
In iOS 18, a new privacy feature allows users to lock and hide apps, making them inaccessible without a Face ID or Touch ID authentication. This feature enhances privacy by preventing unauthorized access to specific apps, and also hides them from search, notifications, and other areas of the operating system.

In iOS 18, users can lock an app on their iPhone by following these steps:
Not all apps can be locked, as Apple does not provide this option for certain apps like Maps, Clock, Calculator, and Stocks. However, most other apps, including third-party apps, can be locked using this method.
When an app is locked, users can also choose to hide it. This moves the app into a locked, hidden apps folder that requires authentication to open. To hide an app, follow the same steps mentioned above and select the "Hide App" option after choosing the "Require Face ID" or "Require Touch ID" option.
Locked or hidden apps are not only unable to be opened but also hidden from search, notifications, and other places across the operating system. To turn off the locking feature, long press on the app icon and choose the "Don't Require Face ID" or "Don't Require Touch ID" option2. Turning the lock on and off requires a Face ID or Touch ID scan, so it cannot be turned off without your knowledge. This feature also works on iPads with iOS 18.

Yes, there are some apps that cannot be locked using the new iOS 18 privacy feature. Apple does not provide an option to lock certain innocuous apps such as Maps, Clock, Calculator, and Stocks. However, almost every other app, including third-party apps, can be locked and hidden using this feature.