MDN’s new design is in Beta! A sneak peek:

Add-ons using the techniques described in this document are considered a legacy technology in Firefox. Don't use these techniques to develop new add-ons. Use WebExtensions instead. If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions.

From Firefox 53 onwards, no new legacy add-ons will be accepted on (AMO).

From Firefox 57 onwards, WebExtensions will be the only supported extension type, and Firefox will not load other types.

Even before Firefox 57, changes coming up in the Firefox platform will break many legacy extensions. These changes include multiprocess Firefox (e10s), sandboxing, and multiple content processes. Legacy extensions that are affected by these changes should migrate to WebExtensions if they can. See the "Compatibility Milestones" document for more.

A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.

Articles listed here provide a reference for the SDK's tools:

Enables you to test, run, and package add-ons. cfx is is no longer supported as of Firefox 44 and no longer accepted for add-on submission, jpm should now be used instead.
cfx to jpm
A guide to working with jpm if you're already familiar with cfx.
Enables your add-on to log error, warning or informational messages.
jpm is a command-line tool that enables you to test, run, and package add-ons.
The Node-based replacement for cfx --force-mobile. Enables you to run and test add-ons for Firefox Mobile (aka Fennec).
Use .jpmignore to ignore files from your XPI builds created via jpm.
The package.json file contains manifest data for your add-on, providing not only descriptive information about the add-on for presentation in the Add-ons Manager, but other metadata required of add-ons.

Document Tags and Contributors

 Contributors to this page: wbamberg, evold
 Last updated by: wbamberg,