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React Native Academy · Lesson

Universal Links (HTTPS Deep Links) on iOS and Android

Set up Apple App Site Association and Android App Links files on your web server, configure entitlements and intent filters in the app, and verify end-to-end deep linking.

Universal Links (HTTPS Deep Links) on iOS and Android is a free React Native Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the React Native Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why Universal Links Over Custom Schemes

Universal links use real HTTPS URLs to open your app. When a user taps https://myapp.com/profile/123, iOS or Android checks if your app is installed and capable of handling that URL domain. If yes, it opens your app directly — otherwise it falls back to the website in the browser.

This solves two problems with custom schemes: (1) fallback — if your app isn't installed, the user still sees a working web page; (2) security — only your app can claim your domain because the OS verifies ownership through server-hosted files.

How Universal Links Work

When your app is installed, both iOS and Android download a verification file from your server to confirm that your app is authorized to handle URLs on your domain. This verification happens once at install time (and periodically thereafter). The files are served at well-known URLs on your HTTPS domain.

When a user taps an HTTPS link to your domain, the OS checks its cached verification and routes to your app instead of Safari/Chrome — no browser, no redirect, instant in-app navigation.

// iOS: https://myapp.com/.well-known/apple-app-site-association
// Android: https://myapp.com/.well-known/assetlinks.json

// Both files must be:
// - Served over HTTPS
// - Accessible without redirects
// - Correct Content-Type
// - Cached but refreshable

Apple App Site Association (AASA) File

The Apple App Site Association file (AASA) is a JSON file hosted at https://yourdomain.com/.well-known/apple-app-site-association. It specifies which paths on your domain should open the app versus open in Safari. The appIDs field contains your Team ID + Bundle ID.

Paths use wildcards: /profile/* matches any profile URL. Paths can be excluded with a NOT prefix. A well-configured AASA is specific — only deep-link paths that actually exist in your app should be listed.

// https://myapp.com/.well-known/apple-app-site-association
{
  'applinks': {
    'apps': [],
    'details': [
      {
        'appIDs': ['TEAMID1234.com.example.myapp'],
        'components': [
          { '/': '/profile/*' },
          { '/': '/product/*' },
          { '/': '/settings' },
          { '/': '/order/*' },
          { '/': '/404', 'exclude': true }
        ]
      }
    ]
  }
}

Android App Links: assetlinks.json

Android uses Digital Asset Links verified via https://yourdomain.com/.well-known/assetlinks.json. This file lists your app's package name and the SHA256 fingerprint of your signing certificate. Android downloads and caches this file at install time to verify ownership.

The SHA256 fingerprint can be obtained from your keystore using the keytool command. In Expo/EAS Build the fingerprint is shown in the build output. The fingerprint is specific to your signing certificate — debug and release builds have different fingerprints.

// https://myapp.com/.well-known/assetlinks.json
[
  {
    'relation': ['delegate_permission/common.handle_all_urls'],
    'target': {
      'namespace': 'android_app',
      'package_name': 'com.example.myapp',
      'sha256_cert_fingerprints': [
        'AA:BB:CC:DD:EE:FF:00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF:00:11:22:33:44:55:66:77:88:99'
      ]
    }
  }
]

Configuring iOS Entitlements

In addition to the AASA file, your iOS app must declare the Associated Domains entitlement. In Expo managed workflow, add the associatedDomains key under expo.ios in app.json. The format is applinks:yourdomain.com.

After adding this, rebuild the native app with EAS Build. The entitlement gets embedded in the app's signing profile. Without the entitlement, iOS will not attempt to verify the AASA file even if it's correctly hosted.

// app.json
{
  'expo': {
    'ios': {
      'bundleIdentifier': 'com.example.myapp',
      'associatedDomains': [
        'applinks:myapp.com',
        'applinks:www.myapp.com'
      ]
    }
  }
}

Configuring Android Intent Filters

Android requires an intent-filter in AndroidManifest.xml for App Links. In Expo managed workflow, the intentFilters key in app.json under expo.android adds this configuration. The autoVerify: true flag enables the App Links verification process.

The intent-filter declares the scheme as https, the host as your domain, and the path pattern to match. At install time Android downloads the assetlinks.json file to verify ownership.

// app.json
{
  'expo': {
    'android': {
      'package': 'com.example.myapp',
      'intentFilters': [
        {
          'action': 'VIEW',
          'autoVerify': true,
          'data': [
            { 'scheme': 'https', 'host': 'myapp.com' },
            { 'scheme': 'https', 'host': 'www.myapp.com' }
          ],
          'category': ['BROWSABLE', 'DEFAULT']
        }
      ]
    }
  }
}

Hosting Requirements for the Verification Files

Both verification files have strict hosting requirements that cause silent failures if not met:

  • Must be served over HTTPS (not HTTP)
  • Must return 200 status (not 301 redirect)
  • Must have the correct Content-Type: application/json for both
  • Must be accessible without authentication — no login required
  • Must use a valid TLS certificate (not self-signed)

Test with curl to verify: curl -I https://myapp.com/.well-known/apple-app-site-association

# Verify AASA is accessible:
curl -I https://myapp.com/.well-known/apple-app-site-association
# Expect: HTTP/2 200, content-type: application/json

# Verify assetlinks:
curl -I https://myapp.com/.well-known/assetlinks.json
# Expect: HTTP/2 200, content-type: application/json

# Verify content:
curl https://myapp.com/.well-known/assetlinks.json

Adding Universal Links to React Navigation

Add your HTTPS domain to the prefixes array in your React Navigation linking config alongside your custom scheme. This lets the navigation library handle both types of URLs with the same screen map, with no additional routing logic needed.

The screen path patterns are shared — the same path after the prefix maps to the same screen regardless of whether the link came from a custom scheme or an HTTPS universal link.

import * as ExpoLinking from 'expo-linking';

const linking = {
  prefixes: [
    ExpoLinking.createURL('/'),   // Expo Go + production custom scheme
    'https://myapp.com',          // Universal links
    'https://www.myapp.com',
  ],
  config: {
    screens: {
      Home: '',
      Profile: 'profile/:userId',
      Product: 'product/:productId',
    },
  },
};

Debugging Universal Links

Universal link issues are harder to debug than custom scheme issues because verification is done by the OS at install time. Common problems and fixes:

  • iOS: link opens Safari instead of app — AASA file not found, wrong format, or Associated Domains entitlement missing. Re-install the app after fixing.
  • Android: link opens Chrome — assetlinks.json wrong fingerprint or autoVerify not set. Check with the adb verification command.
  • Both: after host changes — OS caches the file; uninstall and reinstall to force re-verification.
# Verify Android App Links:
adb shell pm get-app-link com.example.myapp
# Expected: verified

# Re-verify on device:
adb shell pm verify-app-links com.example.myapp

# iOS: check in Settings > Privacy > Universal Links
# or use Apple's AASA validator:
# https://branch.io/resources/aasa-validator/

Fallback Web Pages

The power of universal links is the automatic fallback. When your app is not installed, tapping https://myapp.com/profile/123 opens your website in the browser. Your website should handle these paths and either show the content directly or show an app download prompt.

Implement smart banners on your web pages (<meta name='apple-itunes-app' content='app-id=...'> on iOS, or Google Play instant app on Android) to prompt users to download the app. This creates a seamless install-then-reopen flow.

<!-- In your web page <head>: -->
<!-- iOS Smart Banner -->
<meta
  name='apple-itunes-app'
  content='app-id=123456789, app-argument=https://myapp.com/profile/123'
/>

<!-- Google Play referrer -->
<a href='https://play.google.com/store/apps/details?id=com.example.myapp&referrer=utm_source%3Dwebsite'>
  Get it on Google Play
</a>

Testing Universal Links End to End

End-to-end testing of universal links requires production or TestFlight/internal testing builds — not Expo Go. Test by sending yourself an email or Slack message with the HTTPS link and tapping it on a real device. The OS routes to your app only if both the entitlement and the server file are correctly configured.

For automated testing, create a checklist: AASA accessible, correct Team ID, correct paths, Associated Domains in entitlement, Android fingerprint matches release keystore, autoVerify in manifest, HTTPS cert valid. Check every item before submission.

// End-to-end test checklist:
// 1. curl AASA: HTTP 200, content-type: application/json
// 2. curl assetlinks.json: HTTP 200, correct fingerprint
// 3. EAS Build production: associatedDomains in entitlement
// 4. Android: adb shell pm get-app-link shows 'verified'
// 5. iOS: open https://myapp.com/profile/test in Notes app
//    → should open app, not Safari
// 6. Android: open URL in any browser
//    → disambiguation dialog or direct open

Quick Check

Test your understanding of React Native Mobile Development concepts from this lesson.

Lesson Recap

In this lesson you learned: universal links use HTTPS URLs with server-side verification files (AASA for iOS, assetlinks.json for Android) to securely route links to your app, iOS requires the Associated Domains entitlement in the app and Android requires an intent-filter with autoVerify, and universal links provide a graceful web fallback when the app is not installed. Next up we add push notifications by registering for push tokens with expo-notifications.

Frequently asked questions

Is the “Universal Links (HTTPS Deep Links) on iOS and Android” lesson free?

Yes — the full text of “Universal Links (HTTPS Deep Links) on iOS and Android” is free to read here on the web, and the React Native Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the React Native Academy course, upgrade to CoddyKit PRO.

What will I learn in “Universal Links (HTTPS Deep Links) on iOS and Android”?

Set up Apple App Site Association and Android App Links files on your web server, configure entitlements and intent filters in the app, and verify end-to-end deep linking. You practise React Native Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start React Native Academy?

No prior experience is required. React Native Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Universal Links (HTTPS Deep Links) on iOS and Android” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this React Native Academy lesson?

Yes. Every React Native Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Configuring Custom URL Schemes
  2. Linking API and URL Parsing
  3. React Navigation Deep Link Configuration
  4. Universal Links (HTTPS Deep Links) on iOS and Android
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