Biometric Authentication in React Native

Passwords are a friction point. On mobile, biometric authentication provides a secure way to verify users in seconds without them typing a single character.

The Tool: Expo Local Authentication

The expo-local-authentication library provides a universal API for checking device capabilities and requesting authentication.

Implementation Steps:

1. Check Hardware: Ensure the device supports biometrics.
2. Enroll Check: Verify the user actually has biometrics set up on their phone.
3. Authenticate: Trigger the system prompt for FaceID or Fingerprint.

const result = await LocalAuthentication.authenticateAsync({
  promptMessage: "Login to your account",
  fallbackLabel: "Enter Password",
});

Best Practice:

Always provide a fallback (like a PIN) for cases where biometrics fail or aren't available. Security and convenience must go hand in hand.