x402

x402 is an open, HTTP-native payment protocol designed to enable programmatic, real-time payments directly within standard web requests. It repurposes the long-unused HTTP 402 “Payment Required” status code to allow servers to request payment before delivering content or API responses. The protocol supports multiple payment networks, including blockchain-based systems and fiat-compatible facilitators, making it flexible and network-agnostic. It is particularly suited for machine-to-machine transactions, such as AI agents paying for APIs, data, or compute resources without human intervention. The system eliminates the need for accounts, sessions, or traditional payment rails by using cryptographic authorization and wallet-based transactions. Developers can integrate payment requirements into endpoints with minimal code using middleware and SDKs. Overall, x402 introduces a new economic layer to the web, enabling micropayments and pay-per-use services natively over HTTP.