HTML, the HyperText Markup Language, is the markup that gives structure to documents on the World Wide Web. It uses angle-bracket tags to mark headings, paragraphs, lists, links, and other elements, and browsers render those tags into a visible page. The earliest documented description of HTML appears in the original WorldWideWeb documentation written by Tim Berners-Lee and colleagues at CERN, which presents HTML as an SGML-based format for hypertext documents transmitted over networks.
A guiding design principle was leniency: that early documentation instructs parsers to disregard unfamiliar tags and unrecognized attributes rather than fail. This tolerance let pages keep working as the language grew and let authors adopt new features without breaking older browsers. The first tag set was small, covering basic document structure and the hyperlink that made the Web a web.
Over the following decades HTML was formalized through a series of W3C specifications. The fifth major revision, HTML5, reached W3C Recommendation status on October 28, 2014. It is described in that specification as “the 5th major revision of the core language of the World Wide Web,” and it added native audio and video elements, the canvas drawing surface, and a range of semantic structural elements and scripting APIs.
HTML remains one of the three core web technologies, working alongside CSS for presentation and JavaScript for behavior. Its combination of simplicity, forgiving parsing, and steady standardization is a large part of why the Web scaled from a CERN research tool to a global platform.