& Lt ;! What is DOCTYPE html & gt;, what is its role, and doctypehtml?

<! What is DOCTYPE html>, what is its role, and doctypehtml?

There is always such a sentence in the header of an HTML document <! DOCTYPE html> many times we ignore its existence. It is actually a declaration that tells the browser which HTML version is used to interpret the HTML document.

Although we do not give this statement, the browser will render the HTML document, but the bug caused by the HTML version may be here.

For common doctype types, see w3school.

The statement of htm5 is <! DOCTYPE html>, so we can use this declaration for the newly written front-end project. Otherwise, some new standard features, such as the <canvas> label, cannot be used.

It is not advisable to declare doctype. Different browsers have different default specifications for this situation. Therefore, you must declare doctype and add an exclamation point.