How to fix the Firefox memory leak on Mac OS and Windows, once and for all, like a boss

Some of you will love this, and some of you are going to flame me. I don’t care about the haters though. Even though a fellow TYPO3 developer friend pointed out regarding my solution, “There has to be a better way. There probably is”, I’m posting this as a help to all the Firefox users of the world who are sick to death of the phantom Firefox memory leaks.

We all know Firefox leaks memory for one reason or another. It’s been years. Plugins have come and gone and Firefox just leaks all the time. Period. What to do?

It’s time to hit Firefox with a sledgehammer. Like a boss.

This requires just the slightest bit of Mac OS savvy, but not much, or else I couldn’t have done it. Windows is a bit easier, but I’ll post the Mac version first and follow up next week with the Windows solution.

The solution is to simply kill and restart Firefox as quickly as possible. Boom. Done. Firefox goes from sappy to snappy in about 1 second. Firefox tries to restore you tabs when it “crashes” so you should be good. On the Mac, you might get the “restore” or “new session” buttons. On the PC, for me at least, it comes right back up without the question.

This has been tested on Firefox 3.x, 4, and now 5 on both Mac and PC. Your mileage may vary.

Make sure you aren’t composing an email in a webmail interface or anything before you test this!

But wait! Am I really sure Firefox has a memory leak? I present my anecdotal evidence:

How to kill and restart Firefox on a Mac in 1 second

  • Create a text file, like “killFirefox.txt” somewhere on your Mac.
  • After saving it as a .txt file, change it to “killFirefox.command”
  • Paste this into it:
    • killall -c firefox-bin
      sleep 1
      open -a Firefox
      sleep 1
  • Now open Terminal and navigate to wherever you saved the file. You’ll have to Google how to use Terminal commands, or get an “open terminal here” plugin for Finder (like I have)
  • Once you are in the directory where “killFirefox.command” is, run the following command to make your .command file executable. This means that after you do this, you’ll be able to double-click “killFirefox.command” and the script will run:
    • chmod 755 killFirefox.command
  • Now go back to Finder or wherever you saved the file, and drag it to the RIGHT side of the “dashed line” on your dock if you want one-click access to the process:
  • Try it!
  • Happy Firefox rebooting! Goodbye slow and sappy Firefox—until a real solution is in place!

You may have to alter the “sleep 1” to something longer, like 2 or 3 seconds if your Mac is too slow. You may also have to put in a different path, but I’m no terminal expert. Also, to set the Terminal window to close after the process finishes, you’ll have to edit the preferences like this: Terminal > Preferences > Settings > When the shell exits = Close the window

How to kill and restart Firefox on a PC in 1 second

  • Create a file, like “killfirefox.txt” on your desktop or somewhere handy
  • Paste this into it:
    • taskkill /f /im firefox.exe
      start /wait "" "C:\Documents and Settings\[--Your User Account Here--]\Local Settings\Application Data\Mozilla Firefox\firefox.exe"
  • You’ll want to make sure you put in your user account name in the path, and delete the “Your User…” holder text
  • Your path to firefox.exe, as listed above, might also be in a different place. You’ll have to find it and confirm.
  • Rename the file extension from “.txt” to “.bat”
  • Double click your new .bat file and voila!
  • Make a shortcut and drag to your quick links bar, or some other handy place

So you have a better way to do this?

Save your negative comments for the comments section on In the meantime, post instructions on a better way. For example, how to do this in AppleScript so you end up with a real “app” you can put in the Dock in a nice way.

Any other thoughts? Let’s here them!


  1. says

    Thanks Jon – I’m trying the first one now. We’ll see how well it stays updated with the FF releases! Short of developing an add-on, at least my method is “version and platform independent” :) We’ll also have to see how well it works when FF gets really bad after a few hours of use. I’ll post something back after I use it for a while!

  2. Benjamin says

    Hi Douglas,

    I’m on a Mac and since the last Firefox update it doesn’t work anymore.

    The command prompt says :
    “No matching processes belonging to you were found”

    I’m using the version 7.0.1 of Firefox.

    Do you know what the new workaround for this is ?

    Thanks a lot,


  3. says

    Hi Jon: I tried Restartless Restart 8 when I went to Firefox 7, and it’s one step easier. You can put the icon for it right in the toolbar. Give that a whirl and see how it goes. 7, on my Mac, does seem faster and better, but the memory leaks, no matter what Mozilla says, is the same as it ever was, thus, the need for a quick restart that keeps all your tabs remains. Bummer!

  4. Tom Hunter says

    For the record:

    OS X 10.8.4

    Firefox 21.0 (21! This problem has gone unfixed for 17 releases!!!!)

    Firefox running ONE TAB. Memory usage for Firefox (as told by Mac Activity Monitor) creeps up to 3 GB before it hangs forever.

    How about you stop with the stupid releases for no good reason and fix this fundamental issue?

  5. says

    I know, right? My solution is to use the add-on Startless Restart. Every few hours my memory usage is just over or under a gig! Chrome looks better by the day except a few extensions I love aren’t ported for it yet.

  6. says

    Firefox still leaks like crazy! LAME! I’m using FF 29.0.1 on OSX 10.6.8. I used to be a die hard FF fan. Not any more…. This browser kills me. Creating new FF profiles does not fix the problem. I’m super close to trashing this junk browser all together. Thanks for the write up Doug.

  7. says

    I gave up, went Chrome, and haven’t looked back. Make the decision to junk it, and go to a better browser. I was a diehard FF fan for so long, but leaving it behind was really nice. No more having to restart X times a day! How archaic!

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