x402 turns the long-dormant HTTP 402 status code into a working payment rail — letting APIs, AI agents, and software pay each other in stablecoins, instantly, with no accounts or invoices. Here's what it actually does, and how to use it.
A client — a browser, an app, or an AI agent — requests a resource over normal HTTP. Nothing unusual yet.
If the resource is paid, the server replies with status 402 and the exact terms: price, accepted token, network, and where to send it.
The client signs a stablecoin payment (usually USDC) and retries the same request with the payment attached in a header.
A facilitator verifies the payment on-chain. Once confirmed, the server returns 200 OK with the resource. The whole loop takes seconds.
There's no signup, no card minimum, no subscription. A request costing a fraction of a cent is now economically possible — which it never was under card networks.
Coinbase shipped the original spec; it's now stewarded by the x402 Foundation alongside Cloudflare, with Google, Visa, Stripe, and AWS among the members. No single company controls it.
| Facilitator | Networks | Free tier | Best for |
|---|---|---|---|
| Coinbase CDP | Base, Polygon, Arbitrum, World, Solana | 1,000 tx/mo, then $0.001/tx | Most reference implementations; best documentation |
| Cloudflare | Base (native Workers support) | Included with Workers plans | Teams already running on Cloudflare infrastructure |
| Solana-native facilitators | Solana | Varies by provider | Sub-second finality, very high transaction volume |
This table reflects the publicly documented state of each provider and changes as the protocol evolves. Always confirm current pricing and network support directly with the provider before integrating.