HTML5 Differences from HTML4
Abstract
"HTML5 Differences from HTML4" describes the differences of the HTML5 specification from those of HTML4.
Status of This Document
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This is the 9 December 2014 W3C Working Group Note produced by the HTML Working Group, part of the HTML Activity. The Working Group intends to publish this document as a Working Group Note. The appropriate forum for comments is W3C Bugzilla. (public-html-comments@w3.org, a mailing list with a public archive, is no longer used for tracking comments.)
Publication as a Working Group Note does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This document is governed by the 14 October 2005 W3C Process Document.
1 Introduction
1.1 Scope of This Document
This document covers the W3C HTML5 specification. It does not cover the W3C HTML5.1 specification or the WHATWG HTML standard. [HTML5] [HTML5NIGHTLY] [HTML]
1.2 History of HTML
HTML has been in continuous evolution since it was introduced to the Internet in the early 1990s. Some features were introduced in specifications; others were introduced in software releases. In some respects, implementations and Web developer practices have converged with each other and with specifications and standards, but in other ways, they have diverged.
HTML4 became a W3C Recommendation in 1997. While it continues to serve as a rough guide to many of the core features of HTML, it does not provide enough information to build implementations that interoperate with each other and, more importantly, with Web content. The same goes for XHTML1, which defines an XML serialization for HTML4, and DOM Level 2 HTML, which defines JavaScript APIs for both HTML and XHTML. HTML replaces these documents. [DOM2HTML] [HTML4] [XHTML1]
The HTML specification reflects an effort, started in 2004, to study contemporary HTML implementations and Web content. The specification:
Defines a single language called HTML which can be written in HTML syntax and in XML syntax.
Defines detailed processing models to foster interoperable implementations.
Improves markup for documents.
Introduces markup and APIs for emerging idioms, such as Web applications.
1.3 Open Issues
See the "Status of This Document" section of the HTML5 specification.
1.4 Backward Compatibility
HTML is defined in a way that is backward compatible with the way user agents handle content. To keep the language relatively simple for Web developers, several older elements and attributes are not included, as outlined in the other sections of this document, such as presentational elements that are better handled using CSS.
User agents, however, will always have to support these older elements and attributes. This is why the HTML specification clearly separates requirements for Web developers (referred to as "authors" in the specification) and user agents; for instance, this means that Web developers cannot use the isindex
or the plaintext
element, but user agents are required to support them in a way that is compatible with how these elements need to behave for compatibility with Web content.
Since HTML has separate conformance requirements for Web developers and user agents there is no longer a need for marking features "deprecated".
2 Syntax
HTML defines a syntax, referred to as "the HTML syntax", that is mostly compatible with HTML4 and XHTML1 documents published on the Web, but is not compatible with the more esoteric SGML features of HTML4, such as processing instructions and shorthand markup as these are not supported by most user agents. Documents using the HTML syntax are served with the text/html
media type.
HTML also defines detailed parsing rules (including "error handling") for this syntax which are largely compatible with HTML4-era implementations. User agents have to use these rules for resources that have the text/html
media type. Here is an example document that conforms to the HTML syntax:
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>Example document</title>
</head>
<body>
<p>Example paragraph</p>
</body>
</html>
The other syntax that can be used for HTML is XML. This syntax is compatible with XHTML1 documents and implementations. Documents using this syntax need to be served with an XML media type (such asapplication/xhtml+xml
or application/xml
) and elements need to be put in the http://www.w3.org/1999/xhtml
namespace following the rules set forth by the XML specifications. [XML] [XMLNS]
Below is an example document that conforms to the XML syntax of HTML.
<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Example document</title>
</head>
<body>
<p>Example paragraph</p>
</body>
</html>
2.1 Character Encoding
For the HTML syntax, Web developers are required to declare the character encoding. There are three ways to do that:
At the transport level; for instance, by using the HTTP
Content-Type
header.Using a Unicode Byte Order Mark (BOM) character at the start of the file. This character provides a signature for the encoding used.
Using a
meta
element with acharset
attribute that specifies the encoding within the first 1024 bytes of the document; for instance,<meta charset="UTF-8">
could be used to specify the UTF-8 encoding. This replaces the need for<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
although that syntax is still allowed.
For the XML syntax, Web developers have to use the rules as set forth in the XML specification to set the character encoding.
2.2 The Doctype
The HTML syntax requires a doctype to be specified to ensure that the browser renders the page in standards mode. The doctype has no other purpose. [DOCTYPE]
The doctype declaration for the HTML syntax is <!DOCTYPE html>
and is case-insensitive. Doctypes from earlier versions of HTML were longer because the HTML language was SGML-based and therefore required a reference to a DTD. This is no longer the case and the doctype is only needed to enable standards mode for documents written using the HTML syntax. Browsers already do this for <!DOCTYPE html>
.
To support legacy markup generators that cannot generate the preferred short doctype, the doctype <!DOCTYPE html SYSTEM "about:legacy-compat">
is allowed in the HTML syntax.
The strict doctypes for HTML 4.0, HTML 4.01, XHTML 1.0 as well as XHTML 1.1 are also allowed (but are discouraged) in the HTML syntax.
In the XML syntax, any doctype declaration may be used, or it may be omitted altogether. Documents with an XML media type are always handled in standards mode.
2.3 MathML and SVG
The HTML syntax allows for MathML and SVG elements to be used inside a document. An math
or svg
start tag causes the HTML parser to switch to a special insertion mode which puts elements and attributes in the appropriate namespaces, does case fixups for elements and attributes that have mixed case, and supports the empty-element syntax as in XML. The syntax is still case-insensitive and attributes allow the same syntax as for HTML elements. Namespace declarations may be omitted. CDATA sections are supported in this insertion mode.
Some MathML and SVG elements cause the parser to switch back to "HTML mode", e.g. mtext
and foreignObject
, so you can use HTML elements or a new math
or svg
element.
For instance, a very simple document using some of the minimal syntax features could look like:
<!doctype html>
<title>SVG in text/html</title>
<p>
A green circle:
<svg> <circle r="50" cx="50" cy="50" fill="green"/> </svg>
</p>
2.4 Miscellaneous
There are a few other changes in the HTML syntax worthy of mentioning:
The
⟨
and⟩
named character references now expand to U+27E8 and U+27E9 (mathematical left/right angle bracket) instead of U+2329 and U+232A (left/right-pointing angle bracket), respectively.Many new named character references have been added, including all named character references from MathML.
Void elements (known as "EMPTY" in HTML4) are allowed to have a trailing slash.
The ampersand (
&
) may be left unescaped in more cases compared to HTML4.Attributes have to be separated by at least one whitespace character.
Attributes with an empty value may be written as just the attribute name omitting the equals sign and the value, even if the attribute is not a boolean attribute. (It is commonly believed that HTML4 allowed the value to be omitted for boolean attributes. Instead, HTML4 allowed using only the attribute value and omitting the attribute name, for enumerated attributes, but this was not supported in browsers.)
Attributes omitting quotes for the value are allowed to use a larger set of characters compared to HTML4.
The HTML parser does not do any normalization of whitespace in attribute values; for instance, leading and trailing whitespace in the
id
attribute is not ignored (and thus now invalid), and newline characters can be used in thevalue
attribute of theinput
element without using character references.The
optgroup
end tag is now optional.The
colgroup
start tag is now optional and is inferred by the HTML parser.
3 Language
This section is split up in several subsections to more clearly illustrate the various differences from HTML4.
3.1 New Elements
The following elements have been introduced for better structure:
section
represents a generic document or application section. It should be used together with theh1
,h2
,h3
,h4
,h5
, andh6
elements to indicate the document structure.article
represents an independent piece of content of a document, such as a blog entry or newspaper article.main
represents the main content of the body of a document or application.aside
represents a piece of content that is only slightly related to the rest of the page.header
represents a group of introductory or navigational aids.footer
represents a footer for a section and can contain information about the author, copyright information, etc.nav
represents a section of the document intended for navigation.figure
represents a piece of self-contained flow content, typically referenced as a single unit from the main flow of the document.<figure>
<video src="example.webm" controls></video>
<figcaption>Example</figcaption>
</figure>figcaption
can be used as caption (it is optional).template
can be used to declare fragments of HTML that can be cloned and inserted in the document by script.
Then there are several other new elements:
video
andaudio
for multimedia content. Both provide an API so application Web developers can script their own user interface, but there is also a way to trigger a user interface provided by the user agent.source
elements are used together with these elements if there are multiple streams available of different types.embed
is used for plugin content.mark
represents a run of text in one document marked or highlighted for reference purposes, due to its relevance in another context.progress
represents a completion of a task, such as downloading or when performing a series of expensive operations.meter
represents a measurement, such as disk usage.time
represents a date and/or time.bdi
represents a span of text that is to be isolated from its surroundings for the purposes of bidirectional text formatting.wbr
represents a line break opportunity.canvas
is used for rendering dynamic bitmap graphics on the fly, such as graphs or games.datalist
together with the a newlist
attribute forinput
can be used to make comboboxes:<input list="browsers">
<datalist id="browsers">
<option value="Safari">
<option value="Internet Explorer">
<option value="Opera">
<option value="Firefox">
</datalist>keygen
represents control for key pair generation.output
represents some type of output, such as from a calculation done through scripting.
The input
element's type
attribute now has the following new values:
The idea of these new types is that the user agent can provide the user interface, such as a calendar date picker or integration with the user's address book, and submit a defined format to the server. It gives the user a better experience as his input is checked before sending it to the server meaning there is less time to wait for feedback.
3.2 New Attributes
Several attributes have been introduced to various elements that were already part of HTML4:
The
area
element, for consistency with thea
andlink
elements, now also has thehreflang
,type
andrel
attributes.The
base
element can now have atarget
attribute as well, mainly for consistency with thea
element. (This is already widely supported.)The
meta
element has acharset
attribute now as this was already widely supported and provides a nice way to specify the character encoding for the document.A new
autofocus
attribute can be specified on theinput
(except when thetype
attribute ishidden
),select
,textarea
andbutton
elements. It provides a declarative way to focus a form control during page load. Using this feature should enhance the user experience compared to focusing the element with script as the user can turn it off if the user does not like it, for instance.A new
placeholder
attribute can be specified on theinput
andtextarea
elements. It represents a hint intended to aid the user with data entry.<input type=search name=q placeholder="Enter search phrase..."> <button>Search</button>
<label>Email <input type=email name=email placeholder="john@example.com"></label>
The
placeholder
attribute should not be used as a replacement for thelabel
element.<!-- Do not do this: -->
<input type=email name=email placeholder="Email">The new
form
attribute forinput
,output
,select
,textarea
,button
,label
,object
andfieldset
elements allows for controls to be associated with a form. These elements can now be placed anywhere on a page, not just as descendants of theform
element, and still be associated with aform
.<table>
<tr>
<th>Key
<th>Value
<th>Action
<tr>
<td><form id=1><input name=1-key></form>
<td><input form=1 name=1-value>
<td><button form=1 name=1-action value=save>✓</button>
<button form=1 name=1-action value=delete>✗</button>
...
</table>The new
required
attribute applies toinput
(except when thetype
attribute ishidden
,image
or some button type such assubmit
),select
andtextarea
. It indicates that the user has to fill in a value in order to submit the form. Forselect
, the firstoption
element has to be a placeholder with an empty value.<label>Color: <select name=color required>
<option value="">Choose one
<option>Red
<option>Green
<option>Blue
</select></label>The
fieldset
element now allows thedisabled
attribute which disables all descendant controls (excluding those that are descendants of thelegend
element) when specified, and thename
attribute which can be used for script access.The
input
element has several new attributes to specify constraints:autocomplete
,min
,max
,multiple
,pattern
andstep
. As mentioned before it also has a newlist
attribute which can be used together with thedatalist
element. It also now has thewidth
andheight
attributes to specify the dimensions of the image when usingtype=image
.The
input
andtextarea
elements have a new attribute nameddirname
that causes the directionality of the control as set by the user to be submitted as well.The
textarea
element also has three new attributes,maxlength
,minlength
andwrap
which control max input length and submitted line wrapping behavior, respectively.The
form
element has anovalidate
attribute that can be used to disable form validation submission (i.e. the form can always be submitted).The
input
andbutton
elements haveformaction
,formenctype
,formmethod
,formnovalidate
, andformtarget
as new attributes. If present, they override theaction
,enctype
,method
,novalidate
, andtarget
attributes on theform
element.The
script
element has a new attribute calledasync
that influences script loading and execution.The
html
element has a new attribute calledmanifest
that points to an application cache manifest used in conjunction with the API for offline Web applications.The
link
element has a new attribute calledsizes
. It can be used in conjunction with theicon
relationship (set through therel
attribute; can be used for e.g. favicons) to indicate the size of the referenced icon, thus allowing for icons of distinct dimensions.The
ol
element has a new attribute calledreversed
. When present, it indicates that the list order is descending.The
iframe
element has new attributes calledsandbox
andsrcdoc
which allow for sandboxing content, e.g. blog comments.The
object
element has a new attribute calledtypemustmatch
which allows safer embedding of external resources.The
img
element has a new attribute calledcrossorigin
to use CORS in the fetch and if it is successful, allows the image data to be read with thecanvas
API.
Several attributes from HTML4 now apply to all elements. These are called global attributes: accesskey
, class
, dir
, id
, lang
, style
, tabindex
and title
. Additionally, XHTML 1.0 only allowed xml:space
on some elements, which is now allowed on all elements in XHTML documents.
There are also several new global attributes:
The
contenteditable
attribute indicates that the element is an editable area. The user can change the contents of the element and manipulate the markup.The
data-*
collection of Web developer-defined attributes. Web developers can define any attribute they want as long as they prefix it withdata-
to avoid clashes with future versions of HTML. These are intended to be used to store custom data to be consumed by the Web page or application itself. They are not intended for data to be consumed by other parties (e.g. user agents).The
hidden
attribute indicates that an element is not yet, or is no longer, relevant.The
role
andaria-*
collection attributes which can be used to instruct assistive technology.The
spellcheck
attribute allows for hinting whether content can be checked for spelling or not.The
translate
attribute gives a hint to translators whether the content should be translated.
HTML also makes all event handler attributes from HTML4, which take the form onevent
, global attributes and adds several new event handler attributes for new events it defines; for instance, theonplay
event handler attribute for the play
event which is used by the API for the media elements (video
and audio
). The specification has an index of all events.
3.3 Changed Elements
These elements have slightly modified meanings in HTML to better reflect how they are used on the Web or to make them more useful:
The
address
element is now scoped by the nearest ancestorarticle
orbody
element.The
b
element now represents a span of text to which attention is being drawn for utilitarian purposes without conveying any extra importance and with no implication of an alternate voice or mood, such as key words in a document abstract, product names in a review, actionable words in interactive text-driven software, or an article lede.The
blockquote
element still represents content that is quoted from another source but now also allows including a citation in afooter
orcite
element as well as inline changes such as annotations and abbreviations.The
dl
element now represents an association list of name-value groups, and is no longer said to be appropriate for dialogue.The
hr
element now represents a paragraph-level thematic break.The
i
element now represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose in a manner indicating a different quality of text, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, or a ship name in Western texts.For the
label
element the browser should no longer move focus from the label to the control unless such behavior is standard for the underlying platform user interface.The
noscript
element is no longer said to be rendered when the user agent doesn't support a scripting language invoked by ascript
element earlier in the document.The
s
element now represents contents that are no longer accurate or no longer relevant.The
script
element can now be used for scripts or for custom data blocks.The
small
element now represents side comments such as small print.The
strong
element now represents importance rather than strong emphasis.The
u
element now represents a span of text with an unarticulated, though explicitly rendered, non-textual annotation, such as labeling the text as being a proper name in Chinese text (a Chinese proper name mark), or labeling the text as being misspelt.
3.4 Changed Attributes
Several attributes have changed in various ways.
The
alt
attribute onimg
has more elaborate requirements, and in some cases can also be omitted. For details, see the specification.The
accept
attribute oninput
now allows the valuesaudio/*
,video/*
andimage/*
.The
accesskey
global attribute now allows multiple characters to be specified, which the user agent can choose from.The
action
attribute onform
is no longer allowed to have an empty URL.The
border
attribute ontable
only allows the values "1" and the empty string.The
colspan
attribute ontd
andth
now has to be greater than zero.The
coords
attribute onarea
no longer allows a percentage value of the radius when the element is in the circle state.The
data
attribute onobject
is no longer said to be relative to thecodebase
attribute.The
defer
attribute onscript
now explicitly makes the script execute when the page has finished parsing.The
dir
global attribute now allows the valueauto
.The
enctype
attribute onform
now supports the valuetext/plain
.The
width
andheight
attributes onimg
,iframe
andobject
are no longer allowed to contain percentages. They are also not allowed to be used to stretch the image to a different aspect ratio than its intrinsic aspect ratio.The
href
attribute onlink
is no longer allowed to have an empty URL.The
href
attribute onbase
is now allowed to contain a relative URL.All attributes that take URLs, e.g.
href
on thea
element, now support IRIs if the document's encoding is UTF-8 or UTF-16.The
http-equiv
attribute onmeta
is no longer said to be used by HTTP servers to create HTTP headers in the HTTP response. Instead, it is said to be a pragma directive to be used by the user agent.The
id
global attribute is now allowed to have any value, as long as it is unique, is not the empty string, and does not contain space characters.The
lang
global attribute takes the empty string in addition to a valid language identifier, just likexml:lang
does in XML.The
media
attribute onlink
now accepts a media query list and defaults to "all".The event handler attributes (e.g.
onclick
) now always use JavaScript as the scripting language.The
value
attribute of theli
element is no longer deprecated as it is not presentational. The same goes for thestart
andtype
attributes of theol
element.The
style
global attribute now always uses CSS as the styling language.The
tabindex
global attribute now allows negative values which indicate that the element can receive focus but cannot be tabbed to.The
target
attribute of thea
andarea
elements is no longer deprecated, as it is useful in Web applications, e.g. in conjunction withiframe
.The
type
attribute onscript
andstyle
is no longer required if the scripting language is JavaScript and the styling language is CSS, respectively.The
usemap
attribute onimg
no longer takes a URL, but instead takes a valid hash-name reference to amap
element.
3.5 Obsolete Elements
The elements in this section are not to be used by Web developers. User agents will still have to support them and various sections in HTML define how. E.g. the obsolete isindex
element is handled by the parser section.
The following elements are not in HTML because their effect is purely presentational and their function is better handled by CSS:
The following elements are not in HTML because using them damages usability and accessibility:
The following elements are not included because they have not been used often, created confusion, or their function can be handled by other elements:
acronym
is not included because it has created a lot of confusion. Web developers are to useabbr
for abbreviations.isindex
usage can be replaced by usage of form controls.
Finally the noscript
element is only conforming in the HTML syntax. It is not allowed in the XML syntax. This is because in order to not only hide visually but also prevent the content to run scripts, apply style sheets, have submittable form controls, load resources, and so forth, the HTML parser parses the content of the noscript
element as plain text. The same is not possible with an XML parser.
3.6 Obsolete Attributes
Some attributes from HTML4 are no longer allowed in HTML. The specification defines how user agents should process them in legacy documents, but Web developers are not allowed use them and they will not validate.
HTML has advice on what you can use instead.
longdesc
attribute oniframe
.archive
,classid
,codebase
,codetype
,declare
andstandby
attributes onobject
.
In addition, HTML has none of the presentational attributes that were in HTML4 as their functions are better handled by CSS:
align
attribute oncaption
,iframe
,img
,input
,object
,legend
,table
,hr
,div
,h1
,h2
,h3
,h4
,h5
,h6
,p
,col
,colgroup
,tbody
,td
,tfoot
,th
,thead
andtr
.background
attribute onbody
.cellpadding
andcellspacing
attributes ontable
.char
andcharoff
attributes oncol
,colgroup
,tbody
,td
,tfoot
,th
,thead
andtr
.frameborder
attribute oniframe
.marginheight
andmarginwidth
attributes oniframe
.valign
attribute oncol
,colgroup
,tbody
,td
,tfoot
,th
,thead
andtr
.width
attribute onhr
,table
,td
,th
,col
,colgroup
andpre
.
The following attributes are allowed but Web developers are discouraged from using them and instead strongly encouraged to use an alternative solution:
The
border
attribute onimg
. It is required to have the value "0
" when present. Web developers can use CSS instead.The
language
attribute onscript
. It is required to have the value "JavaScript
" (case-insensitive) when present and cannot conflict with thetype
attribute. Web developers can simply omit it as it has no useful function.The
name
attribute ona
. Web developers can use theid
attribute instead.
4 Content Model
The content model is what defines how elements may be nested — what is allowed as children (or descendants) of a certain element.
At a high level, HTML4 had two major categories of elements, "inline" (e.g. span
, img
, text), and "block-level" (e.g. div
, hr
, table
). Some elements did not fit in either category.
Some elements allowed "inline" elements (e.g. p
), some allowed "block-level" elements (e.g. body
), some allowed both (e.g. div
), while other elements did not allow either category but only allowed other specific elements (e.g. dl
, table
), or did not allow any children at all (e.g. link
, img
, hr
).
Notice the difference between an element itself being in a certain category, and having a content model of a certain category; for instance, the p
element is itself a "block-level" element, but has a content model of "inline".
To make it more confusing, HTML4 had different content model rules in its Strict, Transitional and Frameset flavors; for instance, in Strict, the body
element allowed only "block-level" elements, but in Transitional, it allowed both "inline" and "block-level".
To make things more confusing still, CSS uses the terms "block-level element" and "inline-level element" for its visual formatting model, which is related to CSS's 'display' property and has nothing to do with HTML's content model rules.
HTML does not use the terms "block-level" or "inline" as part of its content model rules, to reduce confusion with CSS. However, it has more categories than HTML4, and an element can be part of none of them, one of them, or several of them.
Flow content, e.g.
span
,div
, text. This is roughly like HTML4's "block-level" and "inline" together.Heading content, e.g.
h1
.Phrasing content, e.g.
span
,img
, text. This is roughly like HTML4's "inline". Elements that are phrasing content are also flow content.Interactive content, e.g.
a
,button
,label
. Interactive content is not allowed to be nested.
As a broad change from HTML4, HTML no longer has any element that only accepts what HTML4 called "block-level" elements; e.g. the body
element now allows flow content. Thus, This is closer to HTML4 Transitional than HTML4 Strict.
Further changes include:
The
address
element now allows flow content, but with no heading content descendants, no sectioning content descendants, and noheader
,footer
, oraddress
element descendants.The
noscript
element was a "block-level" element in HTML4, but is phrasing content in HTML.The
table
,thead
,tbody
,tfoot
,tr
,ol
,ul
anddl
elements are allowed to be empty in HTML.Table elements have to conform to the table model (e.g. two cells are not allowed to overlap).
The
table
element now does not allowcol
elements as direct children. However, the HTML parser implies acolgroup
element, so this change should not affecttext/html
content.The
table
element now allows thetfoot
element to be the last child.The
caption
element now allows flow content, but with no descendanttable
elements.The
th
element now allows flow content, but with noheader
,footer
, sectioning content, or heading content descendants.The
a
element now has a transparent content model (except it does not allow interactive content descendants), meaning that it has the same content model as its parent. This means that thea
element can now contain e.g.div
elements, if its parent allows flow content.The
ins
anddel
elements also have a transparent content model. HTML4 had similar rules in prose that could not be expressed in the DTD.The
object
element also has a transparent content model, after itsparam
children.The
map
element also has a transparent content model. Thearea
element is considered phrasing content if there is amap
element ancestor, which means that they do not need to be direct children ofmap
.
5 APIs
HTML has introduced many new APIs and has extended, changed or obsoleted some existing APIs.
5.1 New APIs
HTML introduces a number of APIs that help in creating Web applications. These can be used together with the new elements introduced for applications:
Media elements (
video
andaudio
) have APIs for controlling playback, syncronising multiple media elements, and timed text tracks (e.g. subtitles).An API for form constraint validation (e.g. the
setCustomValidity()
method).An API that enables offline Web applications, with an application cache.
An API that allows a Web application to register itself for certain protocols or media types, using
registerProtocolHandler()
andregisterContentHandler()
.Editing API in combination with a new global
contenteditable
attribute.An API that exposes the components of the document's URL and allows scripts to navigate, redirect and reload (the
Location
interface).An API that exposes the session history and allows scripts to update the document's URL without actually navigating, so that applications don't need to abuse the fragment component for "Ajax-style" navigation (the
History
interface).An API to schedule timer-based callbacks (
setTimeout()
andsetInterval()
).An API for printing the document (
print()
).An API for handling search providers (
AddSearchProvider()
andIsSearchProviderInstalled()
).The
Window
,Navigator
andExternal
interfaces have been defined.
5.2 Changed APIs
The following features from DOM Level 2 HTML are changed in various ways:
document.title
now collapses whitespace on getting.document.domain
is made settable, which can change the document's effective script origin.document.open()
now either clears the document (if invoked with two or less arguments), or acts likewindow.open()
(if invoked with three or four arguments). In the former case, throws an exception in XML.document.close()
,document.write()
anddocument.writeln()
throw an exception in XML. The latter two now support variadic arguments; they can add text to the document's input stream while it is still being parsed, imply a call todocument.open()
, or be ignored altogether in some cases.document.getElementsByName()
now returns all HTML elements with aname
attribute matching the argument.elements
onHTMLFormElement
now returns anHTMLFormControlsCollection
ofbutton
,fieldset
,input
,keygen
,object
,output
,select
andtextarea
elements.length
returns the number of nodes inelements
.add()
onHTMLSelectElement
now also accepts an integer as its second argument.remove()
onHTMLSelectElement
now removes the first element in the collection if the argument is out of bounds.The
click()
,focus()
andblur()
methods are now available on all HTML elements.
5.3 Extensions to Document
DOM Level 2 HTML had an HTMLDocument
interface that inherited from Document
and provided HTML-specific members on documents. HTML has moved these members to the Document
interface, and extended it in a number of ways. Since all documents use the Document
interface, the HTML-specific members are now available on all documents, so they are usable in e.g. SVG documents as well. It also has several new members:
location
,lastModified
andreadyState
to help resource metadata management.dir
,head
,embeds
,plugins
,scripts
, and a generic name getter, to access various parts of the DOM tree.activeElement
andhasFocus
to determine which element is currently focused and whether theDocument
has focus respectively.designMode
,execCommand()
,queryCommandEnabled()
,queryCommandIndeterm()
,queryCommandState()
,queryCommandSupported()
,queryCommandValue()
for the editing API.All event handler IDL attributes. Also,
onreadystatechange
is a special event handler IDL attribute that is only available onDocument
.
Existing scripts that modified the prototype of HTMLDocument
should continue to work because window.HTMLDocument
now returns the Document
interface object.
5.4 Extensions to HTMLElement
The HTMLElement
interface has also gained several extensions in HTML:
translate
,hidden
,tabIndex
,accessKey
,contentEditable
,spellcheck
andstyle
reflect content attributes.dataset
is a convenience feature for handling thedata-*
attributes, which are exposed as camel-cased properties; for instance,elm.dataset.fooBar = 'test'
sets thedata-foo-bar
content attribute onelm
.click()
,focus()
andblur()
allow scripts to simulate clicks and moving focus.accessKeyLabel
gives the shortcut key that the user agent has assigned for the element, which the Web developer can influence with theaccesskey
attribute.isContentEditable
returns true if the element is editable.All event handler IDL attributes.
Some members were previously defined on HTMLElement
but been moved to the Element
interface in the DOM standard: [DOM]
id
reflects theid
content attribute.className
reflects theclass
content attribute.classList
is a convenient accessor forclassName
. The object it returns exposes methods (contains()
,add()
,remove()
, andtoggle()
) for manipulating the element's classes.getElementsByClassName()
returns a list of elements with the specified classes.
5.5 Extensions to Other Interfaces
Some interfaces in DOM Level 2 HTML have been extended.
HTMLOptionsCollection
now has a legacy caller, setter creator, and the membersadd()
,remove()
andselectedIndex
HTMLLinkElement
andHTMLStyleElement
now implement theLinkStyle
interface from CSSOM. [CSSOM]HTMLFormElement
now has a named getter and an indexed getter, as well as thecheckValidity()
method.HTMLSelectElement
now has a getter,item()
andnamedItem()
methods, a setter creator,selectedOptions
andlabels
IDL attributes, and members for the form constrain validation API:willValidate
,validity
,validationMessage
,checkValidity()
,reportValidity()
, andsetCustomValidity()
.HTMLOptionElement
now has a constructorOption
.HTMLInputElement
now has the membersfiles
,height
,indeterminate
,list
,valueAsDate
,valueAsNumber
,width
,stepUp()
,stepDown()
, the form constraint validation API members,labels
, and members for the text field selection API:selectionStart
,selectionEnd
,selectionDirection
,setSelectionRange()
andsetRangeText()
.HTMLTextAreaElement
now has the memberstextLength
, the form constraint validation API members,labels
and the text field selection API members.HTMLButtonElement
now has the form constraint validation API members andlabels
.HTMLLabelElement
now has the membercontrol
.HTMLFieldSetElement
now has the memberstype
,elements
and the form constraint validation API members.HTMLAnchorElement
now has the membersrelList
,text
, and implements theURLUtils
interface which has the membershref
,origin
,protocol
,username
,password
,host
,hostname
,port
,pathname
,search
,searchParams
andhash
.HTMLLinkElement
andHTMLAreaElement
also have therelList
IDL attribute.HTMLAreaElement
also implements theURLUtils
interface.HTMLImageElement
now has a constructorImage
, and the membersnaturalWidth
,naturalHeight
andcomplete
.HTMLObjectElement
now has the memberscontentWindow
, the form constraint validation API members and a legacy caller.HTMLMapElement
now has the memberimages
.HTMLTableElement
now has the memberscreateTBody()
.HTMLIFrameElement
now has the membercontentWindow
.
In addition, most new content attributes also have corresponding IDL attributes on the elements' interfaces, e.g. the sizes
IDL attribute on HTMLLinkElement
which reflects the sizes
content attribute.
5.6 Obsolete APIs
Some APIs are now either removed altogether, or marked as obsolete.
All IDL attributes that reflect a content attribute that is itself obsolete, are now also obsolete; for instance, the bgColor
IDL attribute on HTMLBodyElement
which reflects the obsolete bgcolor
content attribute is now obsolete.
The following interfaces are marked obsolete since the elements are obsolete: HTMLAppletElement
, HTMLFrameSetElement
, HTMLFrameElement
, HTMLDirectoryElement
and HTMLFontElement
.
The HTMLIsIndexElement
interface is removed altogether since the HTML parser expands an isindex
tag into other elements. The HTMLBaseFontElement
interface is also removed since the element has no effect.
The following members of the HTMLDocument
interface (which have now moved to Document
) are now obsolete: anchors
and applets
.
Acknowledgments
The editors would like to thank Ben Millard, Bruce Lawson, Cameron McCormack, Charles McCathieNevile, Dan Connolly, David Håsäther, Dennis German, Frank Ellermann, Frank Palinkas, 羽田野太巳 (Futomi Hatano), Gordon P. Hemsley, Henri Sivonen, James Graham, Jens O. Meiert, Jeremy Keith, Jukka K. Korpela, Jürgen Jeka, Krijn Hoetmer, Leif Halvard Silli, Maciej Stachowiak, Mallory van Achterberg, Marcos Caceres, Mark Pilgrim, Martijn Wargers, Martin Leese, Martyn Haigh, Masataka Yakura, Michael Smith, Mike Taylor, Ms2ger, Olivier Gendrin, Øistein E. Andersen, Philip Jägenstedt, Philip Taylor, Randy Peterman, Robin Berjon, Steve Faulkner, Toby Inkster, Xaxio Brandish, Yngve Spjeld Landro and Zhong Yu for their contributions to this document as well as to all the people who have contributed to HTML over the years for improving the Web!
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