Face ID was introduced with iPhone X (10) and allows users to unlock their iPhones using the camera for personal recognition. On iPhone 12 and later models, you can use Face ID with a mask that covers your mouth and nose.
Go to Settings > Face ID & Passcode, then do any of the following:
Allow Face ID to work while you wear a face mask: Turn on Face ID with a Mask, then follow the onscreen instructions. Note: If you usually wear glasses, you can improve the accuracy of Face ID by wearing a pair of transparent glasses (not sunglasses) when you turn on Face ID with a Mask.
Add a pair of transparent glasses (not sunglasses) to your appearance:Tap Add Glasses, then follow the onscreen instructions.
Don’t allow Face ID to work while you wear a face mask: Turn off Face ID with a Mask.
Alternatively, you can use Apple Watch (Series 3 and later) with all models of iPhone that support Face ID to unlock the iPhone while you wear a face mask. This is the only method available if you have an iPhone X or 11.
Go to Settings > Face ID & Passcode.
Scroll down to Unlock with Apple Watch, then toggle on the Apple Watch.