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Coinbase's x402 Protocol Adds Native Payment Method for APIs and AI Agents
Coinbase's x402 protocol, built on top of the HTTP standard, allows APIs, apps, and AI agents to pay for services in stablecoins like USDC. The protocol, launched in May 2025, is the first major effort to use the 402 'Payment Required' code from the 1990s. It is now supported by multiple chains including Ethereum, Solana, Polygon, Arbitrum, and traditional card payments. The protocol is not a blockchain or a coin, but a set of rules for message formats and request-response flow that any server or client can follow.