Online payments can turn a useful web app into a business, but payment handling must be designed carefully. Use a reputable payment processor and follow its current documentation rather than collecting card details yourself.
Define what the customer is buying
Decide whether the app sells a one-time purchase, subscription, or service. Make price, billing interval, renewal terms, refund policy, and cancellation path clear before checkout.
Keep privileged credentials server-side
Private payment keys must never appear in browser code or public repositories. Create checkout sessions through a trusted backend and use the processor’s test mode while building.
Verify payment status
Do not treat a success page or browser redirect as proof of payment. Confirm transactions through a trusted server-side response or signed webhook, and handle duplicate events safely.
Test failure paths
Test successful payments, declines, abandoned checkout, delayed confirmation, duplicate notifications, cancellations, and refunds using test tools. Confirm order status remains consistent.
Payment launch checklist
- Prices and terms are visible before checkout.
- Private keys remain server-side.
- Payment confirmation is verified securely.
- Duplicate events are handled safely.
- Failed, cancelled, and refunded payments are tested.
- Customers receive clear confirmation.
Payment features deserve extra testing because mistakes affect both trust and money. Start in test mode and verify every important outcome.