org/1999/xhtml"> </span> </bogus> </div>
To enable assistive technology products to expose a more fine-grained interface than is
otherwise possible with HTML elements and attributes, a set of annotations
for assistive technology products can be specified (the ARIA role
and aria-*
attributes). [ARIA]
The following event handler content attributes may be specified on any HTML element:
onabort
onautocomplete
onautocompleteerror
onblur
*oncancel
oncanplay
oncanplaythrough
onchange
onclick
onclose
oncontextmenu
oncuechange
ondblclick
ondrag
ondragend
ondragenter
ondragexit
ondragleave
ondragover
ondragstart
ondrop
ondurationchange
onemptied
onended
onerror
*onfocus
*oninput
oninvalid
onkeydown
onkeypress
onkeyup
onload
*onloadeddata
onloadedmetadata
onloadstart
onmousedown
onmouseenter
onmouseleave
onmousemove
onmouseout
onmouseover
onmouseup
onwheel
onpause
onplay
onplaying
onprogress
onratechange
onreset
onresize
*onscroll
*onseeked
onseeking
onselect
onshow
onsort
onstalled
onsubmit
onsuspend
ontimeupdate
ontoggle
onvolumechange
onwaiting
The attributes marked with an asterisk have a different meaning when specified on
body
elements as those elements expose event handlers of the
Window
object with the same names.
While these attributes apply to all elements, they are not useful on all elements.
For example, only media elements will ever receive a volumechange
event fired by the user agent.
Custom data attributes (e.g. data-foldername
or data-msgid
) can be specified on any HTML element, to store custom data specific to the page.
In HTML documents, elements in the HTML namespace may have an xmlns
attribute specified, if, and only if, it has the exact value "http://www.w3.org/1999/xhtml
". This does not apply to XML
documents.
In HTML, the xmlns
attribute has absolutely no effect. It
is basically a talisman. It is allowed merely to make migration to and from XHTML mildly easier.
When parsed by an HTML parser, the attribute ends up in no namespace, not the "http://www.w3.org/2000/xmlns/
" namespace like namespace declaration attributes in
XML do.
In XML, an xmlns
attribute is part of the namespace
declaration mechanism, and an element cannot actually have an xmlns
attribute in no namespace specified.
The XML specification also allows the use of the xml:space
attribute in the XML namespace on any element in an XML
document. This attribute has no effect on HTML elements, as the default
behaviour in HTML is to preserve whitespace. [XML]
There is no way to serialise 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 U+000A LINE FEED (LF)
characters, the content is split into multiple lines. Each U+000A LINE FEED (LF) 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
,
abbr
, or menuitem
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 recognised 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.
When an element is in the no-translate state, the element's attribute values 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 menuitem
,
menu
,
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 stateOther specifications may define other attributes that are also translatable
attributes. For example, ARIA would define the aria-label
attribute as translatable.
The 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>
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 a root element, the directionality of the element is 'ltr'.
Otherwise, the directionality of the element the same as the element's parent element's directionality.
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 menuitem
,
menu
,
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
attribute.)
style
Returns a CSSStyleDeclaration
object for the element's style
attribute.
The style
IDL attribute is defined in the CSS Object
Model (CSSOM) specification. [CSSOM]
In the following example, the words that refer to colours are marked up using the
span
element and the style
attribute to make those
words show up in the relevant colours 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 not known to the administrators of the site that uses the attributes. For generic extensions that are to be used by multiple independent tools, either this specification should be extended to provide the feature explicitly, or a technology like microdata should be used (with a standardised vocabulary).
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.
Similarly, a page author could write markup that provides information for a translation tool that they are intending to use:
<p>The third <span data-mytrans-de="Anspruch">claim</span> covers the case of <span translate="no">HTML</span> markup.</p>
In this example, the "data-mytrans-de
" attribute gives specific text
for the MyTrans product to use when translating the phrase "claim" to German. However, the
standard translate
attribute is used to tell it that in all
languages, "HTML" is to remain unchanged. When a standard attribute is available, there is no
need for a custom data attribute to be used.
Every HTML element may have any number of custom data attributes specified, with any value.
dataset
Returns a DOMStringMap
object for the element's data-*
attributes.
Hyphenated names become camel-cased. For example, data-foo-bar=""
becomes element.dataset.fooBar
.
The dataset
IDL attribute provides convenient
accessors for all the data-*
attributes on an element. On
getting, the dataset
IDL attribute must return a
DOMStringMap
object, associated with the following algorithms, which expose these
attributes on their element:
data-
" and whose remaining characters (if any) do not include any
uppercase ASCII letters, in the order that those attributes are listed in the
element's attribute list, add a name-value pair to list whose
name is the attribute's name with the first five characters removed and whose value is the
attribute's value.SyntaxError
exception and abort these steps.data-
at the front of name.setAttribute()
would have thrown an exception when setting an attribute with
the name name, then this must throw the same exception.data-
at the front of name.This algorithm will only get invoked by the Web IDL specification for names that are given by the earlier algorithm for getting the list of name-value pairs. [WEBIDL]
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 behaviour 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 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 requirements specified in ARIA in HTML. 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]
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.
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:
Conformance checkers are required to implement document conformance requirements for use of the ARIA role and aria-* attributes on HTML elements, as defined in ARIA in HTML.
User agents are required to implement ARIA semantics on all HTML elements, as defined in the ARIA specifications [ARIA] and [ARIAIMPL].
User agents are required to implement Accessibility API semantics on all HTML elements, as defined in the HTML Accessibility API Mappings specification.
The ARIA attributes defined in the ARIA specifications, and the HTML Accessibility API Mappings specification, 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 HTML Accessibility API Mappings specification, as well as [ARIA] and [ARIAIMPL].
This section is non-normative.
The following table provides an informative reference to the ARIA roles, states and properties permitted for use in HTML. All ARIA roles, states and properties are normatively defined in the [ARIA] specification. Links to ARIA roles, states and properties in the table reference the normative [ARIA] definitions.
Role | Description | Required Properties | Supported Properties |
---|---|---|---|
any | ARIA global states and properties can be used on any HTML element. | none | |
alert | A message with important, and usually time-sensitive, information. See related alertdialog and status. | none | |
alertdialog | A type of dialog that contains an alert message, where initial focus goes to an element within the dialog. See related alert and dialog. | none | |
application | A region declared as a web application, as opposed to a web document. | none | |
article | A section of a page that consists of a composition that forms an independent part of a document, page, or site. | none | |
banner | A region that contains mostly site-oriented content, rather than page-specific content. | none | |
button | An input that allows for user-triggered actions when clicked or pressed. See related link. | none | |
checkbox | A checkable input that has three possible values: true, false, or mixed. | ||
columnheader | A cell containing header information for a column. | none | |
combobox | A presentation of a select; usually similar to a textbox where users can type ahead to select an option, or type to enter arbitrary text as a new item in the list. See related listbox. | ||
complementary | A supporting section of the document, designed to be complementary to the main content at a similar level in the DOM hierarchy, but remains meaningful when separated from the main content. | none | |
contentinfo | A large perceivable region that contains information about the parent document. | none | |
definition | A definition of a term or concept. | none | |
dialog | A dialog is an application window that is designed to interrupt the current processing of an application in order to prompt the user to enter information or require a response. See related alertdialog. | none | |
directory | A list of references to members of a group, such as a static table of contents. | none | |
document | A region containing related information that is declared as document content, as opposed to a web application. | none | |
form | A landmark region that contains a collection of items and objects that, as a whole, combine to create a form. See related search. | none | |
grid | A grid is an interactive control which contains cells of tabular data arranged in rows and columns, like a table. | none | |
gridcell | A cell in a grid or treegrid. | none | |
group | A set of user interface objects which are not intended to be included in a page summary or table of contents by assistive technologies. | none | |
heading | A heading for a section of the page. | none | |
img | A container for a collection of elements that form an image. | none | |
link | An interactive reference to an internal or external resource that, when activated, causes the user agent to navigate to that resource. See related button. | none | |
list | A group of non-interactive list items. See related listbox. | none | |
listbox | A widget that allows the user to select one or more items from a list of choices. See related combobox and list. | none | |
listitem | A single item in a list or directory. | none | |
log | A type of live region where new information is added in meaningful order and old information may disappear. See related marquee. | none | |
main | The main content of a document. | none | |
marquee | A type of live region where non-essential information changes frequently. See related log. | none | |
math | Content that represents a mathematical expression. | none | |
menu | A type of widget that offers a list of choices to the user. | none | |
menubar | A presentation of menu that usually remains visible and is usually presented horizontally. | none | |
menuitem | An option in a group of choices contained by a menu or menubar. | none | |
menuitemcheckbox | A checkable menuitem that has three possible values: true, false, or mixed. | ||
menuitemradio | A checkable menuitem in a group of menuitemradio roles, only one of which can be checked at a time. | ||
navigation | A collection of navigational elements (usually links) for navigating the document or related documents. | none | |
note | A section whose content is parenthetic or ancillary to the main content of the resource. | none | |
option | A selectable item in a select list. | none | |
presentation | An element whose implicit native role semantics will not be mapped to the accessibility API. | none | |
progressbar | An element that displays the progress status for tasks that take a long time. | none | |
radio | A checkable input in a group of radio roles, only one of which can be checked at a time. | ||
radiogroup | A group of radio buttons. | none | |
region | A large perceivable section of a web page or document, that the author feels is important enough to be included in a page summary or table of contents, for example, an area of the page containing live sporting event statistics. | none | |
row | A row of cells in a grid. | none | |
rowgroup | A group containing one or more row elements in a grid. | none | |
rowheader | A cell containing header information for a row in a grid. | none | |
scrollbar | A graphical object that controls the scrolling of content within a viewing area, regardless of whether the content is fully displayed within the viewing area. | ||
search | A landmark region that contains a collection of items and objects that, as a whole, combine to create a search facility. See related form. | none | |
separator | A divider that separates and distinguishes sections of content or groups of menuitems. |
|
|
slider | A user input where the user selects a value from within a given range. | ||
spinbutton | A form of range that expects the user to select from among discrete choices. | ||
status | A container whose content is advisory information for the user but is not important enough to justify an alert, often but not necessarily presented as a status bar. See related alert. | none | |
tab | A grouping label providing a mechanism for selecting the tab content that is to be rendered to the user. | none | |
tablist | A list of tab elements, which are references to tabpanel elements. | none | |
tabpanel | A container for the resources associated with a tab, where each tab is contained in a tablist. | none | |
textbox | Input that allows free-form text as its value. | none | |
timer | A type of live region containing a numerical counter which indicates an amount of elapsed time from a start point, or the time remaining until an end point. | none | |
toolbar | A collection of commonly used function buttons represented in compact visual form. | none | |
tooltip | A contextual popup that displays a description for an element. | none | |
tree | A type of list that may contain sub-level nested groups that can be collapsed and expanded. | none | |
treegrid | A grid whose rows can be expanded and collapsed in the same manner as for a tree. | none | |
treeitem | An option item of a tree. This is an element within a tree that may be expanded or collapsed if it contains a sub-level group of treeitems. | none |