Firefox may not have closed properly the previous time and session restore may be kicking in.

Are you using Clear Recent History to clear the browsing history?

• Edit > Preferences > Privacy : History: [X] Clear history when Firefox closes > Settings
• https://support.mozilla.org/kb/Clear+Recent+History

Try to use "File > Quit" to close Firefox if you are currently doing that by clicking the close X on the title bar.

See also:

• "Hang at exit": http://kb.mozillazine.org/Firefox_hangs
• "Firefox hangs when you quit it": https://support.mozilla.org/kb/Firefox+hangs

Since the time of Sea Monkey and Netscape, this problem has not arisen for me. It did not happen in Firefox 12. Only when I upgraded to Firefox 15 did this problem start happening. To me, a retired computer programmer, this feels like a regression. I'd guess at either an uninitialized vairable or a race condition.

In any case, Firefox should be able to handle being closed by clicking on the x in the titlebar. I shall continue doing so.

There has never been a hang at exit for me, so that is not something I will pursue.

In addition, since the problem did not occur ever until Firefox 15, I have done the following:

   sudo yum downgrade firefox xulrunner

Both are now at firefox 12 level. To keep things at that level, I've added to /etc/yum.conf the following:

   exclude=firefox, xulrunner

I'm certain that my recent actions to downgrade will solve the problem and show that this is a regression.

Oh, yes, I forgot. I already clear history (except for cookies, which clear themselves when they expire) when Firefox closes. I've been doing that all along as well.

Note that if you use Clear Recent History to clear the browsing history when you close that Firefox won't reopen the pages from the previous session and you get blank tabs (those tabs are treated as history and that history is gone).

First of all I use Fedora Linux. Firefox may work differently in Fedora than it does in Windows. Are you a Windows user?

When Firefox closes in Fedora, it truly closes. It does not minimize into an icon. It is gone. When I restart it, it is a fresh start of Firefox with one window, no additional tabs. That window should, according to my preferences, contain my home page. It should not be blank. In addition, I have set it so that when I open a new tab, that should also start in my home page. And, it has reliably done so.

I'm on Linux as well (OpenSUSE).

It is quite possible on Linux as well that Firefox or the plugin-container doesn't close properly and that there is still a Firefox process visible in the System Monitor after closing Firefox. Such issues are usually caused by plugins (Flash) that may prevent Firefox from closing properly.

Firefox should make sure everything is closed and terminated when one closes Firefox. To do otherwise is a bug in the program.

When I'm done with a tab, I close it. When I'm done with a page, I go back to my home page. So, when I close Firefox, it is from my home page with nothing extraneous going on. There should at that time be no active plugins or anything else. So, I don't see why Firefox would open incorrectly when I restart it.

I'm not interested enough in this to pursue it much further. Since the developers don't want to fix this problem, I will just live with it. An intermittent bug is extremely difficult to resolve. And I'm convinced it is a bug.