rn-mrz-scanner

A React Native Expo module that opens a native full-screen camera scanner to read the MRZ (Machine Readable Zone) from passports and ID cards.

| Platform | OCR Engine | | -------- | --------------------------------- | | iOS | Apple Vision (VNRecognizeTextRequest) | | Android | Google ML Kit Text Recognition |

Supports TD-1 (ID cards — 3 × 30 chars) and TD-3 (passports — 2 × 44 chars).

Installation

npx expo install rn-mrz-scanner

or

npm install rn-mrz-scanner
# yarn add rn-mrz-scanner

Expo Config Plugin (managed workflow)

Add the plugin to your app.json / app.config.js:

{
  "expo": {
    "plugins": [
      [
        "rn-mrz-scanner",
        {
          "cameraPermissionText": "We need camera access to scan your document's MRZ."
        }
      ]
    ]
  }
}

Then rebuild:

npx expo prebuild --clean
npx expo run:ios   # or run:android

The plugin automatically adds NSCameraUsageDescription (iOS) and CAMERA permission (Android).

Usage

import { scanMRZ } from "rn-mrz-scanner";

export default function App() {
  const handleScan = async () => {
    try {
      const mrz = await scanMRZ();
      console.log("MRZ result:", mrz);
      // TD-3 example:
      // "P<UTOERIKSSON<<ANNA<MARIA<<<<<<<<<<<<<<<<<<<\nL898902C36UTO7408122F1204159ZE184226B<<<<<10"
    } catch (error) {
      if (error.code === "ERR_CANCELLED") {
        console.log("User cancelled the scan");
      }
    }
  };

  return <Button title="Scan MRZ" onPress={handleScan} />;
}

Return Value

scanMRZ() returns a Promise<string> containing the raw MRZ text. Lines are separated by \n.

• TD-1 (ID card): 3 lines, each 30 characters
• TD-3 (Passport): 2 lines, each 44 characters

You can parse the result with libraries like mrz.

API

scanMRZ(): Promise<string>

Opens a full-screen camera view that automatically detects and reads MRZ text.

Throws:

| Code | Description | | --- | --- | | ERR_CANCELLED | User dismissed the scanner | | ERR_NO_ACTIVITY | (Android) No activity available | | ERR_UI | (iOS) Could not present the scanner | | ERR_MRZ | (Android) MRZ could not be read |

Requirements

• iOS: 15.0+
• Android: API 21+ (CameraX)
• Expo SDK: 49+

How It Works

1. A native full-screen camera view is presented.
2. Each frame is processed with OCR (Vision on iOS, ML Kit on Android).
3. Detected text is filtered and matched against MRZ regex patterns.
4. A StringTracker stabilises the result over multiple frames to avoid false positives.
5. Once a stable MRZ is detected, the camera closes and the result is returned.

License

MIT