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I had 2 windows open in my browser. Only one with tabs I wanted to save (I was keeping them open, probably a bad habit, I know). I closed the "good" window first, and the "bad" windows second. Firefox only saved the tabs from the bad window, but these are the tabs I am not interested in. In the past sessions Firefox saved all the tabs from the first window. But this time, having a second one open, I lost them all. Is there a way to retrieve them all? I appreciate any help. Thanks

I had 2 windows open in my browser. Only one with tabs I wanted to save (I was keeping them open, probably a bad habit, I know). I closed the "good" window first, and the "bad" windows second. Firefox only saved the tabs from the bad window, but these are the tabs I am not interested in. In the past sessions Firefox saved all the tabs from the first window. But this time, having a second one open, I lost them all. Is there a way to retrieve them all? I appreciate any help. Thanks

Chosen solution

Especially if you have multiple windows open then you should always use "File -> Exit" or use the Power button in the "3-bar" Firefox menu button drop-down list. If you close individual windows then only the last closed window can be reopened on the next start.

Did you look in "History -> Recently Closed Windows" to see whether you could restore this window ?

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


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).

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Chosen Solution

Especially if you have multiple windows open then you should always use "File -> Exit" or use the Power button in the "3-bar" Firefox menu button drop-down list. If you close individual windows then only the last closed window can be reopened on the next start.

Did you look in "History -> Recently Closed Windows" to see whether you could restore this window ?

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


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).

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Thanks. I followed your instructions and I found the file with the list of tabs. I was unable to restore it, but I could extract the URLs.