One-Time Purchase Integration - EVM Contract Settlement

This guide walks you through integrating Coinflow checkout to accept one-time credit card purchases with USDC settlement to your whitelisted EVM contract (Base, Polygon, Arbitrum, etc.).

Prerequisites

Quick Reference

Choose Your Implementation

$
  curl -X POST https://api-sandbox.coinflow.cash/api/checkout/link \
>
    -H "x-coinflow-auth-user-id: payer123" \
>
    -H "Authorization: YOUR_API_KEY" \
>
    -H "Content-Type: application/json" \
>
    -d '{
>
  "email": "payer123@gmail.com",
>
  "subtotal": {
>
    "cents": 500,
>
    "currency": "USD"
>
  },
>
  "blockchain": "polygon",
>
  "transactionData": {
>
    "transaction": {
>
      "data": "0x...",
>
      "to": "0x..."
>
    }
>
  }
>
}'

1
<iframe
2
  allow="payment"
3
  src="CHECKOUT_LINK_FROM_STEP_1"
4
  style="width: 100%; height: 600px; border: none;"
5
/>

1
window.addEventListener('message', (event) => {
2
  if (typeof event.data === 'string') {
3
    const data = JSON.parse(event.data);
4
    if (data.data === 'success') {
5
      console.log('Payment ID:', data.info.paymentId);
6
      // Handle successful payment
7
    }
8
  }
9
});

3DS Authentication

After implementing basic checkout, add 3DS for enhanced security. Contact Coinflow to enable 3DS on your account.

Chargeback Protection

Improve approval rates and reduce fraud by sharing payer events with Coinflow.

Send user events

Track key user actions throughout their journey on your app.

$
curl --request POST \
>
     --url https://api-sandbox.coinflow.cash/api/events \
>
     --header 'Authorization: YOUR_API_KEY' \
>
     --header 'content-type: application/json' \
>
     --data '{
>
       "eventType": "SignUp",
>
       "customerId": "user-123-abc",
>
       "country": "US",
>
       "username": "johndoe",
>
       "email": "john@example.com",
>
       "firstName": "John",
>
       "lastName": "Doe"
>
     }'

Required headers for checkout

When processing payments, include these headers for chargeback protection:

Next Steps