Support for extensions using XUL/XPCOM or the Add-on SDK was removed in Firefox 57, released November 2017. As there is no supported version of Firefox enabling these technologies, this page will be removed by December 2020.

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.

Starting from Firefox 53, no new legacy add-ons will be accepted on addons.mozilla.org (AMO) for desktop Firefox and Firefox for Android.

Starting from Firefox 57, only extensions developed using WebExtensions APIs will be supported on Desktop Firefox and Firefox for Android.

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 use WebExtensions APIs if they can. See the "Compatibility Milestones" document for more information.

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

An UpdateListener receives messages from an update check for a single add-on, though it is possible to pass the same UpdateListener to as many calls to findUpdates() as you like. For each individual update check, the following methods will be called on the listener:

Method Overview

void onCompatibilityUpdateAvailable(in Addon addon)
void onNoCompatibilityUpdateAvailable(in Addon addon)
void onUpdateAvailable(in Addon addon, in AddonInstall install)
void onNoUpdateAvailable(in Addon addon)
void onUpdateFinished(in Addon addon, in integer error)

Methods

onCompatibilityUpdateAvailable()

Called when the update check found compatibility information for the application and platform version that the update check was being performed for.

void onCompatibilityUpdateAvailable(
  in Addon addon
)
Parameters
addon
The Addon that was being checked for updates

onNoCompatibilityUpdateAvailable()

Called when the update check found no new compatibility information for the application and platform version that the update check was being performed for.

void onNoCompatibilityUpdateAvailable(
  in Addon addon
)
Parameters
addon
The Addon that was being checked for updates

onUpdateAvailable()

Called when a new version of an add-on has been found for install.

void onUpdateAvailable(
  in Addon addon,
  in AddonInstall install
)
Parameters
addon
The Addon that was being checked for updates
install
An AddonInstall for the updated version

onNoUpdateAvailable()

Called when no new version of an add-on has been found for install.

void onNoUpdateAvailable(
  in Addon addon
)
Parameters
addon
The Addon that was being checked for updates

onUpdateFinished()

Called when the update check is complete.

void onUpdateFinished(
  in Addon addon,
  in integer error
)
Parameters
addon
The Addon that was being checked for updates
error
Any error from the update checkAddon