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 addons.mozilla.org (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.

UpdateCheckListeners are passed the results of update checks performed by the AddonUpdateChecker.

Method Overview

void onUpdateCheckComplete(in UpdateInfo results[])
void onUpdateCheckError(in integer status)



Called when the update check completed successfully.

void onUpdateCheckComplete(
  in UpdateInfo results[]
An array of UpdateInfo objects representing the available add-on versions


Called when the update check fails.

void onUpdateCheckError(
  in integer status
A value representing the type of failure; see the range of possible values.

Document Tags and Contributors

 Contributors to this page: bunnybooboo, Leif-AMO, kscarfone, Sheppy, trevorh, Mossop
 Last updated by: bunnybooboo,