Fingerprints, face recognition, and iris scans provide security based on unique physical traits.
Biometrics are convenient and increasingly common on phones and laptops. When you unlock your phone with your fingerprint, the device compares your scan against a stored template — a mathematical representation of your fingerprint — rather than storing the actual fingerprint image.
The critical limitation of biometrics is permanence. If your password is stolen, you change it. If your fingerprint template is stolen, you cannot change your fingerprint. This makes biometric data especially worth protecting, and biometric systems worth keeping updated.
Biometrics work best as a convenience layer on top of a PIN or password, not as a standalone replacement. Your fingerprint unlocks the device quickly in normal use, but the PIN remains the fallback — and the stronger security anchor — when the biometric fails or is unavailable.
Face unlock quality varies significantly. Basic 2D face unlock can sometimes be fooled with a photograph. 3D structured-light systems (like Face ID on iPhone) are far more resistant to spoofing. Know which type your device uses.