Not sure if this will help your exact problem but since ive had something similar happen to me yesterday I might as well share my fix which might be able to help you too - it will delete all tabs but you can recover them later if you make a backup of the now mentioned sessionstore file/folder. (Also just kind of copy pasted from another help post but should be fairly simple) This might help; You may have corrupt sessionstore [v56] sessionstore.jsonlz4 file(s). Delete all sessionstore* files and the sessionstore-backups folder. Don't delete the files if you need to rescue any data from them, just move them out of the profile folder to some location where Firefox doesn't look for them. You can try to read out their contents using this tool: https://www.jeffersonscher.com/res/scrounger.html Type about:support<enter> in the address box. Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox. Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory. Locate the above file. Then rename or delete it. Restart Firefox.