Checkout API

Build custom checkout experiences with Volr Checkout API. Accept stablecoin payments from kiosks, POS systems, mobile apps, websites, or any platform with your own UI.

Overview

Volr Checkout provides the following features:

• QR Code-based Payment: Customers scan EIP-681 QR codes with any mobile wallet (MetaMask, Trust Wallet, etc.)
• Wallet-Direct Payment: Customers connect their browser wallet and pay via ERC-20 transfer() directly
• Multi-Fiat Currency Support: Set prices in USD, KRW, EUR, or other supported currencies - automatically converted to stablecoin amounts at the exchange rate when checkout is created
• Real-time Payment Detection: Automatically detects and verifies blockchain transactions
• Webhook Notifications: Sends server notifications when payments complete
• Multi-Language Support: Checkout UI available in English, Korean, Japanese, and Spanish (?lang=ko)

Payment Paths

Volr Checkout supports two payment paths that converge on the same verification flow:

Path 1: QR Code (Mobile)

Customer scans an EIP-681 encoded QR code with their mobile wallet. The QR encodes the token contract, recipient address, amount, and chain ID — so the wallet auto-fills everything.

Path 2: Wallet-Direct (Desktop)

Customer clicks "Pay with wallet", connects their browser wallet (MetaMask, Coinbase Wallet, etc.), and the checkout page executes an ERC-20 transfer() call directly.

Both paths submit the transaction hash for backend verification and converge to the same success state.

Architecture

Key Concepts

Checkout

A payment request unit. Each Checkout has a unique ID and deposit address.

Deposit Address

A deterministic address generated via CREATE2. When customers send tokens to this address, funds are automatically settled to the merchant.

Fiat Payment

Set prices in any supported fiat currency (USD, KRW, EUR, etc.) and Volr API calculates the stablecoin amount using the exchange rate at checkout creation time. Manage exchange rate risk with the expiryMinutes parameter (default 30 minutes, max 1440 minutes).

Pricing Modes

Volr Checkout supports two pricing modes to fit different use cases:

1. Crypto Amount (Fixed Token Amount)

Specify the exact token amount you want to receive. No exchange rate conversion.

{
  "chainId": 8453,
  "tokenAddress": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
  "amount": "499000000"
}

Use case: "I want to receive exactly 499 USDC"

• Customer pays exactly 499 USDC
• No exchange rate risk
• Best when you want predictable crypto amounts

2. Fiat Amount (Fixed Fiat Value)

Specify the fiat value and let Volr calculate the token amount at current exchange rate.

{
  "chainId": 8453,
  "tokenAddress": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
  "fiatAmount": "499",
  "fiatCurrency": "USD"
}

Use case: "I want to receive $499 worth of USDC"

• Token amount calculated at checkout creation (e.g., if USDC = $0.9996, customer pays ~499.2 USDC)
• Exchange rate locked at creation time
• Best when you want predictable fiat value

Choosing the Right Mode

• Crypto pricing: Use when selling crypto-native products or when you want exact token amounts
• Fiat pricing: Use when your business operates in fiat terms (e.g., "$99 product")

Supported Tokens

Stablecoins currently supported for fiat conversion:

Token	Networks	Fiat Conversion
USDC	Base	Supported
USDT	Base	Supported

Coming Soon

Support for additional networks (Arbitrum, Polygon) is planned for future releases.

Next Steps

1. Quick Start - Get your first payment in 5 minutes
2. Authentication - API Key setup and authentication
3. Create Checkout - Create Checkout API reference