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React Native permissions generator

React Native face id / fingerprint permission

Unlocking the app or confirming an action with Face ID, Touch ID or an Android fingerprint needs android.permission.USE_BIOMETRIC on Android and, on iOS, an NSFaceIDUsageDescription — the one biometric that shows a consent prompt, because Face ID can be triggered without the user touching anything.

expo-local-authentication declares both and authenticateAsync performs the check. The usage description is shown the first time Face ID is used by the app, so it should say what is being protected — 'to unlock your vault' — not merely that Face ID is used.

Face ID / fingerprint at a glance

Android grants
android.permission.USE_BIOMETRIC
iOS Info.plist key
NSFaceIDUsageDescription
Expo package
expo-local-authentication
Config plugin
expo-local-authentication
What it enables
Unlock the app or confirm an action with biometrics.
What the user agrees to
Use Face ID or your fingerprint

The declarations, for Expo and the bare workflow

Expo config

app.json
{
  "expo": {
    "ios": {
      "infoPlist": {
        "NSFaceIDUsageDescription": "TODO: why this app uses Face ID."
      }
    },
    "android": {
      "permissions": [
        "android.permission.USE_BIOMETRIC"
      ]
    },
    "plugins": [
      "expo-router",
      "expo-local-authentication"
    ]
  }
}

Prebuild writes these into the native projects; the config plugin is what makes the package's native code part of the build.

Bare workflow, Android

android/app/src/main/AndroidManifest.xml
<uses-permission android:name="android.permission.USE_BIOMETRIC" />

Bare workflow, iOS

ios/<App>/Info.plist
<key>NSFaceIDUsageDescription</key>
<string>TODO: why this app uses Face ID.</string>

The TODO is deliberate: the usage description is shown in the consent prompt and App Review rejects boilerplate.

Install the library

terminal
npx expo install expo-local-authentication

Face ID / fingerprint permission, answered

The longer version is in the guide React Native permissions that satisfy both stores.

What permission does React Native need for face id / fingerprint?
On Android, declare android.permission.USE_BIOMETRIC in AndroidManifest.xml (or expo.android.permissions in app.json). On iOS, add NSFaceIDUsageDescription to Info.plist (or expo.ios.infoPlist) with a sentence explaining why — the user reads it in the consent prompt. expo-local-authentication exposes the runtime request.
Do I still have to request face id / fingerprint at runtime?
Yes. The declaration only makes the request possible. The first time the feature is used, call the request API from expo-local-authentication; the operating system shows the prompt ("Use Face ID or your fingerprint") and remembers the answer. A declared but never requested permission does nothing, and a requested but never declared one fails.
Why was my app rejected over the face id / fingerprint permission?
Most often the NSFaceIDUsageDescription string: App Review rejects a missing one at once and a vague or boilerplate one frequently. Write what the app does with the data in your own words. Google Play reviews the declaration against the app's visible features, so a grant no screen uses is also a finding.

Declare every feature the app uses

The React Native permissions generator builds the complete set from the same catalogue — tick each device feature and copy the paired Android grants and iOS usage descriptions, the Expo app.json fragment and the install line together. In the Nodlume workspace the declarations come from the screens themselves: a screen that uses the camera is what adds the camera permission to the Expo Router project it exports.

Open the generator

Other React Native permissions

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