x402 Lets Software Agents Pay for APIs Through HTTP Requests

The x402 open payment standard lets software request APIs and other digital services with payment terms carried in HTTP, allowing a client to authorize a charge as part of the same exchange.

Coinbase introduced x402 on May 6, 2025. The protocol uses HTTP’s 402 Payment Required response, whose purpose RFC 9110 leaves open for future use. x402 uses that response to communicate that payment is needed and provide the requirements for it.

A client begins by requesting a resource from an online service. If payment is required, the service can reply with a 402 response that includes payment requirements. The client signs an authorization and sends the request again with a payment payload. The service can verify and settle the payment itself or delegate those steps to a facilitator. After payment is verified and settled, the service returns the resource. A facilitator can handle verification and blockchain settlement, reducing the payment infrastructure a provider needs to operate itself.

The protocol standardizes the payment messages, while each implementation sets its own asset and network choices. A service specifies the payment it accepts, and available options depend on support from the network and facilitator. That means x402 payments do not all use the same crypto asset or blockchain. A service may accept stablecoins such as USD Coin (USDC).

The standard is designed for pay-per-request access to APIs and other digital services. Glassnode offers one example: its metrics and metadata can be requested through an x402 implementation that uses USDC on Base. Those payment terms reflect that service’s setup; they do not define what every x402 service must accept.

Wallet and software operators set how much an agent can spend. That control is separate from x402’s payment messages. A completed payment also does not determine whether an off-chain service’s response is accurate or useful, so the payment process does not replace evaluating the service itself.

The x402 Foundation became operational July 14, 2026, with 40 member organizations to steward the standard under open governance.