Pinned tabs are stored in sessionstore.jsonlz4 when Firefox is closed, so if you lose pinned tabs then it looks that Firefox doesn't create this sessionstore file. Firefox would normally create a upgrade.jsonlz4-<build_id> (backup created during an upgrade of Firefox) in the sessionstore-backups folder in the profile folder that should have your pinned tabs.

Thanks for the info. I appreciate it.

Dear Firefox, mm maybe I am not very smart, but what does this help me? Now I know where my old tabs are, but how do I get the old tabs back. cannnot read this previous.jsonlz4 How to use this knowledge to get my pins back? Thanks for your answer.

You either need to restore an older copy of sessionstore.jsonlz4 or you can possibly use one of the files in the sessionstore-backups folder.

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 Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

You can look at this tool to inspect a compressed sessionstore file.

• https://www.jeffersonscher.com/res/scrounger.html