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.
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Bugzilla. (public-html-comments@w3.org,
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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.
Table of Contents
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 as
application/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 a charset
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 the
value attribute of the input 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 the h1, h2, h3,
h4, h5, and h6 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 and
audio 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.
track provides text tracks
for the video element.
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.
ruby,
rt, and
rp allow for marking up ruby
annotations.
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 new list attribute for
input 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 the
a and link elements, now also has the
hreflang, type and rel attributes.
The base element can now have a target
attribute as well, mainly for consistency with the
a element. (This is already widely supported.)
The meta element has a charset
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 the
input (except when the type attribute is
hidden), select, textarea and
button 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
the input and textarea 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 the
label element.
<!-- Do not do this: -->
<input type=email name=email placeholder="Email">
-
The new form attribute for input,
output, select, textarea,
button, label, object and fieldset 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 the
form element, and still be associated with a form.
<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 to
input (except when the type attribute is
hidden, image or some button type such as
submit), select and textarea. It indicates that the user
has to fill in a value in order to submit the form. For select, the first option 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 the
disabled attribute which disables all descendant controls (excluding those that are descendants of the legend element)
when specified, and the name attribute which can be used for script access.
The input element has several new attributes to
specify constraints: autocomplete, min,
max, multiple, pattern and
step. As mentioned before it also has a new
list attribute which can be used together with the
datalist element. It also now has the width and height attributes to specify the dimensions of the image when using type=image.
The input and textarea elements have
a new attribute named dirname 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 and
wrap which control max input
length and submitted line wrapping behavior, respectively.
The form element has a novalidate
attribute that can be used to disable form validation submission (i.e.
the form can always be submitted).
The input and button elements have
formaction, formenctype,
formmethod, formnovalidate, and
formtarget as new attributes. If present, they override
the action, enctype, method,
novalidate, and target attributes on the
form element.
The input element also has the new
minlength attribute.
The script element has a new attribute called
async that influences script loading and execution.
The html element has a new attribute called
manifest that points to an application cache manifest
used in conjunction with the API for offline Web applications.
The link element has a new attribute called
sizes. It can be used in conjunction with the
icon relationship (set through the rel
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 called
reversed. When present, it indicates that the list order
is descending.
The iframe element has new attributes called
sandbox
and srcdoc
which allow for sandboxing content, e.g. blog comments.
The object element has a new attribute called typemustmatch which allows safer embedding of external resources.
The img element has a new attribute called
crossorigin to use CORS in the fetch and if it is successful, allows the image data to be
read with the canvas 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 with data- 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 and
aria-*
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, the onplay
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 ancestor article
or body 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 a footer or
cite 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 a script 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 on img
has more elaborate requirements, and in some cases can also be omitted.
For details, see the specification.
The accept attribute on input now allows the values
audio/*, video/* and image/*.
The accesskey global attribute now allows multiple
characters to be specified, which the user agent can choose from.
The action
attribute on form is no longer allowed
to have an empty URL.
The border attribute on table only allows the values "1" and the
empty string.
The colspan attribute on td and th
now has to be greater than zero.
The coords attribute on area no longer allows a percentage value of
the radius when the element is in the circle state.
The data
attribute on object is no longer said
to be relative to the codebase attribute.
The defer attribute on script now explicitly makes the script
execute when the page has finished parsing.
The dir global
attribute now allows the value auto.
The enctype attribute on form now supports the value
text/plain.
The width
and height
attributes on img, iframe and object 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 on link is no longer allowed
to have an empty URL.
The href
attribute on base is now allowed to
contain a relative URL.
All attributes that take URLs, e.g. href on the a element, now support IRIs if the document's
encoding is UTF-8 or UTF-16.
The http-equiv attribute on meta 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 like xml:lang does in XML.
The media attribute on link 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 the li element is no
longer deprecated as it is not presentational. The same goes for the start and type attributes of the
ol 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 the a and area
elements is no longer deprecated, as it is useful in Web applications,
e.g. in conjunction with iframe.
The type
attribute on script and style is no longer required if the scripting
language is JavaScript and the styling language is CSS, respectively.
The usemap attribute on img no longer takes a URL, but instead takes
a valid hash-name reference to a map 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 use abbr for
abbreviations.
applet has been obsoleted in favor of
object.
isindex usage can be replaced by usage of form controls.
dir has been obsoleted in favor of ul.
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.
In addition, HTML has none of the presentational attributes
that were in HTML4 as their functions are better handled by
CSS:
align attribute on caption,
iframe, img, input,
object, legend, table,
hr, div, h1, h2,
h3, h4, h5, h6,
p, col, colgroup,
tbody, td, tfoot,
th, thead and tr.
alink, link, text and
vlink attributes on body.
background attribute on body.
bgcolor attribute on table, tr,
td, th and body.
border attribute on object.
cellpadding and cellspacing attributes on
table.
char and charoff attributes on
col, colgroup, tbody,
td, tfoot, th, thead
and tr.
clear attribute on br.
compact attribute on dl,
ol and ul.
frame attribute on table.
frameborder attribute on iframe.
height attribute on td and
th.
hspace and vspace attributes on
img and object.
marginheight and marginwidth attributes on
iframe.
noshade attribute on hr.
nowrap attribute on td and th.
rules attribute on table.
scrolling attribute on iframe.
size attribute on hr.
type attribute
on li, and ul.
valign attribute on col,
colgroup, tbody, td,
tfoot, th, thead and
tr.
width attribute on hr, table,
td, th, col, colgroup
and pre.
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 on img. It is required to have
the value "0" when present. Web developers can use CSS
instead.
The language attribute on script. It is required to have the value
"JavaScript" (case-insensitive) when present and cannot
conflict with the type attribute. Web developers can simply omit it as
it has no useful function.
The name attribute on a. Web developers can use the id 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.
Metadata content, e.g. link, script.
Flow content, e.g. span, div, text. This is roughly like HTML4's
"block-level" and "inline" together.
Sectioning content, e.g. aside,
section.
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.
Embedded content, e.g. img, iframe, svg.
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 no header,
footer, or address element descendants.
HTML4 allowed object in head. HTML does not.
The noscript element was a
"block-level" element in HTML4, but is phrasing content in HTML.
The table, thead, tbody, tfoot, tr,
ol, ul and dl 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
allow col elements as direct children.
However, the HTML parser implies a colgroup element, so this change should not
affect text/html content.
The table element now allows the
tfoot element to be the last child.
The caption element now allows
flow content, but with no descendant table elements.
The th element now allows flow
content, but with no header, 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 the a element can now contain e.g. div elements, if its parent allows flow
content.
The ins and del 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 its param children.
The map element also has a
transparent content model. The area
element is considered phrasing content if there is a map element ancestor, which means that they
do not need to be direct children of map.
The fieldset element no longer
requires a legend child.
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:
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 like window.open() (if invoked with
three or four arguments). In the former case, throws an exception in XML.
document.close(), document.write() and
document.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 to document.open(), or be ignored altogether in
some cases.
document.getElementsByName()
now returns all HTML elements with a name attribute matching
the argument.
elements
on HTMLFormElement now returns an
HTMLFormControlsCollection of button, fieldset, input, keygen, object, output, select and textarea elements. length returns the
number of nodes in elements.
add() on
HTMLSelectElement now also accepts an
integer as its second argument.
remove()
on HTMLSelectElement now removes the
first element in the collection if the argument is out of bounds.
a and area elements now stringify to their href attribute.
The click(),
focus() and blur() 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 and readyState to
help resource metadata management.
dir,
head, embeds, plugins, scripts, and a
generic name getter, to access various parts of the DOM tree.
activeElement and hasFocus to
determine which element is currently focused and whether the Document 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 on
Document.
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:
Some members were previously defined on HTMLElement but been moved to the Element
interface in the DOM standard: [DOM]
id reflects the id content attribute.
className reflects the class content attribute.
classList is a convenient accessor for
className. The object it returns exposes methods (contains(), add(),
remove(), and toggle()) 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 members add(), remove() and selectedIndex
HTMLLinkElement and HTMLStyleElement now implement the
LinkStyle interface from CSSOM. [CSSOM]
HTMLFormElement now has a named
getter and an indexed getter,
as well as the checkValidity() method.
HTMLSelectElement now has a
getter, item()
and namedItem() methods, a setter creator,
selectedOptions and labels IDL attributes,
and members for the form constrain validation API: willValidate,
validity, validationMessage, checkValidity(),
reportValidity(),
and setCustomValidity().
HTMLOptionElement now has a
constructor Option.
HTMLInputElement now has the
members files,
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()
and setRangeText().
HTMLTextAreaElement now has the
members textLength, the form constraint
validation API members, labels and the text field selection API
members.
HTMLButtonElement now has the
form constraint validation API members and labels.
HTMLLabelElement now has the
member control.
HTMLFieldSetElement now has the
members type,
elements
and the form constraint validation API members.
HTMLAnchorElement now has the
members relList,
text, and implements the URLUtils interface which has the members
href, origin,
protocol, username,
password, host,
hostname, port,
pathname, search,
searchParams and hash.
HTMLLinkElement and HTMLAreaElement also have the relList IDL attribute.
HTMLAreaElement also implements the URLUtils interface.
HTMLImageElement now has a
constructor Image, and the
members naturalWidth, naturalHeight and
complete.
HTMLObjectElement now has the
members contentWindow, the form constraint
validation API members and a legacy caller.
HTMLMapElement now has the
member images.
HTMLTableElement now has the
members createTBody()
.
HTMLIFrameElement now has the
member contentWindow.
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!
References
- [CSSOM]
- CSS Object Model (CSSOM), Simon Pieters and Glenn Adams. W3C.
- [DOCTYPE]
- Activating Browser Modes with Doctype, Henri Sivonen.
- [DOM]
- DOM, Anne van Kesteren, Aryeh Gregor and Ms2ger. WHATWG.
- [DOM2HTML]
- Document Object Model (DOM) Level 2 HTML Specification, Johnny Stenback, Philippe Le Hégaret and Arnaud Le Hors. W3C.
- [HTML]
- HTML, Ian Hickson. WHATWG.
- [HTML4]
- HTML 4.01 Specification, Dave Raggett, Arnaud Le Hors and Ian Jacobs. W3C.
- [HTML5]
- HTML5, Ian Hickson, Robin Berjon, Steve Faulkner, Travis Leithead et al.. W3C.
- [HTML5NIGHTLY]
- HTML 5.1 Nightly, Robin Berjon, Steve Faulkner, Travis Leithead et al.. W3C.
- [XHTML1]
- XHTML™ 1.1 - Module-based XHTML - Second Edition, Murray Altheim and Shane McCarron.
- [XML]
- Extensible Markup Language, Tim Bray, Jean Paoli, C. M. Sperberg-McQueen et al.. W3C.
- [XMLNS]
- Namespaces in XML, Tim Bray, Dave Hollander, Andrew Layman et al.. W3C.