Some data, such as bookmarks and passwords, can be shared between different versions of Firefox and different computer systems.

Other data, like settings, and add-ons can not.

Since when? I have always synced settings and addons on android until firefox 95.2 on android.

You can sync add-ons and settings for some extensions that support this feature.

You can also disable syncing the enabled state of extensions to other devices if you want to have a different set of extensions on each device.

See "Can I have different enabled states on different machines?":

• https://wiki.mozilla.org/Services/Sync/Addon_Sync
• about:config => services.sync.addons.ignoreUserEnabledChanges = true
• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

WARNING: Changing preferences through this interface not officially supported Hidden settings edited using the about:config tool are explicitly not supported, which means that Mozilla makes no guarantees they will be supported in the future, or that Mozilla will fix them if they break. Mozilla does not test these preferences, and will not in the future. That includes security and performance testing which these preferences may affect.

For information about what information you can sync, check out the following article: How do I choose what information to sync on Firefox? If you need any help with the instructions on that page, let us know.

Quote: Mozilla does not test these preferences, and will not in the future.

That isn't necessarily true for all prefs, for instance there is a test for this services.sync.addons.ignoreUserEnabledChanges pref to ensure that it keeps working.

• https://searchfox.org/mozilla-release/source/services/sync/tests/unit/test_addons_store.js

This pref allows changes to the enabled flag of an extension to be ignored and is also part of syncing prefs to other devices (services.sync.prefs.sync.addons.ignoreUserEnabledChanges = true)

Hi cor-el, The fact that you're citing a test for a single pref indicates to me that you don't know what about:config is and why it exists. Many settings in Firefox are stored as pref strings. Most of what you see in the Settings window are just front-end interfaces that will change the value of specific pref strings. The prefs that are not exposed through a menu option or checkbox are not intended for end-users. If you see a pref that is supported, always point the user to the end-user method of changing that pref, not about:config.

This is a policy for the support.mozilla.org website, which has been discussed at length with the Firefox team. I was personally involved in those discussions when we first created this site, and it was re-established again this past year because too many volunteers would point users to about:config without explaining what it is. When a preference stops working in a future release, the users would complain that the "feature" no longer works. That's why there's a big warning when you first try to access it.

If you'd like to discuss this further, contact me in the sumo matrix room.