Your passwords are stored in two different files, both of which are required:

   key4.db - This file stores your key database for your passwords. To transfer saved passwords, you must copy this file along with the following file.
   logins.json - Saved passwords. 

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

I saved a profile last November. It contains key3.db, not key4.db which the new version requires.

I copied all the files from the old profile to a new profile. No saved logins!!!

How can I convert the old db file to the new format?

You need to delete an existing key4.db file to make Firefox fallback to logins.json and key3.db.

You may have to remove pkcs11.txt and secmode.db.

File deletions and setting the environment variable failed. No logins!

What Firefox version created/used the profile with the logins.json and key3.db files you used?

Do these files work in a separate profile with the current Firefox release?

cor-el said

What Firefox version created/used the profile with the logins.json and key3.db files you used? Do these files work in a separate profile with the current Firefox release?

I have no clue. I began using Nightly when a windows update killed the audio in videos. Everything was lost in a crash. All I have left that I can find is one profile. I am presently searching a 1TB external for key4.db and doubt there is any hope.

I can not make Nightly or Thunderbird recognize old profiles, must make a new profile and copy files into it. The Profile Mgr. does not see them. The current try comes from a backup made 11/18/17.

Search came back empty. The backup I used, from last May, did not replace all files. It is nothing but a long list of zip folders with no indication of the contents. A search for key4.db came up empty.

Why don't you try the current Firefox release?

Nightly updates twice a day and is an unstable development branch meant for experienced users.

You can find the full version of the current Firefox release (62.0.3) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/
• https://www.mozilla.org/en-US/firefox/62.0.3/releasenotes/

I had both installed, generally used Nightly, I like it. I doubt that FF will differ in regard to the profile but I will try it. In the mean time I have no access to my logins.

I have fat finger syndrome and visual impairment so I depend on the saved passwords!

Firefox gives the same result except that now neither program will set new history. Both report that another program is using the file even though only one is running.

Solved. I am not sure how. After extensive searching, I found a cmd line to set environment varfiables. It did not work. Having no knowledge of environment vars. or how to set them, I clipped off the problematic part and ran "set NSS_DEFAULT_DB_TYPE=sql" through Windows Power Shell. That is supposed to force FF to use the old sqlite db files. No change, of cuss. I created a new profile, renamed it and renamed the year old profile to match it. Bingo! both programs now have my old logins!

Thanks for your help!!!

Note that 'sql' (SQLite) is the newer format and the old format was 'dbm' (Berkeley Database) although SQL has been supported since 2011. So you would have to use set NSS_DEFAULT_DB_TYPE=dbm to use key3.db

Tried the rename trick on 760, it worked without setting any env. vars.