What is HTTP 402 Payment Required?
An HTTP status code reserved for payment that HTTP itself never defined in detail, now used by agent payment schemes such as x402.
RFC 9110 lists 402 as "reserved for future use". Because browsers and HTTP libraries already understand the code, protocols that let software pay per request reuse it: the server answers 402 with what it costs, and the client pays and retries.
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Related terms
- x402An open payment standard, introduced by Coinbase in 2025, that uses HTTP 402 so an API can charge per request and a client or AI agent can pay instantly, typically in stablecoins.