When you understand how App Check will affect your users and you're ready to proceed, you can enable App Check enforcement.
To enable enforcement for Realtime Database, Cloud Firestore, Cloud Storage, and Authentication (beta), follow the instructions below. Once you enable enforcement for a product, all unverified requests to that product will be rejected.
Open the App Check section of the Firebase console.
Expand the metrics view of the product for which you want to enable enforcement.
Click Enforce and confirm your choice.
(Your project must be upgraded to Firebase Authentication with Identity Platform to enable enforcement for Authentication.)
Note that it can take up to 15 minutes after you enable enforcement for it to take effect.