Some time ago part of development for Firefox shifted from integrating new features and experiments in the core browser directly to using system add-ons for that.
Mozilla did integrated Pocket in Firefox natively first for instance, but changed that by removing the code from Firefox to distribute Pocket as a system add-on instead.
System add-ons work in many regards similarly to add-ons: they can be updated independently from the browser, and come as self-contained packages.
One difference to add-ons is that users don’t have full control over them. That’s understandable on the one hand, as they may introduce important functionality to the Firefox browser. On the other hand, it is used to push features that some users may not want.
System add-ons are not listed in the add-ons manager of Firefox. You get a listing of them when you open about:support. Firefox users find them listed under “Firefox Features” on the page. You may find eight or more system add-ons listed on about:support in Firefox Stable currently, and more if you run a development version of the browser.
One issue that Firefox users have with these system add-ons is that they cannot be disabled on about:support or about:addons.
Some system add-ons come with preferences that you may configure to disable them. Pocket for instance can be turned off by flipping the preference extensions.pocket.enabled to false. But some system add-ons don’t come with this option even though you may want to remove it from Firefox.
The Ghacks user.js file for Firefox is an excellent resource when it comes to configuring Firefox to your needs and liking. It focuses on privacy and security, and is designed to provide you with information on preferences that the browser ships with.
Read also: How to override the Firefox Add-on Signing requirement
One of the recent additions to it is a new system add-ons section. It basically lists preferences for Firefox system add-ons to control their behavior. Note that the listing is limited to what Mozilla integrates; if Mozilla does not add an option to disable a system add-on, you cannot do so from within Firefox.
You may delete the system add-on in the Firefox installation directory, but it will be added again when you update the web browser.
I suggest you check out the master user.js file on the linked GitHub page above; here is just a short list of important preferences related to system add-ons for Firefox that you may want to be aware of:
- user_pref(“experiments.enabled”, false); — Opt out of experiments
- user_pref(“experiments.manifest.uri”, “”); — Opt out of experiments
- user_pref(“experiments.supported”, false); — — Opt out of experiments
- user_pref(“experiments.activeExperiment”, false); — — Opt out of experiments
- user_pref(“experiments.activeExperiment”, false); — Prevent Mozilla from opting you into tests silently.
- user_pref(“network.allow-experiments”, false); — Blocks the URL used for system add-on updates
- user_pref(“extensions.pocket.enabled”, false); — Disable Pocket
- user_pref(“dom.flyweb.enabled”, false); — Disable Flyweb
- user_pref(“extensions.shield-recipe-client.enabled”, false); — Disable Shield Telemetry system
- user_pref(“extensions.shield-recipe-client.api_url”, “”); — Disable Shield Telemetry system
Again, you find additional preferences and links to resources on the Ghacks user.js Github page. Also, it will get updated regularly as new system add-ons get released (and they will).
Now You: What is your take on system add-ons?