The <!DOCTYPE html> declaration, also known as the document type declaration (DTD) is present in an HTML document before the <html> tag to give information about the HTML version used in that document. It is neither a tag nor an element but is an instruction to the browser. Being a null element, it neither contains a closing tag nor any content within it. Adding a declaration to an HTML document is a good practice. It is not case-sensitive.

The 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. are the various types of HTML. The different HTML versions differ in the <!DOCTYPE> declaration. In HTML 4.01, which is based on SGML, the <!DOCTYPE> declaration refers to the Document Type Declaration (DTD). The rules for markup languages are defined by DTD so that the browsers recognize the content correctly. The HTML 5 is however not based on SGML.

Syntax: For HTML 5:

<!DOCTYPE html>


<!DOCTYPE html>
<p>Hello World!!</p>


In the above example, we displayed the use of the HTML <!Doctype> Tag.

Supporting Browsers:

Chrome, IE, Firefox, Opera, and Safari.