x402
x402
x402 is an open payment standard that enables AI agents and software to autonomously pay for APIs, data, and digital services using stablecoins, by repurposing the long-dormant HTTP 402 "Payment Required" status code. Developed by Coinbase in 2025, it processes instant on-chain settlement within the HTTP request-response cycle without requiring API keys, accounts, or subscriptions. Unlike credit card and subscription-based payment infrastructure optimized for human users, x402 provides an internet-native payment layer for machine-to-machine autonomous commerce.
Sources
- Wikipedia (EN) definition, history (developed by Coinbase, repurposing HTTP 402), technical specification (three-phase flow, EIP-3009), use cases (micropayments, agentic payments, pay-per-API, M2M)
- galaxy.com Galaxy Research report (Jan 2026): background, payment flows, x402 V2, ecosystem adoption, comparison with incumbent payment standards
- x402.org x402 whitepaper (May 2025): motivation, how x402 works, payment flow, settlement on Base/Solana/Stellar, facilitator model, EIP-3009 gasless transfers