This is the method to "swap" an older session history file (e.g., recovery.baklz4 or previous.jsonlz4) for the current one:

(0) Have the file you want to use in a safe location, i.e., outside of any folder Firefox will be touching during shutdown.

(1) From inside Firefox, open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter/Return

In the first table on the page, click the "Open Folder" button. This should launch a Windows Explorer window listing the various files and folders in your profile.

(2) Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup -- these changes should occur:

• recovery.jsonlz4 is moved from the sessionstore-backups folder to the main level of the profile folder and renamed to sessionstore.jsonlz4

• recovery.baklz4 is deleted from sessionstore-backups

(3) Once Firefox has stopped updating things, while viewing the main level of the profile folder:

• right-click > Rename sessionstore.jsonlz4 to sessionstoreOLD.jsonlz4

• If you see an older sessionstore.js or sessionstore.bak file, move it somewhere else or delete it

• {OPTIONAL} right-click > Rename the sessionstore-backups folder to sessionstore-backupsOLD (usually not needed, but sometimes helps if Firefox keeps restoring other session history files)

(4) Copy in the other file you want to restore, and rename it with the name appropriate for its format:

• Compressed file (Firefox 56+) => sessionstore.jsonlz4
• Uncompressed .js file (pre-Fx56) => sessionstore.js

(5) Start Firefox and it should read the swapped in sessionstore file and restore whatever was in the substitute file; if you do not have Firefox set to restore your previous windows and tabs automatically, use History > Restore Previous Session

Any luck?

Thank you!

I have to ask for a little clarification.

Given that I have a recovery.baklz4 file, after I rename sessionstore-backups into sessionstore-backupsOLD, am I supposed to rename recovery.baklz4 into recovery.jsonlz4 and then create a NEW sessionstore-backups folder to palce it in?

Or do I rename it into sessionstore.jsonlz4 and put it in the profile folder?

Sorry, by "given that I have a recovery.baklz4 file" I mean that that's what I'm trying to restore from.

Firefox will look for sessionstore.jsonlz4 in the main level of the profile folder at your next startup. Therefore, we suggest copying recovery.baklz4 into the profile folder and renaming it to sessionstore.jsonlz4.

jscher2000 said

Firefox will look for sessionstore.jsonlz4 in the main level of the profile folder at your next startup. Therefore, we suggest copying recovery.baklz4 into the profile folder and renaming it to sessionstore.jsonlz4.

I've tried doing this, but when I run FFox it just gives me a blank tab. There's the option to restore session, but when I click it it just adds another blank tab.

At the point where you have the two blank tabs, is there anything available when you check (either):

• "Library" toolbar button > History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)
• (menu bar) History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)

If that doesn't re-open the missing tabs, could you run the recovery.baklz4 file through this tool on my website:

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

It shows which URLs are found under open windows vs. closed windows and the list can be saved off as a clickable list of links in case you can't restore the tabs automatically.

jscher2000 said

At the point where you have the two blank tabs, is there anything available when you check (either):

• "Library" toolbar button > History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)
• (menu bar) History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)

---

If that doesn't re-open the missing tabs, could you run the recovery.baklz4 file through this tool on my website:

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

It shows which URLs are found under open windows vs. closed windows and the list can be saved off as a clickable list of links in case you can't restore the tabs automatically.

I have nothing under recently closed tabs and windows.

When I try to run recovery.baklz4 through the tool on your website it gives me just one empty tab. I guess that means the file is busted :(

Strange. because it is very large (632 kb).

If you look at the content in the box after the file is decompressed, does it look like session file data? For example, starting with:

{"version":["sessionrestore",1],"windows":[

The script that parses out the URLs is looking for certain cues in the file, but it's also possible in principle to just find everything starting with http if that would be helpful. I don't have code at my fingertips, but if you enlarge the box by dragging the lower right corner and then use Find (Ctrl+f) for http and click the Highlight All button you can see whether there are relevant URLs in the file.

Where did you get this recovery.baklz4?

If the file is corrupted (and it sounds it is if there is no session data in it) then it won't work if you try to restore this session.