Did you update directly from 52 to 120 as this isn't recommended ? Best is to update via "Help -> About Firefox" until you reach the current release to ensure that files are update properly to a newer scheme. Especially using Firefox 72.0.2 should be necessary to prevent issues with the logins.

• 1607798 - Add a new watershed for Firefox 72.0.2 and update some existing ones to avoid password migration issues when updating to 73+

Firefox 58 and newer use key4.db (SQLite) for the key file and no longer use key3.db (DBM), but can use key3.db as a fallback when key4.db is missing. Support for key3.db ended with Firefox 73 and newer (i.e. Firefox 72.0.2 is the last version that supported key3.db) and thus 73+ versions can't be used to migrate logins.json and key3.db to key4.db.

You can install Firefox 72 and create a new profile and put logins.json and key3.db files in this profile. Make sure that there is no key4.db and let Firefox create a new key4.db

• https://download-installer.cdn.mozilla.net/pub/firefox/releases/72.0.2/
• https://support.mozilla.org/en-US/kb/custom-installation-firefox-on-windows
• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

Hi, I did follow the recommended update path carefully. I'll install the older browser again. It looks like it can export CSV, but not import it. Hopefully the new new one can import from the new old one without collisions. Thanks for your advice!

You need to enable import CSV in the Password Manager (about:logins) via the about:config page as this menu item is currently hidden for performance reasons.

• about:config => signon.management.page.fileImport.enabled => true
• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

You need to close and restart Firefox to make the Import menu item appear in the gear menu on the about:logins page.

Ah, thank you. That will be a great help.

Alas, I still struggle with this. I tried installing a custom version of FF v72, which created a new profile. I renamed v72's key4.db such that it would not be identified and copied over the v52 login.json and key3.db. I started it up, but it regenerated an empty key4.db instead of pulling in the old logins. Therefore, there was nothing for me to export as CSV.

I also tried a custom installation of FF v52, however, it didn't create a new profile. It deleted or renamed many extensions in the default profile, identified various dbs as corrupt, and generally made a mess of things. I restored the default profile from a backup using WinMerge and am finally back to square one.

Yet I'm still trying to figure out how to recover old logins going back nearly twenty years without destroying my current default profile. Did I make a mistake or miss a step with the v72 method? Thank you!

FYI: To remedy these problems, I installed "Mozilla Firefox, Portable Edition Legacy 52" from PortableApps.com. On opening it and looking at its "about:profiles" page, I saw it still showed my current v121 profile. (I didn't want to mess that up again.)

I renamed the portable v52's default "profile" folder, copied over my backup v52 profile, and named it "profile". I opened the portable browser in Sandboxie to ensure it wouldn't change my current profile. I discovered that Firefox v52 is unable to export passwords at all--it can only import them. However, an old extension called Password Exporter worked to export passwords as CSV and XML. I recovered these files and am sorted until I try to import them in the updated Firefox. (I will try that another day.)