Browser extensions

Extensions can extend and modify the capability of a browser. Extensions for Firefox are built using WebExtension APIs, a cross-browser system for developing extensions. To a large extent the system is compatible with the extension API supported by Google Chrome and Opera and the W3C Draft Community Group. Extensions written for these browsers will in most cases run in Firefox or Microsoft Edge with just a few changes. The API is also fully compatible with multiprocess Firefox.

If you have ideas or questions, or need help migrating a legacy add-on to use WebExtension APIs, you can reach us on the dev-addons mailing list or #extdev on IRC.