Firefox 58+ versions use key4.db for the key file (default salt and master password). Previous Firefox versions used the key3.db file although they can use key4.db (SQLite). Support for SQLite databases (key4.db and cert9.db) exists since 2011.

If you copy logins.json and key4.db to the current profile folder then Firefox should be able to find the usernames and passwords stored in logins.json. Note the logins.json and key4.db should match.

Not sure what you mean by: "Note the logins.json and key4.db should match."

I had already copied all files from my profile backup to the only profile folder on the new computer. I have now deleted all files in the current profile folder, re-copied in all files from the profile backup again and ensured that key4.db and logins.json were included. Unfortunately, the same result - bookmarks and other things are there, but the saved logins are not. Could it be that the profile backup did not work properly? The hard drive on the old computer is nearly dead, therefore I need to access that only if really necessary.

Maybe the size of the files will help - there should be about 100 saved logins: logins.json 27.8 kB key4.db 294.9 kB

It might be helpful to know that I had several tabs open when I created the profile backup. Some of those pages require login. Those tabs are available and opened as logged in on the new computer, so at least that login information has been transferred somehow, just the "Saved Logins" area in Settings is empty.

Thanks again.

That the logins.json and key4.db files need to match means that the encryption keys stored in key4.db need to be the keys that were used to encrypt the data stored in logins.json. If this isn't the case then the usernames and passwords in logins.json can't be decrypted.

If you previously had a master password then Firefox should show the dialog to enter the MP if you access the Password Manager. The logins.json file is a plain text file that stores a record for each login and you can open this file is a Firefox tab to inspect the file with the JSON viewer.

• https://developer.mozilla.org/en-US/Tools/JSON_viewer

You can try to set signon.debug to true on the about:config page and check the Browser Console for password manager related messages.

Since I copied both login.json and key4.db from the same profile, I assume that guarantees they match.

I did have a MP, but under Preferences / Browser Privacy / Forms and Passwords, the MP is not set. If I try to create one, it tells me that it is not possible to change the MP.

I viewed logins.json as suggested, it contains the logins I am trying to recover.

I have set the signon.debug to true and after a restart found these items in the Console: LoginManagerContent:_detectInsecureFormLikes about:blank LoginManagerContent.jsm:488 LoginManagerContent:_detectInsecureFormLikes about:config LoginManagerContent.jsm:488 LoginManagerContent:_detectInsecureFormLikes about:blank LoginManagerContent.jsm:488

Try to remove pkcs11.txt and secmode.db if you copied these files.

You can try the logins.json and key4.db files in a new profile without any other files from the backup.

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

deleting the two files and restarting FF seems to have fixed it!

Many thanks!