What To Do When Firefox Crashes

What To Do When Firefox Crashes
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Firefox is a great web browser. It is quick and easy to use and has several convenient features. The interface is simple, but you can change that by customizing it. Several themes for this web browser are available online. Simply download and install them. In addition, several add-ons and extensions increase the functionality of the browser. Sometimes these customizations may interfere with the normal activity of Firefox and cause it to crash. Sometimes the settings or files are corrupted. Although rare, these crashes are annoying. Find out what you can do to get Firefox back up and running again after it crashes.

Submit a Crash Report

The first thing you want to do is submit a crash report. The details of the crash are sent to the online community at Mozilla for analysis. Sometimes the cause of the crash is identified. If not, others that have encountered similar problems with Firefox will post their data, which will contribute to a solution. To submit a crash report, do the following:

  • Type about:crashes in the location bar of Firefox and click Enter.
  • Under Report ID, click on the latest crash report. This will go to the site: crash-stats.mozilla.com.
  • After the report is processed, a signature is listed. Use this signature to search for related information.
  • Click ‘Search Mozilla Support for Help’ and look for items matching the signature.

With the signature, you can make inquiries in the forum or chat through the Ask a Question feature. Include the signature in the question to expedite the process.

Try to Start in Safe Mode

While you are waiting for a response from the crash report, try to start Firefox in Safe Mode. This will eliminate potential causes of the crash. In Safe Mode, all extensions are disabled and the default theme is used. To start Firefox in Safe Mode, do the following:

  • If the Firefox browser is open, click on File and scroll down to Exit.
  • Open the Start icon on the desktop.
  • Select All Programs and find Mozilla Firefox.
  • Open the Mozilla Firefox folder and click Mozilla Firefox (Safe Mode).
  • In the Firefox Safe Mode window, click Continue in Safe Mode.

If Firefox does not crash in Safe Mode, then a Firefox extension or theme is most likely responsible. If the web browser still crashes, then the problem is not caused by an extension or theme. The probable cause is a plugin or changes to the preference settings.

Check If a Virus is Responsible For the Crash

Another possible cause of Firefox crashes is a virus. Specifically, the Backdoor.Ulrbot.C virus is known to affect the Firefox web browser, and anti-virus software has a difficult time removing it completely from a computer. To address this problem, start by submitting a crash report. Open the Modules tab in the report. Find modules that have no version information. This column will be blank. If there are not any modules without version information, then Backdoor.Ulrbot.C is not on your computer.

If there is a module without version information, record the file name and search for it on your computer. After finding its location on the computer, upload it to an online virus scanner. This one is recommended for finding the Backdoor.Ulrbot.C virus: https://virusscan.jotti.org/en. If the files are identified as this virus, they must be removed from the computer manually. To do this, start the computer in Safe Mode. This is different from starting Firefox in Safe Mode. Have the file names and the following steps written down before proceeding. For Windows XP:

  • Click Start and Shut Down.
  • In the Shut Down window, go to the drop-down list and select Restart. Then click OK.
  • Press the F8 key when the computer is restarting.
  • Use the arrow key to choose Safe Mode then press Enter.

For Windows Vista or Windows 7:

  • Click Start and then click the arrow next to the Lock icon. Select Restart.
  • Press F8 upon restart, but before the Windows icon appears.
  • On the Advanced Boot Options screen, select Safe Mode with the arrow key and press Enter.

Once in safe mode, locate the files that were identified as viruses and delete them. Restart the computer in normal mode.

Corrupted Download History or Trouble With PDFs

If the crash occurred while downloading a file, something might be wrong with the download history. To correct this, open the profiles folder by doing the following:

  • Click the Help menu and select Troubleshooting Information
  • Under Applications Basics, select Open Containing Folder. This will open the profiles folder.
  • Close Firefox by clicking File and selecting Exit.
  • In the profiles folder, find the file downloads.sqlite and delete it.

If Firefox crashes while loading a PDF file, the user agent text may have been modified. To reset it, do the following:

  • In the location bar, type about:config and press Enter. A warning might pop up. Click I’ll be careful, I promise!
  • Type general.useragent in the Filter box.
  • For each preference listed, right-click on it and select Reset.


Firefox Support: Ask a Question; https://support.mozilla.com

Firefox Crashes - https://support.mozilla.com/en-US/kb/Firefox%20crashes

Image Credit - Screenshot taken by author.