XHTMLbased

XHTMLbased refers to content or applications designed primarily around XHTML, the XML-based reformulation of HTML 4.01. In an XHTMLbased approach, documents are authored to satisfy XML well-formedness rules and can be delivered as either text/html or application/xhtml+xml, reflecting the emphasis on XML tooling and validation.

XHTML was developed by the World Wide Web Consortium (W3C) as a bridge between HTML and XML. XHTML 1.0, published in 2000, defined three DTD profiles—Strict, Transitional, and Frameset—while XHTML 1.1 in 2001 pursued a more modular, standards-focused footprint. A proposed XHTML 2.0 was superseded by HTML5 efforts, which sought to unify HTML with modern APIs while maintaining compatibility.

Technical characteristics include case-sensitive tag names, mandatory closing of elements, and the requirement for well-formed XML syntax. Documents declare a namespace (http://www.w3.org/1999/xhtml) and may be validated against a DTD or XML schema. Self-closing empty elements (for example, br /) are standard in XHTML, and all attributes must be quoted.

Delivery considerations vary: application/xhtml+xml triggers XML parsing, while text/html typically uses HTML parsing for compatibility. This dual behavior led to mixed adoption, and HTML5 has largely supplanted XHTML in new projects, combining HTML’s permissive parsing with modern APIs.

Current relevance: XHTMLbased remains in some legacy or enterprise contexts where XML interoperability, data interchange, or strict validation matters. In contemporary web development, XHTML-based markup is far less common, with HTML5 serving as the dominant standard.

See also: XHTML, HTML, XML, HTML5, DTD, XML Schema.