Hi tprince!

You should be able to re-install all of the add-ons at addons.mozilla.org . Have you tried looking into your history to recover the lost tabs? You can access you history at CTRL+H AND select the 'Last Month' option. That should be able to scroll through the tabs you opened on the last month and select the ones that you were using during the power outage.

Thank you for the suggestions. I had so many add-ons, I hate spending the time to remember their names and installing them, but if that is my only option, so be it.

The history is not helpful because all I see are the tabs that I closed, not the tabs that were still open. I have used Firefox for years and cannot believe they would disregard the session manager or at least give us a warning that we could lose our open tabs if we continued with the update. Very unprofessional. Now that I have lost all the open tabs I am thinking this is the time to try Chrome.

Hi tprince, if you were using the legacy extension "Session Manager," it no longer works in Firefox 57+. There are several newer extensions that have similar features. We can come back to that.

After a power cut or other kind of crash, usually Firefox will attempt an automatic crash recovery for non-private windows.

Could you check whether either of these are available (not hidden or grayed out):

• "3-bar" menu button > Restore Previous Session
• (menu bar) History > Restore Previous Session

If they are missing or grayed, 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 help...

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
• various .js files from Firefox 55 or earlier

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/res/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you.

Do you think your Firefox might have performed a Refresh? If you spot a new "Old Firefox Data" folder on your desktop with freshly updated content inside, you may need to mine that folder for old session files, either Firefox's own, or files created by the Session Manager extension, which have a .session extension. The scrounger page I linked earlier can read the .session files.

I found two files that have yesterday's date. One is recovery.jsonlz4 and the other is recovery.baklz4. Using your tool, both look like the missing tabs. Which file and what procedure should I use to reinstate the lost tabs?

There's no way to merge together different session files, but you can swap an old file in for the current one while Firefox is not running. Here's how.

(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, rename sessionstore.jsonlz4 to OLDsessionstore.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 => sessionstore.jsonlz4
• Uncompressed .js file => 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?

BTW My Firefox version is 60.0.2 (64-bit) and I do not see a sessionstore file like I did in the older Firefox versions. Maybe this version does not have such a file?

Success! You have got the answer to this problem down pat. Thank you for your time and talent! Sleep good tonight knowing that you have saved another lost soul :)

Had a similar problem this morning which this solved, thanks jscher! =)

Thanks again, jscher! - your scrounger solved the problem of losing Session Manager in the move to Quantum. You always do a great job of anticipating problems and offering solutions.

Hi John, thank you for the kind words. By now you also have lots of new session management extensions to try out, including:

• https://addons.mozilla.org/firefox/addon/tab-session-manager/
• https://addons.mozilla.org/firefox/addon/session-sync/

Firefox uses the compressed sessionstore.jsonlz4 file in the profile folder to store session data. The sessionstore.jsonlz4 file is only present when Firefox is closed. The sessionstore.jsonlz4 file is created from recovery.jsonlz4 in the sessionstore-backups folder when you close Firefox and is removed and copied to previous.jsonlz4 when you start Firefox to make is possible to restore the session at any time.

jscher2000 said

... By now you also have lots of new session management extensions to try out, including:

• https://addons.mozilla.org/firefox/addon/tab-session-manager/
• https://addons.mozilla.org/firefox/addon/session-sync/

Thanks for the suggestions. After the scrounger cleanup, I thought to try living with Quantum's native session management for a while, but must admit that your second suggestion (Session Sync) looks interesting enough to add to the mix.