What is x402?
x402 is an open payment protocol developed by Coinbase that revives the long-reserved HTTP402 Payment Required status code. It enables AI agents and services to pay for API access autonomously using USDC on Base — no accounts, sessions, or human intervention required.
Payment flow
Agent sends request
Your agent or app sends a normal HTTP POST to a paid endpoint. No auth header needed.
Server returns 402
PropX402 responds with
402 Payment Required plus a payment payload specifying the USDC amount and Base network address.Agent pays and retries
The x402 client signs and broadcasts a USDC transfer on Base mainnet, then retries the request with a payment proof header.
Why x402?
| Traditional API | PropX402 (x402) | |
|---|---|---|
| Auth | API keys, OAuth | None required |
| Billing | Subscriptions, invoices | Pay per query |
| Settlement | Days | ~200ms on Base |
| Agents | Manual setup | Fully autonomous |
| Chargebacks | Yes | Not reversible |
Requirements
- EVM wallet on Base mainnet (Coinbase Wallet, MetaMask, or any Base-compatible wallet)
- USDC balance on Base — bridge at bridge.base.org or buy directly
- x402-compatible HTTP client — x402 SDK on GitHub
Payment receiver
All PropX402 payments settle directly to this address. No intermediaries.Facilitator
Installation
Learn more about the x402 protocol at x402.org or read the Coinbase x402 whitepaper.