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This repository contains compatibility data for Web technologies. Browser compatibility data describes which platforms (where "platforms" are usually, but not always, web browsers) support particular Web APIs.

This data can be used in documentation, to build compatibility tables listing browser support for APIs. For example: Browser support for WebExtension APIs.

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Maintained by the MDN team at Mozilla.


You can install mdn-browser-compat-data as a node package (tutorial).

npm install mdn-browser-compat-data


const bcd = require('mdn-browser-compat-data');;
// returns a compat data object (see schema)

Repository contents

There's a top-level directory for each broad area covered: for example, "http", "javascript", "webextensions". Inside each of these directories is one or more JSON file containing the compatibility data.

Please note that we have not (yet) migrated all compatibility data from the MDN wiki pages into this repository.

  • api/ contains data for each Web API interface.

  • css/ contains data for CSS properties, selectors and at-rules.

  • html/ contains data for HTML elements, attributes and global attributes.

  • http/ contains data for HTTP headers, statuses and methods.

  • javascript/ contains data for JavaScript built-in Objects, statement, operators and or other ECMAScript language features.

  • webextensions/ contains data for WebExtensions JavaScript APIs and manifest keys.

Format of the browser compat json files

The definitive description of the format used to represent compatibility data is the schema file. You can also have a look at the schema documentation.

Please note that we do not (yet) guarantee the stability of the data format. You're welcome to use the data, but its structure is subject to change without notice.


If you find a problem, please file a bug.


We're very happy to accept contributions to this data. Please familiarize yourself with the schema and send us a pull request. See also the Contributing file for more information.

Projects using the data

Here are some projects using the data, as an npm module or directly:

  • Compat Report - Firefox Add-on that shows compatibility data for the current site in the developer tools.
  • mdncomp - View compatibility data on the command line.