644 Extensible Hypertext Markup Language 1.1 XHTML (1.1) Text (Mark-up) Full The Extensible Hypertext Markup Language (XHTML) is a reformulation of the Hypertext Markup Language (HTML) as an application of the Extensible Markup Language (XML). This allows for the automated processing of XHTML documents using a standard XML parser. XHTML 1.1 is now recommended by the W3C over HTML for the creation of web pages. The structure and grammar of an XHTML document is defined using a Document Type Definition (DTD). An XHTML document consists of nested elements, each of which may have attributes and content. It begins with an XHTML Document Type declaration, defining the XHTML version and Document Type Definition (DTD) to which it conforms. XHTML documents are typically encoded in UTF-8 or UTF-16. Text 31 May 2001 1 Digital Preservation Department / The National Archives 11 Mar 2005 v.123- New extension added of .xhtml. Submitted by the Digital Preservation Coalition. 09 Jun 2026 application/xhtml+xml MIME fmt/103 PUID htm File extension html File extension xhtml File extension 40 XHTML 1.1 With DOCTYPE declaration for 1.1 1 Absolute from BOF 0 1024 3C21444F43545950452068746D6C205055424C494320222D2F2F5733432F2F445444205848544D4C20312E31 1 Variable 3C68746D6C20786D6C6E733D22687474703A2F2F7777772E77332E6F72672F313939392F7868746D6C22*3C7469746C653E*3C2F7469746C653E Has lower priority than 310 Internet Archive Has lower priority than 777 Java Archive Format Has lower priority than 1029 WARC Has lower priority than 1158 Internet Archive Has lower priority than 1269 Apple iBook format Has lower priority than 1270 ePub Format Has lower priority than 1670 Apple Safari Webarchive Has lower priority than 2099 WARC Has lower priority than 2173 WARC Has priority over 638 Extensible Markup Language Has priority over 645 Hypertext Markup Language Is subsequent version of 643 Extensible Hypertext Markup Language