A practical guide with examples (including Crashlytics), best practices and common pitfalls

Understanding runZonedGuarded in Flutter

The runZonedGuarded method in Flutter allows you to capture errors occurring inside asynchronous operations that normal try–catch blocks cannot handle. It creates a safe “zone” for error handling.

🌟 What is runZonedGuarded?

It wraps your app in a protected execution zone so that all unhandled async errors are caught and processed.

🔍 Why do we need it?

• To catch errors thrown inside Futures and Streams.
• To avoid app crashes due to unhandled async exceptions.
• To send crash logs to services like Crashlytics or Sentry.

📌 Example usage

void main() {
  runZonedGuarded(() {
    runApp(MyApp());
  }, (error, stackTrace) {
    print("Caught by runZonedGuarded: $error");
  });
}

🧠 When should you use it?

• In main.dart around runApp().
• When you need global error handling.
• When integrating Crashlytics or Sentry.

🎯 Where is it commonly used?

Mostly inside the app's entry point for initializing frameworks and catching app-wide errors.

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  runZonedGuarded(() async {
    await Firebase.initializeApp();
    runApp(MyApp());
  }, (error, stackTrace) {
    FirebaseCrashlytics.instance.recordError(error, stackTrace);
  });
}

⚙️ How does it work?

It overrides the default async error handler inside a new zone. Any error inside the zone is forwarded to the provided callback.

🏁 Conclusion

runZonedGuarded is essential for capturing asynchronous errors globally and maintaining app stability in production environments.