HTTP 402
The 402 status code in the HTTP protocol, originally defined as 'Payment Required' but long reserved and unused. With the rise of AI agents and cryptocurrency micropayments, the code has been revisited as a potential technical foundation for automated machine-to-machine settlement.
Core Facts
x402 is an open protocol that reuses the 402 status code (Payment Required) from the HTTP protocol, enabling software (especially AI Agents) to call APIs on a per-request pay-as-you-go basis and settle directly with cryptocurrency (typically USDC), without requiring accounts, API keys, or traditional checkout pages.
The HTTP 402 Payment Required status code was defined in the HTTP/1.1 specification in 1997 and has long remained in a state of being reserved for future use.
HTTP 402 is a status code reserved in RFC 7231 but rarely used historically, originally designed for future digital payment scenarios.
Timeline (last 90 days)
The x402 protocol lets a server request stablecoin payment via the HTTP 402 status code before returning a resource, and it is already live and governed by the x402 Foundation under the Linux Foundation.
The HTTP 402 Payment Required status code was reserved by Tim Berners-Lee in the 1997 HTTP/1.1 specification (RFC 2068).
In the experiment, after the agent requested a data endpoint and the server returned a 402 challenge, the agent autonomously signed a micropayment transaction of 0.05 USDC on the Base L2 network and then obtained the data.
The HTTP 402 "Payment Required" status code has long been merely a placeholder in the protocol specification—defined but almost never actually used.
The name x402 is derived from HTTP status code 402 (Payment Required), which was defined in the HTTP/1.1 specification but has long been reserved and unused.
The HTTP 402 status code was defined in the HTTP/1.0 specification in 1991, originally envisioned for access control of digital paid content, but remained reserved and unused for a long time due to the lack of viable micropayment infrastructure.
x402 is an open protocol that reuses the 402 status code (Payment Required) from the HTTP protocol, enabling software (especially AI Agents) to call APIs on a per-request pay-as-you-go basis and settle directly with cryptocurrency (typically USDC), without requiring accounts, API keys, or traditional checkout pages.
x402 is an AI-native payment protocol used to automatically complete micropayments between machines and between AI agents and servers, with its name derived from HTTP status code 402 (Payment Required).
The HTTP 402 Payment Required status code was defined in the HTTP/1.1 specification in 1997 and has long remained in a state of being reserved for future use.
Agent Code Payments currently supports the X402 protocol, a modernized implementation of the HTTP 402 status code.
2 more timeline events
All Facts (14)
x402 is an open protocol that reuses the 402 status code (Payment Required) from the HTTP protocol, enabling software (especially AI Agents) to call APIs on a per-request pay-as-you-go basis and settle directly with cryptocurrency (typically USDC), without requiring accounts, API keys, or traditional checkout pages.
65%VerifiedThe HTTP 402 Payment Required status code was defined in the HTTP/1.1 specification in 1997 and has long remained in a state of being reserved for future use.
65%VerifiedHTTP 402 is a status code reserved in RFC 7231 but rarely used historically, originally designed for future digital payment scenarios.
65%UnverifiedHTTP 402（Payment Required）是HTTP/1.1规范中最早定义的状态码之一，长期处于保留状态
90%UnverifiedStripe、GitHub API、Google Cloud等主流平台在配额耗尽或余额不足时均会返回HTTP 402状态码
75%UnverifiedThe x402 protocol lets a server request stablecoin payment via the HTTP 402 status code before returning a resource, and it is already live and governed by the x402 Foundation under the Linux Foundation.
70%UnverifiedThe HTTP 402 Payment Required status code was reserved by Tim Berners-Lee in the 1997 HTTP/1.1 specification (RFC 2068).
50%UnverifiedThe HTTP 402 "Payment Required" status code has long been merely a placeholder in the protocol specification—defined but almost never actually used.
50%UnverifiedIn the experiment, after the agent requested a data endpoint and the server returned a 402 challenge, the agent autonomously signed a micropayment transaction of 0.05 USDC on the Base L2 network and then obtained the data.
50%UnverifiedThe name x402 is derived from HTTP status code 402 (Payment Required), which was defined in the HTTP/1.1 specification but has long been reserved and unused.
50%UnverifiedThe HTTP 402 status code was defined in the HTTP/1.0 specification in 1991, originally envisioned for access control of digital paid content, but remained reserved and unused for a long time due to the lack of viable micropayment infrastructure.
50%Unverifiedx402 is an AI-native payment protocol used to automatically complete micropayments between machines and between AI agents and servers, with its name derived from HTTP status code 402 (Payment Required).
50%UnverifiedAgent Code Payments currently supports the X402 protocol, a modernized implementation of the HTTP 402 status code.
50%UnverifiedHTTP/1.1规范RFC 2616于1999年发布，在定义4xx客户端错误码时保留了402状态码
50%