If you didn't export or backup any data or profile and reinstalled the OS and Firefox and synced Firefox then the sync data is wiped clean to match the current sync login. At this point that data is gone as result of the sync being used if you had backup the data and profile and imported them back and then sync the data would most likely be there update to match but since there is nothing to sync it clears the data thus anything there before is now gone and there's no way to find or recover or restore that data.

thanks for answer.

• headbang**headbang**headbang**headbang**headbang**headbang**headbang*

Also is there a way how to sync your old data to new system without manually exporting it from old system?

If there is no backup there no restore and if you sync with new Firefox install that will clear previous sync data to match new login thus rendering sync data wiped clean. If you had backup profile/bookmarks/data using Firefox options before this happen and then copy back the data and sync then maybe you can get the data back but since this wasn't done it's gone at this point.

Over the years, the Sync team has warned that it's not safe to rely on Sync as a backup (rather than a real-time transfer method). It often works, but not always.

You can check what data is in the Sync cloud for your Mozilla Account using the About Sync add-on:

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

After you install the add-on, you can type or paste about:sync in the address bar and press Enter to load it. The page shows each category of data currently found in the Sync cloud.

Anything newer on the server (from your old computer)? In the "bookmarks" section, you can use the "Records" mini-tabs to see the bookmarks stored for the other device(s) in your account.

Anything more there?

If not, did you have Windows do a reset or was it a more destructive reinstall? In some scenarios, Windows saves your data in a temporary folder named

C:\Windows.old

If you do see that folder:

Set Windows to show hidden files and folders -- this Microsoft article has the steps:

https://support.microsoft.com/en-us/windows/view-hidden-files-and-folders-in-windows-97fbc472-c603-9d90-91d0-1166d1d9f4b5

Then explore that folder up to this point (if it exists):

C:\Windows.old\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\

If you find recent data there, please pause and we can suggest how to restore old bookmark backups

Hello jscher2000,

Sorry for few days old reply, I was busy with work. Thanks for kind answer.

I did install "about:sync" plugin and when I type about:sync I see only 10entries and dates all of those entries are newer than day I installed windows - as you can see on attached screenshot. Honesty I dont understand it at all. I did install new windows on sunday 10th November and earliest hour is 14:30 and that was in new OS.

Everytime I install new windows I format entire ssd, because I dont want any remnants from past OS. So there was no "windows.old". And if I search "appdata" the only results I have are on C (main winOS SSD)

I did setup default windows documents to other SSD. But I havent changed any default folder for appdata.

It seems like I am not that "often it works", but rather "not always" :(

If I selected something wrong in about:sync I would be more than happy to get advice how to use it and if its still there.

I lost all hopes :(

Thank god for Lockwise working, at least I have all passwords...

At least thanks to this bummer situation I realized I would like to move more folders like "appdata" to other SSD if thats even possible in win11.

EDIT: after I posted this post, I realized I could click on bookmarks, but those who are there are the ones I created in new OS.

Thank you for checking on the Sync data. 24 items is not a lot of bookmarks when you consider that it includes the number of folders.

For future reference, see:

• Back up and restore information in Firefox profiles
• Recover important data from an old profile