HTML5

HTML5 is currently under development as the next major revision of the HTML standard. Like its immediate predecessors, HTML 4.01 and XHTML 1.1, HTML5 is a standard for structuring and presenting content on the World Wide Web. The new standard incorporates features like video playback and drag-and-drop that have been previously dependent on third-party browser plug-ins such as Adobe Flash, Microsoft Silverlight, and Google Gears.

W3C standardization process
The Web Hypertext Application Technology Working Group (WHATWG) started work on the specification in June 2004 under the name Web Applications 1.0. , the specification is in the Draft Standard state at the WHATWG, and in Working Draft state at the W3C. Ian Hickson of Google, Inc. is the editor of HTML5.

The HTML5 specification was adopted as the starting point of the work of the new HTML working group of the World Wide Web Consortium (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.

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 by 8 months, and Last Call and Candidate Recommendation were expected to be reached in 2008, but HTML5 is still at Working Draft stage in the W3C. HTML5 has been at Last Call in the WHATWG since October 2009.

Ian Hickson, editor of the HTML5 specification, expects the specification to reach the Candidate Recommendation stage during 2012. The criteria for the specification becoming a W3C Recommendation is “two 100% complete and fully interoperable implementations”. In an interview with TechRepublic, Hickson guessed that this would occur in the year 2022 or later. However, many parts of the specification are stable and may be implemented in products:

Markup
HTML5 introduces a number of new elements and attributes that reflect typical usage on modern websites. Some of them are semantic replacements for common uses of generic block and inline  elements, for example  (website navigation block) and  (usually referring to bottom of web page or to last lines of html code). Other elements provide new functionality through a standardized interface, such as the multimedia elements and HTML5 video. Some deprecated elements from HTML 4.01 have been dropped, including purely presentational elements such as and, whose effects are achieved using Cascading Style Sheets. There is also a renewed emphasis on the importance of DOM scripting (e.g., JavaScript) 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,, which enables standards-compliant rendering in all browsers that use "DOCTYPE sniffing".

HTML5 also incorporates Web Forms 2.0, another WHATWG specification.

New APIs
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. See Canvas 2D API Specification 1.0 specification
 * Timed media playback
 * Offline storage database (offline web applications). See Web Storage
 * Document editing
 * Drag-and-drop
 * Cross-document messaging
 * Browser history management
 * MIME type and protocol handler registration.
 * Microdata
 * Geolocation
 * Local SQL Database. Web SQL Database
 * Indexed hierarchical key-value store (formerly WebSimpleDB). Indexed Database API

Some of the new features are part of HTML5 and some are maintained in separate specifications.

Differences from HTML 4.01 and 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
 * New elements:,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,
 * New types of form controls:,  ,  ,  ,
 * New attributes:  (on   and  ),   (on  ),   (on  )
 * Global attributes (that can be applied for every element):,  ,  ,   (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 will be dropped altogether:,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,

dev.w3.org provides the latest Editors Draft (last dated 24 June 2010) of HTML5 differences from HTML4 which provides a complete outline of additions, removals and changes between HTML5.

Error handling
An HTML5 (text/html) browser will be flexible in handling incorrect syntax. HTML5 is designed so that old browsers can safely ignore new HTML5 constructs. In contrast to HTML 4.01, the HTML5 specification gives detailed rules for lexing and parsing, with the intent that different compliant browsers will produce the same result in the case of incorrect syntax. Although HTML5 now defines a consistent behavior for "tag soup" documents, those documents are not regarded as conforming to the HTML5 standard.