The HTML Standard is the normative specification that defines the HTML language and its associated APIs for web browsers and other user agents.
The project addresses the need for a single authoritative definition of HTML that ensures interoperability across browser implementations. It documents the complete behavior of HTML parsing, rendering, and scripting APIs including Canvas, Web Workers, Web Storage, and Server-Sent Events. The standard is maintained as a single large source file that is processed to generate the human-readable specification published at the official WHATWG website.
Developers and browser vendors use this standard as the reference for implementing HTML support and for resolving ambiguities in how HTML should behave. It is essential for anyone building a browser engine, HTML parser, or tool that needs to understand the precise semantics of HTML. The standard covers not only markup syntax but also the complete DOM API, event handling, and storage mechanisms that modern web applications depend on. Contributors can propose changes through the established guidelines, and the project provides tooling to build and preview the specification locally before submission.
The project maintains an active discussion process for proposed changes, with contributors engaging in technical review of pull requests and issues. The source file is maintained as a single comprehensive document rather than split across multiple files, which requires contributors to use external tools like searchfox for blame tracking due to GitHub's limitations on large files. Tests for the standard are housed separately in the web-platform-tests repository, creating a clear separation between the normative specification and its test suite.
