Hi, probably not. Always :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Please look on your Desktop for a Folder called OldFirefoxProfile, if there is not one please check here :

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

to see if there are 2 Profiles in the folder. If there is : Never work with original files.

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

Please let us know if this solved your issue or if need further assistance.

@Pkshadow I have only one profile folder, and my last backup is 6 month old. i found sessionstore-[1-8].js and sessionstore.jsonlz4. i think those are the backups, but i dont know how to use it

if you created a firefox account you can log in and all will be restored if not then well i dont know

Burt0n said

i found sessionstore-[1-8].js and sessionstore.jsonlz4. i think those are the backups, but i dont know how to use it

First, back up those files and everything from the sessionstore-backups folder to a safe location where Firefox won't replace or remove it.

The kinds of files you may find among your sessionstore-backups files are:

• recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update
• various .js files from Firefox 55 or earlier

Check the "last modified" date/time to see which file(s) seems to be most likely to contain your lost tabs. During an update, a specific snapshot should be created, so that might be best.

To preview the contents of a file, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/res/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you.

Also, did you check whether either of these are available (not grayed out):

• "3-bar" menu button > Restore Previous Session
• (menu bar) History > Restore Previous Session

If they are grayed, check either:

• "Library" toolbar button > History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)
• (menu bar) History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)

Could be too late, but it's always worth a look.

Recent post with steps to substitute an older session history file for the latest one, once you know which one you want to use: https://support.mozilla.org/questions/1211870#answer-1095531

@'jscher2000 Thank You!