x402
x402 is an open payment protocol that uses the HTTP 402 status code to enable per-request USDC payments on the web. Any website or API can require a small USDC payment before serving content. The ecosystem includes SDKs for building x402 clients and servers, infrastructure providers that handle payment verification, and integrations with major platforms. Most x402 activity runs on Base.
SDK
4Coinbase x402 SDK
The reference implementation for x402. TypeScript SDK for building clients and servers that handle per-request USDC payments.
thirdweb x402
x402 middleware from thirdweb that integrates with their smart contract and wallet tooling.
x402 Python SDK
Python library for building x402 clients and servers. Ideal for AI agents and data services.
x402 Go SDK
Go implementation of the x402 protocol for high-performance servers and infrastructure.
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