x402
Open HTTP-native payment protocol from Coinbase that lets agents and apps pay for resources with stablecoins over a standard web request.
x402 revives the dormant HTTP 402 'Payment Required' status code. When an agent requests a paid resource, the server returns 402 with payment instructions, the agent signs a stablecoin transaction, attaches the proof, and retries. The server verifies and returns the data, with zero protocol fees.
Adoption is real and measurable: by March 2026 it had processed over 119 million transactions on Base and 35 million on Solana, and the Coinbase-hosted facilitator settles ERC-20 payments across Base, Polygon, Arbitrum, World, and Solana with a free tier. TypeScript, Go, and Python SDKs are available.
Why builders care
Monetizing an API or an agent used to require accounts, keys, and billing plumbing. x402 collapses that into one HTTP response, which is the missing payment rail for the agent economy. It is a small, learnable primitive you can wire into a project this week.
Build something that charges per call and deploy it hands-on at deployr.airdropsea.com.
Ask the Problem Solver what you can actually build, earn, or fix with this.