George_T said

Using FF 58.0.1 (64-bit). FF now closes when I close the last tab. That is infuriating. Setting "browser.tabs.closeWindowWithLastTab" to false does not work. How do I change this so that the program stays open after I close the last tab?

After you changed the value of that preference - did you then close and restart Firefox, in order for the change to take effect  ?

I just noticed (in your system details) that you have this add-on installed :

https://addons.mozilla.org/en-US/firefox/addon/close-after-last-tab/

You could try to contact the developer - see under 'More Information' : Support Email.

Note that this Close After Last Tab extension states:

1. Please go to Options and set: When Firefox starts: Show your windows and tabs from last time. 2. Go to about:config, set: browser.tabs.closeWindowWithLastTab = false

It didn't solve my problem because I had already set the option to "false." The problem was that I also had the Add-On "Close After Last Tab" running. If the Add-On is enabled, the "false" option is defeated. As soon as I disabled the Add-On, the problem went away - i.e. the setting browser.tabs.closeWindowWithLastTab = false then worked.

Thanks to Happy112 for spotting the problem. No need to contact the developer, simply disabling the add-on did the trick.

Happy112 said

I just noticed (in your system details) that you have this add-on installed : https://addons.mozilla.org/en-US/firefox/addon/close-after-last-tab/ You could try to contact the developer - see under 'More Information' : Support Email.

Happy - You spotted the problem. The add-on, when enabled, defeats the "false" option. Disabling the add-on caused the "false" option to go into effect. Problem solved, thank you.