There is no single iPhone switch named Block App, but Screen Time can restrict an app in several useful ways. For an app that is already installed, an App Limit is the simplest way to restrict daily use.
- Open Settings > Screen Time and turn on Screen Time if necessary.
- Tap App Limits > Add Limit.
- Choose the category or specific app you want to restrict.
- Tap Next, set a very short daily allowance, and turn on Block at End of Limit if that option is available.
- Set a Screen Time passcode so the restriction cannot be casually changed.
Screen Time also has Content & Privacy Restrictions for controlling app installation, purchases, web content, and other features. If you are configuring a child’s iPhone through Family Sharing, manage the child’s Screen Time settings from the family controls rather than relying only on a limit on your own device.