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HTML, CSS, JavaScript, Web APIs and the wider web platform — browsable directly inside Firefox Tomorrow.

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12,147 documents 9 technology areas Local MDN archive

Web platform

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Choose an area to open its complete local reference.

HTML 254 docs

Structure and semantics for the open web.

CSS 1,249 docs

Layout, presentation, responsive design, and visual systems.

JavaScript 1,331 docs

The language, built-ins, syntax, and browser programming.

Web APIs 8,035 docs

Browser interfaces for building capable web applications.

HTTP 374 docs

The protocol that powers communication across the web.

Accessibility 169 docs

Patterns and standards for an inclusive web.

SVG 300 docs

Scalable vector graphics, elements, attributes, and APIs.

Performance 16 docs

Measure, understand, and improve web performance.

Security 46 docs

Build safer sites and understand browser security.

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Foundational references for the language and platform layers every web project builds upon.