Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Please report back to see if this helped you!

It is possible that your security software (firewall, anti-virus) blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

• https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating

Hi Co-rel. My AVG is the free edition which I don't think has a firewall. I already added Firefox to the 'exceptions' in the firewall part of the security center but it was just the same. No worries, as I had previously imported my favourites into both Chrome (which I'm using now with no problems) and IE just in case of something like this as I'd been having trouble with Yahoo mail when using Firefox previously. It now seems more trouble than it's worth so I'll be removing Firefox from my computer in a short while. Thank you all for trying to help. All the best, Jack

Thanks for the advice feer but it did not help I'm afraid. I already removed/cleaned it completely from my computer twice and re-installed it earlier today with no luck. All the best, Jack

Sorry to hear that the suggested solutions didn't help and that you plan to switch to another browser.

You said that Firefox wouldn't start up, even in Safe Mode, which I take to mean Firefox's Safe Mode. (You can start in Firefox Safe Mode by holding down the shift key while starting Firefox.)

In case it helps you or others with issues starting Firefox, these articles contain other possible solutions.

• Firefox won't start - find solutions
• http://kb.mozillazine.org/Browser_will_not_start_up

Hello handicracker, you can also try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) and check firefox again.

(If works in Windows Safe mode then you have a problem with other software, like security software or maybe a system driver, that is running on your computer).

thank you

Thanks Ideato but yesterday I removed firefox from my computer. Maybe I'll give it another try in about 6 months as I prefer it to chrome (when it is working right) and I don't really like Google's attempts to dominate the planet. All the best, Jack

Hi Alice, sorry but I already removed firefox yesterday. My reasoning was that if both chrome and i.e. work fine why doesn't firefox? Thank you for trying to help. All the best, Jack

Hello handicracker,

Sometimes Firefox may not open due to numerous reasons (firewall, add-ons, malware, hardware). We need to figure out this issue. I understand that uninstalling Firefox and moving to another another browser is your choice but if you prefer to check with us again in 6 months, it may still be the same thing because it may be caused by something on your computer and nothing on our side. I hope that you understand by working together, we can fix your issue!

Thanks!

Hi Feer. Because I am not technical it would take me too much time to figure it out. For instance when I tried to start the computer in safe mode I was taken to a page about the BIOS, not to a place where I could direct it to start in safe + networking mode. I tried to start in safe mode 3 times, pressing F8 in the following ways which were all advised on the internet: 1) holding down F8 key immediately after the computer had finished closing down 2) waiting until the screen went dark and pressing F8 repeatedly and 3) as 2 but just holding the F8 key down. Nothing worked. At this stage I decided I was just not technical enough to figure it out and also did not want to spend any more time with it when I had 2 ways to access the internet with no problems. I hope you understand. All the best, Jack

You do NOT hold F8 down while shutting down, you hold it while the computer is booting up before the windows screen appears. Hope this helps!

If Firefox will start when you reboot the computer in Windows Safe Mode, it's likely that other software installed on your computer that starts automatically in Windows normal mode (or malware) is causing the problem.

To start Windows in Safe Mode see http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode

Hi Alice - I'll just repeat what I said earlier: Because I am not technical it would take me too much time to figure it out. For instance when I tried to start the computer in safe mode I was taken to a page about the BIOS, not to a place where I could direct it to start in safe + networking mode. I tried to start in safe mode 3 times, pressing F8 in the following 3 ways which were all advised on the internet: 1) holding down F8 key immediately after the computer had finished closing down 2) waiting until the screen went dark and pressing F8 repeatedly and 3) as 2 but just holding the F8 key down. Nothing worked. At this stage I decided I was just not technical enough to figure it out and also did not want to spend any more time with it when I had 2 ways to access the internet with no problems. I hope you understand. All the best, Jack

Jack, as I posted earlier:

You do NOT hold F8 down while shutting down, you hold it while the computer is booting up before the windows screen appears. Hope this helps!

Yes, that's what I did - 3 times in different ways. Each time I got into the BIOS settings and no matter which button I pressed there the page giving me the choice of starting in safe + networking mode did not appear. I spent about half an hour doing this then reasoned that if the other 2 browsers worked ok why didn't firefox? So that's why I've removed it and will try again in about 6 months. I also had trouble accessing my mail in Yahoo when using firefox although I think Yahoo also has problems of its own. Thanks for trying to help.

Please see this.

Important: DISCLAIMER: The above-mentioned URL would take you to a non-Mozilla Web site. Mozilla does not control it and is not responsible for information outside of Mozilla web sites.

Thanks Feer I downloaded Firefox again and was able to start in safe mode after reading the page you kindly sent me. Firefox opened ok. I then changed the settings back and tried again just in case but of course Firefox could not open. So I guess something is interfering with Firefox but I have no idea what. At least you have improved my technical knowledge a little! Thank you, Jack

You might want to start by checking for malware. You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

I first scanned with Spybot which found a few problems and eliminated them. I then immediately scanned with Malwarebytes which found nothing. After all this Firefox still would not start and just came up with the usual little box which I clicked to send the umpteenth fault report. I have now uninstalled Firefox and will wait 6 months. Thanks to everyone who tried to help. Now let's please leave it for 6 months. Thank you. Jack

Ah, so you are getting a crash when you start up Firefox. That's more useful than just Firefox not starting up. With a crash report we can actually see what the issue is. Please re-install Firefox, then use the instructions below to give us the crash report.

1. Press the following shortcut to get a Run window: [Windows] + [R]. This should bring up a window that contains a text field.
2. In that text field, enter %APPDATA% and press Enter. An explorer window should open.
3. From that explorer window, double-click on the Mozilla folder, then double-click on Firefox and then on Crash reports. Double-click on submitted.
4. Now, you should see a list of files that contain reports. Go to View > Arrange Icons by > Modified to get the most recent files at the top of the window.
5. Open the most recent 5 files with a text editor and copy the IDs.
6. Paste each ID with bp- into the reply window on the forums.

Thanks in advance!

You can find more information and troubleshooting steps in the Troubleshoot Firefox crashes (closing or quitting unexpectedly) article.