Face ID is a biometric authentication facial recognition system designed and developed by Apple Inc. for the iPhone and iPad Pro.

The system can be used for unlocking a device,[1] making payments, accessing sensitive data, providing detailed facial expression tracking for Animoji, as well as six degrees of freedom (6DOF) head-tracking, eye-tracking, and other features.

Multiple security features largely limit the risk of the system being bypassed using photos or masks, and only one proof-of-concept attempt using detailed scans has succeeded.

Debate continues over the lack of legal protections offered by biometric systems as compared to passcode authentication in the United States.

[19] To avoid involuntary authentication, the system requires the user to open their eyes and look at the device to attempt a match, although this can be disabled through an accessibility setting.

As the system is used, it learns about typical variations in a user's appearance, and will adjust its registered face data to match aging, facial hair growth, and other changes using the Neural Engine.

[25] Authentication with Face ID is used to enable a number of iOS features, including unlocking the phone automatically on wake, making payments with Apple Pay, and viewing saved passwords.

Additionally, Face ID can be used without authentication to track over 50 aspects of a user's facial expression and positioning, which can be used to create live effects such as Animoji or camera filters.

It is used to enable control of the camera angle through head-motion-in games and eye-tracking to share attention with audience in streams, but also augmentative and alternative communication (AAC) and biometric research.

[30] Apple states that the probability of a false match is different for twins and siblings, as well as children under 13 years of age, as "their distinct facial features may not have fully developed".

[36] In August 2018, the FBI obtained a warrant to search the property (which includes electronic devices) of a man accused of transmitting child pornography; they unlocked the suspect's iPhone by holding it up to his face, without needing his passcode.

[38] In November 2017, Vietnamese security firm Bkav announced in a blog post that it had created a $150 mask that successfully unlocked Face ID, but WIRED noted that Bkav's technique was more of a "proof-of-concept" rather than active exploitation risk, with the technique requiring a detailed measurement or digital scan of the iPhone owner's face, putting the real risk of danger only to targets of espionage and world leaders.

"[43] With the release of iOS 13.5, Apple added a feature that automatically brought up the passcode screen if it detected that the user was wearing a mask.