Accept BTC, USDC, USDT & EURC in your store.
Without ever touching crypto custody.

One API, three ways to get paid

Enable AI agents

Agentic commerce is here — customers increasingly send an AI agent to research, order, and pay. Every send21 checkout is machine-readable (structured JSON, standard payment URIs, /llms.txt, OpenAPI, and a native MCP server at send21.io/mcp), so an agent can complete a purchase in your shop end to end and pay from its operator's own wallet. No stored cards, no chargebacks. How it works.

Enable crypto in your webshop

One API call at checkout returns a hosted pay page and QR. Your customer pays the exact fiat price you quoted — in BTC, USDC, USDT, or EURC at a locked rate — straight to your address. The HMAC-signed webhook carries your order id, the amount, and the conversion rate, so orders reconcile themselves.

Enable crypto on payment devices

Turn any terminal, tablet, or kiosk into a crypto point of sale: the device creates a payment request for the basket total and shows the QR; the customer scans and pays from their own wallet. The confirmation webhook closes the sale on the device — no card rails, no acquirer fees, funds land directly in your wallet.

How a checkout works

1. Create a payment request — one API call or a click in the dashboard

   Set the price in any of the 165 supported world currencies (USD, EUR, SEK, NGN, VND, …) and list which currencies you accept, each with your own receiving address. You get back a hosted pay link and QR code.

   curl -X POST https://send21.io/api/v1/payment-requests \
     -H "Authorization: Bearer s21_yourkey" \
     -H "Content-Type: application/json" \
     -d '{
       "fiatCurrency": "EUR",
       "fiatAmount": 49.90,
       "orderId": "shop-order-1042",
       "memo": "Order #1042 — Blue hoodie",
       "options": [
         { "currency": "Btc",  "network": "Mainnet",  "address": "bc1q..." },
         { "currency": "Usdc", "network": "Solana",   "address": "5Gv7..." },
         { "currency": "Usdt", "network": "Ethereum", "address": "0xAb..." }
       ]
     }'

2. Show the customer the pay page or QR

   Redirect to the hosted page, embed the link in an invoice, or show the QR at the counter. The customer picks BTC, USDC, USDT, or EURC — the exchange rate locks the moment they choose, so your price is guaranteed.

3. Customer scans and pays from their own wallet

   One standard QR (BIP-21 / Solana Pay / EIP-681) — works with ordinary wallets, no PSBT knowledge needed. Funds move directly from the customer's wallet to your address.

4. Get a webhook with everything your books need

   When the payment confirms, the signed webhook tells you what was sent, what it was worth in your currency, and the exact conversion rate — plus your own order id.

   {
     "event": "draft.confirmed",
     "data": {
       "draftId": "7d21…",
       "status": "Confirmed",
       "txId": "3QzV…",
       "confirmations": 1,
       "sentCurrency": "USDC",
       "network": "Solana",
       "sentAmount": "53.870000",
       "fiatCurrency": "EUR",
       "fiatAmount": 49.90,
       "conversionRate": 0.9263,
       "rateSource": "coinbase",
       "orderId": "shop-order-1042"
     }
   }

Using Shopify? There's a ready-made integration

The send21 Shopify app adds crypto payments to your store without touching your theme's checkout code: the customer picks “Crypto (send21)” at checkout, receives the pay link, pays from their own wallet — and the app marks the Shopify order paid automatically when the payment confirms on-chain. Your order confirmation email carries the pay link; reconciliation runs on your order ids.

1. Create a send21 API key and webhook

   In your send21 account, create an API key with drafts:read + drafts:write, save your receiving addresses in the address book (“My own — I receive here”), and add a webhook for draft.confirmed pointing at the app.

2. Install the app on your store

   Install the send21 app, then approve the requested order permissions (read_orders, write_orders) — the app subscribes to new orders automatically.

3. Add the manual payment method

   In Shopify admin: Settings → Payments → Manual payment methods → create “Crypto (send21)”, and add the pay link snippet to your order confirmation email. That's it — orders paid in BTC, USDC, USDT, or EURC settle straight to your wallet and flip to paid on their own.

Setup details and the email snippet: [email protected]. Refunds are out of band (crypto is push-only): refund from your own wallet, then refund the order in Shopify admin. Other platforms (WooCommerce, custom carts) integrate with the same one-call payment-request API.

Why retailers pick send21

Questions about integrating your shop or agent? Write to [email protected].

Ready for customers who send an AI agent

Agentic commerce is here: people increasingly let AI agents research, order, and pay on their behalf. Card checkouts break for agents — sharing card numbers with an agent is a liability, and form-filling is fragile. A send21 checkout is different: it is an API-first, machine-readable payment instruction that an agent can read, verify, and pay from its operator's own wallet — without your shop or the agent ever touching a card number or a private key it shouldn't have.

agent places order → your backend creates a payment request → agent reads the machine-readable options → pays from its operator's wallet → signed webhook confirms with your order id

Nothing extra to build: the same payment request that renders a QR for a human is the one an agent consumes. Integrating your shop today makes it agent-ready by default.

Person-to-person requests too

The same flow works between individuals: create a request for what a friend owes you, send them the link, and they pay in whichever offered currency suits them. You are always the receiver; they always sign in their own wallet.