Biometric information refers to unique physical and behavioral characteristics that can be used to identify individuals. Biometric identifiers are distinctive, measurable characteristics used to label and describe individuals, and they are often categorized as physiological characteristics related to the shape of the body. Examples of biometric identifiers include fingerprints, palm veins, face recognition, DNA, palm print, hand geometry, iris recognition, retina, odor/scent, voice, shape of ears, and gait. Biometric authentication is based on biometric recognition, which is an advanced method of recognizing biological and behavioral characteristics of an individual.

Biometric data is collected at the time of enrollment and is then saved to be matched with future attempts at access. Biometric technology is typically used to identify individuals or to verify that they are authorized to do certain things, such as driving a car or gaining access to a secure or restricted zone. Biometric data can be used to access information on a device like a smartphone, but there are also other ways biometrics can be used.

The most significant privacy issue of using biometrics is that physical attributes, like fingerprints and retinal blood vessel patterns, are generally static and cannot be modified. This is distinct from non-biometric factors, like passwords and tokens, which can be replaced if they are breached or otherwise compromised. In recognition of the privacy concerns surrounding biometric information, some states have enacted laws to regulate its collection, storage, and use.