'''''"Does Refresh Firefox cause sync to refresh everywhere else?"''''' There is no direct connection between the the Refresh feature in one Firefox installation and Sync, so I wouldn't expect Sync to automatically remove your add-ons from other devices connected to that Sync account. But this does raise an interesting question. If and how are the other connected devices affected by a Refresh? Will the device that got the Refresh automatically reinstall those add-ons when Firefox is launched the next time or the next day? Sorry, I can't answer those questions. I stopped "testing" Sync, or "playing with Sync" before the Sync feature for Addons came about. And since I no longer have more than one device I haven't really had a need for Sync for close to two years now. My suggestion is to Disconnect the device that you want to Refresh '''''before proceeding with the Refresh''''', and then if your intention is to not re-install the same extensions after the Refresh disable '''Addons''' in Preferences > Sync -> '''Sync across all all devices''' on that device. But allow Sync to synchronize the other data types when you re-Connect back to the Sync server.