After deleting an app in iOS, what data stored in Key Chain or UserDefaults will remain in the system?

After deleting an app on iOS:

• UserDefaults: data saved in UserDefaults is removed along with the app. They are stored in the app's container, which is deleted when the app is removed.

• Keychain: data in the Keychain is usually preserved after the app is deleted. The Keychain is a shared secure storage, and entries in it are not automatically deleted when the app is removed. This is done to retain important data (e.g., passwords) between app installations.

Therefore, after deleting the app, data in UserDefaults will disappear, but data in the Keychain will remain in the system unless specifically configured otherwise (for example, using special attributes to delete keys upon app removal).