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Format

Extensible Hypertext Markup Language

Download XML

Summary

Name
Extensible Hypertext Markup Language
Version
1.0
Identifiers
  • MIME: application/xhtml+xml
  • PUID: fmt/102
Format type
Text (Mark-up)
Disclosure
Full
Description
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 1.0 represents the reformulation of HTML 4.01 in XML. 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.
File extensions
html, htm, xhtml
Source
Digital Preservation Department / The National Archives
Developed by
World Wide Web Consortium

Relationships

Has lower priority than
Has priority over
Is previous version of

Internal signatures

XHTML 1.0

Note
With DOCTYPE declaration for 1.0

Byte sequences

Min Frag Length
Absolute from BOF
Offset
0
Max offset
1024
Byte Sequence
3C21444F43545950452068746D6C205055424C494320222D2F2F5733432F2F445444205848544D4C20312E30
Endianness
None
Min Frag Length
Variable
Offset
None
Max offset
None
Byte Sequence
3C68746D6C20786D6C6E733D22687474703A2F2F7777772E77332E6F72672F313939392F7868746D6C22*3C7469746C653E*3C2F7469746C653E
Endianness
None

Changelog

  • Updated in V123

    Release date
    9 June 2026

    Extensible Hypertext Markup Language 1.0: New extension added of .xhtml. Submitted by Digital Preservation Coalition.

  • Updated in V94

    Release date
    17 September 2018

    Extensible Hypertext Markup Language 1.0: Corrected priority relationship between XML and XHTML. XHTML is more specific so should have priority. Error reported by Nationaal Archief, and NedGraphics b.v.

  • Updated in V49

    Release date
    5 April 2011

    Extensible Hypertext Markup Language 1.0: Priority information changed to avoid potential clash with Cascading Style Sheet identification.