HTML

HTML, or HyperText Markup Language, describes the structure and meaning of a web document. An HTML document is text containing elements such as headings, paragraphs, links, images, lists, tables, and forms. A browser parses that text into a document tree. It then combines the tree with CSS for presentation and JavaScript for behavior.

HTML is not a programming language. It does not express general algorithms or manage application state by itself. Its main job is to identify what each part of a document represents and how those parts relate.

From source text to a document tree

A server commonly sends HTML with the text/html media type. A browser's HTML parser reads the byte stream, determines its character encoding, tokenizes the markup, and constructs nodes in the Document Object Model, or DOM. Elements become element nodes, text becomes text nodes, and nesting establishes parent-child relationships.

The parser follows defined error-recovery rules. Missing end tags or incorrectly nested elements may still produce a usable tree, but the resulting DOM can differ from the source indentation. Browser tolerance keeps older pages working; it does not make malformed markup reliable.

CSS selectors match the resulting element tree and assign presentation. JavaScript can read and change the same DOM. Assistive technologies use element semantics, names, states, and relationships to present the document through interfaces such as screen readers. Search engines and other consumers also use document structure as a signal.

HTML

HTML

From source text to a document tree

The document shell

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