Profile data can be removed or not recorded in several ways;

• 1) Running Firefox in Private Mode (nothing is recorded)
• 2) Privacy settings; (In the address bar, type about:preferences#privacy<enter>)
• 3) Many disk cleaners and anti-virus type programs can remove data from browsers
  Open their settings and have them leave the browsers alone.
• 4) Mal-ware.

I discovered that removing storage.vacuum.last.places.sqlite from advanced preferences causes the history to return. Unfortunately after I closed and re-opened Firefox a few times the preference reappeared and history disappeared, .

Note that your System Details list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file will only be present if you or other software has created this file and normally won't be present.

You can check its content with a text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

You can delete the user.js file if you didn't create this file yourself.

cor-el, thanks for your response. I find 2 profile files, one labelled .default-release and the other .default. When I try to open either of these using Atom it fails to do so, simply reopening the original profile.

Over the past few days Firefox has been moving from periods when "Show all history" does actually show all history and others when it shows only today's history. What is the explanation for this?

This morning when I opened Firefox and clicked on "Show all history" I was shown yesterday's history. Firefox then updated to v 88.0.1 and when restarted only shows today. What in heaven's name is going on?

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 profile folder in your file explorer.

https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox Title bar to make sure that Firefox closes properly.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit