Did you check "History -> Recently Closed Windows/Tabs" ?

• https://support.mozilla.org/en-US/kb/restore-previous-session

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox Title bar, especially if you have multiple windows or Private Browsing windows open to prevent losing tabs in unnoticed windows.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit

Yes, the recently closed tab/window option was empty

If a single private window can wreck it for the rest of the windows, that is a disaster. I think as long as the last window you close is a regular, non-private window, then your session history should be preserved.

If you quit the browser without restoring the last session (Ctrl+Shift+T) then it will be overwritten.

Are you sure you are using the correct installation or profile? You can see your profiles by visiting about:profiles in the address bar.

When I closed the private window, the other were closed. Once I exited the private window, I opened a regular one and wanted to restore the previous session @jscher2000 I use the default profiles. What I was thinking is, that the private window shouldn't store history, so there is no reason for it to overwrite the regular history. Is that not correct?

Go the sessionstore-backups folder in your profile. Then follow the steps in the screenshot with either the recover or previous files until you have your session before the issue happened. Make sure Firefox is closed when moving and renaming files. You want to use files with biggest size.

You can also check the upgrades file that was created when you last updated Firefox.

You can look at this tool to inspect a compressed jsonlz4 sessionstore file. This tool works locally, no uploading done.

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