Browser extensions
Extensions, or add-ons, can modify and enhance the capability of a browser. Extensions for Firefox are built using the WebExtensions API cross-browser technology.
The technology for extensions in Firefox is, to a large extent, compatible with theextension API supported by Chromium-based browsers (such as Google Chrome, Microsoft Edge, Opera, Vivaldi). In most cases, extensions written for Chromium-based browsers run in Firefox withjust a few changes.
Key resources
- Guides
Whether you're just beginning or looking for more advanced advice, learn about how extensions work and use the WebExtensions API from our extensive range oftutorials and guides.
- References
Get comprehensive details about the methods, properties, types, and events of theWebExtensions APIs and full details about themanifest keys.
- Firefox workflow
Discover how to build and publish extensions for Firefox: get the lowdown on developer tools, publication and distribution, and porting onExtension Workshop.
Note:If you have ideas or questions or need help, you can reach us on thecommunity forum or in theAdd-ons Room onMatrix.
Get started
Discoverwhat extensions can do before buildingyour first extension andyour second extension. Learn about theanatomy of an extension and get an overview of theextension development and publication workflow, Firefox style. Explore a little deeper with a comprehensive selection ofexample extensions that you can run right in Firefox. Continue your learning bydiscovering a list of resources to follow.
Concepts
Get detailed information on the concepts that underpin extensions.
User interface
Discover all theuser interface components you can use in your extensions, with coding examples and tips.
How to
A range of tutorials to get you started on specific aspects of extension development.
- Intercept HTTP requests
- Modify a web page
- Safely insert external content into a page
- Share objects with page scripts
- Add a button to the toolbar
- Implement a settings page
- Work with the Tabs API
- Work with the Bookmarks API
- Work with the Cookies API
- Work with contextual identities
- Interact with the clipboard
- Extend the developer tools
- Build a cross-browser extension
Firefox workflow
When you are ready to create your extension for Firefox or port your Chrome extension, head over toExtension Workshop. It has details on:
- The Firefox workflow, such astemporarily installing extensions during development,debugging,request the right permissions, and more.
- Theweb-ext developer tool.
- Porting a Google Chrome extension,differences between desktop and Android, and more.
- Publishing and distribution overview,promoting your extension, theextension lifecycle best practices, and more.
Reference
JavaScript APIs
Get comprehensive details about the methods, properties, types, and events for all theJavaScript APIs. There is also detailed information about the compatibility of each API with the major browsers. Most reference pages also include coding examples and links to the extension examples that use the API.
Manifest keys
Get full details about themanifest keys, including all their properties and settings.