x402 Explained: HTTP 402 for Machine-Native Payments

x402 is Coinbase’s open protocol that revives the long-dormant HTTP 402 “Payment Required” status so that software can pay for resources programmatically, typically with stablecoins, in amounts and at frequencies that card rails handle poorly. It is not a consumer-checkout protocol. It sits at the settlement layer and exists for software paying software: an agent paying for an API call, compute, data, or content.

How payment flows

The mechanism is the elegant part. A client requests a resource from a service; the service responds with a 402 and a payment requirement; the client pays; and a facilitator verifies and settles the payment on-chain on the merchant’s behalf before the resource is delivered. The facilitator model is what makes x402 practical: the merchant does not have to run blockchain infrastructure itself, it relies on the facilitator to verify and settle. Settlement is in stablecoins such as USDC, which suits micro-transactions and per-call billing where traditional rails are too slow or too expensive.

Who is behind it

x402 comes from Coinbase, and is crypto-native by design. Coinbase and Cloudflare announced an x402 Foundation in September 2025 to steward the protocol, and it is now organized under the Linux Foundation, giving it neutral, multi-party governance. That early move to a foundation is a familiar pattern: the crypto-native standard leans on neutral stewardship sooner, while provider-backed standards often start under their sponsors.

Where it sits in the stack

x402 is one of two machine-native settlement standards, alongside MPP. Both build on HTTP 402 and target the same agent-to-agent and micro-transaction use cases; the difference is sponsorship and rails, and Stripe supports both. For a side-by-side, see x402 vs MPP.

It also connects to the authorization layer. An A2A x402 extension, built by Google with Coinbase, the Ethereum Foundation, and MetaMask, brings x402-style stablecoin payments to the A2A agent-to-agent protocol, which is how AP2 composes with crypto settlement. So x402 handles the money movement, while AP2 and A2A handle authorization and coordination around it. For the full map, see the protocol stack.

FAQ

What is x402? Coinbase’s open protocol reviving HTTP 402 so software can pay for resources programmatically, typically in stablecoins. It is a settlement-layer standard for machine-to-machine and micro-transaction use cases.

How does payment work? A 402 response carries a payment requirement, the client pays, and a facilitator verifies and settles on-chain before the resource is delivered, so the merchant needs no blockchain infrastructure of its own.

How is it different from MPP? Both are HTTP 402-based settlement standards. x402 is Coinbase’s stablecoin-focused, on-chain protocol; MPP is Stripe and Tempo’s, settling in stablecoins as well as cards and BNPL through Stripe. Stripe supports both.