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Public Facts about HTML5

HTML5 is a markup language used for structuring and presenting content on the World Wide Web. It is the fifth and final major HTML version that is a World Wide Web Consortium (W3C) recommendation.
The current specification is known as the HTML Living Standard. It is maintained by the Web Hypertext Application Technology Working Group (WHATWG).
WHATWG is a consortium of the major browser vendors (Apple, Google, Mozilla, and Microsoft). HTML5 was first released in a public-facing form on 22 January 2008, with a major update and “W3C Recommendation” status in October 2014.

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To subsume not only HTML 4 but also XHTML 1 and DOM Level 2 HTML.
HTML5 includes detailed processing models to encourage more interoperable implementations.
To improve the language with support for the latest multimedia and other new features.
It extends, improves, and rationalises the markup available for documents and introduces markup and application programming interfaces (APIs) for complex web applications.
Also to keep the language both easily readable by humans, computers and devices such as web browsers, parsers, etc and to remain backward-compatible with older software.
For facilitating cross-platform mobile applications because it includes features designed with low-powered devices in mind.