HTML <! Doctype> (transferred from W3school)

Definition and usage

<! The doctype> declaration must be the first line in the HTML document, before the

<! The doctype> declaration is not an HTML tag; it is a directive that instructs the Web browser to write which HTML version of the page to use.

In HTML 4.01, <! The doctype> declaration references a DTD because HTML 4.01 is based on SGML. The DTD prescribes the rules of the markup language so that the browser renders the content correctly.

HTML5 is not based on SGML, so you do not need to reference a DTD.

Tip: Always add <! to your HTML document Doctype> declaration so that the browser can learn the document type.

The difference between HTML 4.01 and HTML5

There are three types of <! in HTML 4.01 Doctype> statement. There is only one of the HTML5:

<! DOCTYPE html>

HTML Elements and document types (Doctype)

See this HTML element table, which lists which document type each element appears in.

Hints and Notes

Note: <! Doctype> declaration does not have an end tag.

Tip: <! The doctype> declaration is not case sensitive.

Tip: Please use the authenticator to check if you have written a valid html/xhtml document!

Common DOCTYPE Declaration HTML 5

<! DOCTYPE html>

HTML 4.01 Strict

The DTD contains all the HTML elements and attributes, but does not include the display and deprecated elements (such as font). Frameset (framesets) is not allowed.

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01//en" "HTTP://WWW.W3.ORG/TR/HTML4/STRICT.DTD" >

HTML 4.01 Transitional

The DTD contains all the HTML elements and attributes, including both display and deprecated elements (such as font). Frameset (framesets) is not allowed.

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

HTML 4.01 Frameset

The DTD is equivalent to the HTML 4.01 transitional, but allows the frameset content.

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 frameset//en" "HTTP://WWW.W3.ORG/TR/HTML4/FRAMESET.DTD" >

XHTML 1.0 Strict

The DTD contains all the HTML elements and attributes, but does not include the display and deprecated elements (such as font). Frameset (framesets) is not allowed. tags must be written in well-formed XML.

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 strict//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" >

XHTML 1.0 Transitional

The DTD contains all the HTML elements and attributes, including both display and deprecated elements (such as font). Frameset (framesets) is not allowed. tags must be written in well-formed XML.

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">

XHTML 1.0 Frameset

The DTD is equivalent to XHTML 1.0 transitional, but allows frameset content.

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 frameset//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd" >

XHTML 1.1

The DTD is equivalent to XHTML 1.0 Strict, but allows models to be added (for example, to provide Ruby support for East Asian languages).

<! DOCTYPE HTML PUBLIC "-//w3c//dtd XHTML 1.1//en" "Http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd" >

HTML <! Doctype> (transferred from W3school)