x402

A client asks for a resource. The server answers with status 402 and the payment terms. The client builds a payment, signs it and sends the request again with the payment attached. A facilitator checks the payment and settles it, and the server returns the resource. The seller adds the payment requirement to an endpoint with a few lines of middleware and does not have to run blockchain infrastructure itself.

The protocol is network-neutral. x402.org lists all EVM-compatible chains and Solana, names stablecoins as the main use and calls the standard extensible to traditional payment methods. The protocol itself charges no fees; the payer covers the costs of the network used.

The Coinbase Developer Platform started x402 and has handed the protocol to the x402 Foundation under the Linux Foundation. The Coinbase documentation lists Amazon Web Services, American Express, Cloudflare, Coinbase, Google, Mastercard, Shopify, Solana Foundation, Stripe and Visa as premier members, and forty organizations joined at launch.

The membership list matters for payments people: the card schemes and large acquirers sit in the same body as the stablecoin side. That makes x402 a candidate for a common way to ask for a payment on the web, whichever rail then moves the money.

The main uses are paid APIs, content behind a paywall and agentic commerce: an agent that needs data or computing time pays per call without an account, an API key or a subscription. That makes x402 a building block for micropayments and machine-to-machine payments.

For European providers the open points are regulatory. A facilitator that settles payments for others may need a license under PSD2 or MiCA, payments in euro stablecoins fall under the rules for e-money tokens, and travel rule and anti-money laundering checks apply to the flows. A payment without an account also comes without the chargeback a card buyer has.

x402 is an open payment protocol that uses the HTTP status code 402 "Payment Required". A server states a price in its response, the client pays, mostly in stablecoins, and receives the resource within the same web request.

x402 was created by the Coinbase Developer Platform. It is now governed by the x402 Foundation under the Linux Foundation, whose premier members include Visa, Mastercard, American Express, Stripe, Google and Cloudflare.

Stablecoins are the main use today, but the format can also accommodate traditional payment methods. The request and response format does not depend on one network.