x402
An open standard for requesting and making payment inside an HTTP exchange, using the Payment Required status.
x402 is an open standard, stewarded by the x402 Foundation, for making payments inside ordinary HTTP exchanges by using the long-reserved Payment Required status code. When a request for a paid resource arrives without payment, the server replies with that status and its payment requirements, and the client pays and retries the request with proof of payment. The standard is designed for programmatic buyers such as agents, and its site describes stablecoin payments as the common case today.
Agent Minute explains this term on 16 January 2027.
Related terms
Agent Payments Protocol (AP2)An open protocol for agent payments built on signed mandates, available as an extension to A2A.Settlement finalityThe point at which a transfer becomes irrevocable and unconditional, so it cannot be unwound.Know Your Agent (KYA)Checking which agent is acting, who operates it and whom it acts for, before letting it act.Instant paymentA credit transfer executed within seconds, at any time of day, every day of the year.