RevenueCat Integration: From Zero to Subscriptions in Hours

I’ve shipped 3 apps with RevenueCat. Each time, the integration gets faster.

Muse Otter took 4 hours from zero to working subscriptions on iOS and Android.

Here’s how.

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Why RevenueCat

Before RevenueCat, I spent weeks on StoreKit 1, then StoreKit 2, then Google Billing Library. Different APIs. Different edge cases. Different headaches.

RevenueCat gives you:

What	Why It Matters
One SDK	Same code for iOS, Android, and Web
Receipt validation	No server-side code needed
Subscription state	Handles renewals, cancellations, grace periods
Webhooks	Real-time sync to your backend
Analytics	Revenue, churn, LTV out of the box

The math: 2 weeks of native implementation vs 4 hours with RevenueCat. Easy choice.

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The Architecture

Here’s how Muse Otter handles subscriptions:

┌─────────────┐   Purchase    ┌─────────────┐
│ Flutter App │──────────────►│  RevenueCat │
│             │               │             │
│ purchases_  │   Entitle-    │  (handles   │
│ flutter     │◄──────────────│   stores)   │
└──────┬──────┘    ments      └──────┬──────┘
       │                             │
       │ Read from                   │ Webhook
       │ Firestore                   │ events
       ▼                             ▼
┌─────────────────────────────────────────────┐
│                 FIRESTORE                    │
│                                              │
│  users/{userId}                              │
│  └── subscriptionStatus: free | pro | lifetime │
│                                              │
│         ══ Single source of truth ══         │
└─────────────────────────────────────────────┘

Key insight: The app reads subscription status from Firestore, not RevenueCat. The webhook keeps Firestore in sync.

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Step 1: RevenueCat Setup (30 min)

Dashboard Configuration

1. Create app in RevenueCat dashboard
2. Add products:
   • monthly_10 — $9.99/month
   • yearly_80 — $79.99/year
3. Create entitlement: Muse Otter Pro
4. Create offering: default
5. Attach products to offering

App Store / Play Store

Set up products in App Store Connect and Google Play Console. Match the IDs exactly.

---

Step 2: Flutter Integration (1 hour)

Install SDK

# pubspec.yaml
dependencies:
  purchases_flutter: ^9.10.0

Initialize

Future<void> initRevenueCat() async {
  await Purchases.setLogLevel(LogLevel.debug);

  PurchasesConfiguration config;
  if (Platform.isIOS) {
    config = PurchasesConfiguration('appl_your_api_key');
  } else {
    config = PurchasesConfiguration('goog_your_api_key');
  }

  await Purchases.configure(config);
}

Login User

Future<void> loginUser(String firebaseUid) async {
  await Purchases.logIn(firebaseUid);
}

Important: Use your Firebase UID as the RevenueCat user ID. This links everything together.

Fetch Offerings

Future<Offerings?> getOfferings() async {
  try {
    return await Purchases.getOfferings();
  } catch (e) {
    logger.e('Failed to fetch offerings: $e');
    return null;
  }
}

Make Purchase

Future<bool> purchasePackage(Package package) async {
  try {
    await Purchases.purchasePackage(package);
    return true;
  } on PurchasesErrorCode catch (e) {
    if (e != PurchasesErrorCode.purchaseCancelledError) {
      logger.e('Purchase failed: $e');
    }
    return false;
  }
}

---

Step 3: Firebase Webhook (2 hours)

This is where Firestore becomes the source of truth.

Cloud Function

import { onRequest } from 'firebase-functions/v2/https';
import { getFirestore } from 'firebase-admin/firestore';

export const revenueCatWebhook = onRequest(
  { region: 'europe-west1', secrets: ['REVENUECAT_WEBHOOK_SECRET'] },
  async (req, res) => {
    // Verify authorization
    const authHeader = req.headers.authorization;
    if (authHeader !== process.env.REVENUECAT_WEBHOOK_SECRET) {
      res.status(401).send('Unauthorized');
      return;
    }

    const event = req.body;
    const userId = event.app_user_id;
    const eventType = event.type;

    // Map event to subscription status
    let newStatus: string | null = null;

    switch (eventType) {
      case 'INITIAL_PURCHASE':
      case 'RENEWAL':
      case 'UNCANCELLATION':
        newStatus = 'pro';
        break;
      case 'EXPIRATION':
        newStatus = 'free';
        break;
      // CANCELLATION: no change (user keeps access until expiry)
      // BILLING_ISSUE: no change (grace period)
    }

    if (newStatus) {
      const userRef = getFirestore().doc(`users/${userId}`);
      const userDoc = await userRef.get();

      // Don't override protected statuses
      const currentStatus = userDoc.data()?.subscriptionStatus;
      if (currentStatus === 'donation' || currentStatus === 'lifetime') {
        res.status(200).send('Protected status - no change');
        return;
      }

      await userRef.update({
        subscriptionStatus: newStatus,
        subscriptionUpdatedAt: new Date(),
      });
    }

    res.status(200).send('OK');
  }
);

Configure Webhook in RevenueCat

1. Go to Project Settings → Integrations → Webhooks
2. Add your Cloud Function URL
3. Set authorization header
4. Select events: INITIAL_PURCHASE, RENEWAL, EXPIRATION, CANCELLATION, UNCANCELLATION

---

Step 4: App Reads from Firestore (30 min)

Riverpod Provider

@riverpod
Stream<bool> isPro(IsProRef ref) {
  final user = ref.watch(currentUserProvider);
  if (user == null) return Stream.value(false);

  return FirebaseFirestore.instance
    .doc('users/${user.uid}')
    .snapshots()
    .map((doc) {
      final status = doc.data()?['subscriptionStatus'] ?? 'free';
      return status != 'free';
    });
}

Gate Pro Features

class ProGate extends ConsumerWidget {
  final Widget child;
  final Widget fallback;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final isPro = ref.watch(isProProvider);

    return isPro.when(
      data: (pro) => pro ? child : fallback,
      loading: () => fallback,
      error: (_, __) => fallback,
    );
  }
}

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The Patterns That Work

1. Firestore as Source of Truth

Don’t check RevenueCat SDK every time. Write status to Firestore once, read from there always.

Why: Faster, works offline, one source of truth.

2. Protected Statuses

Some users get free access (testers, contest judges, supporters). Protect them:

if (currentStatus === 'donation' || currentStatus === 'lifetime') {
  // Don't change anything
  return;
}

3. Login with Firebase UID

Always use the same user ID in RevenueCat and Firebase. Makes webhooks trivial.

4. Soft Paywall First

Don’t block immediately. Show value, then ask for money:

Free: 20 messages/day
Pro: Unlimited

Users hit the limit organically. Then the paywall feels fair.

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Results

Muse Otter subscription system:

• 4 hours to integrate
• 100% event coverage via webhooks
• Works offline (reads from Firestore cache)
• Protected statuses for manual grants
• A/B testable via Firebase Remote Config

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Try It

RevenueCat’s free tier handles up to $2.5k/month. That’s enough to validate your product.

Don’t build subscription infrastructure. Just ship.

The best payment system is the one you don’t have to maintain.