From Decrypt · By Decrypt Agent
In brief
x402 is an open payment standard from Coinbase that uses the web's long-unused HTTP 402 code to let AI agents and apps pay for online services.
Payments are mostly made in USDC on Base and settled through facilitators, so buyers sign an authorization instead of creating accounts or API keys.
More than 50 companies, including Visa, Mastercard and Google, have joined the x402 Foundation, which now governs the protocol under the Linux Foundation.
Nobody really built the web with payments in mind. Early HTTP specifications included a status code, 402 "Payment Required", that was reserved for a future system of online payments. Then it sat unused for about 30 years. Payments were slow and expensive, and they needed accounts, card details and middlemen who could reverse charges. None of that works for a small payment made by software.
That gap matters more now because AI agents are starting to browse, call APIs and buy services for their users. An agent can't fill in a checkout form or sign up for a monthly plan for every tool it uses. Cloudflare says more than half of internet traffic is now non-human, and it reports seeing a billion HTTP 402 responses on its network every day.
x402 is an attempt to finally give the internet a native way to pay. This guide covers what it is, how it works, who backs it, and whether there's a token involved.
Did you know?
The 402 "Payment Required" code has been in the HTTP standard since the 1990s. It was set aside "for future use", and x402 is the first big effort to actually use it.
What is x402?
x402 is an open payment standard built on top of HTTP, the protocol that moves data around the web. Coinbase launched it in May 2025 with partners including AWS, Anthropic, Circle and NEAR. It lets APIs, apps and AI agents pay for services in stablecoins as part of an ordinary web request.
x402 is not a blockchain and it is not a coin. It's a set of rules: message formats, headers and a request-and-response flow that any server or client can follow. Payments are mostly made in USDC, Circle's dollar-backed stablecoin, with Coinbase's Ethereum layer-2 network Base as the main settlement chain. The protocol works with any chain, though, and it now supports Solana, Polygon, Arbitrum and others, as well as traditional card payments.
On April 2, 2026, the Linux Foundation announced it was launching the x402 Foundation, with Coinbase contributing the protocol and companies including Microsoft, Google, Visa and Mastercard expressing initial support. The new x402 Foundation became fully operational on July 14, 2026, and now stewards the protocol under vendor-neutral governance.
We are excited to introduce x402–a new open source payments protocol built on HTTP rails.