x402 is an open protocol that lets software pay for a web resource inside
the HTTP request itself. It’s built on HTTP’s long-reserved status code
402 Payment Required: a client calls a URL, the server replies with 402
and a machine-readable price, the client attaches a signed stablecoin payment
(typically USDC) and retries, and the server returns the resource plus an
on-chain receipt. No account, no API key, no checkout page — the payment is
the authentication.
The exchange, concretely
GET /r/acme/firmographics → 402 { price: $0.015 USDC,
payTo: 0x…, network: base }
GET /r/acme/firmographics
X-PAYMENT: <signed payload> → 200 { …data… } + tx receipt
Why it exists
Every prior payment rail assumed a human: card forms, signups, invoices, subscriptions. AI agents — software with budgets and tasks — can do none of that, but they can sign a payment and retry a request. Coinbase introduced x402 to close exactly that gap; in April 2026 it moved to the neutral x402 Foundation under the Linux Foundation, backed by Google, AWS, Microsoft, Stripe, Visa and Mastercard, having carried on the order of 165 million transactions in under a year.
What it’s good for (and not)
x402 shines where accounts are heavier than the purchase: per-call data lookups, per-download files, metered tool use, machine-to-machine commerce. It is not a subscription manager or an enterprise procurement replacement — a $250k annual data license still wants a contract, not a header.
Where you can watch it work
Every listing on datapoint.market — API, MCP tool, or dataset file — is an x402 endpoint; a first call with no payment returns the price (or a free trial), so trying it costs nothing: buy a call, raw HTTP · the whole flow from an agent · a real $0.01 purchase, receipt included