FRR

In biometrics, the rate at which legitimate users are wrongly denied.

FRR measures how often a biometric system incorrectly rejects a legitimate, enrolled user, representing false negatives that harm usability and can drive users toward weaker workarounds. Tightening the matching threshold to improve security raises the FRR, illustrating the inherent tradeoff in biometric tuning. The exam pairs it with FAR, the rate of wrongly accepting unauthorized users, and with the CER, where the two rates intersect. A high FRR frustrates valid users, while a high FAR weakens security, so administrators balance the two.