Firefox is set up so that; in the event the browser thinks it has crashed, the last session is restored when the browser is started again. Note: This can also be caused by not shutting down the browser properly. Menu > File > Exit.

You may have corrupt sessionstore [v56] sessionstore.jsonlz4 file(s). Delete all sessionstore* files and the sessionstore-backups folder.

Don't delete the files if you need to rescue any data from them, just move them out of the profile folder to some location where Firefox doesn't look for them. You can try to read out their contents using this tool: https://www.jeffersonscher.com/res/scrounger.html

Type about:support<enter> in the address bar.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder

Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory.

Locate the above file. Then rename or delete it. Restart Firefox.

This problem still persists and occurs randomly. Sometimes when I launch Firefox it reports that it cannot restore previous sessions, more often it comes up with my selected preference, which is a blank page.

The "Open previous windows and tabs" tick box in Settings->General->Startup is NOT ticked.

I have Firefox installed on multiple PCs running Windows 8.1 or 10 all of which randomly exhibit this quirk.

Recently I have completely wiped a laptop, then downloaded and installed Windows 10 Pro from Microsoft's download system. Then I downloaded and installed Firefox from mozilla.org. This laptop also randomly shows this problem.

It is not a major issue as I can click the new session button and proceed as normal if this peculiarity arises. However, if I ignore the failed restore message and go to the address bar to enter a search or URL, occasionally while I am typing it may suddenly restore a previous session wiping out what I have already entered in the address bar.

I haven't been able to find any pattern as to when this problem occurs, and it does not seem to be related to accessing any specific web pages. It also seems to make no difference how I close down Firefox, or whether I close all tabs at once or one at a time. I very rarely have two actual Firefox windows open but may have one or more tabs open in the one window I have started. I do not tend to open Firefox many times in a day, but open extra tabs and close tabs I am no longer using within the same Firefox window.

Suggestion; Open all the links you are talking about. Then save those links in a separate bookmarks folder. If or when you want, open the Bookmarks Manager and right-click that folder, and select Open All Bookmarks. You could keep that folder in the Bookmarks Toolbar for easy access.

It is not a major issue as I can click the new session button and proceed as normal if this peculiarity arises. However, if I ignore the failed restore message and go to the address bar to enter a search or URL, occasionally while I am typing it may suddenly restore a previous session wiping out what I have already entered in the address bar. I haven't been able to find any pattern as to when this problem occurs, and it does not seem to be related to accessing any specific web pages. It also seems to make no difference how I close down Firefox, or whether I close all tabs at once or one at a time. I very rarely have two actual Firefox windows open but may have one or more tabs open in the one window I have started. I do not tend to open Firefox many times in a day, but open extra tabs and close tabs I am no longer using within the same Firefox window.

Is there any relationship with either (A) time of day/week when you are starting Firefox, or (B) system events such as restarts or routine updates?

The reason I ask is:

Some third party software may "clean" browser data such as session history files, and if one of those files is missing/locked/corrupted, then Firefox may try to restore an earlier session. Such software may run on a schedule or at system startup.

To FredMcD,

"Suggestion; Open all the links you are talking about. Then save those links in a separate bookmarks folder. If or when you want, open the Bookmarks Manager and right-click that folder, and select Open All Bookmarks. You could keep that folder in the Bookmarks Toolbar for easy access."

Sorry, this seems to be suggesting the opposite of the issue I have. I don't want any windows or tabs from a previous session opening when I launch Firefox. It used to work this way every time until an update to Firefox sometime around July or August (2021), but since then it randomly appears to be trying and failing to restore some previous session. It happens on all my Windows 8.1 and 10 PCs, and even on the one Windows 10 PC I have just completely wiped and reinstalled Windows and Firefox.

As I said before, when this issue occurs I can hit the button to start a new session without restoring or I can open a new tab then close the tab displaying the restore failure message.

One suspicion I have had is that, as Firefox seems to run in multiple threads, and possibly one thread is randomly getting ahead of another one that it should be following.

jscher2000 said

" Is there any relationship with either (A) time of day/week when you are starting Firefox, or (B) system events such as restarts or routine updates?

The reason I ask is:

Some third party software may "clean" browser data such as session history files, and if one of those files is missing/locked/corrupted, then Firefox may try to restore an earlier session. Such software may run on a schedule or at system startup. "

I have not seen any correlation between the timing either of booting the PCs, launching Firefox or when updates are being installed.

On one PC, the only software that has been installed are Windows 10, Firefox, and drivers that were not installed as part of the Windows installation. As this is happening on multiple PCs, some running Windows 8.1, some running Windows 10, that are using either Microsoft's own antivirus software or Kaspersky Internet Security. I have no significant different between PCs using these different AV products.

Today, I had closed down Firefox session with two open tabs. I did some work on a Microsoft Excel spreadsheet, and then I launched Firefox again. When it launched, it opened the two tabs on the sites they had been accessing when I shut down the browser earlier. I closed Firefox again, then relaunched it. This time it said it was unable to restore the previous session(s). I closed and relaunched Firefox, and this third time it worked in accordance with the setting of not opening previous windows or tabs.

As it is only a minor issue, I wonder whether anyone else has reported this effect. I cannot imagine that no other Firefox users have not experienced this anomaly.

. . . . I cannot imagine that no other Firefox users have not experienced this anomaly.

You would be surprised how many contact us for help with a problem, and they are the only one reporting the problem.