Hi Peter, If you close Firefox, then start Firefox in Safe Mode, does the problem still occur? To start in Safe Mode, hold down the Shift key while starting Firefox.

If the problem does not occur in Safe Mode, then you can disable your extensions one-by-one until you find out which one is causing the problem. For more info, visit Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

I'm not sure if your suggestion helped or not, Chris!

After posting my question, I discovered how to pin tabs. I now have 22 pinned tabs and just eight regular tabs. (There are still 10 tabs or so I used to have that I haven't managed to find and recreate.)

When I close Firefox and reopen it, all 22 pinned tabs and eight regular tabs reappear -- in regular mode and, of course, also in safe mode.

So maybe the problem somehow fixed itself. Or maybe the problem doesn't occur when I don't have too many regular tabs, even if I have a lot of pinned tabs. Or maybe the problem will recur when I shut down the computer (which I haven't tried yet), as opposed to just closing Firefox.

I still don't see anything saying "Restore previous session" on my menu -- but maybe that doesn't appear unless the previous session didn't restore properly.

And I still don't know any way to find the remaining tabs from my old previous session.

But pinning seems to have kept the problem from happening every time I close Firefox.

(Does anyone know what will happen when there are more pinned tabs than will fit in one row across the top -- and no room left for the regular tabs? I guess I'll find out soon.)

At the very least, Chris, you have given me something to try if the problem recurs. I didn't know Firefox had a safe mode, and now I do.

So thank you!

--Peter

Note that pinned tabs are window dependent and are stored a part of sessionstore, so make sure to use "File -> Exit/Quit" to close Firefox to avoid surprises with unnoticed background windows and lose the window with the pinned tabs.

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

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

Thank you, cor-el.

I'll try to remember not to close Firefox the "obvious" way.

I have a lot to learn!

Hello, I think I have if not the same at least similar problem.

Since my upgrade to 67.0.1 or just 67 which is about week or two, sometimes when I start the browser (which set to keep tabs) about half-dozen last in the line from previous time are lost. I'm one of thous weirdo who use 'em instead of bookmarks, and have about three hundreds in all, but active at once about the same one-three dozen, no pined. I'm not sure yet does disappear only opened in last session or any from the tab-line, and why some times it happens and some times not, because close the browser rarely, not even once at week sometimes, but I definitely have some problem. Now I'm forced to open a few whatever-junk tabs every time I close the browser, to be sure I'm not loosing the needed ones.

P. S. I'm also one of thous who had that 67-upgrade suspend profile bug right before all of this. Ubuntu 18.04.