<!DOCTYPE> tag in HTML
<!DOCTYPE> declaration is must because it is an instruction to the web browser about what version of the markup language the page is written in HTML document.
Important Description
- Always add the <!DOCTYPE> declaration to your HTML documents.
- The <!DOCTYPE> declaration refers to a DTD in HTML 4.01, because HTML 4.01 was based on SGML.
- The DTD specifies the rules for the markup language so that the browsers render the content correctly.
Example HTML5 Documents
<doctype> Tag Browser Support
| Element |
Chrome |
Edge |
Firefox |
Safari |
Opera |
| <doctype> |
Yes |
Yes |
Yes |
Yes |
Yes |
Important Notes
- The <!DOCTYPE> declaration is NOT Case Sensitive.
- The <!DOCTYPE> must not contain any content, and does not need a closing tag.
Common DOCTYPE Declarations
HTML 4.01 Strict
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
HTML 4.01 Transitional
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
HTML 4.01 Frameset
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
XHTML 1.0 Strict
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
XHTML 1.0 Transitional
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
XHTML 1.0 Frameset
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
XHTML 1.1
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">