What about the rest of your profile? Settings, bookmarks, history, passwords . . . .

Ar you using any password add-ons/programs?

Look on your desktop. Do you see a folder called; Old Firefox? Look inside. Look for the folder with the latest creation date.

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

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.

Do you notice that you lost more personal data?

Firefox 67 and later can use a dedicated profile for each of the Firefox update channels and will lock the profile, so it can only be used by Firefox in a specific installation folder. For Release versions this profile would be a xxxxxxxx.default-release profile, profiles used in older Firefox versions usually used a xxxxxxxx.default profile (a refresh adds a time stamp).

• https://support.mozilla.org/en-US/kb/dedicated-profiles-firefox-installation
• https://blog.mozilla.org/2019/01/14/moving-to-a-profile-per-install-architecture/

You can open the about:profiles page via the location bar to check whether multiple profiles are present and what profile Firefox currently is using.

• Do NOT click any Remove button on this page.
• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

See also "Determine if Firefox has created a new profile":

• https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks

You can check if you have a logins.json.corupt file in the profile folder.

Thanks

To answer your question about loss, No history, no passwords, no cache but the cookies are there logins,Json.corruprrupt is there as also presence of last few updates as logins.json.corrupt-n where n is 1-6 and logins,json.corrupt presence of a few other . corrupt files such as handlers,json.corrupt from about 6 weeks ago

It looks to me like a complete remove and install might be necessary

Thanks again no old firefox, therefore no old profiles

I guess that (as I said above) I need to remove and reinstall

bj123 said

I guess that (as I said above) I need to remove and reinstall

No. It looks like only the profile is corrupted.

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

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

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Type about:profiles<enter> in the address bar. How many profiles are listed? How many should be there? Also, open the folder in your file explorer

Some other users mentioned a logins.json.corrupt appearing after a recent update. Sometimes the file isn't corrupt, and a possible workaround is:

• Exit Firefox
• In your profile folder: If there is a fresh logins.json that doesn't have anything in it yet, you can remove it
• Right-click > Copy logins.json.corrupt (whichever one looks most promising)
• Right-click > Paste and Windows should create something like logins.json - Copy.corrupt
• Right-click > Rename that back to logins.json
• Restart Firefox and hopefully it will realize that it knows how to read logins.json and it isn't corrupt after all

Thanks very much: That is workaround -- turns out it is an interaction between new Firefox and new AVG

Mozilla created an extension to recover logins.json from a logins.json.corrupt file.

• https://addons.mozilla.org/firefox/addon/restore-logins/

See also:

• https://support.mozilla.org/en-US/kb/passwords-disappearing-avg-security-software