Default Search Engines

The search service specifies default search engines via the configuration schema.

Changing Defaults

The default engine may change when:

  • The user has the default engine set and the configuration for the locale/region changes.

  • The user has the default engine set and their locale/region changes to one which has a different default.

  • The user chooses to set a different engine via preferences.

  • The user installs an add-on which sets its default as one of the application provided engines.

  • The user installs an add-on which supplies a different engine and allows the different engine to be set as default.

Add-ons and App-provided Engines

An add-on may set the name of the search provider in the manifest.json to be the name of an app-provided engine. In this case:

  • If the add-on is a non-authorised partner, then we set the user’s default engine to be the name of the app-provided engine.

  • If the add-on is from an authorised partner, then we set the users’ default engine to be the same as the app-provided engine, and we allow the app-provided urls to be overridden with those of the add-on.

If the specified engine is already default, then the add-on does not override the app-provided engine, and it’s settings are ignored and no new engine is added.

The list of authorised add-ons is stored in remote settings in the search-default-override-allowlist bucket. The list includes records containing:

  • Third-party Add-on Id: The identifier of the third party add-on which will override the app provided one.

  • Add-on Id to Override: The identifier of the app-provided add-on to be overridden.

  • a list of the url / params that are authorised to be replaced.

When an authorised add-on overrides the default, we record the add-on’s id with the app-provided engine in the overriddenBy field. This is used when the engine is loaded on startup to known that it should load the parameters from that add-on.

The overriddenBy annotation may be removed when:

  • The associated authorised add-on is removed, disabled or can no longer be found.

  • The user changes their default to another engine.

If the overriddenBy annotation is present, but the add-on is not authorised, then the annotation will be maintained in case the add-on is later re-authorised. For example, a url is updated, but the update is performed before the allow list is updated.