Oh, I'd also like to mention, that sometimes this won't happen for months; even for a year until this time; but then will happen again and continue to happen for a while. It's very strange.

A possible cause is that Firefox isn't closing properly.

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit

If it happens again then check the sessionstore-backups folder in the profile folder and

Backup the session files in the sessionstore-backups folder in the Firefox Profile Folder to make sure not to lose possible important session data. Do NOT close Firefox when Firefox is already running.

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:preferences page.

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

See also this tool that you can use to inspect a compressed sessionstore file.

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

cor-el said

A possible cause is that Firefox isn't closing properly. Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit

---

If it happens again then check the sessionstore-backups folder in the profile folder and

Backup the session files in the sessionstore-backups folder in the Firefox Profile Folder to make sure not to lose possible important session data. Do NOT close Firefox when Firefox is already running.

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:preferences page.

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

See also this tool that you can use to inspect a compressed sessionstore file.

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

I will try closing via file > exit and the power button and report back if it happens again, and also see if renaming a backed up session restores it if it does. Anything else I should know?

Thanks.

Make sure you give Firefox enough time (e.g. up to one minute) to close properly before you power down the computer, especially if you use "Clear history when Firefox closes".

cor-el said

Make sure you give Firefox enough time (e.g. up to one minute) to close properly before you power down the computer, especially if you use "Clear history when Firefox closes".

I do clear my history daily, though not with that setting. I will factor this in as well, thanks.

Okay. I've been closing with file>exit and the 3-bar menu button. The issue still happens sometimes.

rareliving said

cor-el said

Make sure you give Firefox enough time (e.g. up to one minute) to close properly before you power down the computer, especially if you use "Clear history when Firefox closes".

I do clear my history daily, though not with that setting. I will factor this in as well, thanks.

How are you clearing history?

the-edmeister said

rareliving said

cor-el said

Make sure you give Firefox enough time (e.g. up to one minute) to close properly before you power down the computer, especially if you use "Clear history when Firefox closes".

I do clear my history daily, though not with that setting. I will factor this in as well, thanks.

How are you clearing history?

History > clear history > today. I don't clear all my history as I like to save some logins and I've had this happen on days I didn't clear it as well. I used to think it was some kind of messed up history as entirely wiping my history and relogging in to everything seemed to delay this problem once for many months. It didn't these past times, however.