A fingerprint recognition feature available on some Mac computers. With Touch ID, you can purchase items from the iTunes Store and sign in to your iTunes Store account.
Touch ID is located at the top-right corner of the keyboard, next to the Touch Bar or row of function keys, depending on the model of your Mac.
Note: With your first purchase, you must use your Apple ID and password to authorize the purchase; after that, you can choose to use Touch ID on future purchases.
To use Touch ID, place your finger on it. To set up Touch ID, choose Apple menu > System Preferences, then click Touch ID.
For more information about Touch ID, see this Apple Support article.