Firefox in Force Quit Applications, but not in Activity Monitor

Firefox stopped responding whenever I attempted to access a site. I could verify network connectivity to various sites with ping, but if I attempted to access a URL in the Firefox browser on my MacBook Pro running OS X El Capitan, Firefox (version 45.7.0) would not display any webpage. I've had this problem in the past; when it occurred, I would quit Firefox, sometimes using Force Quit Applications, which is available by clicking on the Apple icon at the top, left-hand corner of the screen and then selecting Force Quit and then selecting Firefox from the Force Quit Applications list of running applications and then clicking on the Force Quit button. When I did that today, I saw the message below as usual:

Do you want to force "Firefox" to quit?

You will lose any unsaved changes.


I clicked on Force Quit, but that seemed to have no effect. I closed and reopened Force Quit Applications and went through the same process numerous times, but no matter how many times I repeated the process, Firefox remained in the list of running applications that it showed.

Force Quit Applications - 

But I didn't see any instances of Firefox running when I checked the running applications with the OS X Activity Monitor application, nor did I see any Firefox processes running when I opened a Terminal window and looked for those with the ps command.

$ ps -ef | grep -i "firefox" | grep -v "grep"

The Activity Monitor showed that memory usage was somewhat high, but not exceptionally high and even after I closed some windows so the difference between the physical memory value and memory used was 4 GB, there was no change in what happened if I tried to forcibly quit Firefox using the Force Quit Applications program. CPU utilization was less than 20%.

I tried to relaunch Firefox several times; the first time I did so, I saw its icon bouncing in the dock at the bottom of the screen, but it never opened. So I used the force quit option, which stopped it from bouncing, but then it still appeared in the Force Quit Applications list of running applications, but not in the Activity Monitor, nor when I checked running processes with the ps command. If I right-clicked on the Firefox icon in the dock, I saw "Application Not Responding" in gray text, but choosing "Force Quit", which appeared below that text didn't seem to do anything; I was still in the same situation as before.

Firefox Dock - not responding

If Firefox shuts down abnormally, a lock file that would normally be removed when you exit Firefox may remain. The file can be found in your profile folder and, depending on the operating system under which Firefox is running will be named:

On a OS X/macOS system, your profile can be found under ~/Library/Application\ Support/Firefox/Profiles/xxxxxxxx.default, where xxxxxxxx is a random sequence of letters and numbers. You can see if it is present from a terminal prompt by issuing a command similar to the one below:

$ ls -al ~/Library/Application\ Support/Firefox/Profiles/bgq13udo.default/.parentlock
-rw-r--r--  1 jasmith1  1286109195  0 May  3 10:00 /Users/jasmith1/Library/Application Support/Firefox/Profiles/bgq13udo.default/.parentlock

Since the lock file was present, I deleted the file.

$ rm ~/Library/Application\ Support/Firefox/Profiles/bgq13udo.default/.parentlock

Firefox still remained in the Force Quit Applications list and remained after I tried Force Quit again from within that application and right-clicking on the icon in the dock showed the same results as previously. I also could not relaunch it. No new .parentlock file was created when I tried to relaunch it.

$ ls -al ~/Library/Application\ Support/Firefox/Profiles/bgq13udo.default/.parentlock
ls: /Users/jasmith1/Library/Application Support/Firefox/Profiles/bgq13udo.default/.parentlock: No such file or directory

So the presence of that file didn't seem to be the cause of Firefox not restarting nor for it remaining in the Force Quit Applications list.

I tried opening Firefox in "safe mode" by holding down the option key while double-clicking on Firefox in the Applications folder, but saw the message below (image):

You can't open the application "" becuse it is not responding.

But there were still no instancess of Firefox in the process list.

$ ps | grep -i firefox | grep -v firefox

I tried opening Firefox in safe mode from the command line interface (CLI), i.e., a Terminal window with the open utility, but though I didn't see any messages, it didn't open, either.

$ open /Applications/ --args -safe-mode
$ ps | grep -i firefox | grep -v grep

I was able to open a new instance of Firefox, though, using open /Applications/ --new.

$ open /Applications/ --new
$ ps | grep -i firefox | grep -v grep
$ ps -ef | grep -i firefox | grep -v grep
723184451 45212     1   0  9:46PM ??         0:06.11 /Applications/

In addition to then seeing the process listed in the output of the ps command, I also saw Firefox listed in the Activity Monitor list.

Activity Monitor - Firefox

When I double-clicked on the Firefox entry, I could see the parent process was listed as launchd.

Save on a Computer: Run Windows, Mac, and Linux with VirtualBox
Save on a Computer: Run Windows,
Mac, and Linux with VirtualBox
1x1 px

Activity Monitor - Firefox

When Firefox opened, I saw the Restore Session tab and had the option to restore the prior session. I was thankful that worked, since I had a lot of other open applications and files and didn't want to have to reboot the system to resolve the problem.

I still received the message "You can't open the application '' becuse it is not responding" when I clicked on a link in an email message, but that wasn't a significant issue, since I could right-click on the link the copy it and then open a tab in the instance of Firefox I now had open and paste in the link.


  1. Profile in use
    Last modified: March 24, 2015