This is not a bug, but is how closing windows and closing Firefox works.
Only the last closed window is restored and if that is a PB mode window then you can't restore the previously closed regular window automatically.
If you close windows accidentally then you can check "History -> Recently Closed Tabs/Windows" for possible windows you can restore.

Make it a habit to use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox Title bar and to prevent losing important windows.

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

Thanks for your reply! Unfortunately this is new and wasn't implemented in earlier Firefox versions, (at least it didn't happen to me before). Would be great to have the restore option back at any time. Thanks!

Hmm, it's strange, if I create a new profile and test this out,

menu button > Restore Previous Session

brings back the closed regular window every time. And if I set it for automatic session restore, it works seamlessly.

So at least in theory, Firefox 79 works just the way you want. But perhaps there are some settings that affect it that I didn't discover in my brief tests.

Thanks. Yes strange and it really seems to be related to whether I close the privat window before or after the "normal" firefox.

I think I performed the test correctly. I had one regular and one private window open, I closed the regular window first, then spent a minute or two reading a page or navigating in the private window before closing it. Then I waited about 10 seconds before launching that profile again (launching in a new window from the about:profiles page where you create test profiles).

I can't explain why we are getting different results.

Thanks again! I'll try and error a little more.

The problem is with multi-windows in general, not specific to private windows. If you close one of the multi windows by error and try to reopen one blank of course the just closed tabs will not be restarted.

(linux kubuntu firefox 83.0) the correct test is : - open firefox1 and have several tabs opened it it - start a new firefox2 window (it does not have to be private) - open some tabs firefox2 - close firefox1 with X on the corner - don t close the firefox2 - open firefox3 with the os application menu

the firefox1 session is not restored maybe because the firefox2 window is still active. this is the behaviour indicated by cor-el in the first comment.

I am using the extension "firefox multi-account containers"

For help: recently closed tabs and windows are in the history menu.

Hi p92, are all of the three windows in the same session of Firefox? Opening an additional window in the same session should not trigger restoration of a previous session or previously closed window. You need to restore it manually using the "Recently Closed Windows" menu or Ctrl+Shift+n keyboard shortcut.