Firebase Analytics

---
name: firebase-analytics
description: "Use when logging analytics events, setting user properties, configuring default event parameters, building funnels, or adding screen-view tracking."
license: MIT
---

# Firebase Analytics Skill

This skill defines how to correctly implement Firebase Analytics in Flutter applications, covering setup, event logging, user properties, and data collection best practices.

## When to Use

Use this skill when:

* Setting up and configuring Firebase Analytics in a Flutter project.
* Logging predefined or custom analytics events.
* Setting user properties or default event parameters.
* Implementing screen view tracking with GoRouter or Navigator observers.
* Building conversion funnels or tracking user flows.

---

## 1. Setup and Configuration

```
flutter pub add firebase_analytics
flutter run
```

```dart
import 'package:firebase_analytics/firebase_analytics.dart';

// After Firebase.initializeApp():
FirebaseAnalytics analytics = FirebaseAnalytics.instance;
```

- Initialize Firebase before using any Firebase Analytics features.
- Analytics **automatically logs** some events and user properties — no additional code needed for those.
- On iOS, if your app does not use the IDFA (Advertising Identifier), use the IDFA-free Analytics dependency (`FirebaseAnalyticsCore` under Swift Package Manager, or `FirebaseAnalytics/Core` under CocoaPods) instead of the default `FirebaseAnalytics` dependency to avoid App Store review questions about advertising identifiers:
  - **Swift Package Manager:** set `FIREBASE_ANALYTICS_WITHOUT_ADID=true` when building (`FIREBASE_ANALYTICS_WITHOUT_ADID=true flutter build ios`).

### Add Navigator Observer for Automatic Screen Tracking

```dart
MaterialApp(
  navigatorObservers: [
    FirebaseAnalyticsObserver(analytics: FirebaseAnalytics.instance),
  ],
);
```

For GoRouter, log screen views manually on route changes:

```dart
GoRouter(
  observers: [FirebaseAnalyticsObserver(analytics: FirebaseAnalytics.instance)],
);
```

### Verification Checklist

1. Confirm `Firebase.initializeApp()` completes before accessing `FirebaseAnalytics.instance`.
2. Run the app and check the Firebase DebugView console for incoming events.
3. Confirm automatic events (`first_open`, `session_start`) appear without extra code.

---

## 2. Event Logging

Use **predefined event methods** when possible for maximum detail in reports and access to future Google Analytics features:

```dart
await FirebaseAnalytics.instance.logSelectContent(
  contentType: "image",
  itemId: itemId,
);
```

Use the general `logEvent()` method for both predefined and custom events:

```dart
await FirebaseAnalytics.instance.logEvent(
  name: "select_content",
  parameters: {
    "content_type": "image",
    "item_id": itemId,
  },
);
```

### Custom Event Example — E-commerce Add-to-Cart

```dart
Future<void> logAddToCart(String productId, String productName, double price) async {
  await FirebaseAnalytics.instance.logEvent(
    name: 'add_to_cart',
    parameters: {
      'product_id': productId,
      'product_name': productName,
      'price': price,
      'currency': 'USD',
    },
  );
}
```

- Event names are **case-sensitive** — names differing only in case create two distinct events.
- Up to **500 different event types** with no limit on total event volume.
- Event names must start with an alphabetic character, contain only alphanumeric characters and underscores, and be no longer than **40 characters**.

---

## 3. Parameters and Properties

- Parameter names: up to **40 characters**, must start with an alphabetic character, contain only alphanumeric characters and underscores.
- String parameter values: up to **100 characters**.
- The prefixes `firebase_`, `google_`, and `ga_` are **reserved** — do not use them for parameter names.
- Up to **25 custom parameters** per event.
- Register custom parameters in the Analytics console to use them as dimensions or metrics in reports.

Set default parameters for all future events (not supported on web):

```dart
await FirebaseAnalytics.instance.setDefaultEventParameters({
  'app_version': '1.2.3',
  'environment': 'production',
});
```

Clear a default parameter by setting it to `null`.

---

## 4. User Properties

```dart
await FirebaseAnalytics.instance.setUserProperty(
  name: 'favorite_food',
  value: favoriteFood,
);
```

Set the user ID to correlate events across devices:

```dart
await FirebaseAnalytics.instance.setUserId(id: 'user_12345');
```

- Create custom definitions for user properties in the Analytics console before using them.
- Up to **25 custom user properties** per project.
- Use user properties for audience segmentation, report filtering, or A/B test targeting.

---

## 5. Best Practices

- **Request necessary permissions** before collecting user data, especially on platforms with strict privacy controls.
- **Never log** sensitive or personally identifiable information in events or user properties.
- Use **consistent naming conventions** (snake_case) for custom events and parameters.
- Group related events to track user flows and conversion funnels.
- Use **DebugView** in the Firebase console during development — enable it on a physical device with:
  - **Android:** `adb shell setprop debug.firebase.analytics.app <package_name>`
  - **iOS:** Add `-FIRDebugEnabled` to scheme arguments in Xcode.
- **Test** analytics implementation before deploying to production by confirming events appear in DebugView.

---

## References

- [FlutterFire GitHub Repository](https://github.com/firebase/flutterfire)