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Awesome Open Source

Welcome to MDN data

Note We are in the process of deprecating the mdn/data package in favor of w3c/webref. If you depend on this project, let us know in our community GitHub discussions. Thank you.

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This repository contains general data for Web technologies and is maintained by the MDN team at Mozilla.

Repository contents

The data in this repository is used in MDN Web Docs to build information boxes and sidebar navigation. External tools make use of this data as well, for example, the CSSTree CSS parser.

There's a top-level directory for each broad area covered: for example, api and css. Inside each of these directories is one or more JSON files containing the data.


Contains data about Web APIs:

  • API inheritance (interface inheritance and mixin implementations)


Contains data about:

  • CSS at-rules
  • CSS properties
  • CSS selectors
  • CSS syntaxes
  • CSS types
  • CSS units

For more information, see the CSS data documentation and the Updating CSS JSON DB guide.


The l10n folder contains localization strings that are used in the various json files throughout this repository.


If you find a problem, please file an issue.


We're very happy to accept contributions to this data. Please familiarize yourself with the schema for the data you're editing, and send us a pull request. See the document for more information.

See also

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Javascript (1,158,774
Css (162,562
Json (40,085
Web (37,759
Inheritance (2,031
Json Files (1,464
Json Data (1,460
Mdn (829
L10n (678