Android App Links Fix: Remove URL Header in Google Play Builds

A common frustration for Android developers arises when their app behaves differently in debug mode versus a Google Play Store release. HeimdalApps recently highlighted a classic example in the GitHub Community: an app running perfectly without a URL header when connected via cable in Android Studio, but mysteriously displaying a persistent URL header in a closed test version on Google Play. This scenario is a frequent point of friction in developer activity, often stemming from a subtle but critical configuration difference.

Developer comparing an Android app with and without a URL header on two smartphones.

The Persistent URL Header: Debug vs. Play Store Builds

The core of HeimdalApps' problem, and many like it, lies in how Android App Links (also known as Deep Links) are verified. When an Android app is configured to handle specific URLs directly, it relies on a digital asset link file (assetlinks.json) hosted on the associated domain. This file contains SHA256 fingerprints of the app's signing certificates, allowing Android to verify that the app is indeed authorized to open those URLs seamlessly, bypassing the browser header.

The critical distinction is the signing key. When you run an app directly from Android Studio, it's typically signed with a "debug keystore." However, when you upload an app to Google Play, even for closed testing, Google Play App Signing often re-signs your app with a different, Google-managed signing key. If your assetlinks.json doesn't include the fingerprint of *this* specific Google Play signing key, the App Links verification fails, and Android defaults to opening the URL in a WebView or Custom Tab, complete with the unwanted URL header.

Magnifying glass examining an assetlinks.json file with SHA256 fingerprints, set against a Google Play Console background.

Key Solutions for Seamless Android App Links

Community experts quickly pointed HeimdalApps toward the solution, emphasizing that this isn't usually an assetlinks.json problem per se, but rather a "signing + intent-filter mismatch" between debug and release environments. Here’s a breakdown of the necessary steps to ensure your App Links work flawlessly in Google Play builds, streamlining your developer activity:

1. Obtain the Correct App Signing Key from Google Play Console

Navigate to your app in the Google Play Console.
Go to Setup > App Integrity.
Locate and copy the "App signing key certificate" (SHA256 fingerprint). It's crucial not to confuse this with the "Upload key certificate." Double-check every character for accuracy.

2. Update Your `assetlinks.json` File

Your assetlinks.json file must include the SHA256 fingerprint of the Google Play App Signing key. While you might include your debug and upload keys for internal testing or sideloading, the Play signing key is paramount for Play Store versions. An updated structure might look like this:

[
  {
    "relation": [
      "delegate_permission/common.handle_all_urls",
      "delegate_permission/common.use_as_origin"
    ],
    "target": {
      "namespace": "android_app",
      "package_name": "app.base.championsmanager",
      "sha256_cert_fingerprints": [
        "GOOGLE_PLAY_APP_SIGNING_KEY_SHA256",
        "YOUR_UPLOAD_KEY_SHA256_IF_NEEDED",
        "YOUR_DEBUG_KEY_SHA256_IF_NEEDED"
      ]
    }
  }
]

Replace the placeholder values with your actual fingerprints. For production, you might only need the Google Play signing key.

3. Verify Your Android Manifest Intent Filter

Ensure your in AndroidManifest.xml includes android:autoVerify="true" and that the scheme, host, and path prefixes precisely match the URLs you intend to handle.

4. Confirm `assetlinks.json` Accessibility

The assetlinks.json file must be publicly accessible at https://yourdomain.com/.well-known/assetlinks.json, served with the correct Content-Type: application/json header, and without any redirects. Google's Asset Links Tool can help verify this.

5. Reinstall the App on Test Devices

App Links verification results are cached on Android devices. After updating your assetlinks.json and redeploying, it's essential to uninstall and then reinstall the app on your test devices to force a re-verification.

By meticulously addressing these points, developers can overcome the common hurdle of the persistent URL header, ensuring a seamless user experience and validating their efforts in effective developer activity and app deployment.

Mastering Android App Links: Eliminating the URL Header in Google Play Builds