# Biometric access control

URL: https://ayonix.com/glossary/biometric-access-control
Updated: 2026-09-08 | Published: 2026-09-08 | Author: Jan Mocary, Chief Technology Officer, Ayonix AI

Biometric access control grants or refuses entry to a door, gate or turnstile using a physical trait such as a face or fingerprint instead of a card or PIN. The credential cannot be lent or lost, which is why it is chosen for areas where knowing who entered matters as much as controlling entry.

## How do the common biometric credentials compare?

The three modalities most often deployed on doors, compared on the properties that decide a fit.

Face is chosen for throughput and because it works with the cameras a site often already has. The trade is that a face credential is captured at a distance and without contact, so the boundary between access control and surveillance has to be drawn by policy rather than by the hardware.

- Face — Contact required: No — Throughput: High, walk-through — Typical objection: Perceived as surveillance if not clearly scoped
- Fingerprint — Contact required: Yes — Throughput: Moderate, one at a time — Typical objection: Hygiene, and failure on worn or damaged fingers
- Iris — Contact required: No, but close range — Throughput: Moderate, requires positioning — Typical objection: Cost and the need for user cooperation

## Where should biometric templates be stored?

The storage decision is the privacy decision. Everything else about a deployment can be adjusted later; where the templates live determines who can be compelled to produce them, what a breach exposes and which jurisdictions the data has entered.

- On the credential: the template stays on a card or phone the holder carries, and the reader compares against it.
- On the device: the reader or local controller holds the templates for the doors it serves.
- On premises: a local server holds them for the site, which is what multi-door and multi-site policies usually require.
- In a vendor cloud: templates leave the organisation entirely, which several regulators and most defence buyers rule out.

## What must the fallback path cover?

Every biometric system rejects legitimate people sometimes, and some people cannot enrol at all. A deployment without a working fallback converts a routine false reject into someone locked out of their workplace, which is why the fallback is part of the design rather than an exception to it.

- Provide a second credential, such as a card or PIN, for anyone the biometric rejects or who cannot enrol.
- Define what happens during a power or network failure, including whether doors fail open or fail secure.
- Give staff a route to report repeated rejection, since a rising rate for one person usually means a poor enrolment rather than an impostor.
- Record fallback use, because a fallback that becomes the normal path is a system that is not working.

## Frequently asked questions

**What is biometric access control?**
Biometric access control grants or refuses entry using a physical trait such as a face, fingerprint or iris instead of a card or PIN. Because the credential cannot be lent or lost, it is chosen where the record of who entered matters as much as controlling whether entry happened.

**Is face or fingerprint better for door access?**
Face suits high-throughput entrances because it works without contact and at walking pace; fingerprint suits low-traffic doors where a positive contact step is acceptable. The deciding factors are usually throughput, hygiene policy and whether existing cameras can be reused, rather than any accuracy comparison.

**Where are biometric templates stored?**
Depending on the design: on a card or phone the holder carries, on the reader or local controller, on a site server, or in a vendor cloud. The choice determines what a breach exposes and which jurisdictions the data enters, so it is a privacy decision more than a technical one.

**What happens if the biometric system rejects an employee?**
A fallback credential should let them in and the rejection should be logged. Repeated rejection of one person almost always indicates a poor enrolment image rather than an impostor, so the practical fix is re-enrolment, not a lower threshold for everyone.

**Does biometric access control work during a network outage?**
It does if matching happens on the reader or a local controller, which is why on-premise designs are common for doors. Systems that call a cloud service for every comparison stop admitting anyone during an outage, so the failure mode belongs in the requirements.

**Do employees have to consent to biometric access control?**
In many jurisdictions yes, and consent given as a condition of employment is scrutinised closely. Several biometric privacy statutes require written notice, a stated retention period and a deletion process, and a practical deployment offers a non-biometric alternative to anyone who declines.