Could you check whether any of the older windows are listed under either:

• "3-bar" menu button > History > Recently Closed Windows
• "Library" toolbar button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows

Note: Each window also has its own Recently Closed Tabs list.

Assuming no luck, then:

Alternate Profile?

If you lost other data besides tabs, it's possible you are using a different profile. To check on that...

Profile Manager Page

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile that Firefox is currently using will have this:

This is the profile in use and it cannot be deleted.

Do you have any other profile(s) listed on this page? If so, you can check whether it is the one you were using recently by clicking its Launch profile in new browser button.

If it isn't what you want, simply close that new window.

If it IS what you want, you have choices:

(A) Switch profiles: click the Set as default profile button for that profile so Firefox uses it automatically at the next startup.

(B) Extract useful files (you can use the Open Folder button on the Root Directory row to access them).

Backups

If the newest files in the sessionstore-backups folder in your live profile are too new to contain the missing tabs, you could check for possible backups in Windows' restore points. Please DO NOT run Windows' system restore as you probably would lose other data. Instead:

Exploring Restore Points Safely

Set Windows to show hidden files and folders: https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

Then download and run either of these two programs:

• ShadowExplorer: http://www.shadowexplorer.com/
• Shadow Copy View: https://www.nirsoft.net/utils/shadow_copy_view.html

Within the most recent restore point shown in the program, you can explore along this path to see whether you can find a shadow copy of your profile:

\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles\your-profile

Look for either a sessionstore.jsonlz4 in that folder, or any files in a sessionstore-backups subfolder.

You can export relevant files to a convenient location such as a new folder on your currently live desktop. Anything recent enough to be interesting?

Note that you are running a Firefox 95.0a1 Nightly build and it is always possible that you run into issues, so it would be more important to have a backup.

Are you on Windows 10 or Windows 11 in case this makes a difference ?

You can look at a utility to browse System Restore points to see if you can locate an older version of sessionstore.jsonlz4.

• https://www.shadowexplorer.com/
• https://www.nirsoft.net/utils/shadow_copy_view.html