We are planning to deprecate the use, in Firefox, of the techniques described in this document.
If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions or the SDK instead.
Add-ons developed using these techniques might not work with multiprocess Firefox (e10s), which is already the default in Firefox Nightly and Firefox Developer Edition, and will soon be the default in Beta and Release versions of Firefox. We have documentation on making your add-ons multiprocess-compatible, but it will be more future-proof for you to migrate to WebExtensions or the Add-on SDK.
A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.
This page contains links to documentation for the approach to developing extensions for Gecko-based applications which uses:
- XUL overlays to specify the interface
- APIs available to privileged code, such as
XUL School is a comprehensive add-on development tutorial, focusing on Firefox extension development but mostly applicable to other Gecko-based applications.
- Setting up your environment
- Setting up the application for extension development.
- Tutorials and reference for the user interface language used by XUL extensions.
- Code snippets
- Sample code for many of the things you'll want to do.
- Installing extensions
- How to install an extension by copying the extension files into the application's install directory.
- Firefox add-ons developer guide
- A guide to developing overlay extensions.
- Extension preferences
- How to specify the preferences for your extension that will appear in the Add-ons Manager.
- Extension packaging
- How extensions are packaged and installed.
- Binary Firefox extensions
- Creating binary extensions for Firefox.