Payment Links & QR Codes

Payment links let you create reusable or one-time payment pages without writing any checkout UI. QR codes are generated from payment links and can be printed, embedded in emails, or shown on POS screens.

---

Create a payment link

POST /api/v1/links

curl -X POST https://4pay.online/api/v1/links \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "link": {
      "amount": {
        "default": 1000
      },
      "amount_type": "static",
      "notify_url": "https://yoursite.com/webhooks/payment",
      "description": "Payment for service"
    }
  }'

Parameters

Field	Type	Description
amount.default	integer	Default amount in smallest currency unit
amount_type	string	static (fixed amount) or dynamic (payer enters amount)
notify_url	string	Webhook URL for payment notifications
description	string	Description shown on the payment page
currency	string	ISO 4217 currency code (default: terminal currency)
expires_at	ISO 8601	Optional expiry datetime

Response

{
  "id": "abc12345-...",
  "url": "https://4pay.online/pay/link/abc12345-...",
  "qr_url": "https://4pay.online/pay/link/abc12345-.../qr",
  "amount": { "default": 1000 },
  "amount_type": "static",
  "created_at": "2026-03-01T10:00:00Z"
}

Share the url directly or display the qr_url image as a QR code.

---

Get a payment link

GET /api/v1/links/:id

curl https://4pay.online/api/v1/links/abc12345-... \
  -H "x-api-key: YOUR_API_KEY"

---

List payment links

GET /api/v1/links

curl https://4pay.online/api/v1/links \
  -H "x-api-key: YOUR_API_KEY"

---

Update a payment link

PUT /api/v1/links/:id

curl -X PUT https://4pay.online/api/v1/links/abc12345-... \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "link": {
      "amount": { "default": 2000 },
      "description": "Updated description"
    }
  }'

---

Delete a payment link

DELETE /api/v1/links/:id

curl -X DELETE https://4pay.online/api/v1/links/abc12345-... \
  -H "x-api-key: YOUR_API_KEY"

---

Webhook for link payments

When someone pays via a link, you receive a webhook with type: "link":

{
  "type": "link",
  "link": "abc12345-...",
  "txid": "generated-txid",
  "id": "550e8400-...",
  "status": "charged",
  "amount": 1000,
  "amount_dest": 950,
  "amount_with_fee": 1050,
  "error_description": ""
}

---

QR Code Products

For retail or POS use cases, you can create products with QR codes that trigger a fixed-price payment flow:

POST /api/v1/products

curl -X POST https://4pay.online/api/v1/products \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "product": {
      "name": "Coffee",
      "amount": 350,
      "currency": "USD",
      "notify_url": "https://yourpos.com/webhooks/payment"
    }
  }'

Each product generates a dedicated QR code that can be printed and used indefinitely.