You can check for problems with the sessionstore.jsonlz4 file in the Firefox profile folder that stores session data.

• delete sessionstore.jsonlz4 and sessionstore.js

When sessionstore.jsonlz4 is deleted you lose pinned tabs and open tabs and you will have to recreate them, so if necessary make a note or bookmark them.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Two other notes:

(1) If you use CCleaner, you've probably updated it since last October but, if not, definitely update it since the program used to cause this problem but it was fixed in November.

(2) Also, if you have no need to restore an old session, you can hide all the other old session history files as follows:

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, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

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

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

Pause while Firefox finishes its cleanup, then right-click the folder sessiontore-backups and rename it sessionstore-backupsOLD (or whatever, anything to hide it from Firefox).

I deleted sessionstore.jsonlz4 and everything in the sessionsstore-backups folder. I couldn't find a file named "sessionstore.js." No luck, I still have 61 tabs opening each time I reopen Firefox. I don't use CCleaner, but I do use Clean Master for PC. Attached shows some of the files in my folder...

Did you try to remove sessionstore.jsonlz4 used currently instead of sessionstore.js used previously?

You can check the home page setting.

• Options/Preferences -> General -> Startup: Home page
• https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

Firefox supports multiple home pages separated by '|' (pipe) symbols.

Cor-el helped solve the problem. He noted: "Firefox supports multiple home pages separated by '|' (pipe) symbols."

On a hunch, I looked at my homepage url and started scrolling to the right. I found all 61 of the url's that were opening as tabs, one after another with the '|' (pipe) symbol separating each.

Not sure what caused this to occur (61 home pages, representing past url visits) in my settings in the first place, but the problem is solved.