Deleting App / NSUserDefaults data on macOS

As a side note to anyone like me who ends up at this question, if you're developing a macOS screensaver and storing configuration settings in UserDefaults, you need to do

defaults delete com.apple.ScreenSaver.Engine.legacyScreenSaver

to delete your screensaver settings. This will likely wipe out all settings for any custom screensavers installed but I wasn't able to find another way.

If you are trying to delete your preferences to reset them then you need to use the defaults command. MacOS uses a cache system for preferences and deleting the preferences file itself has not been recommended by Apple for a long time. In Terminal enter:

defaults delete your.app.bundle.id

This will remove the file and any cached settings.

If you wish to delete the whole app then that depends on whether it is sandboxed or not. First delete the preferences as above.

If it is sandboxed you delete the directory ~/Library/Containers/your.app.bundle.id.

If it is not sandboxed you must remove individually anything you've added to paths such as ~/Library/Application Support etc.

In both cases you need to delete the name.app file itself.

HTH