I'm not convinced. Recently moved to a new computer and firefox didn't sync my settings in about:config and didn't sync my container assignments (had to go in and enable it manually in both the source and target computers, buried deep in the settings for the containers extension). It doesn't sync addons or addon settings. I don't think it synced all the interface customization (like removing pocket icon from the url bar, separate urlbar/search box), only some of it. I got my bookmarks, so that was helpful. To sync a lot of other stuff I was able to copy my prefs.js from the old to the new, and most of those settings worked.
LtWorf|2 years ago