You can host a Firefox sync server yourself. You could run that on something like a Raspberry Pi in your local network. If you need remote access, use something like cloudflare tunnels (although I guess that’s something else to be paranoid about).

Personally, I consider Firefox Sync safe, as your data is end-to-end-encrypted.

If you want an alternative, xBrowserSync exists. Or you can self-host a Firefox Sync server, although this is relatively tricky.

In principle, it is possible to synchronize by just copying files, but with some pretty big caveats:

• Will not work for Android or iOS.
• Firefox won’t like it, if it’s running and you swap out the files underneath it.
• Bookmarks, browsing and download history are all stored in the same file (places.sqlite). So, without writing some custom software, you can’t sync only the bookmarks. And naively copying the history to other devices will cause you to lose the history on those devices.

I don’t know how exactly it’s possible. You’d have to figure that out yourself. However, if you use a tool like chezmoi you can most probably sync the correct folders inside your profile.

May I ask what part you’re paranoid about since Firefox Sync is fully encrypted anyway?

This is for what I have created a Extension called “SyncMarks”. It’s available for Firefox from AMO. The same exist for all Chromium based browser, including Chromium, Chrome, Edge and a lot more. For Edge its available in the Microsoft Edge Store, all others can sideload the extension. The extension is cross-browser compatible, so that you can sync bookmarks between Firefox and Chromium. As a backend for best results, you can use the PHP based backend for selhosting or any WebDAV as a alternative (not all functions available). Installation of the backend is super easy. You can find everything at Codeberg.

BTW. The PHP backend works as WebApp, so that you can access the bookmarks also, when the extension is not installed, from any browser.

It only works on desktop, but I use Syncthing to sync the whole profile (with the cache etc folders excluded).

You do need to make sure the profile path is identical on both machines as it’s hardcoded in the extensions json file, and otherwise your extensions won’t work properly.

So long as you close the browser on one machine before opening it on the other, it will sync your open tabs as well.

You can just write an HTML/markdown page with your bookmarks and host it on some web server (your own or eg github). Works on any browser, from anywhere, no syncing required. You can use git or whatever. You can share it with others, organize it in any way that makes sense you to, etc.

The bookmarks are a single json file and a lot of backups. The current version could for sure be synced with Git though.

FFs own versioning may get confused though.

The extensions get randomized ID names, but you could still sync them. But they will be called differently on every client, so you need to rename the dirs or something.

Does Firefox sync work for you? To this day, I could not sync any add-ons, I don’t really care about history, and don’t use bookmarks - which makes it useless for me. I am going to delete my account too.