What is HTML <!DOCTYPE> Declaration

All HTML documents must start with a `<!DOCTYPE>` declaration.

The declaration is not an HTML tag. It is an "information" to the browser about what document type to expect.

In HTML 5, the declaration is simple:

<!DOCTYPE html>

Browser Support <!DOCTYPE> Declaration

Output should be:

Older HTML Documents

HTML 4.01:

index.html

Example: HTML

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

XHTML 1.1:

index.html

Example: HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

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Single Articles

Browser Support <!DOCTYPE> Declaration	HTML Tag
Older HTML Documents	HTML Tag

Read Full:	HTML Tag
Category:	Web Tutorial
Sub Category:	HTML Tag
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Reffered: https://www.w3schools.com/tags/tag_doctype.asp