How does a Web browser differentiate between HTML5 and HTML4?

Question

possible duplicate of [What's the key difference between HTML 4 and HTML 5?](http://stackoverflow.com/questions/134727/whats-the-key-difference-between-html-4-and-html-5) — dokaspar, Oct 27 '14 at 22:06
See [Don't forget to add a doctype](http://www.w3.org/QA/Tips/Doctype) — Boaz, Oct 27 '14 at 22:06
@Dominik The OP seems to be asking *how the browser knows* the difference between the two, not *what is* the difference between them. — Boaz, Oct 27 '14 at 22:07
@AHmédNet Yes, the browser determines the markup's version according to the doctype declaration. — Boaz, Oct 27 '14 at 22:09
@Boaz: good point, the two questions are really not duplicates. — dokaspar, Oct 27 '14 at 22:12

score 4 · Accepted Answer · answered Oct 27 '14 at 22:20

According to w3schools, the following DOCTYPE defines a document as HTML5:

<!DOCTYPE html>

And the three types of HTML4 are defined by the following DOCTYPE declarations:

HTML 4.01 Strict

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

HTML 4.01 Transitional

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

HTML 4.01 Frameset

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">

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