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 also check the sessionstore-backups folder that is used to store session data during the current session.

You will normally find these files in the sessionstore-backups folder:

• previous.jsonlz4 (cleanBackup: copy of sessionstore.jsonlz4 from previous session that was loaded successfully)
• recovery.jsonlz4 (latest version of sessionstore.jsonlz4 written during runtime)
• recovery.baklz4 (previous version of sessionstore.jsonlz4 written during runtime)
• upgrade.jsonlz4-<build_id> (backup created during an upgrade of Firefox)

You can copy a file from the sessionstore-backups folder to the main profile and rename the file to sessionstore.jsonlz4 to replace the current file (make sure to backup the current sessionstore.jsonlz4).

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
• https://support.mozilla.org/en-US/kb/Profiles

The two (2) files named sessionstore.jsonlz4 and sessionstore.js have not been found. I have checked every Mozilla directory for its contents. That would be the Program Files (486) and the Program Files.

If I perform a search at the bottom left corner of the Win 10 screen, I am directed to webpages. No specific directory.

Under Users\(Username)\App Data\Local Mozilla\Firefox\Profiles\Roaming\I3j2214s.default. I found the Sessionstore-backups folder. This folder does contain two files: Recovery.baklz4 and Recovery.jsonlz4

SO, my question is where is the location of the original two (2) files you wrote about.

Attempted to take a screen shot, but could not find a format that would upload.

I am asking because it happened again and I had to remove many, many tabs.

Thank you Kent

The sessionstore.jsonlz4 file is only present when Firefox is closed. During a session only the files in sessionstore-backups folder are used.

Easiest to go to the profile folder is to use the button on the "Help -> Troubleshooting Information" (about:support) page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/Profiles

On the about:profiles page you need to click the button to go to the Root Directory.

Firefox uses two locations for the Firefox profile folder, so make sure to look in the correct location. Location used for the main profile that keeps your personal data (Root Directory on about:profiles).

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

Location used for the disk cache and other temporary files (Local Directory on about:profiles).

• C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profiles\<profile>\

Hi Kent, is your Firefox set to restore your previous session at startup? That's the first checkbox on the Options page:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

It's in the Startup section.

If not, Firefox might restore your previous session anyway if:

• At startup, Firefox believes it did not shut down normally (crashed)
• At startup, Firefox finds a command in an optional user.js file instructing it to restore the previous session this one time (more info on the user.js file here: How to fix preferences that won't save)

But since you don't have any ancient session history files available to restore, just the latest ones, it's hard to explain tabs from older sessions showing up.

Since you mentioned bookmarks, you probably have noticed or are aware of the "Open All in Tabs" feature for bookmarks (or a folder of bookmarks). If that was getting triggered, it certain could explain older bookmarked pages opening. However, there's a warning before opening a large number, so that doesn't seem like the most probably explanation.

By the way, let's say the first tab is what you want and everything to the right of that is unwanted. Right-click that first tab and use Close Tabs to the Right to get rid of them in one fell swoop.