HTML5 is a markup language for structuring and presenting content for the World Wide Web and a core technology of the Internet. It is the fifth revision of the HTML standard and, as of December 2012, is a W3C Candidate Recommendation. Its core aims have been to improve the language with support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers and devices (web browsers, parsers, etc.).

HTML5 must be built on the following principles:

• Less dependence on plugins for functionality.
• Scripting should be replaced with markup whenever possible.
• Device independence (i.e., available on all devices and providing the same end experience).
• Public development process so people can see what’s going on.

More specifically, HTML5 adds a whole bunch of new markup tags:

• <header> and <footer> tags to help you isolate the tops and bottoms of content blocks. Can be used more than once on a single page.
• <article> tag which identifies a specific, singular piece of content, e.g., a blog post or a user comment.
• <nav> tag to specify which sections should be considered navigational blocks.
• <section> tag that lets you define a generic section of content; similar to the currently existing <div> tag.
• <audio> and <video> tags to mark the inclusion of audio or video content.
• <canvas> tag that lets you draw graphics using a separate scripting language.
• <embed> tag to embed external content or applications into the page.

HTML5 also deprecates some tags: <acronym>, <applet>, <font>, <frame>, <frameset>, <noframes>, and a handful of others.

The full standards specification for HTML5 is planned to be completed by 2014, but HTML5 has made lots of progress already and it can be used to implement site features even today. The full standards specification for HTML5.1 is planned to be completed by 2016.