Introduction

OpenCheckout is an open-source, self-hosted checkout system for accepting payments on the web. It provides a hosted checkout page and a Stripe-compatible API that you deploy on your own infrastructure. Your customers pay using their Open Payments wallet address — a URL-based identifier for their bank account, digital wallet, or mobile money account.

Under the hood, OpenCheckout orchestrates the full Open Payments protocol flow:

1. Creates an incoming payment on your wallet to receive funds
2. Requests a quote from the customer’s account provider to confirm the payment cost
3. Facilitates an interactive grant where the customer approves the payment at their own financial institution
4. Issues an outgoing payment instruction to move the money

OpenCheckout does not touch funds or execute payments — it separates payment instructions from payment execution. This means you can include payment functionality in your application without registering as a licensed money transmitter.

Why OpenCheckout

Aspect	OpenCheckout	Stripe / PayPal / Paystack
Deployment	Self-hosted on your server	Platform-hosted on their servers
Data ownership	You own all payment data	They own your payment data
Per-transaction fees	None	2.9% + $0.30 typical
License	Open-source (AGPLv3)	Proprietary
Payment method	Any Open Payments wallet	Cards, bank transfers, their wallet
Wallet compatibility	Works with any compliant ASE	Locked to their ecosystem
API compatibility	Stripe-compatible sessions API	Stripe’s own API

Key Features

• Stripe-compatible checkout sessions API — same endpoint shape, response format, and idempotency behavior
• Wallet-agnostic — any bank, digital wallet, or mobile money provider implementing Open Payments
• Cross-currency payments — customers pay in their currency; you receive in yours
• Interactive payment consent — customers approve payments at their own financial institution via GNAP
• Merchant dashboard — transaction history, API key management, webhook configuration
• Webhook delivery — HMAC-SHA256 signed events with automatic retries
• Cryptographic security — Ed25519 request signing, AES-256-GCM encryption at rest
• Single-command deployment — docker compose up with SQLite included

How It Works

Step 1: Your backend creates a checkout session
  POST /api/checkout/sessions  →  { id, url, status: "open" }

Step 2: Redirect your customer to the checkout page
  https://checkout.yourdomain.com/pay/cs_abc123

Step 3: Customer enters their wallet address
  e.g., https://mybank.com/username

Step 4: OpenCheckout orchestrates the Open Payments flow
  incoming payment → quote → interactive grant → outgoing payment

Step 5: Customer is redirected to your success URL
  https://yourstore.com/order/123?session_id=cs_abc123&status=complete

Step 6: A webhook fires to your backend with full payment details

Quick Example

Create a $20.00 checkout session from your backend:

curl -X POST https://checkout.yourdomain.com/api/checkout/sessions \
  -H "Authorization: Bearer sk_YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: order-456-unique-key" \
  -d '{
    "mode": "payment",
    "line_items": [{
      "price_data": {
        "currency": "usd",
        "product_data": { "name": "T-shirt", "description": "Cotton crew neck" },
        "unit_amount": 2000
      },
      "quantity": 1
    }],
    "success_url": "https://yourstore.com/order/456?session_id={CHECKOUT_SESSION_ID}",
    "cancel_url": "https://yourstore.com/cart",
    "metadata": { "order_id": "456" }
  }'

Response:

{
  "id": "cs_abc123xyz",
  "status": "open",
  "url": "https://checkout.yourdomain.com/pay/cs_abc123xyz",
  "amount_total": 2000,
  "currency": "usd",
  "mode": "payment",
  "expires_at": "2026-06-17T00:00:00Z",
  "created_at": "2026-06-16T00:00:00Z"
}

Redirect your customer to url. OpenCheckout handles everything else.

Open Payments Protocol

OpenCheckout is built on the Open Payments protocol — an open API standard maintained by the Interledger Foundation. The standard defines three server roles:

• Wallet Address Server — exposes public information about an Open Payments-enabled account
• Resource Server — exposes APIs for creating incoming payments, quotes, and outgoing payments
• Authorization Server — exposes GNAP-compliant APIs for obtaining grants

OpenCheckout acts as a client that orchestrates calls across all three servers. You do not need to understand the protocol internals — the SDK handles key management, request signing, grant negotiation, and hash verification automatically.

Who This Is For

• Developers and startups who want to accept payments without per-transaction fees
• Merchants who want full control over their payment data and checkout experience
• Marketplace platforms that need to orchestrate payments between multiple parties
• Non-profits and open-source projects that want a payment solution aligned with their values
• Anyone with an Open Payments-enabled wallet who wants to receive payments on their website