Flawed Finder in Catalina
QSince I upgraded my Mac to Catalina, Firefox won’t run properly. When
I can start it up, it soon hangs or crashes, and often won’t open again until after I’ve restarted my Mac. Isn’t it compatible with Catalina?
ARecent versions of Firefox should be fully compatible with Catalina. Unless you’re running an older release, this is either due to corruption of the app itself, or something stored in its folder inside your Home folder’s Library.
Trash your current copy of the Firefox app, download the current version, and install that. If that still doesn’t work normally, you’ll need to remove its other files, which may reset its preferences to the defaults. Quit the app, and in the Finder press the ç, å and . (full stop) keys at the same time to show invisible items. In your Home folder, select the Library folder, and within that locate the Mozilla folder. Drag that to the trash, and press ç, å and . a second time to hide invisible items again.
If Firefox has recently crashed, restart your Mac to give it a clean start, and empty the Trash. When you now open the Firefox app, it should create a fresh Mozilla folder inside the Application Support folder instead. Another trick worth trying is is to start up your Mac in Safe mode, with the ß key held during startup. This stops third-party extensions from loading, and could eliminate any conflict which might be causing this. Sometimes a minute or two in Safe mode then restarting normally is enough to fix clashes. It’s worth updating Firefox to the latest version anyway – a serious security flaw was discovered (and patched) in January.