x402

x402 is an open payment protocol that puts the long-unused HTTP 402 'Payment Required' status code to work. A client (an AI agent, an app or a person's browser) requests a resource, receives a 402 response stating the price and accepted payment options, sends a signed payment and gets the resource back in the same exchange. There is no account to create, API key to provision or checkout page to fill in, which is why it suits autonomous AI agents paying per request.

Coinbase launched x402 in May 2025. In April 2026 the Linux Foundation announced the x402 Foundation to govern it, and on July 14, 2026 the foundation became operational with Coinbase's contribution complete and 40 member organizations, including Coinbase, Cloudflare, Google, AWS, Stripe, Visa, Mastercard, American Express, Adyen and Shopify (Linux Foundation).

The current version is V2 (x402 V2 announcement). It moved all payment data into HTTP headers (PAYMENT-REQUIRED, PAYMENT-SIGNATURE and PAYMENT-RESPONSE), identifies networks and assets with CAIP standards so one format works across chains such as Base and Solana, and lets facilitators plug in traditional rails like ACH, SEPA or card networks. It also added wallet-based identity and reusable sessions, so a client that has already paid for access does not repay on every call, along with a discovery extension that lets facilitators index paid endpoints and their prices. In practice most settlement so far has been in USDC stablecoin through facilitators that verify and settle payments for the server.

Usage is real but smaller and more concentrated than headline counts suggest. The x402 team said the protocol processed over 100 million payments in its first six months or so. CoinDesk reported in July 2026 about 75 million transactions worth roughly $24 million over the previous 30 days, mostly sub-dollar payments. An independent tracker's October 2026 report counted 91 businesses earning meaningful organic revenue in the prior 30 days, with the top ten wallets holding 76% of volume, which suggests a large share of raw transactions are tests or automated traffic.

x402 handles only the payment step. It does not model carts, refunds or authorization limits. Other standards cover those layers: the Agent Payments Protocol proves an agent was authorized to spend, and Google has connected x402 to it as a settlement option; the Agentic Commerce Protocol handles product feeds and checkout; Web Bot Auth identifies which agent is making a request; and Really Simple Licensing states what a buyer may do with content.

For publishers and GEO teams, x402 is part of the machinery behind pay per crawl and metered APIs. It makes it technically simple to charge AI agents for content or data per request. That creates a trade-off worth thinking through: anything an AI system will not pay for is content it cannot retrieve, summarize or cite. Charging agents can make sense for proprietary data and APIs, while content meant to build brand visibility in AI answers usually works better when it stays freely accessible to retrieval crawlers.