Stripe

Think of the card reader at a shop that talks to the bank and prints a receipt. Stripe is an online service that processes payments and manages recurring billing for your app.

It keeps sensitive card details away from your app, reduces compliance burden, and provides tools for refunds, invoices, and trials. Mobile apps can use Stripe or the app stores' in-app purchases for payments.

You use Stripe SDKs on the device and secret keys on the server. Set up webhooks, messages Stripe sends to your server when something happens like a payment succeeds, to keep your database in sync.