I'm not sure where your tabs went, but here are two things to check:

(1) Was your main window closed prematurely? Check for the main window on either:

• "3-bar" menu button > History > Recently Closed Windows
• (menu bar or Alt+S) History > Recently Closed Windows

(2) Is your main window off-screen/invisible? Check Firefox View, which you can call up using either:

• click the file drawer icon at the left end of the tab bar
• type or paste about:firefoxview in the address bar and press Enter to load it

In the left column, click Open Tabs. Firefox should show a box of tabs for each open window. Are there any here that are not currently visible on screen?

Another thing : I thought that when I create groups of tabs, and save them I coul retrieve them across all my synced devices, but the other devices can not see those groups, is this a normal behaviour?

Sync has not been updated to store information about whether an open tab is part of a group, but other devices should still see your open tabs. But groups you close using Save & Close are not sync'd as open tabs because they are no longer open. That list is purely local.

If you weren't able to recover your closed tab groups, I would suggest the following:

Firefox stores closed tab groups in your session history file alongside open tabs. Firefox doesn't keep a lot of backups of session history files, but you could mine the files you do have to see what might be useful in there. Here's how:

(1) To open your profile folder...

You can open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, find the Profile Folder row and click the "Open Folder" button. This should launch Windows' File Explorer listing the contents of your current profile folder.

(2) Copy out session history files

In your profile folder, double-click into the sessionstore-backups folder. Save all files here to a safe location such as your Documents folder.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

• recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session - this file is created at startup from the file Firefox found
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update - for example, when you installed 141.0 a while ago or 141.0.2 in the past 24 hours

Sometimes you can tell from the last modification time which one will have your missing tabs, but not always.

Optional File Contents Preview

These compressed files are a pain to view, so I created a tool on my website to list out their contents. If you want to try that, you can drag and drop it onto the large box on the following page, then click the "Scrounge URLs" button:

https://www.jeffersonscher.com/ffu/scrounger.html

If you don't get a list within 15 seconds, that probably means the script is caught in a loop. You may need to close the tab to avoid a tab crash and then try again in a new tab.

The page should be organized into (1) Open Windows, (2) Saved/Closed Tab Groups, and (3) Closed Windows

If you get a useful list, use the "Save List" button to archive it as a web page of clickable links for future reference, in case no other approach is successful.

Hi , thank you for your support .

Neither of these help -->

(1) Was your main window closed prematurely? Check for the main window on either:

   "3-bar" menu button > History > Recently Closed Windows
   (menu bar or Alt+S) History > Recently Closed Windows 

(2) Is your main window off-screen/invisible? Check Firefox View, which you can call up using either:

The windows was not closed prematurely, and honestly I had not seen in Recently Closed windows, now maybe is too late because I see 3 tabs closed 5 minutes ago.

The main windows is visible, I usually just use one of it.

The most important thing for me was to understand why this happened, but I guess is not common then, thank you anyway.

I have moved from chrome because I like this project but I am having some bugs that makes it really hard for me to work with, the group tabs syncronization is another huge issue. In this way there is no actual sync between devices...

Anyway , thank you again , If I will be able to reproduce the bug I will report it

This morning too, same problem powered on laptop and no tabs saved... I attach a screenshot.

Hi Vals, it's weird that you have zero recent history.

Could you double-check your History settings here:

Settings page > Privacy & Security > scroll down to the History section

If needed, change the selector to: "Firefox will: Use custom settings for history"

Is the box to "Clear history when Firefox closes" checked? If so, click the "Settings" button to the right to review what is getting cleared. If you want to be able to restore your session, make sure Firefox is NOT clearing "Browsing & download history" since that also clears the session history files used for session restore.

If that isn't what causes zero history, hmm, I wonder whether some external cleaner is wiping your history.

Hi jscher, I feel really dumb but yes you were right, I don't know why or when but I had "Browsing & download history" enabled , maybe playing 3 days ago with the auto-delete of cookies with exception .

Thank you very much, really, this was the biggest problem.

For cookies it seems like the exceptions are working fine except for google products like gmail but it's not a problem, maybe it's even better.

Thank you again , problem solved.