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About the WebExtensions API

WebExtension APIs provide a user-controlled, web-focused extension development platform used to extend the features of Firefox. The APIs strike a balance between the functionality extensions bring to Firefox and the risks they introduce to the user experience.

Designed to offer cross-browser compatibility with Chromium-based browsers—such as Chrome, Edge, and Opera—the APIs:

  • Include features to extend the capabilities of Firefox to interact with web content.
  • Simplify the development and maintenance of extensions for Firefox and other browsers.
  • Make it easier for users to personalize Firefox, using extensions and themes.
  • Minimize the impact that changes to Firefox internals have on extensions.
  • Improve the performance, safety, and security of extensions in Firefox.

Since its introduction, Mozilla has expanded the capabilities of the API as part of a commitment to push innovation and adoption of the API in browsers. These expanded capabilities include features such as the Contextual Identities a.k.a. the containers API.