HTML5 is the newest version of HTML that incorporates features from previous versions and adds new tools for web developers. It is still a work in progress with no full browser support expected until 2018. Key goals of HTML5 include supporting existing pages, reducing need for plugins, improving semantic meaning of elements, and making rendering universal across devices. New elements were introduced and features like audio, video, Canvas, and offline apps are now supported within HTML5. The DOCTYPE and HTML declarations were also simplified for easier reading and writing of code.