Hi gspagnol2, please ignore the spam/scam message with a toll-free number. That's not official and we have no idea what they will do to your system if you engage.

Hi gspagnol2, 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.

Hello,

You may have seen a post or received a notification regarding support for Firefox or Thunderbird with a link to another site or a phone number being posted. This is a scam and is not a method to receive support from Mozilla. Mozilla does not have telephone or email support. Please do not click on the link and do not interact by calling any phone numbers or email addresses listed. I apologize for any inconvenience caused. You are currently posting on the official Mozilla website and will receive assistance here.

@jscher2000: Thank you so much for your help. Yes I had found those files and the scrounger link helped. One of my upgrade.jsonlz4 is from yesterday and contains everything I want to recover!! :) What do I need to do next?

Hi gspagnol2, you can save a list of clickable links from the Scrounger page. That's your fallback if file substitution doesn't work or would lose too much newer session history.

You can substitute the old session for your latest one through a file substitution. This is a little complicated because Firefox is going to try other files first, but if you set Firefox to restore the previous session automatically, exit Firefox, and hide all other files, then Firefox should use the older one. Possibly you'll need to rename it, too.

During its normal shutdown, Firefox should create a file named sessionstore.jsonlz4 at the main level of your profile folder (i.e., the level above the sessionstore-backups subfolder). You need to hide (rename or remove):

• Profiles\[profile.folder]\sessionstore.jsonlz4
• Profiles\[profile.folder]\sessionstore-backups\recovery.jsonlz4
• Profiles\[profile.folder]\sessionstore-backups\recovery.baklz4
• Profiles\[profile.folder]\sessionstore-backups\previous.jsonlz4

The you can rename the file you want Firefox to use to recovery.jsonlz4 (still in the sessionstore-backups folder). (Still keep your backups just in case, though.)

At the next startup, when it doesn't find sessionstore.jsonlz4, Firefox should use your recovery.jsonlz4 file instead.

@jscher2000, I tried to substitute files from that folder without success. I ended up using the list of clickable links from the Scrounger page. It was a slow process but I got it done. Thank you so much for your time and help.