Description

All HTML documents must start with a <!DOCTYPE> declaration, which is read by web browsers to determine the document type.

The declaration is not an HTML tag.

All HTML5 documents must start with the below declaration.

<!DOCTYPE html>

The declaration is not case sensitive, so it can have any of the below declarations.

<!DOCTYPE html>
<!doctype html>
<!DocType html>
<!Doctype html>
<!docType html>

HTML4 and XHTML Declarations

All older documents (HTML4 or XHTML 1.1) may contain any of the below declarations.

HTML4 declaration looks as below.

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

XHTML 1.1 declaration looks as below.

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

Attributes

The following table shows the list of supported and unsupported attributes for the <!DOCTYPE> declaration.

Attribute Type Details
Tag-Specific Attributes It doesn't have any tag-specific attributes.
Global Attributes It doesn't support any HTML Global Attributes.
Event Attributes It doesn't support any HTML Event Attributes.

Browser Compatibility

The declaration <!DOCTYPE> is supported in most modern browsers.

  • Google Chrome 1+
  • Internet Explorer or Edge 2+
  • Firefox 1+
  • Apple Safari 1+
  • Opera 4+

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