This article covers the situation where Firefox displays a message about crashing when you try to quit or exit the program. The crash message may look like one of the following:
Alternately, Firefox may close but display a message similar to the following when you restart it:
If you are seeing crash related messages in another context, please see our general Firefox crashes article for links to pages that may address your specific symptoms better.
The most common cause of a crash on exit or improper shutdown is extensions. Our article on Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems should help in identifying the extension at fault.