Sorry, but you reinstalled your pc, then opened the empty browser, and then logged into sync... GAME OVER!

The new browser with nothing from before you reinstalled is what synced which is why you have nothing.

GAME OVER! </blockquote>

that doesn't seem true, I did this MANY times before and it always synced history and bookmarks, did they changed something in sync in last 6 months? This is ridiculous no surprise they are losing users

I've done it in the past, once you sign into Firefox with nothing... that will eventually sync. When you're logged into your Firefox account, just look at the sync tab to see what you have. see screenshots

This is why I run multiple version of Firefox on Linux and Windows. They are backups to each other. Sync will see each version as a different device and they all have the same bookmarks and can see the others tabs. It was rare, but Nightly updated and everything was gone, but I was able to open another version of Firefox and send Tabs to Nightly. The bookmarks populated after I logged into Nightly.

Hi Jakub, Would you be able to provide more details about the first step? It's possible that when "reinstalling your PC" you erased the data, which then got synced to the server (erasing the data on the server).

You didn't reset the password of the Sync account as that will clear al data on the server ?

You can install the About Sync extension in Firefox 72 and newer on desktop to check what data is stored on the Sync server via the about:sync page provided by this extension.

• About Sync https://addons.mozilla.org/firefox/addon/about-sync/

Close and restart Firefox and access the about:sync page added by this extension (see the about:about page for possible about pages).