From MozillaZine Knowledge Base

This article deals with Firefox crashing completely - that is, an error occurs and Firefox closes itself. It does not deal with hangs, which is when Firefox stops responding to user input. Crash logs may help you to locate the problem. See Still experiencing problems?, below.

Update Firefox

Use the latest public release version of Firefox, which will have the most recent fixes. You can download and install the latest version of Firefox from mozilla.com or choose Help -> Check for Updates.

Extensions

Problematic extensions may cause crashes. Start in Safe Mode, which disables all extensions, to help determine if an extension is causing the problem.

Plugins

Plugins are programs that work within Firefox and allow you to experience multimedia content such as video, animation or sound. Plugins can crash within their own code, and can also cause a crash within Firefox code.

If you cannot solve the problem by updating your plugins to the latest versions, you should file a bug report with the plugin manufacturer. You can find basic plugin information, installation instructions, known issues and download links at PluginDoc.

In this example, the Flash plugin was found to crash both Firefox and a non-Mozilla browser. The source of the crash was confirmed by the Windows Event Viewer. Plugins that can crash include:

• Adobe (Macromedia) Flash
• Shockwave
• Real Player or Real Alternative
• Java
• VLC Media Player
• Yahoo! Application State plugin for Yahoo! Mail

VLC Media Player

If you are using the VLC Media Player plugin, Firefox may crash when viewing WMV media. The VLC Media Player browser plugin conflicts with the Windows Media Player plugin, so you need to remove the VLC plugin npvlc.dll from the Firefox installation directory plugins folder for embedded WMV files to play properly.

Yahoo! Application State

If you have installed Yahoo! Messenger on your system, you may experience crashes when using Yahoo! Mail. This is caused by the Yahoo! Application State plugin (bug 322363, bug 326344). To see if this is the cause of your problems:

Type about:plugins in the Location Bar and press Enter. If you find "Yahoo! Application State" ("npYState.dll") in the installed plugins list, exit Firefox, open the C:\Program Files\Yahoo!\shared folder and rename the file "npYState.dll" to "XnpYState.dll" to disable the plugin. Open Firefox and test Yahoo! Mail.

Crash when downloading

You may be able to solve this problem by clearing the download history from the Clear Private Data tool, located on the Tools menu. Otherwise, exit Firefox completely and delete the downloads.rdf file in the Firefox profile folder (Windows 2000/XP/Vista users: read this for help finding it). For more information, see the article Unable to save or download files.

Damaged plist file - Mac OS X

On Mac OS X, sometimes a recurring crash pattern is caused by a preference file being damaged. Quit Firefox, then go to your user Library -> Preferences, find the file "org.mozilla.firefox.plist" and move it to your desktop (don't trash it; just leave it on the desktop). When you restart Firefox, a new .plist file will be generated. If the new preferences file is working well, you can trash the .plist file on the desktop. More information on corrupt .plist files can be found here. [1]

Windows compatibility mode

On Windows XP, sometimes Firefox must be run in Windows 2000 compatibility mode. Right click on your Firefox desktop icon and click on Compatibility > change the setting to Windows 2000 > click Apply.[2]

Hardware problems

Hardware problems, especially bad RAM chips, can cause Firefox to crash. [3] Download Memtest86 for Windows and Intel Linux or Rember for Mac to test if you have bad RAM chips.

Still experiencing problems?

• The standard diagnostic may resolve crashes not specifically mentioned in this article.
• Older versions of video card drivers can cause crashes. Make sure your drivers are up to date.
• Make sure Talkback (Firefox 2) or Breakpad (Firefox 3) is installed and enabled. Post on the Firefox Support forum what steps cause Firefox to crash and your Talkback crash ID or Breakpad report ID. Those who read it may be able to look up your crash on the Talkback website and find an existing bug report or file a new one for you. Also, if the crash you experience is common, it may be marked as a "topcrasher", making it more likely to be fixed in the next release.
• Your operating system system log may also have a crash report. The information will probably include the name of the module that caused the crash. On recent Windows versions, go to Start > Settings > Control Panel > Administrative Tools > Event Viewer. In the application tab, right-click on the event and select Properties. When you report the event, you should copy the information from the log.