At startup, Firefox usually will look first for sessionstore.jsonlz4 at the main level of your profile folder and if it finds it, use its contents to create recovery.jsonlz4 -- if you restore automatically -- or previous.jsonlz4 -- if you do not restore automatically. So you could try replacing that file if you haven't already (as well as recovery.jsonlz4).

As a fallback, you could try my page that extracts your session and lets you archive it as a list of clickable links. Not as handy as having everything opened automatically, but still could be useful.

The tool is here, and after loading your previous.jsonlz4 into the page, click the Scrounge URLs button to build the list:

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

If it takes more than 15 seconds, the scripts probably have hung. Sorry, it sometimes happens. You can close the tab and try again in a new tab.

If you get a useful result, click the Save List button to keep it for future use.

Now that I read your question more carefully, I see you have replaced sessionstore.jsonlz4. Please test with the scrounger page to see whether it reports any problems with the previous.jsonlz4 file.

Thank you jscher2000, your page and Scrounger work perfectly. URLs recovered!

However, not only that, but I think I may have also found out the reason why I lost my tabs, again, thanks to your magic Scrounger:

The last session I enjoyed my myriad of tabs was also a session which opened two instances of Firefox: one containing my tabs, the other just consisting of my startup page – this second due to my anxiety clicking Firefox’s shortcut. Back then I just closed the Firefox window just including the startup page and continued for several hours using the window holding my dear tabs.

Now, after using your Scrounger, I can see this at the bottom of the URL list:

Closed Window 2

Tab 1

[Startup page] [12/11/2020 16:36:11]

As I suspected, I now believe I was correctly following the steps to replace files, only that what Firefox was restoring every time was that “Closed Window 2”, and not the window containing my precious tabs. Does that make sense to you?

That presumption may arise several questions:

- Why does Firefox try to restore a window just composed by one tab, closed one hour before [16:36:11] I closed the other window comprising 84 tabs [17:42:43]?

- Would it be possible for me to edit my ‘previous.jsonlz4’ file in order to delete the information concerning that ‘Closed Window 2’ so as Firefox loads the 84 tabs window?

- Is this the reason why I lose my tabs nearly half the time Firefox is updated?

- Will I still put up with Firefox’s lack of reliability after being using it since I was fifteen years old (fourteen years)?

In any case, I’ll just use the ‘upgrade.jsonlz4-20201112153044’ (from 22/11/2020 10:34) to recover the vast majority of my tabs and then your fantastic Scrounger to recover the rest of the tabs I opened since then.

Thank you very much

Hmm, Firefox should restore all the windows that were still open when you used either:

• menu button > Exit
• (menu bar) File > Exit

I don't know why it would restore a closed window in preference to the open ones. Perhaps something glitched in the file?

Regarding editing a session history file, if you save the JSON format, you can edit that and rename it to sessionstore.js (not .json). If none of the compressed files are found at startup, I think Firefox will still look for that older file name.

Of course, the trick is knowing what needs fixed. Is the 84-tab window listed as an open window in the scrounged list? If so, it really should restore. I can only test on a small universe of my own session history files, so I'm definitely not familiar with all the potential weird scenarios.

I am certain I did close the bowser properly, no task manager or anything involved. The scrounger shows:

        Session History

        Extracted from previous.jsonlz4 as of 22/11/2020 17:42:43.

        Closed Windows
                 Closed Window 1
                          Tab 1
                          Tab 2
                          […]
                          (Closed Tabs)
                          Closed Tab 1
                          […]
                 Closed Window 2
                          Tab 1 [Startup page]

That’s the information the scrounger gives. As you can see, no tab is listed as an open window.

Nevertheless, I’ve already recovered my tabs, maybe not as easily as having everything opened automatically, but almost.

The thing is, it has become quite common for me to lose all my tabs from time to time, and I’m getting tired of it. Being Firefox what it is, I am surprised nobody has yet addressed the issue of having sessions safeguarded.

I consider to be pretty ridiculous the fact that half the threads and questions concerning tabs and sessions lost start by telling the OP NOT to close the window, so that Firefox may not rewrite the ‘sessionstore-backups’ folder of the profile. I deem considerably remarkable not to have any other kind of guarantee for the safety of the browser session aside from the rewritable and rather concealed ‘sessionstore-backups’ folder. I think Firefox lacks an easily, fail-safe system to manage profile sessions.

Actually, if it hadn’t been for the Upgrade generated jsonlz4 files, I would have lost all my tabs, yet again.

Regardless, I give thanks to this community, Firefox developers, and jscher2000, who has helped me recover my tabs.

I can't recall ever seeing a session history file with no open windows. Perhaps that might be caused by closing all the regular windows first and then closing a private window? Or perhaps there was a glitch in generating the file. If at any time you restore a session but don't see what you are looking for, try to restore closed windows using either:

• Ctrl+Shift+n (Undo Close Last Window)
• "3-bar" menu button > Library > History > Recently Closed Windows
• "Library" toolbar button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows

As for why there are still imperfections in the feature, I suspect it is because it is difficult to gather enough information to identify root causes to be eliminated.

I’m sure I did not close a private window last. Like I said, I’ve lost my tabs quite a few times – many of them due to my fault – and I’m very familiar with the message “You are about to close X tabs. Are you sure [...]?”; I’m considerably careful when closing windows.

Regarding the history file with no open windows, I’d be more inclined to believe it to be caused by a glitch, as you said. This is because, just about every time I’ve lost my tabs in the past few years, it has occurred right after a Firefox update. That’s why I think there’s some kind of glitch related to the browser’s update system and tabs. Actually, I’ve been half-subconsciously avoiding or postponing Firefox’s updates until I reduce the amount of tabs opened – so as not to have so much to lose – for a long time now, precisely owing to that tendency I’m speaking about.

Thanks for the recovery suggestions.

Well, I'm not exactly sure of what you two are saying entirely, but I can certainly relate to delfion.815 when that person says, "I always have dozens of tabs opened, if not hundreds." I have lost my tabs about 4 or 5 times in the last years, and I can never figure out why. I close it out the same time every time, when I don't lose them and when I do. If they do get lost sometimes I'll see the restore previous session tab and that works most of the time, but when they are completely lost, I can't see that as a highlighted option, and I still haven't figured out why this happens. This has happened to me about 4 or 5 times, losing all my tabs, and although I know about Bookmarks and do use that feature, it's difficult to remember what it is I needed to read or take care of when storing those tabs in Bookmarks and, therefore, why I keep the tabs open. I also don't know what, "I did a backup of the ‘sessionstore-backups’ folder" means. I can totally relate when delfion.815 writes, "I’ve been trying to recover my tabs for hour by now and don’t find what I am doing wrong." That's me. Wasting so much precious time trying to find out why and where these tabs are and now, wasting even more by having to search around Firefox/Mozilla Support. I also don't understand jscher2000's instructions on what to do and the link they have included nor what a "Scrounger Page" is. The second to the last time this happened, I didn't panic too much and just decided to turn my computer off and not turn it back on again until the following day, and amazingly enough, all my tabs came back. I see that delfion.815 believes that this possibly due to a FireFox update. Could be; I don't know. As this just happened to me last week, I believe I thought that that maybe was the reason but, I think, when I looked up the last update, there had been no update around the time I lost my tabs but a few weeks before that so I'm not sure. I just don't get it, and this has been the source of such grief for me as it included prosperous info and such regarding my job, future jobs, as well as schooling. So frustrating. I also don't know what the 60something or 84 tab thing means. When delfion.815 says this, "The thing is, it has become quite common for me to lose all my tabs from time to time, and I’m getting tired of it. Being Firefox what it is, I am surprised nobody has yet addressed the issue of having sessions safeguarded", I agree wholeheartedly! If anyone knows, please let the rest of us in on it. ~ Thank you

Well, I'm not exactly sure of what you two are saying entirely...

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