Which standard to use: HTML5 or XHTML5?

XHTML is abandoned, all versions. The old ones are still supported by browsers. Version 5, as far as I know, is not supported by none and will not be except for things that match HTML5. The path is HTML5.

Particularly I consider it an error, even if allowed, to use any element of XHTML, for example, trailling slash .

Programmer Response .

HTML5 is the latest evolution of the standard that defines HTML. It is a new version of the HTML language, with new elements, attributes, and behaviors. Once it has become standard it is time for every web developer to migrate to it, even because in my view it is cleaner and more flexible.