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Firefox crashes on startup

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  • Last reply by zarat99b

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The latest version of Firefox, 39.0, crashes immediately upon startup. Attempting to start in safe mode and using various command line switches results in the same error. Running after uninstalling and reinstalling results in the same error. No workarounds found.

The crash report: https://crash-stats.mozilla.com/report/index/293d608e-95d4-4cf7-acc1-c5c5f2150802. It states: "EXCEPTION ACCESS VIOLATION READ."

The latest version of Firefox, 39.0, crashes immediately upon startup. Attempting to start in safe mode and using various command line switches results in the same error. Running after uninstalling and reinstalling results in the same error. No workarounds found. The crash report: https://crash-stats.mozilla.com/report/index/293d608e-95d4-4cf7-acc1-c5c5f2150802. It states: "EXCEPTION ACCESS VIOLATION READ."

Chosen solution

Try a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

  • Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

  • (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
  • (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then create a new profile.


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Chosen Solution

Try a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

  • Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

  • (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
  • (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then create a new profile.


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I did an uninstall, manually removed the Firefox folder, and did a clean reinstall. Didn't fix the problem. I also went to %APPDATA%\Mozilla\Firefox\Profiles\ and deleted all the profiles. Also deleted %AppData%\Local\Mozilla. Firefox still crashes on startup, no improvement.