After App Check is enforced for a backend service, your app's features that
depend on that backend service won't run in an emulator or from a
continuous integration (CI) environment because these environments don't qualify
as valid devices. To run your app in these environments during development and
testing, you need to create a debug build of your app that uses the
App Check *debug provider* instead of a production attestation provider.

> [!WARNING]
> **Warning:** **Keep your debug token and debug build private.** A valid debug token and the debug provider in your debug build allow access to your backend services from unverified devices. Do ***not*** commit your debug token to a public repository, and do ***not*** ship your debug token or debug build in production builds of your app. If a registered token is ever compromised, delete it immediately in the Firebase console.

## Apple platforms

Here's how to use the debug provider while running your app in a simulator
interactively (for example, during local development):

1. Activate App Check with the debug provider right after you've
   initialized your Firebase app:

   ```dart
   import 'package:flutter/material.dart';
   import 'package:firebase_core/firebase_core.dart';

   // Import the firebase_app_check plugin
   import 'package:firebase_app_check/firebase_app_check.dart';

   Future<void> main() async {
     WidgetsFlutterBinding.ensureInitialized();
     await Firebase.initializeApp();
     await FirebaseAppCheck.instance.activate(
       // Set appleProvider to `AppleProvider.debug`
       appleProvider: AppleProvider.debug,
     );
     runApp(App());
   }
   ```
2. Enable debug logging in your Xcode project (v11.0 or newer):

   1. Open **Product \> Scheme \> Edit scheme**.
   2. Select **Run** from the left menu, then select the **Arguments** tab.
   3. In the **Arguments Passed on Launch** section, add `-FIRDebugEnabled`.
3. Obtain your debug token:

   1. Open `ios/Runner.xcworkspace` with Xcode and run your app in the
      simulator or on your test device.

   2. Open the Xcode console and look for the App Check debug token.
      For example:

          <Warning> [AppCheckCore][I-GAC004001] App Check debug token: '123a4567-b89c-12d3-e456-789012345678'.

   3. Copy the token (for example, `123a4567-b89c-12d3-e456-789012345678`).

4. Register your debug token with App Check:

   1. In the Firebase console, go to the **Security** \> **App Check** \>
      [**Apps** tab](https://console.firebase.google.com/project/_/appcheck/apps/?useAutoProject=true).

   2. Find your app, click the three-dot overflow menu
      (), and then select
      **Manage debug tokens**.

   3. Follow the on-screen instructions to register your debug token.

   ![Screenshot of the Manage Debug Tokens menu item in the Firebase console](https://firebase.google.com/static/docs/app-check/manage-debug-tokens.png)

After you register the token with App Check, your backend services will
accept it as valid.

This token allows access to your backend services without a valid device,
so it's crucial that you keep it private. Do ***not*** commit it to a
public repository or ship it in production builds of your app. If a
registered token is ever compromised, delete it immediately using
**Manage debug tokens** in the Firebase console.

## Android

Here's how to use the debug provider while running your app in an emulator
interactively (for example, during local development):

1. Activate App Check with the debug provider right after you've
   initialized your Firebase app:

   ```dart
   import 'package:flutter/material.dart';
   import 'package:firebase_core/firebase_core.dart';

   // Import the firebase_app_check plugin
   import 'package:firebase_app_check/firebase_app_check.dart';

   Future<void> main() async {
     WidgetsFlutterBinding.ensureInitialized();
     await Firebase.initializeApp();
     await FirebaseAppCheck.instance.activate(
       // Set androidProvider to `AndroidProvider.debug`
       androidProvider: AndroidProvider.debug,
     );
     runApp(App());
   }

   ```
2. Obtain your debug token:

   1. Run your app in the emulator or on your test device.

   2. Look for the App Check debug token in your logs. For example:

          D DebugAppCheckProvider: Enter this debug secret into the allow list
          in the Firebase Console for your project: 123a4567-b89c-12d3-e456-789012345678

   3. Copy the token (for example, `123a4567-b89c-12d3-e456-789012345678`).

3. Register your debug token with App Check:

   1. In the Firebase console, go to the **Security** \> **App Check** \>
      [**Apps** tab](https://console.firebase.google.com/project/_/appcheck/apps/?useAutoProject=true).

   2. Find your app, click the three-dot overflow menu
      (), and then select
      **Manage debug tokens**.

   3. Follow the on-screen instructions to register your debug token.

   ![Screenshot of the Manage Debug Tokens menu item in the Firebase console](https://firebase.google.com/static/docs/app-check/manage-debug-tokens.png)

After you register the token with App Check, your backend services will
accept it as valid.

This token allows access to your backend services without a valid device,
so it's crucial that you keep it private. Do ***not*** commit it to a
public repository or ship it in production builds of your app. If a
registered token is ever compromised, delete it immediately using
**Manage debug tokens** in the Firebase console.

## Web

Here's how to use the debug provider while running your app from `localhost`
(for example, during local development):

> [!WARNING]
> **Warning:** Do ***not*** try to enable `localhost` debugging by adding `localhost` to the allowed domains for reCAPTCHA. Doing so would allow anyone to run your app from their local machines!

1. In the file `web/index.html`, enable debug mode by setting
   `self.FIREBASE_APPCHECK_DEBUG_TOKEN` to `true`:

   ```html
   <body>
     <script>
       self.FIREBASE_APPCHECK_DEBUG_TOKEN = true;
     </script>

     ...

   </body>
   ```
2. Run your web app locally and open the browser's developer tools. In the
   debug console, you'll see a debug token. For example:

       AppCheck debug token: "123a4567-b89c-12d3-e456-789012345678".
       You will need to safelist it in the Firebase console for it to work.

   This token is stored locally in your browser and will be used whenever you
   use your app in the same browser on the same machine. If you want to use the
   token in another browser or on another machine, set
   `self.FIREBASE_APPCHECK_DEBUG_TOKEN` to the token string instead of `true`.
3. Register your debug token with App Check:

   1. In the Firebase console, go to the **Security** \> **App Check** \>
      [**Apps** tab](https://console.firebase.google.com/project/_/appcheck/apps/?useAutoProject=true).

   2. Find your app, click the three-dot overflow menu
      (), and then select
      **Manage debug tokens**.

   3. Follow the on-screen instructions to register your debug token.

   ![Screenshot of the Manage Debug Tokens menu item in the Firebase console](https://firebase.google.com/static/docs/app-check/manage-debug-tokens.png)

After you register the token with App Check, your backend services will
accept it as valid.

This token allows access to your backend services without a valid device,
so it's crucial that you keep it private. Do ***not*** commit it to a
public repository or ship it in production builds of your app. If a
registered token is ever compromised, delete it immediately using
**Manage debug tokens** in the Firebase console.