To check if a website is in HTML5 all you have to do is check the source code:
- Right click on a page
- Select "View Source Code" or "View Page Code"
- The first line will have the DOCTYPE which shows the HTML version of the page.
- If it's in HTML5 then it will say "<!DOCTYPE html>"
Detect HTML5 usage
If you want to see if a website is using HTML5 elements, you only need to view the source of the website.
If the source code starts with the following declaration:
you're onto a HTML5 marked up website.
Also, it may be using some new elements introduced: