HTML Doctype
The HTML doctype declaration <!DOCTYPE html> tells the browser the document type and version and triggers standards-mode rendering.
Purpose
To ensure the browser renders the page in standards mode (not quirks mode); it is the required first line of an HTML document.
Mechanism
HTML5: <!DOCTYPE html> (short). HTML 4.01/XHTML 1.0: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "url"> (referencing a DTD). Modern documents need only the short HTML5 form.
Use cases
- Standards mode for HTML documents
- XHTML strict mode
- Browser compatibility