We need to decide how to handle profile reset on a profile that had Firefox Sync setup. Keep in mind that the user may have mobile devices or other desktops using the same account. Some options: 1) Do nothing special. Their username/password and sync key will be migrated with their other passwords. User would have to "Setup sync" in the new profile which would mean either wiping the server or the user find the sync key in password manager. Doing a merge with the sync key didn't duplicate data from what I can tell. IIRC, Sync would see the profile as a new client. 2) Setup sync for the user but have it disabled for all data types. 3) Setup sync and enable syncing for certain data types (ie. not add-ons) 4) Do nothing and suggest that users with Sync setup a new profile and sync their data to it instead of using the reset feature. It's very similar and actually safer in how data is migrated. See Bug 670989 for that.

Thanks for filing this, Matt. > 1) Do nothing special. Their username/password and sync key will be > migrated with their other passwords. If you don't migrate Sync prefs, you should not migrate their Sync Key and password; the account is tied to a server and the username, both of which are stored in prefs, not in password manager. > 2) Setup sync for the user but have it disabled for all data types. This will disable Sync on their other devices, too. There is no notion of Sync being set up but disabled; it's either set up and working for the same set of data types on all devices, or it's blown away entirely, with your credentials lost. > 3) Setup sync and enable syncing for certain data types (ie. not add-ons) This decision will propagate to other devices. (Or the reverse will occur, depending on how you do this.) > 4) Do nothing and suggest that users with Sync setup a new profile and sync > their data to it instead of using the reset feature. It's very similar and > actually safer in how data is migrated. See Bug 670989 for that. The caveats here are that Sync doesn't have all the data in your profile. It's missing: * Old history records, subject to TTL * Any data types that aren't synced, such as your Master Password, search providers, non-AMO add-ons, dictionaries, certificates… * Any data that you elected not to sync by unchecking in Preferences or the setup wizard * Anything that you've done since you last synced (which can be a lot for users with Master Password enabled) * Possibly all of your data, if your Sync account has been wiped or lost since you last synced. For "simple" users, who want their bookmarks, passwords, and some representative sample of their history, and have another device hanging around as a hot spare, Sync is a great way to bootstrap an environment. But it's not equivalent to migrating a profile. Note that if you don't migrate Sync, and you consider the old profile disposed of, you should deactivate Sync on that profile before decommissioning it. That'll avoid this device showing up in Tabs From Other Computers, amongst other things.

I just got hit by this.. Could another option be to ask the user, if they want to transfer Sync data? Also.. might a "Reset" be useful to do across your devices as well?

Had the same problem when carelessly resetting Fx … I'd suggest migrating Sync data directly, maybe warn about addons or disable addon sync (they won't be uninstalled on other devices, will they?). Or rather have an option to (fully) migrate Sync data (would be nice to check which data to migrate at all in the first place, having a sensible default).

Forward duping to bug 754933 since there is more discussion there (unfortunately it wasn't linked to the meta bug).