Differences from HTML4 W3C Working Draft 28 May 2013 This Version: http://www.w3.org/TR/2013/WD-html5-diff-20130528/ Latest Version: http://www.w3.org/TR/html5-diff/ Latest Editor's Draft: https://rawgithub.com/whatwg/html-differences/master/Overview.html Participate: File a bug (open bugs) Version History: https://github.com/whatwg/html-differences/commits Previous Versions: http://www.w3.org/TR/2012/WD-html5-diff-20121025/ http://www.w3.org/TR/2012/WD-html5-diff-20120329/ http://www.w3.org/TR/2011/WD-html5-diff-20110525/ http://www.w3.org/TR/2011/WD-html5-diff-20110405/ http://www.w3.org/TR/2011/WD-html5-diff-20110405/ http://www.w3.org/TR/2011/WD-html5-diff-20110113/ http://www.w3.org/TR/2010/WD-html5-diff-20101019/ http://www.w3.org/TR/2010/WD-html5-diff-20100624/ http://www.w3.org/TR/2010/WD-html5-diff-20100304/ http://www.w3.org/TR/2009/WD-html5-diff-20090825/ http://www.w3.org/TR/2009/WD-html5-diff-20090423/ http://www.w3.org/TR/2009/WD-html5-diff-20090212/ http://www.w3.org/TR/2008/WD-html5-diff-20080610/ http://www.w3.org/TR/2008/WD-html5-diff-20080122/ Editor: Simon Pieters (Opera Software ASA) <[email protected]> Previous Editor: Anne van Kesteren <[email protected]> Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C liability, trademark and document use rules apply. Abstract HTML is the core language of the World Wide Web. The W3C publishes HTML5 and HTML5.1. The WHATWG publishes HTML, which is a rough superset of W3C HTML5.1. "Differences from HTML4" describes the differences of the HTML specifications from those of HTML4, and calls out cases where they differ from each other. This document may not provide accurate information, as the specifications are still actively in development. When in doubt, always check the specifications themselves. [HTML5] [HTML5NIGHTLY] [HTML] 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 28 May 2013 W3C Working Draft 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- [email protected], a mailing list with a public archive, is no longer used for tracking comments.) Publication as a Working Draft 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. Table of Contents 1 Introduction 1.1 Scope of This Document 1.2 History of HTML 1.3 Open Issues 1.4 Backward Compatibility 1.5 Development Model 2 Syntax 2.1 Character Encoding 2.2 The Doctype 2.3 MathML and SVG 2.4 Miscellaneous 3 Language 3.1 New Elements 3.2 New Attributes 3.3 Changed Elements 3.4 Changed Attributes 3.5 Obsolete Elements 3.6 Obsolete Attributes 4 Content Model 5 APIs 5.1 New APIs 5.2 Changed APIs 5.3 Extensions to Document 5.4 Extensions to HTMLElement 5.5 Extensions to Other Interfaces 5.6 Obsolete APIs 6 HTML Changelogs 6.1 Changes from 14 September 2012 to 6 May 2013 6.2 Changes from 29 March 2012 to 14 September 2012 6.3 Changes from 25 May 2011 to 29 March 2012 6.4 Changes from 5 April 2011 to 25 May 2011 6.5 Changes from 13 January 2011 to 5 April 2011 6.6 Changes from 19 October 2010 to 13 January 2011 6.7 Changes from 24 June 2010 to 19 October 2010 6.8 Changes from 4 March 2010 to 24 June 2010 6.9 Changes from 25 August 2009 to 4 March 2010 6.10 Changes from 23 April 2009 to 25 August 2009 6.11 Changes from 12 February 2009 to 23 April 2009 6.12 Changes from 10 June 2008 to 12 February 2009 6.13 Changes from 22 January 2008 to 10 June 2008 Acknowledgments References 1 Introduction 1.1 Scope of This Document This document covers the W3C HTML5 specification, W3C HTML5.1 specification, and the WHATWG HTML standard. For readability, these are referred to as if they were a single specification: "the HTML specification" or simply "HTML" when something applies equally to all of them; otherwise, they are called out explicitly. 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: 1. Defines a single language called HTML which can be written in HTML syntax and in XML syntax. 2. Defines detailed processing models to foster interoperable implementations. 3. Improves markup for documents. 4. Introduces markup and APIs for emerging idioms, such as Web applications. 1.3 Open Issues The contents of HTML, as well as the contents of this document which depend on HTML, are still being discussed on the HTML Working Group and WHATWG mailing lists. Open issues for WHATWG HTML, see "Issues:" at the top of the specification. The specification also has annotation boxes in the margin which can link to bugs. Open issues for W3C HTML5 and W3C HTML5.1, see the "Status of This Document" section. 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". 1.5 Development Model The HTML4 specification reached Recommendation status before it was completely implemented in user agents. HTML4 still is not completely implemented, because it contains various bugs that have been fixed in the current HTML specification, which user agents are much closer to implementing than HTML4. The WHATWG HTML standard is under continual development where bugs are fixed and new features are introduced over time. Features can also be removed from the specification if they lack implementor interest, are not being used by Web developers, or for other reasons. The WHATWG does not publish frozen snapshots. The W3C HTML5 specification is trying to reach Recommendation status. New features are generally not added unless they are implemented by at least two browsers and have tests demonstrating interoperability. Minor bug fixes can be applied. This means that W3C HTML5 may contain bugs that have been fixed in WHATWG HTML or W3C HTML5.1, or both. The W3C HTML5.1 specification is similar to WHATWG HTML: it is under continual development where bugs are fixed and new features are introduced over time, and features can be removed from the specification for the same reasons as with WHATWG HTML. It cherry-picks changes from the WHATWG HTML standard and also gets direct changes. It is expected to eventually go through the same procedure as W3C HTML5, and then a new version will be minted. 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.