see the following article for some suggestions

Restore previous session - Configure when Firefox shows your most recent tabs and windows

Are you using "Clear history when Firefox closes" to clear data like the cache or history?

• Tools > Options > Privacy > Firefox will: "Use custom settings for history"

I don't believe I've used "Clear History" for 17 years.

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.

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

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

Hello cor-el - I am not completely clear on "App Tabs" & "Tab Groups" and I'm hesitant to delete the .bak & .js until I figure out what they are.

Thanks again

See:

• https://support.mozilla.org/kb/using-tabs-app-tabs-and-tab-groups
• https://support.mozilla.org/kb/what-are-app-tabs
• https://support.mozilla.org/kb/what-are-tab-groups

Note that you can always rename files or move them to another folder to be able to undo such an action.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

• http://kb.mozillazine.org/Profile_backup
• https://support.mozilla.org/kb/Backing+up+your+information

Ok, now I understand. I have a about 30 pinned sites that I have on the toolbar