About send21
send21 makes crypto pay links and a payment API for people and AI agents. It is non-custodial payment software: it prepares pay links, payment requests and invoices for BTC (on-chain and Lightning), USDC, USDT, EURC, SOL and ETH, then watches the chain until the payment confirms. The money always goes straight from the payer's wallet to the receiver.
What send21 does
- Creates pay links and drafts for a fixed crypto amount, or priced in any of 161 currencies with a locked, recorded exchange rate.
- Watches the chain and tells you by email and signed webhook when a payment arrives and confirms.
- Works for people and AI agents alike. Everything in the app is also available over the REST API and the MCP server, with scoped keys that can never move funds.
What send21 is not
send21 is not a custodian, exchange, broker, money transmitter or payment service provider. It never holds, moves or converts funds and never has access to private keys. It has no signing code and never broadcasts transactions: that always happens in the sender's own wallet. Even a full server break-in could not move a single satoshi. The details are in our terms of service.
How it makes money
One fee per payment, tiered by size: from 0.49% on the smallest payments down to 0.01% above $100,000, capped at $100. No subscription and no spread on exchange rates. See the pricing page.
Privacy by default
No KYC, no tracking, no analytics, no ad pixels. send21 stores your email address (encrypted) and little else. The privacy policy lists exactly what is kept and for how long.
Contact
- General: info@send21.io
- Account or payment questions: support@send21.io
- API and integrations: integration@send21.io
- Privacy and GDPR requests: privacy@send21.io
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