RevenueCat

RevenueCat solves a completely different monetization problem. It does not serve advertisements. Instead, it solves the excruciatingly difficult engineering challenge of implementing and managing In-App Subscriptions (like a $5/month premium tier) across the Apple App Store, Google Play Store, and Stripe on the web. Apple and Google's native subscription APIs are notoriously complex, prone to breaking, and difficult to test. A developer trying to build a fitness app could waste months writing server code just to check if a user successfully renewed their monthly subscription. RevenueCat provides a single, unified API. The developer implements a few lines of code, and RevenueCat handles the entire transaction, standardizing the receipts across all platforms. More importantly, it provides a "Source of Truth" for subscription data. It gives non-technical product managers a clean dashboard showing Monthly Recurring Revenue (MRR), churn rates, and lifetime value. It can automatically trigger webhooks, pinging a Slack channel when a user subscribes, or sending a command to an email marketing tool to send a "please come back" email the exact second a user's subscription expires.