Hello, at present, this problem can't be solved completely at the technical level. You can try other add-on components, and thank you for your suggestions.

You can create a backup of sessionstore.jsonlz4 with Firefox closed to have a backup of all open tabs and windows.

You can also check the session files in the sessionstore-backups folder in the Firefox Profile 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

thank you

cor-el said

You can create a backup of sessionstore.jsonlz4 with Firefox closed to have a backup of all open tabs and windows. You can also check the session files in the sessionstore-backups folder in the Firefox Profile 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

Thank you for your reply, and some kind of suggestion as to what to do to access my windows/tabs on my former machine/installation. Although you gave some instructions, it wasn't really explained so I can understand it (for instance, what do I do with the "backup of sessionstore.jsonlz4" when I find it?, etc.), and what would be happening if I did these things suggested?

I hesitate to mark this "helpful" or not because it really didn't answer my questions: why Sync doesn't retain the separate windows of tabs from another machine use; whether it is technically (not presently - that's a given!) possible for Sync to retain windows of tabs (instead of just all the tabs together from all the windows; and whether it is technically possible for Sync/Firefox to be able to choose the tabs individually to be restored, instead of having to restore each of them one-by-one, or ALL of the tabs (which may be in the hundreds!) at once?

These seem like pretty logical functions, so are they for some reason technically not possible, or have they just been overlooked, or are not just "done" yet, or would probably never be done?

Thanks again for your assistance.

This is about not using Sync as that won't keep the tabs organized, but about backing up your personal data yourself on a removable device (USB jump drive or USB hard drive).

Your (pinned) tabs and windows are stored in sessionstore.jsonlz4 in the profile folder.

If you have used this tabs/widows setup for a longer time then you might have a upgrade.jsonlz4-<build_id> in the sessionstore-backups folder like I posted above. The upgrade file is created when Firefox updates. I have an upgrade for 74.0 and 74.0.1 and 75.0 if I compare the file dates with the update history (Help -> Troubleshooting Information).

Thanks for your reply, but it is clear you don't understand the problem. This is not a "backup" question. I had a windows install that "died" and was not longer able to boot. I had a bunch of research in many Firefox windows, each of them a different facet or subject, with a bunch of tabs in each window.

Using Sync on another machine, I no longer have the delineation of subjects (separate windows); but rather just a whole bunch of tabs - all mixed up now.

If Sync does not keep separate "window delinations" of a Firefox session, then Sync is not very useful. I understood it to have the purpose of having your present Firefox session (including of course settings, previous bookmarks, etc.) available to you where ever you could log on to your account, i.e. working at the office, then continuing your work later at home.

If Sync won't keep separate windows of tabs, then yes, bookmarking and backup up on portable media is the only way to take your "work" with you to another machine. So why even have Sync? Just always backup and write to portable media to take it with you! Sync is only slightly more useful as it will communicate your settings, bookmarks, etc. for use in a different location and machine. And as in this case, when a machine is no longer functioning, at least tabs of your previous session are accessible. But this is certainly not ideal - as it would be having your session available exactly like it was, with the windows preserved.

You still haven't answered my questions about "why" this is. Perhaps you don't know, and if so, a simple "I don't know" would be appreciated. The questions again are "why" does Sync not preserve windows? Is it technically not possible? Is this "function" an oversight? Is this function possible in the future? Or is there some reason it would never see the light of day?

In addition I asked: when restoring Sync tabs, why is it not possible to choose/mark as a group those that you want to restore, instead of having to open them one-by-one (very time consuming with a high number of tabs!); or the only other alternative is to open ALL of them at once from another machine, and possible overwhelm this iteration of Firefox now being used on another machine (which might have less RAM/slower cpu/slower internet speed)?

Thanks if you can directly answer these questions. If not, I'll have to try posting them again in an attempt to get a response and some logical understanding of these issues?

You can simply transfer sessionstore.jsonlz4 from one profile to another profile (device) to transfer all session data and keep the tabs and windows.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

Did you give feedback to the Mozilla developers to implement this feature, btsam, by clicking on the three line hamburger menu on top right; selecting Help at the bottom of the menu; and then Submit Feedback?