Take payments in your app

What you need first

Two of these are decisions, one of them is paperwork you do outside mypage.

• What you are selling and at what price, in one currency.
• A merchant account with a payment provider, in your business name.
• What happens after payment — a confirmation page, an email, a booking marked as paid.

01 · Ask for the order flow first

Before money, build the order: a product, a price, a basket, a confirmation. Get that working and clicking through properly. Payment is the last step, not the first.

02 · Understand where the price is decided

The amount is recalculated on the server from your own product records and compared against what the browser sent. A price changed in the browser is rejected. This is not optional and not something you should ask to be removed.

03 · Keep it to one currency

An order is settled in a single currency. Korean apps are written with won amounts by default — one of our test runs priced classes at 35,000원, 320,000원 and 450,000원 without being told to.

04 · Connect your provider keys

Paste your own keys into the project secrets screen. Until real keys are in, the app marks the attempt as a rehearsal and shows you exactly what it would have sent. It does not pretend a payment succeeded.

05 · Test the double-click

Press the pay button twice on purpose. The order should be counted once. Each attempt carries a key that makes a repeat land on the same order rather than a second one. Up to 1,000 payment calls a day per project.

If you get stuck

Which providers can I use? Stripe, PortOne and Toss are wired, and their callbacks are checked with a signature so a forged “payment complete” message is refused. What you cannot skip is the merchant agreement.

Can I take money without a business registration? No. Payment providers in Korea require a registered business. This is a rule of theirs, not ours.

The footer asks for a registration number. Korean commerce pages need it by law, so the generated footer has a place for it: business name, representative, registration number, mail-order number, address, phone and email. Fill it in before you open.