With a simple glance, Face ID securely unlocks iPhone X. It provides intuitive and secure authentication enabled by the TrueDepth camera system, which uses advanced technologies to accurately map the geometry of your face. Face ID confirms attention by detecting the direction of your gaze, then uses neural networks for matching and anti-spoofing so you can unlock your phone with a glance. Face ID automatically adapts to changes in your appearance, and carefully safeguards the privacy and security of your biometric data.
You can always use your passcode instead of Face ID, and it’s still required under the following circumstances:
• The device has just been turned on or restarted.
• The device hasn’t been unlocked for more than 48 hours.
• The passcode hasn’t been used to unlock the device in the last 156 hours (six and a half days) and Face ID has not unlocked the device in the last 4 hours.
• The device has received a remote lock command.
• After five unsuccessful attempts to match a face.
• After initiating power off/Emergency SOS by pressing and holding either volume button and the side button simultaneously for 2 seconds.
Check out Face ID support document at the link below and click here to download the Security Guide PDF.