Details like websites remembering you (log you in automatically) are stored in a cookie.

• Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Tools > Options > Privacy > "Use custom settings for history" > Cookies: Exceptions

In case you are using "Clear history when Firefox closes":

• do not clear the Cookies
• do not clear the Site Preferences

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/remove-recent-browsing-search-and-download-history

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, passwords, and other website specific data.

Clearing cookies will remove all specified (selected) cookies including cookies with an allow exception that you would like to keep.

Could you describe your current cookie settings?

"3-bar" menu button (or Tools menu) > Options > Privacy

Which of these best matches what you have for your regular cookie setting?

(1) "Firefox will: Remember history"

(2) "Firefox will: Never remember history"

(3) "Firefox will: Use custom settings for history" with either

• "Keep until: they expire" AND "Clear history when Firefox closes" either
  • Not checked
    or
  • In the corresponding Settings, NOT set to clear Cookies
• "Keep until: I close Firefox" AND "Allow" exceptions set for the sites AND "Clear history when Firefox closes" either
  • Not checked
    or
  • In the corresponding Settings, NOT set to clear Site Preferences
• Neither of the above

Which setting do you have for third party cookies?

If necessary, change to "Firefox will: Use custom settings for history" temporarily. Then look for:

(A) "Accept third party cookies: Always"

(B) "Accept third party cookies: From visited"

(C) "Accept third party cookies: Never"

Hi, I have mine to Remember History at the moment, and in custom it accepts third party cookies as well.

If Firefox isn't clearing the cookies, because it is set to remember them, they could get cleared by:

(1) An add-on. I suggest checking Extensions on the Add-ons page. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Anything here related to cookies, privacy, tracking, etc.?

(2) Utility/privacy/cleaning software on your system that cleans up browser data

These tools often have configuration options to make exceptions for either certain browsers or certain sites, but some others may just do a complete wipe of cookies. You'll need to check their settings.

It's also possible that your cookie database has become corrupted so Firefox is not actually storing cookies persistently there. Hmm...

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I don't have any add-ons or extensions installed. I just downloaded it recently and haven't done any customization aside from the pages to open at start-up.

Note that Firefox stores the cookies in the sessionstore.js file as part of the session data in case you reopen pages automatically (Show my windows and tabs from last time) or otherwise restore the session.

You can remove all data stored in Firefox from a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History > Show All History" or "View > Sidebar > History") or via the about:permissions page.

Using "Forget About This Site" will remove all data stored in Firefox from that domain like bookmarks, cookies, passwords, cache, history, and exceptions, so be cautious and if you have a password or other data from that domain that you do not want to lose then make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of the involved files.

It doesn't have any lasting effect, so if you revisit such a 'forgotten' website then data from that website will be saved once again.