HTML tag

On the HTML document you have often seen that there is a declaration before the tag. HTML tag is used to inform the browser about the version of HTML used in the document. It is called as the document type declaration (DTD).

Technically is not a tag/element, it just an instruction to the browser about the document type. It is a null element which does not contain the closing tag, and must not include any content within it.

Actually, there are many type of HTML e.g. HTML 4.01 Strict, HTML 4.01 Transitional, HTML 4.01 Frameset, XHTML 1.0 Strict, XHTML 1.0 Transitional, XHTML 1.0 Frameset, XHTML 1.1 etc.

The declaration refers Document Type Declaration (DTD) in HTML 4.01; because HTML 4.01 was based on SGML. But HTML 5 is not SGML based language.

DTD defines the rules for the markup languages so that the browsers recognize the content correctly.

The doctype declaration differs between HTML versions. The HTML 5 doctype declaration is given below.


Following are some specifications about the HTML

Display None
Start tag/End tag Start tag only
Usage Structural

Let's see an example of HTML document with doctype declaration.

Test it Now

Note: It is always a good practice to add a declaration to your HTML documents to enable web browser to recognize that what type of document to expect.

Supporting Browsers

Element chrome browser Chrome ie browser IE firefox browser Firefox opera browser Opera safari browser Safari
Yes Yes Yes Yes Yes

Note: DOCTYPE declaration is not case sensitive.

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