Your logged in status is kept in special cookies. Removing those cookies means you need to log in again.

Type about:preferences#privacy<enter> in the address bar.

The button next to History, select Use Custom Settings.

Turn off Always Use Private Browsing Mode Turn on Remember My Browsing And Download History At the bottom of the page, turn on Clear History When Firefox Closes. At the far right, press the Settings button. Turn on ONLY Cache and Form And Search History leaving the others off.

I followed the steps you outlined above and my problem has persisted.

I am now on Firefox 60.0.2 and still have not been able to fix this issue. I am logged out of accounts when a session is closed, even if the "keep me logged in" features are enabled.

Profile data can be removed or not recorded 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.

You can use these steps to make a website recognize and remember you:

• create an "Allow" exception to keep specific cookies, especially in case of secure websites and when cookies expire when Firefox is closed
• Options/Preferences -> Privacy & Security
  Cookies and Site Data: Exceptions

Use this startup setting.

• Options/Preferences -> General -> Startup: "When Firefox starts":
  "Show my windows and tabs from last time

Don't use "Clear history when Firefox closes" at all to see if that works. Close all open windows and the Firefox application at once in case you currently first close open windows, but leave the nu bar visible.

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

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

I feel like FredMcD and cor-el are both misunderstanding my problem. The problem is not when I QUIT Firefox. When I quit Firefox and restart it, all my tabs reopen with the logins intact.

The problem is when I close a tab, and then re-open a tab and attempt to access a website I was previously logged into. Closing a tab (but keeping Firefox running) logs me out of any session, whether I have "save login" enabled. Anytime I close a tab, open a new tab, and attempt to access a just-visited website with "save login" enabled, I have to re-log in to it.

FredMcD: I don't run disk cleaners or anti-virus. I run Malwarebytes for macOS once a month and have never found malware.

cor-el: I already have all the steps you suggested enabled. Those settings were already enabled when this problem started.

Hope this makes sense.

The problem started three months ago with the upgrade to 59.0.1 and subsequent Firefox updates have not solved this issue. I have already tried disabling my add-ons and this did not solve the issue.

I would say this has to be caused by an add-on, also based on the fact you talk about a "save login" option which is not part of the Firefox text strings. Try running Firefox in Safe Mode and see if you can reproduce the problem.

Either that, or a tab was opened in a separate container. Make sure you don’t use them for those websites.

Testing in a clean profile is a quick way to find profile related issues, including those with add-ons. And in order to make sure "the problem started with the update to Firefox 59.0.1", you could revert to Firefox 58 that you can find here, either with a new or (perhaps better) your current profile. You won’t lose settings and data when uninstalling the current version, though copying the profile folder as a backup is always recommended.

Tonnes:

Turns out you were right, it was an add-on. I swear, I disabled all add-ons when this first happened and the behavior didn't change. Maybe I missed an add-on when I was disabling them all. I don't know. But as it turns out, it was one of them, and I've removed it. Everything is working fine now.

BTW:

"you talk about a "save login" option which is not part of the Firefox text strings"

I was talking about the "save login" feature that some websites offer.

Thanks for your help.

That was very good work. Well done.

Please tell us what caused the problem so others can be helped. And flag that post as Solved Problem so others will know.