HTML 1.HTML or HyperText Markup Language is the main markup language for creating web pages and other information that can be displayed in a web browser. 2.Filename extension .html, .htm 3.Internet media type text/html 4.Developed by W3C & WHATWG 5.Extended from SGML 6.Function Web pages are written in HTML. XHTML 1. XHTML (Extensible HyperText Markup Language) is a family of XML markup languages that mirror or extend versions of the widely used Hypertext Markup Language (HTML), the language in which web pages are written. 2..Filename extension .xhtml, .xht, .xml, .html, .htm 3.Internet media type application/xhtml+xml 4.Developed by World Wide Web Consortium 5.Extended from XML, HTML 6.Function Extended version of HTML that is stricter and XML-based.