In-App Purchases

Implement in-app purchases and subscriptions across iOS, Android, and Flutter with RevenueCat, paywalls, receipt validation, and subscription analytics.

When to Use

User needs to implement in-app purchases, subscriptions, paywalls, or monetization flows. Agent handles native APIs (StoreKit 2, Google Play Billing), cross-platform SDKs (RevenueCat, Adapty, Qonversion), paywall design, server verification, and subscription analytics.

Quick Reference

Topic	File
iOS StoreKit 2	storekit.md
Android Billing	google-play.md
Flutter packages	flutter.md
RevenueCat SDK	revenuecat.md
Platform comparison	platforms.md
Server verification	server.md
Paywall design	paywalls.md
Subscription metrics	analytics.md
Testing & sandbox	testing.md

Core Rules

1. Choose Your Architecture

Approach	When to Use	Tradeoff
Native only	Single platform, full control	More code, no cross-platform sync
RevenueCat/Adapty	Cross-platform, fast launch	1-2% fee, dependency
Hybrid	Native + own backend	Full control, more work

2. Platform SDKs (Managed)

Platform	Pricing	Best For
RevenueCat	Free <$2.5k MTR, then 1%	Most apps, best docs
Adapty	Free <$10k MTR, then 0.6%	Cost-conscious, A/B paywalls
Qonversion	Free <$10k MTR, then 3%	Simple setup
Superwall	Paywall-focused	Paywall A/B only
Glassfy	Free <$10k, then 0.5%	Budget option

3. Product Types

Type	iOS	Android	Use Case
Consumable	✅	✅	Credits, coins, lives
Non-consumable	✅	✅	Unlock feature forever
Auto-renewable	✅	✅	Subscriptions
Non-renewing	✅	❌	Season pass, time-limited

4. Server Verification is Non-Negotiable

Never trust client-side validation alone:

• iOS: App Store Server API with JWS verification
• Android: Google Play Developer API
• RevenueCat: Webhooks + REST API

5. Handle All Transaction States

State	Action
Purchased	Verify → grant → finish
Pending	Wait, show pending UI
Failed	Show error, don't grant
Deferred	Wait for parental approval
Refunded	Revoke immediately
Grace period	Limited access, prompt payment
Billing retry	Maintain access during retry

6. Subscription Lifecycle Events

Must handle all of these (native or via webhooks):

• INITIAL_PURCHASE → grant access
• RENEWAL → extend access
• CANCELLATION → mark will-expire
• EXPIRATION → revoke access
• BILLING_ISSUE → prompt to update payment
• GRACE_PERIOD → limited access window
• PRICE_INCREASE → consent required (iOS)
• REFUND → revoke + flag user
• UPGRADE/DOWNGRADE → prorate

7. Restore Purchases Always

Required by App Store guidelines:

• Prominent restore button
• Works for logged-out users
• Handles family sharing (iOS)
• Cross-device sync

8. Paywall Best Practices

See paywalls.md for detailed patterns:

• Show value before price
• Anchor pricing (3 options, highlight middle)
• Free trial prominent
• Social proof if available
• A/B test everything

9. Testing Strategy

Environment	iOS	Android
Dev/Debug	StoreKit Config file	License testers
Sandbox	Sandbox accounts	Internal testing
Production	Real accounts	Production

Sandbox subscription times:

• 1 week → 3 minutes
• 1 month → 5 minutes
• 1 year → 1 hour

10. App Store Guidelines

• No external payment links (anti-steering)
• Must use IAP for digital goods
• Physical goods/services can use Stripe
• Reader apps have exceptions
• 15-30% commission applies

Common Traps

• Testing with real money → use sandbox/test accounts
• Not finishing transactions → auto-refund (Android 3 days)
• Hardcoding prices → always fetch from store (regional pricing)
• Missing transaction observer → lose purchases made outside app
• No server verification → trivially bypassable
• Ignoring grace period → users churn when they could recover
• Poor paywall UX → kills conversion regardless of price
• Not tracking metrics → can't optimize what you don't measure
• Forgetting restore button → App Store rejection
• Not handling family sharing → confused users