We're sorry to hear that your Firefox seems to be crashing when you open it. Please perform the following steps to give us a crash report ID that helps us find out more about the cause of the crash.

1. On the keyboard, press [Windows] The image "Windows key" does not exist. + [R]. This should bring up a Run window that contains a text field.
2. In that text field, type %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.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. Is the problem still there?

While still in Safe Mode,

In the address bar, type about:crashes<enter>. Note: If any reports do not have BP in front of the numbers/letters, click it and select Submit.

The crash report is several pages of data. We need the report numbers to see the whole report.

Using your mouse, mark the most resent 7 - 10 crash reports, and copy them. Now go to the reply box below and paste them in.

If you can't get Firefox to open, you will have to do this the hard way. https://support.mozilla.org/en-US/kb/mozillacrashreporter Open the file browser / explorer on your computer. Note: You may have to enable Show Hidden Folders / Files. Enter this in the address bar;

Windows: %APPDATA%\Mozilla\Firefox\Crash Reports\submitted Win 7/Vista: C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Crash Reports\submitted Win XP/2000: C:\Documents and Settings\<username>\Application Data\Mozilla\Firefox\Crash Reports\submitted

Mac OS: /Users/<username>/Library/Application Support/Firefox/Crash Reports/submitted Linux: /home/<username>/.mozilla/firefox/Crash Reports/submitted

Copy the last 5-7 Recent File Names in the folder. Post the information in the reply box below.

Firefox would not start in safe-mode. I installed a version of Firefox that was 2 releases back and it worked fine.

Sounds good. Please sen the crash reports you have.

I never set Firefox not to automatically update, so over the weekend it updated to the latest version and as soon as I restarted it it crashed again. I have rolled back to 42.0 and it is working perfectly. I deleted most of the crash reports when I deleted everything. Is there a way to attach the crash reports? I do not have much in the "Crash Reports" folder, "events" and "pending" are empty, a couple "installTime" files, LastCrash and submit files. I tried to paste the contents of the "lastcrash" file but it only showed the number below.

1450708100

The problem is most likely that I am running Windows XP on this system, but can not upgrade from this since we run a software package on this system that is only supported under XP.

hi, this is just a guess, but in case you have nvidia's network access manager or forceware network manager software installed, please go into your system control panel and uninstall it (or go there and have look if it is listed there, if you're unsure about this) and try updating to firefox 43 again afterwards.

Philipp hit it on the head. The system was a Sun Ultra 24 with a nVidia system board, so the Nvidia Network Access Manager was installed. I un-installed it, updated Firefox and the problem was alleviated. Thanks, Michael