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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.

AddonListeners can be registered with addAddonListener() and will then receive notification of changes to the add-ons currently installed. These notifications come in the form of calls to methods on the listener object. A listener only needs to implement the methods corresponding to the events it cares about; missing methods will not cause any problems.

Method Overview

void onEnabling(in Addon addon, in boolean needsRestart)
void onEnabled(in Addon addon)
void onDisabling(in Addon addon, in boolean needsRestart)
void onDisabled(in Addon addon)
void onInstalling(in Addon addon, in boolean needsRestart)
void onInstalled(in Addon addon)
void onUninstalling(in Addon addon, in boolean needsRestart)
void onUninstalled(in Addon addon)
void onOperationCancelled(in Addon addon)
void onPropertyChanged(in Addon addon, in string properties[])

Methods

onEnabling()

Called when an add-on is about to be enabled.

void onEnabling(
  in Addon addon,
  in boolean needsRestart
)
Parameters
addon
The Addon that is being enabled
needsRestart
True if an application restart is necessary for the change to take effect

onEnabled()

Called when an add-on has been enabled.

void onEnabled(
  in Addon addon,
)
Parameters
addon
The Addon that has been enabled

onDisabling()

Called when an add-on is about to be disabled.

void onDisabling(
  in Addon addon,
  in boolean needsRestart
)
Parameters
addon
The Addon that is being disabled
needsRestart
True if an application restart is necessary for the change to take effect

onDisabled()

Called when an add-on has been disabled.

void onDisabled(
  in Addon addon,
)
Parameters
addon
The Addon that has been disabled

onInstalling()

Called when an add-on is about to be installed.

void onInstalling(
  in Addon addon,
  in boolean needsRestart
)
Parameters
addon
The Addon that is being installed
needsRestart
True if an application restart is necessary for the change to take effect

onInstalled()

Called when an add-on has been installed.

void onInstalled(
  in Addon addon,
)
Parameters
addon
The Addon that has been installed

onUninstalling()

Called when an add-on is about to be uninstalled.

void onUninstalling(
  in Addon addon,
  in boolean needsRestart
)
Parameters
addon
The Addon that is being uninstalled
needsRestart
True if an application restart is necessary for the change to take effect

onUninstalled()

Called when an add-on has been uninstalled.

void onUninstalled(
  in Addon addon,
)
Parameters
addon
The Addon that has been uninstalled

onOperationCancelled()

Called when a pending operation for an add-on is cancelled.

void onOperationCancelled(
  in Addon addon,
)
Parameters
addon
The Addon that has had a pending operation cancelled

onPropertyChanged()

Called when one or more properties of Addon has changed.

Only applies to the following properties:

  • applyBackgroundUpdates
void onPropertyChanged(
  in Addon addon,
  in string properties[]	
)
Parameters
addon
The Addon that has had its properties changed
properties
An array of the names of properties that changed.

Document Tags and Contributors

 Last updated by: bunnybooboo,