Revenuecat

RevenueCat eliminates the hardest part of mobile subscriptions: reliable purchase receipt validation across App Store, Google Play, and Amazon IAP. It normalizes all three stores into a single subscriber/entitlement model, handles subscription renewals and grace periods, and emits normalized webhook events for every lifecycle change. For backend agents: the REST API enables querying current subscriber state (active entitlements, subscription status, expiry date), granting promotional entitlements, and subscribing to lifecycle webhooks for downstream CRM or analytics updates. Free up to $2.5k MRR. Confidence is docs-derived.

REST API at api.revenuecat.com/v1. Resources: subscribers, entitlements, products, offerings. GET /subscribers/{app_user_id} returns full subscriber state: active subscriptions, entitlement access, purchase history, non-subscription purchases. POST /subscribers/{app_user_id}/entitlements/{entitlement_id}/promotional_entitlements grants a promotional entitlement. DELETE /subscribers/{app_user_id} deletes subscriber data (GDPR). POST /receipts validates a receipt and creates/updates subscriber. Webhooks for all subscription lifecycle events (INITIAL_PURCHASE, RENEWAL, CANCELLATION, BILLING_ISSUE, EXPIRATION, PRODUCT_CHANGE, etc.). Response: JSON.

Secret API key auth: Authorization: Bearer {secret_api_key} header for server-side calls. Public API keys for client SDK (not REST API). Keys from RevenueCat Dashboard → Project Settings → API Keys. HTTPS enforced. Webhook signature: shared secret for HMAC validation. No OAuth2. Revenue-generating keys should be secrets — never expose in client-side code.

Standard HTTP status codes with JSON error bodies. 404 for unknown app_user_id (subscriber not yet created), 401 for invalid API key. Webhook delivery: RevenueCat retries with exponential backoff (up to 5 days). Event ordering not guaranteed — use timestamps for sequencing. Subscriber state is eventually consistent: allow seconds for purchase → API reflect lag. Status at status.revenuecat.com. Rate limiting: 150 requests/second per project.

revenuecat.com/docs is excellent — comprehensive SDK integration (Swift, Kotlin, Flutter, React Native, Unity), REST API docs, webhook payload reference, and platform migration guides. Getting started: create project, connect App Store/Google Play credentials, integrate SDK in 20–30 minutes. Webhook event reference documents every event type with full payload examples. Community via RevenueCat Slack (10k+ members) and GitHub.