API Reference

Create Payment Link

Create a hosted crypto checkout link for your customers. Supports multiple networks and tokens, success/cancel redirects, and webhooks.

Quickstart Reference

Endpoint

POST

/api/create-payment-link

Auth: Authorization: Bearer <api_key> or X-API-Key: <api_key>

Quickstart

1. Get your API key from the dashboard (supports live and test).
2. Make a request to POST /api/create-payment-link with your payload.
3. Redirect your customer to the returned payment_link URL.

Provide a global payout configuration or include payout_address for each allowed token.

curl -X POST https://fync.xyz/api/create-payment-link \
 -H "Content-Type: application/json" \
 -H "Authorization: Bearer YOUR_API_KEY" \
 -d '{
  "amount": "20.00",
  "currency": "USD",
  "order_id": "ORD-983245",
  "description": "Payment for Order #983245",
  "allowed_payment_tokens": [
    {"name":"BitCoin","symbol":"btc","network":"bitcoin","payout_address":"CPj7TP5..."},
    {"name":"ethereum","symbol":"ETH","network":"ethereum","payout_address":"CPj7TP5..."},
    {"name":"Solana","symbol":"SOL","network":"solana","payout_address":"CPj7TP5..."},
    {"name":"Matic","symbol":"POL","network":"polygon","payout_address":"CPj7TP5..."},
    {"name":"trx","symbol":"trx","network":"tron","payout_address":"CPj7TP5..."},
    {"name":"USDC","symbol":"usdc","network":"solana","payout_address":"So1..."},
    {"name":"USDT","symbol":"usdt","network":"ethereum","payout_address":"0x..."}
  ],
  "callback_url": "https://merchant.com/api/payment/callback",
  "success_url": "https://merchant.com/payment/success",
  "cancel_url": "https://merchant.com/payment/cancel",
  "expire_minutes": 60,
  "customer": {"name":"John Doe","email":"john@example.com"},
  "metadata": {"important":"P12345"}
}'

import requests

url = "https://fync.xyz/api/create-payment-link"
headers = {"Content-Type": "application/json", "X-API-Key": "YOUR_API_KEY"}
payload = {
  "amount": "20.00",
  "currency": "USD",
  "order_id": "ORD-983245",
  "description": "Payment for Order #983245",
  "allowed_payment_tokens": [
    {"name":"BitCoin","symbol":"btc","network":"bitcoin","payout_address":"CPj7TP5..."},
    {"name":"ethereum","symbol":"ETH","network":"ethereum","payout_address":"CPj7TP5..."}
  ],
  "callback_url": "https://merchant.com/api/payment/callback",
  "success_url": "https://merchant.com/payment/success",
  "cancel_url": "https://merchant.com/payment/cancel",
  "expire_minutes": 60,
  "customer": {"name":"John Doe","email":"john@example.com"},
  "metadata": {"important":"P12345"}
}
resp = requests.post(url, json=payload, headers=headers, timeout=30)
print(resp.status_code, resp.json())

const res = await fetch("https://fync.xyz/api/create-payment-link", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "Authorization": "Bearer YOUR_API_KEY"
  },
  body: JSON.stringify({
    amount: "20.00",
    currency: "USD",
    order_id: "ORD-983245",
    description: "Payment for Order #983245",
    allowed_payment_tokens: [
      { name: "BitCoin", symbol: "btc", network: "bitcoin", payout_address: "CPj7TP5..." },
      { name: "ethereum", symbol: "ETH", network: "ethereum", payout_address: "CPj7TP5..." }
    ],
    callback_url: "https://merchant.com/api/payment/callback",
    success_url: "https://merchant.com/payment/success",
    cancel_url: "https://merchant.com/payment/cancel",
    expire_minutes: 60,
    customer: { name: "John Doe", email: "john@example.com" },
    metadata: { important: "P12345" }
  })
});
const data = await res.json();
console.log(data);

Request

Method: POST

Path: /api/create-payment-link

Auth: Authorization: Bearer <key> or X-API-Key: <key> (request body fallback api_key supported)

Body (JSON)

amount (string, required)
currency (string, required; ISO, e.g., USD)
order_id (string, optional)
description (string, optional)
allowed_payment_tokens (array[object], optional but payout address is required via this array or merchant defaults)
- name (string)
- symbol (string; e.g., btc, eth, usdc)
- network (string; e.g., bitcoin, ethereum, solana, polygon, tron)
- payout_address (string; required if merchant global payout not set)
callback_url (string, optional)
success_url (string, optional)
cancel_url (string, optional)
expire_minutes (integer, optional; minutes until expiry)
customer (object, optional)
metadata (object, optional)

Response

201 Created on success

{
  "success": true,
  "payment_link": "https://your-domain.com/pay/txn_...",
  "transaction_id": "txn_..."
}

Note: The URL will be a publicly accessible link served by GET /pay/<transaction_id>.

Errors

400 Bad Request

{"success": false, "error": "Missing required fields: amount, currency"}

401 Unauthorized

{"success": false, "error": "Missing API key"}

403 Forbidden

{"success": false, "error": "Invalid API key"}

500 Internal Server Error

{"success": false, "error": "<details>"}

Webhook (optional)

If you pass callback_url, Fync will POST settlement events to your endpoint. Example:

{
  "type": "payment_settled",
  "transaction_id": "txn_...",
  "stage": "settled",
  "status": "success",
  "amount": 12.345678,
  "asset": {"token": "usdc", "network": "solana"}
}

Secure your webhook endpoint with your own auth or allow-listing. Signature delivery may be added in future versions.