It looks like way back in 2013 there were options to actually reject sync:
A window displaying the Sync options will open then Select the action you want to take:
- Recommended: Merge this computer’s data with my Sync data
- Replace all data on this computer with my Sync data
- Replace all other devices with this computer’s data
Why was this removed?
Currently sync works this way:
a) logging in from “new” browser (for example broken browser or restored profile which logged you out of sync) = all your data are replaced by data from cloud (download)
b) logging in from old logged in browser = all your data replace data on the cloud (upload)
I recently got annoyed by this when I was trying to fix my ram usage and removed folder with add-ons from my firefox profile. After launching firefox it sent broken profile version into the cloud (without addons).
After this, whenever I restored my profile from backup it was logged out at first and after logging in it removed all add-ons because it thought that is the correct state of my profile. Finally I got around this problem because I logged in into profile (which removed my add-ons) and then restored some of my profile files again which caused browser to launch in logged in state but with add-ons and it uploaded correct version into cloud instead of downloading broken one from it. It was nerve-racking experience.
Currently there are no ways to reject or remove changes in cloud. Removing broken device from sync account does not help too because data are already in cloud and will ruin all connected computers.
3 hypothetical situations:
- Your kid, hacker or angry friend gets access to your pc and removes all your bookmarks. Then all your PCs have their bookmarks removed as soon as they sync and you cannot undo this because firefox does not have trash functionality.
- You use new computer for some time. You have new bookmarks and new add-ons but you forgot to log-in into your sync. Then you do it. Boom - your bookmarks got removed and were replaced by data from cloud. (I am not entirely sure what happens here because maybe bookmarks will merge, however add-ons will probably be removed and replaced by cloud add-ons like it happened to me).
- You take your old pc somewhere but get logged out from sync for some reason. Or restore old profile which is logged out of sync by default and use it for some time. You work as usual. Adding and removing some bookmarks and add-ons - you pretty much create latest version of your profile which is offline. Then you figure out sync is not working and you log in into sync. Boom - you end up with complete mess because new bookmarks were removed, old ones were restored, and same happens with add-ons.
Answer to these problems:
- You take 2nd pc, create profile backup, quickly disconnect from cloud, then log-in into the cloud again. You are presented a message asking you what to do because you just logged in into sync from new device. You select “merge this computer’s data with my Sync data” and bookmarks are restored into the cloud. Problem solved!
- You log-in into sync and select merge. Problem solved.
- You log-in into sync and select override. Your pc is considered latest profile version and overrides all other PCs with correct, latest version of your profile which you like.
Why choice was taken away from users? To annoy them? Pls restore it…
P.S. Perfect cloud add-on would be to have possibility to restore online profile to older state. For example 1 time per day backup is made and every time you want you can restore your browser to state from 1-7 days ago. After this time backups are removed and replaced by newer.
Google has this with contacts:
If you accidentally remove all your contacts you can restore backup from up to 30 days ago.