Flutter Deep Linking (with GoRouter v17.x)

Goal

Implement secure, professional Deep Links (HTTPS Domain Association) to successfully route organic URLs, marketing campaigns (Google Ads), and Magic Link auth payloads directly into a Flutter application. Avoid older Custom URL Schemes (myapp://) whenever possible, guaranteeing a seamless fallback to web browsers if the app is currently uninstalled.

Instructions

1. Android App Links Setup

#### `AndroidManifest.xml` Insert the intent-filter explicitly instructing Android to autoVerify the HTTPS domain. This lives directly inside the core <activity> tag (usually .MainActivity):

<intent-filter android:autoVerify="true">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />
    <!-- Replace with the actual requested domain -->
    <data android:scheme="https" android:host="yourdomain.com" />
</intent-filter>

#### Web Hosting (`assetlinks.json`) You must host a JSON payload securely proving ownership at exactly: https://yourdomain.com/.well-known/assetlinks.json

[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "com.yourcompany.yourapp",
    "sha256_cert_fingerprints": [
      "YOUR_SHA256_CERT_FINGERPRINT_1"
    ]
  }
}]

Constraints:

• The file must be served strictly over HTTPS.
• Must return a Content-Type: application/json header natively.

2. iOS Universal Links Setup

#### Xcode Entitlements

1. Open ios/Runner.xcworkspace utilizing Xcode.
2. Select the Runner Target -> "Signing & Capabilities".
3. Add the Associated Domains capability.
4. Add the exact required string entry: applinks:yourdomain.com

#### Web Hosting (`apple-app-site-association`) You must host an AASA (Apple App Site Association) file proving ownership at exactly: https://yourdomain.com/.well-known/apple-app-site-association

{
  "applinks": {
    "apps": [],
    "details": [
      {
        "appID": "TEAM_ID.com.yourcompany.yourapp",
        "paths": ["*"]
      }
    ]
  }
}

Constraints:

• The file MUST NOT possess a .json extension physically.
• Must return a Content-Type: application/json header natively.
• Must not be gzipped by the server (Apple's CDN rejects compresses formats silently).

3. Flutter Integration (GoRouter)

By default, the Flutter Framework natively captures validated Intents/NSUserActivity payloads triggered by the operating systems. If your application uses go_router, it will intercept the path and autonomously navigate if a matching GoRoute exists.

final router = GoRouter(
  routes: [
    // A Deep Link opening "https://yourdomain.com/events/123" maps here natively!
    GoRoute(
      path: '/events/:id',
      builder: (context, state) => EventScreen(id: state.pathParameters['id']!),
    ),
  ],
);

No external third-party plugins (like `uni_links` or `app_links`) are required strictly for navigation if go_router governs the MaterialApp.router.

Constraint: If migrating an older codebase heavily utilizing legacy plugins, verify flutter_deeplinking_enabled is NOT manually disabled natively inside AndroidManifest.xml or Info.plist.

Verification & Testing

CLI Testing

Simulate clicking a Deep Link from totally outside the app environment natively checking if the OS launches the sandbox:

Android (adb):

adb shell am start -a android.intent.action.VIEW \
    -c android.intent.category.BROWSABLE \
    -d "https://yourdomain.com/events/123" com.yourcompany.yourapp

iOS (xcrun):

xcrun simctl openurl booted "https://yourdomain.com/events/123"

DevTools Validator

The absolute best practice for heavily debugging failing configuration domains is exclusively launching the Flutter Deeplinking Validator built directly inside Dart DevTools. It strictly verifies your assetlinks.json and apple-app-site-association cloud deployments, explicitly flagging missing headers or misaligned App IDs easily.