What is x402?

x402 is an open protocol that brings the HTTP 402 status code to life. That code, "Payment Required," has been part of the web since the 1990s but was never widely implemented because there was no good way to handle payments natively on the internet.

Coinbase changed that. In early 2025, they released x402 as an open-source standard that lets any website or API require a USDC payment before serving content or data. Instead of subscriptions, API keys, or ad-supported models, a server can simply say "pay me 0.001 USDC and I'll give you what you asked for." The payment happens on-chain, primarily on Base, and the content is delivered instantly.

Think of it like a toll booth for the internet, except the tolls can be fractions of a cent and there's no account to create.

The flow is straightforward:

1. You (or your app, or an AI agent) make a request to a server, like asking for an API response or a piece of premium content.

2. The server responds with HTTP 402 — "Payment Required." The response includes a payment address, an amount (in USDC), and a network (usually Base).

3. Your wallet or client signs a USDC payment for the exact amount and sends it back with the request.

4. A facilitator (a lightweight verification service) confirms the payment landed on-chain, and the server delivers the content.

The entire round trip takes about a second on Base. There's no sign-up, no subscription, no credit card form. The protocol is open source, so anyone can run a facilitator or build a client.

Three shifts make x402 significant.

Agentic payments. AI agents increasingly need to interact with paid services, but they can't fill out credit card forms or manage subscriptions. x402 gives agents a way to pay for exactly what they use, autonomously. An AI research agent can pay for a premium data feed. A coding assistant can pay for an API call. This is a building block for the agentic economy.

True micropayments. Credit card networks have a floor, typically around $0.30 per transaction in fees. x402 on Base has no practical floor. You can charge a thousandth of a cent per request. That unlocks business models that were never viable before: per-paragraph articles, per-query APIs, per-second streaming data.

Global access. Billions of people don't have credit cards or bank accounts that work with Western payment processors. x402 only requires a crypto wallet with some USDC. If you have a phone and internet access, you can pay for and receive payment through x402. No bank account, no credit check, no country restrictions.

x402 started at Coinbase but has grown into a broader ecosystem.

Coinbase created the protocol and maintains the reference SDK. It includes TypeScript, Python, and Go libraries for both clients and servers.

Stripe announced x402 integration in February 2026, allowing any Stripe merchant to accept per-request USDC payments alongside traditional card processing.

Cloudflare co-founded the x402 Foundation and built a Workers template that lets developers add x402 payment gates to any Cloudflare-hosted site in minutes.

Google's Agent Payments Protocol builds on x402 concepts for AI agent-to-service payments.

thirdweb offers x402 middleware that integrates with their smart contract tooling.

Kobaru provides managed x402 infrastructure so developers don't need to run their own facilitator.

You can explore the full ecosystem in our x402 directory.

USDC is the default currency of x402. The protocol was designed around it from the start.

Why USDC specifically? Three reasons. First, price stability. Neither the buyer nor the seller wants the payment amount to fluctuate between the request and the response. USDC is always $1. Second, speed. On Base, USDC transfers confirm in about a second with fees under a penny. That's fast enough and cheap enough for per-request payments. Third, programmability. USDC is an ERC-20 token with wide tooling support, making it straightforward to integrate into payment verification flows.

x402 positions USDC as more than a store of value or a trading pair. It positions USDC as the internet's native payment layer, the currency that machines and humans use to pay for things online, one request at a time.

For everyday users, you don't need to do anything yet. As services adopt x402, your wallet will handle the payment flow automatically. You'll see a small USDC charge when you access paid content, similar to how your browser handles HTTPS without you thinking about it.

For developers, the SDKs are available at x402.org. The quickest path is the TypeScript SDK, which lets you add x402 payment gates to an Express or Next.js server in a few lines of code. You can also explore the Cloudflare Workers template for edge deployment or Kobaru for managed infrastructure.

If you don't own any USDC yet, start with our guide on how to buy USDC safely. You'll want USDC on Base, since that's where most x402 transactions happen today.