Hi KB19,

If you still have access to the old C: drive from your previous PC, you can recover your open Firefox tabs by copying part of your old Firefox profile data to your new computer. The open tabs are stored in a file called sessionstore.jsonlz4 (and sometimes in backup files).

Here’s how you can do it safely:

1. Locate your old Firefox profile

On your old drive (now connected as another volume), go to:

C:\Users\<your-old-username>\AppData\Roaming\Mozilla\Firefox\Profiles\

You’ll see one or more folders with names like:

xxxxxxxx.default-release

Inside that folder, look for files like:

sessionstore.jsonlz4 sessionstore-backups\

2. Find your new Firefox profile

On your new PC, open Firefox and type in the address bar:

about:profiles

Click Open Folder next to your current profile — this opens the same type of directory on the new system.

3. Copy the session files

• Close Firefox completely.

• Copy the following files from your old profile into the new one (overwrite if prompted):

• sessionstore.jsonlz4

• The entire sessionstore-backups folder

• Start Firefox again.

• Your open tabs and windows from the old computer should now reappear.

4. If that doesn’t restore tabs

Check the sessionstore-backups folder for files named like:

recovery.jsonlz4 previous.jsonlz4 upgrade.jsonlz4-<version>

You can rename one of those to sessionstore.jsonlz4 and try launching Firefox again.

Optional: If you still have Sync enabled

If you had Firefox Sync set up on the old PC, signing in with the same Firefox Account on the new machine may also restore your open tabs automatically under Synced Tabs (accessible via the menu or sidebar).

This method works even if your old PC no longer boots — as long as you can access the old user folder, you can recover the tabs.

Well done; the doing is describe perfect. Nathan, much thanks.