x402 revives HTTP 402 Payment Required with on-chain micropayments — so autonomous AI agents can discover price, pay within a bounded quota, and settle in the same programmatic request flow, without a human clicking approve on every call.
A 402 response triggers on-chain settlement inline — no checkout redirects, confirmed in milliseconds for machine-to-machine commerce.
Every unlock maps to an on-chain transaction receipt: auditable, traceable, and usable as proof inside agent workflows.
Pair with agent wallets and allowlists so agents pay automatically inside a budget — humans authorize once, not per request.
Compare a traditional unlock with x402 on an article. The same 402 intercept → sign → retry loop is what agents use to pay for APIs, data, and downstream agent services.
Checkout redirects, card binding, and clearing delays measured in seconds or days cannot support high-frequency, per-call payments that autonomous agents need.
Return HTTP 402 from Express/Next.js middleware; the wallet or agent runtime intercepts, signs within policy, and retries with a receipt.
