"God never said that the journey would be easy, but He did say that the arrival would be worthwhile." I am not a god, but a mere human. God may have the patience to change Firefox theme of his laptop, sync his other computer, and change both of his computer's theme to the "default" one. He might then change both of his computer's and laptop's themes, and turn on his raspberry pi, and all the three computers now has the "default" theme. These things were like this for ages. I think I am wrong thinking sync shouldn't work this way. Say in google, when you type something, it's saved to your search history, you remove it from one device, then it's gone from all the devices. But maybe Firefox devs think sync is merely syncing all the devices together. There should be a timestamp in sync. When you change one theme in the future, you should change it for all the devices. You shouldn't change your laptop's theme to the desktop ones again because simply it should override the theme on the Firefox server. "Tis strange - but true; for truth is always strange; Stranger than fiction" Yes, yes, reality is strange, changing a thing in Firefox in future syncs all the works from the past. It's messes up everything, the data isn't updated to the server, rather I don't know what kind of convoluted thing it does to perplex mere humans. What do you think? Should sync mess up with all the devices?