HTML 5 (or HTML5) is the current version of HTML. It is the fifth major revision of HTML - the core language of the World Wide Web. The previous version was HTML 4.01.
HTML5 includes many elements brought forward from HTML 4.01, as well as many new elements.
Here is a list of the HTML 5 tags/elements.
When was HTML5 Started?
Work on the HTML 5 specification began in 2004.
When did HTML5 become a Recommendation?
HTML5 became a W3C Recommendation on 28 October 2014. Work continues on the HTML 5.1 specification and it is expected to become a Recommendation in late 2016.
The WHATWG HTML Living Standard is already
ready in the sense that it is an evolving standard. It does not base its standard on any
snapshot in time, rather, it is a continual work in progress.
Please Explain? (W3C vs WHATWG)
There are actually two groups maintaining slightly different specifications for HTML.
One group, the World Wide Web Consortium (W3C), maintains the HTML5 specification, which is a "snapshot" of the specification at a particular point in time.
The W3C also maintains a
HTML 5.1 Nightly, which includes modifications to the specification that will be released at a later date (and under a new version number - HTML 5.1).
The reason for the version numbers is that it gives developers and browser makers a solid recommendation in which to base their work on. They can be confident in the knowledge that, once they implement a feature, the recommendation is not going to suddenly change under their feet. If it does change, they will get sufficient warning, due to any updated specifications going through a lengthy review period (and various status milestones) before finally becoming a recommendation.
The other group, the Web Hypertext Application Technology Working Group (WHATWG), maintains what they call a
Living Standard for HTML. This is a standard that is continually updated. There are no version numbers (i.e. it is
HTML5). The standard can (and does) change on a regular basis. The reason behind this is in order to stay relevant with browser implementations. It can also avoid issues with browsers implementing features from a "snapshot" specification that potentially contains known bugs, issues or limitations.
Differences Between HTML5 and HTML Living Standard?
Fortunately the differences between the W3C HTML5 specification and the WHATWG HTML Living Standard are quite minor (well they are at the time of writing). Those differences will increase over time, due to the HTML5 spec being a "snapshot" and the Living Standard constantly evolving. Having said that, the HTML 5.1 draft is also evolving, and tends to remain somewhat aligned with the HTML Living Standard.
As a Web Developer, Which Standard/Recommendation Should I Adhere To?
You will need to decide on what approach works best for you and your website users. You can either follow the W3C specification, follow the WHATWG standard, or follow them both. Of course, you can also choose to ignore them both if you really want but that's a choice you will need to be comfortable with.