HTML5 is the next major revision of HTML (Hypertext Markup Language), the core markup language of the World Wide Web. The Web Hypertext Application Technology Working Group (WHATWG) started work on the specification in June 2004 under the name Web Applications 1.0. As of October 2009, the specification is in the "Last Call" state at the WHATWG.
HTML5 is the proposed next standard for HTML 4.01, XHTML 1.0 and DOM Level 2 HTML.
HTML5 aims to reduce the need for proprietary plug-in-based rich Internet application (RIA) technologies such as Adobe Flash, Microsoft Silverlight, and Sun JavaFX.
The ideas behind HTML5 were pioneered in 2004 by the WHATWG; HTML5 incorporates Web Forms 2.0, another WHATWG specification. The HTML5 specification was adopted as the starting point of the work of the new HTML working group of the W3C in 2007. This working group published the First Public Working Draft of the specification on January 22, 2008. The specification is an ongoing work, and is expected to remain so for many years, although parts of HTML5 are going to be finished and implemented in browsers before the whole specification reaches final Recommendation status. The editors are Ian Hickson of Google, Inc. and David Hyatt of Apple, Inc.
HTML5 introduces a number of new elements and attributes that reflect typical usage on modern Web sites. Some of them are semantic replacements for common uses of generic block (<div>) and inline (<span>) elements, for example <nav> (website navigation block) and <footer>. Other elements provide new functionality through a standardized interface, such as the <audio> and <video> elements.
Some deprecated elements from HTML 4.01 have been dropped, including purely presentational elements such as <font> and <center>, whose effects are achieved using CSS. There is also a renewed emphasis on the importance of DOM scripting in Web behavior.
The HTML5 syntax is no longer based on SGML despite the similarity of its markup. It has, however, been designed to be backward compatible with common parsing of older versions of HTML. It comes with a new introductory line that looks like an SGML document type declaration, <!DOCTYPE html>, which enables standards-compliant rendering in all browsers that use "DOCTYPE sniffing".
In addition to specifying markup, HTML5 specifies scripting application programming interfaces (APIs). Existing document object model (DOM) interfaces are extended and de facto features documented. There are also new APIs, such as:
* The canvas element for immediate mode 2D drawing
* Timed media playback
* Offline storage database
* Document editing
* Cross-document messaging
* Browser history management
* MIME type and protocol handler registration
Some of the new features are part of HTML5 mainly because there are no volunteers to split HTML5 and maintain separate specifications of these features.
Differences from HTML 4.01/XHTML 1.x
The following is a cursory list of differences and some specific examples.
* New parsing rules oriented towards flexible parsing and compatibility; not based on SGML
* Ability to use inline SVG and MathML in text/html
* New elements – section, article, footer, audio, video, progress, nav, meter, time, aside, canvas, hgroup
* New types of form controls – dates and times, email, url, search
* New attributes – ping (on a and area), charset (on meta), async (on script)
* Global attributes (that can be applied for every element) – id, tabindex, hidden, data-* (custom data attributes)
* Forms will get support for PUT and DELETE methods too instead of just GET and POST (see Representational State Transfer for use cases)
* Deprecated elements dropped – center, font, strike, frameset
Ian Hickson, editor of the HTML5 specification, expects the specification to reach the W3C Candidate Recommendation stage during 2012, and W3C Recommendation in the year 2022 or later. However, many parts of the specification are stable and may be implemented in products. According to the W3C timetable, it is estimated that HTML5 will reach W3C Recommendation by late 2010. However, the First Public Working Draft estimate was missed with 8 months, and Last Call and Candidate Recommendation were expected to be reached in 2008 but as of late 2009 HTML5 had not reached W3C Last Call.