x402
Open payment standard that lets agents and clients pay for APIs and content inside HTTP requests with stablecoins
x402 is an open, neutral standard for internet-native payments that builds payment into HTTP. When a client, which can be an AI agent, requests a paid resource, the server answers with HTTP 402 Payment Required, and the client pays and retries, with no accounts, API keys or forms.
Key features:
- Require payment on any endpoint with one line of server middleware.
- Set the price and accepted networks per route.
- Let agents pay per API call, unlock paywalled content or trade with other agents.
- Settle in stablecoins on EVM chains, Solana and other networks.
- Skip accounts and personal information on both sides.
x402 is governed by the x402 Foundation, and anyone can build on or extend it, with SDKs for TypeScript, Python and Go. There are no protocol fees beyond nominal payment network fees, and the site reports about 75 million transactions in the last 30 days.