What Is x402? How AI Agents Pay With Crypto

No one designed the internet for payments

Standard x402: How AI agents pay with cryptocurrencies for online services

An HTTP status code that has been unreleased for three decades is now at the center of a digital payments revolution. Knowledge of how this system works is essential for understanding the future of AI-driven trade.

Essentially, x402 is an open payment standard, initiated by Coinbase, that uses the HTTP 402 code, originally reserved for future uses, to allow AI agents and applications to purchase online services. Transactions are predominantly conducted in USDC on the Base network, with facilitators handling the completion of payments, which eliminates the need for buyers to create accounts or API keys. More than 50 companies, including Visa, Mastercard and Google, have joined the x402 Foundation, which now administers the protocol under the auspices of the Linux Foundation.

No one designed the internet for payments. Early HTTP specifications included the status code 402 Payment requested , reserved for a future online payment system. It remained unused for about 30 years. Payment processes were slow and costly, requiring accounts, card details and intermediaries who could cancel transactions. None of these requirements is practical for a small payment made by software. This gap is getting bigger and bigger as AI agencies start browsing, invoking APIs, and buying services for their users. An agent may not complete a payment form or register for a monthly subscription for each instrument he uses. Cloudflare states that over half of Internet traffic is now non-human, and it reports that it sees a billion HTTP 402 responses on its network daily. x402 is an attempt to finally give the Internet a native way to pay.

x402 is an open payment standard built on HTTP, the protocol that transports data over the web. Coinbase launched it in May 2025, alongside partners such as AWS, Anthropic, Circle, and NEAR. It allows APIs, applications, and AI agents to pay for services in stable currencies as part of a regular web application. x402 is not a blockchain and not a currency. It's a set of rules: messaging, antetypes, and a demand-response flow that any server or client can follow. Payments are largely made in USDC, the stable currency backed by the dollar issued by Circle, with the Base network, layer 2 of Ethereum from Coinbase, as the main finalisation chain. The protocol works with any chain, although it now supports , , Arbitrum and others, as well as traditional card payments.

On April 2, 2026, the Linux Foundation announced the launch of the x402 Foundation, with Coinbase's contribution to the protocol and initial support expressed by companies such as Microsoft, Google, Visa, and Mastercard. The new x402 Foundation became fully operational on 14 July 2026 and now administers the protocol under a supplier-neutral governance.

* Request: An AI agent or application

The x402 function is based on a short sequence of interactions in a normal web application:

Request: An AI agent or application requests something from a server, such as an API call, a dataset, or an article. Response 402: The server answers 402 Requested Paymentand includes machine-readable terms: price, coins accepted, and payment wallet address. Payment: The customer signs a payment authorization with his wallet and sends the request again with that signature attached to an ante. Delivery: The server verifies the payment, completes it on the chain, and returns what was requested.

Most of the work on the chain is done by an facilitator, a service that verifies payments and finalizes them on the blockchain, so vendors don't have to manage their own crypto setup. On EVM chains, x402 uses EIP-3009, a standard that allows someone to transfer tokens by signing a permit instead of sending a transaction itself. This means that the buyer does not have to hold the ETH for the gas.

The main selling point of x402 is the making of very small payments made by machines. Finishing on Base takes a few seconds and costs well under a penny, which makes sense to pay in fractions of a penny for a single API call. There's no registration, there's no API key and there's no subscription. The agent simply pays and gets what he asked for.

Adoption has grown rapidly. Coinbase launched x402 V2 in December 2025, adding wallet-based identity so agents don't have to pay again on every call, automatic service discovery, and support for multiple chains. In May 2026 completion was added to the batch, where agents transmit to sellers signed bonds which p