Sorry to hear about this problem.

Since you already restored your session, could you check whether any of these allow access to more closed windows:

• "3-bar" menu button > History > Recently Closed Windows
• "Library" toolbar button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows

Note: Each window also has its own Recently Closed Tabs list.

If that doesn't help...

Firefox creates numerous session history files, but because session history is only for the immediately previous session, it is unfortunately too easy to lose it. Could you start by making a backup of your existing session history files? Here's how:

(1) To open your profile folder...

If Firefox is still running:

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. On that row, 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
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs?

Optional File Contents Preview

The .jsonlz4 files are compressed and can't be read easily. To preview the contents of a file, you can drag and drop it onto a tool on my site, then click Scrounge URLs:

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.

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.

Thanks for your reply. 1... 3 bar menu button > history> recently closed windows greyed out 2... Library toolbar button missing 3... menu bar history >recently closed windows greyed out ....... 4... profile folder.. previous.jsonlz4, recovery.baklz4, and recovery.jsonlz4 are all dated today's date 20th Sept, which is after the tabs disappeared, so none would be useful in getting a list of previous tabs. There are 3 upgrade.jsonlz4 files, the most recent of which is 11th Sept. It was only yesterday morning that I got a message that Firefox was updating and would open shortly when I clicked on the Firefox icon on the desktop. There was no warning that I was closing multiple tabs when I closed Firefox at 1.30 last night. I just looked and the option to do that had also been unchecked, although I don't think it was checked anyway.

I had previously done a backup of all my tabs in April but that wouldn't be any use. Is it a hopeless case?? Win

You can check the most recent upgrade.jsonlz4 file in the scrounger tool.

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

previous.jsonlz4, recovery.baklz4, and recovery.jsonlz4 are all dated today's date 20th Sept, which is after the tabs disappeared, so none would be useful in getting a list of previous tabs. There are 3 upgrade.jsonlz4 files, the most recent of which is 11th Sept. It was only yesterday morning that I got a message that Firefox was updating and would open shortly when I clicked on the Firefox icon on the desktop.

You could scrounge the 9/11 file to see how much it yields. Better than nothing.

Is it possible your Firefox performed a Refresh or that you have multiple Firefox profiles?

The tell-tale sign of a Refresh is a new "Old Firefox Data" on your desktop. Anything like that?

To explore other profiles:

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile that Firefox is currently using will have this:

This is the profile in use and it cannot be deleted.

Do you have any other profiles listed on this page? If so, you can check whether it is the one you were using recently by clicking its Launch profile in new browser button.

If this doesn't have the missing tabs (after restoring if needed), simply close that new window.

If it DOES have the missing tabs, hmm, leave the window open and we can consider options.

Thanks for your prompt answer.. I checked the profiles, there is one other than the default, but launching that profile doesn't help, no tabs at all other than the home page. No sign of "old Firefox data" on desktop. You say.... "You could scrounge the 9/11 file to see how much it yields. Better than nothing." Could you please give me full details as to which file and what to do... think Firefox for Dummies. Win

You say.... "You could scrounge the 9/11 file to see how much it yields. Better than nothing." Could you please give me full details as to which file and what to do...

If you go back to my earlier reply, I mentioned backing up various files and after that how to preview ("scrounge") the contents of one of the files.

I just saw the support email from cor-el which came in a little earlier, thank you... I dragged the most recent upgrade file in to the suggested site and clicked on the HTML list command Scrounge URLs and now have a list of what tabs were open on that 11th Sept date. This will be very helpful... What do I do with them? Can I save that list in to a Word doc so that the links are still active, or do I have to open each one again and save all the open pages? I am encouraged !! Win

Thanks so much for your help, I have saved the list. I'll go through it at some later stage, so I don't have so many tabs open again in the future, must learn to deal with each one straight away, instead of putting it off. Much appreciated Win

Hi Win, the "Save List" button on the Scrounger page will save the list as a web page of clickable links. Or you could copy/paste into Word if you prefer.