Hi, it depends on whether you mean: '''Bookmarks''' Firefox Sync will store your bookmarks (in an encrypted format) in the Sync cloud and when you connect a new installation of Firefox to your Sync account, it should download an add those bookmarks. However!! That isn't perfect, so it's also a good idea to create backup files in both available formats, and store them somewhere secure like Microsoft OneDrive, Google Drive, Dropbox, etc., or even attach them to an email and send them to yourself. Here's what I mean about the two formats: * [[Restore bookmarks from backup or move them to another computer]] ("Manual Backup" section) * [[Export Firefox bookmarks to an HTML file to back up or transfer bookmarks]] '''Open Tabs''' Firefox Sync also can share a list of your open tabs with a new installation, but this is re-checked in real time, so if the other installation is offline or deleted, its tabs might no longer be available. So... To save all the tabs in your current window as bookmarks, you can press Ctrl+Shift+D and create a new bookmark folder with the URLs of all the currently open tabs. Then those tabs will be available from your bookmark backup. Does this make sense so far? '''General Backup''' It's a bit too easy to forget something when making a list of data to keep when refreshing a system. A general purpose backup should include the data under C:\Users\<username>\AppData\Roaming\Mozilla\Firefox Note that AppData is a hidden folder, so some backup programs might skip it. To make sure you have a backup, check out the following article: [[Back up and restore information in Firefox profiles]] You mentioned changing OS. If you switch between Windows, Linux, and Mac, some of the data in the backup might be irrelevant, but I suggest adding to this thread or starting a new question to get into those details. For now, check out: [[Recover important data from an old profile]]

By the way, since you mentioned "other browser," most browsers now can scan your system and find data for other major browsers. If you don't want to rely on that, the most cross-compatible bookmarks file is the HTML export.