HTML itself doesn't have it because HTML was understood to be an SGML application/vocabulary, and SGML does have mechanisms for fragment inclusion/sharing. For

HTML itself doesn't have it because HTML was understood to be an SGML application/vocabulary, and SGML does have mechanisms for fragment inclusion/sharing. For your requirements (pretty much the simplest case), you'd use entities: <!doctype html [ <!entity hdr system "header.html"> ... ]> &header <!-- content of header.html gets included here --> ... page body content goes here ... SGML can also take care of inferring omitted <html>, <head>, and <body> tags here. Moreover, you can also use more sophisticated entity expansion and template mechanisms with type checking, proper HTML-aware auto-escaping (for things such as potentially malicious user-provided comments), table-of-content/nav generation, etc. etc.