DOCTYPE, the first piece of a webpage, is the doctype line. In HTML5, it looks like this:
<!DOCTYPE html>. This species that the webpage is written in HTML, and more particularly in the HTML5 dialect. If we do not specify it, the browser will just guess what version of HTML we are writing in.
Frequently Asked Question for DOCTYPE in Interviews
Question: What is the first markup element of every HTML5 webpage?
The doctype declaration is not case-sensitive.
All modern browsers support HTML5 DOCTYPE declaration.