doctypes
A doctype, short for document type declaration, is a declaration at the top of a markup document that identifies the document type and, in SGML-based systems, the DTD or schema used to validate the content. Doctypes originate from SGML and help parsers determine how to interpret markup, influence validation, and guide rendering or processing in various tools.
In the context of HTML, the doctype is not an actual tag but a declaration placed before
HTML5 simplifies this with a minimal declaration: <!DOCTYPE html>. It serves mainly as a signal to use
In XML, a DOCTYPE declaration can reference a DTD or schema to enable validation. Typical forms include
Doctypes thus function as a bridge between document markup language versions and the processors that render,