Hi Ed, is Firefox still running? If so -- don't start it if you already closed it -- is there anything here:

• "3-bar" menu button > Library > History > Recently Closed Windows
• "Library" toolbar button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows

Firefox creates numerous session history files, but because session history is only for the immediately previous session, it is unfortunately too easy to lose it. Could you start by making a backup of your existing session history files? Here's how:

Do not exit Firefox, or if you closed it, don't re-open it.

(1) To open your profile folder...

If Firefox is still running:

You can open your current Firefox settings (AKA Firefox profile) folder using either

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

In the first table on the page, click the "Open Folder" (or "Show in Finder") button.

If Firefox is closed:

Type or paste the following into the Windows Run dialog or the system search box and press Enter to launch Windows Explorer:

%APPDATA%\Mozilla\Firefox\Profiles

In that folder, do you see a semi-randomly-named folder? If so, click into it. If you find multiple such folders, find the one that was most recently updated.

(2) Copy out session history files

In your profile folder, double-click into the sessionstore-backups folder. Save all files here to a safe location such as your Documents folder.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

• recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs?

To preview the contents of a file, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/ffu/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you. (Note: if you don't get a response within 15 seconds, the tab probably crashed.)

Unfortunately FF has been started and stopped several times since yesterday, I now have 78 tabs open and 7 active. I will try your suggestions with FF open and see where it leads me. Thanks for the suggestions and I will report back on what I find. I did print out the E-Mail so I can use it as a check list.

Well, there are only three files in the Sessionstore backup folder and they all are from today. Looks like I am screwed.

Looking in the Recycle bin, I see no files from Mozilla in the roaming folder.

Hmm, usually there are snapshot files from recent backups. Do you have another Firefox profile folder either

• in an Old Firefox Data folder on your desktop
• in your Windows user folder under %APPDATA%\Mozilla\Firefox\Profiles (there must be at least one folder here, the active one, but are there any others?)

Note: %APPDATA% is a shortcut for C:\Users\username\AppData\Roaming which is a hidden path. To unhide the path: https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

Here are some other (less reliable) data recovery suggestions:

Deleted File Recovery

A tool like Recuva can recover some erased files. This could be useful to track down recently removed session history files. Make sure Windows is set to show hidden files and folders:

• https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files
• https://www.ccleaner.com/recuva

As noted above, the typical files names for session history files are:

• recovery.jsonlz4
• recovery.baklz4
• previous.jsonlz4
• upgrade.jsonlz4-20201027185343 (the number varies, indicating the "build" that was installed)

Shadow Copies

You can use a utility program to search inside restore points to try to locate an old file that's usable. (Please do NOT try to use the built-in Windows System Restore for this because you probably would lose data.)

(1) Set Windows to show hidden files and folders:

https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

(2) Download and run one of these two programs:

• ShadowExplorer: http://www.shadowexplorer.com/
• Shadow Copy View: https://www.nirsoft.net/utils/shadow_copy_view.html

Within the most recent restore point shown in the program, you can explore along this path to see whether you can find a shadow copy of your profile:

\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles\

(3) Check in the sessionstore-backups folder of each profile for older backups. You can export interesting files to a convenient location such as your currently live desktop.

Any luck?

Ok, I dropped the oldest file in your page and I don't understand what I am looking at or what to do with it. I clicked on the link to save uncompressed JSON file but again, I am at a loss. Any help is appreciated.

I have several other profiles listed, I will have to check them though they seem to date from 2019.

Looking in the other profiles, the latest file is June 30, 2019.

I did start a Recuva session on the current Session Store Backup file, says 52 minutes remaining.

Using the Shadow Copy View program, I found this file, upgrade.jsonlz4-20201026153733 with a date of 10-28-2020 and a time before FF Crashed. I did copy it to my desktop but am at a loss what to do with it from there.

Using the Shadow Copy View Program, I did find this file, upgrade.jsonlz4-20201026153733, which I copied to my DeskTop. It dates from 28-October 2020 and from about 07:30 well before the FF Crash. I am at a loss on what to do with it from here. Thanks, Ed

Using Shadow Explorer I copied "previous.jsonlz4" to my desktop. This is from 11:54 on the 28th of October again well before the crash.

Recuva just finished and didn't find any files.

Using the Shadow Copy View Program, I did find this file, upgrade.jsonlz4-20201026153733, which I copied to my DeskTop. It dates from 28-October 2020 and from about 07:30 well before the FF Crash.

Using Shadow Explorer I copied "previous.jsonlz4" to my desktop. This is from 11:54 on the 28th of October again well before the crash.

You can view the contents of a session history file by dropping it onto my page here and clicking Scrounge URLs:

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

If you recover a useful list, click Save List to archive it as an HTML page you can use to re-open tabs as your leisure.

It may also be possible to persuade Firefox to use it at the next startup if you want to try that.

How would I persuade FF to use the file in the next startup?

I now have an HTML page with 757 tabs to open, this is going to be fun, I might even close some after looking at them again. I do have some that are desperately wanted. Thanks. Now if I could just persuade FF to open this file on it's own, I would not have to go through each tab. Thank you, Ed

Hi Ed, to try swapping in an older session history file so Firefox will load it, the standard "manual swap" method is as follows (assuming Firefox is still running):

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

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

In the first table on the page, click the "Open Folder" button. This should launch a File 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 Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup -- a file named sessionstore.jsonlz4 should appear in the folder. (If it never appears, don't be alarmed, but skip Step 3.)

(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.

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

• Compressed file such as previous.jsonlz4 => sessionstore.jsonlz4
• Uncompressed file such as previous.js => sessionstore.js

(5) Right-click the sessionstore-backups folder and rename it to sessionstore-backupsOLD to prevent Firefox from using another file in there at startup

(6) 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?

Ok, I will give it a try later on this evening or tomorrow morning, I have to be somewhere else in the next half hour. Thank you for all your help, Ed

Ok, it worked, I now have my missing FF back up on the line and is now re-set as the default browser. Thanks for all your help.

jscher2000 THANK YOU!! I went through the steps you suggested above on 10/29/2020 and was *happily* able to recover all (I think) of the pinned tabs that disappeared during the FF update last night. So grateful you would take all the time and detail to post step by steps bc I am FAAAAARR from understanding the behind the scene workings and hidden files or whatever or FF or any software! Your explanation made it dummy proof. Thank you again!!! Jennifer