Coinbase's x402 is a payment primitive designed to integrate directly into HTTP, reviving the HTTP status code 402 "Payment Required." This mechanism allows servers to respond to client requests with machine-readable payment terms, including amount, asset, network, and recipient. Clients pay in USDC and retry with a cryptographic payment proof. By December, the protocol had processed 75 million transactions worth $24 million for paid APIs and AI agents. Version 2 adds modularity with network-agnostic identifiers and a "Bazaar" discovery layer. Cloudflare will integrate x402 and co-launch the x402 Foundation, while Google Cloud's Agent Payments Protocol uses x402 for on-chain settlement. Solana and Base are the production networks. The protocol's complexity lies in the facilitator, which monitors blockchain networks and verifies payments.

Coinbase's x402 is a payment primitive designed to integrate directly into HTTP, reviving the HTTP status code 402 "Payment Required." This mechanism allows servers to respond to client requests with machine-readable payment terms, including amount, asset, network, and recipient. Clients pay in USDC and retry with a cryptographic payment proof. By December, the protocol had processed 75 million transactions worth $24 million for paid APIs and AI agents. Version 2 adds modularity with network-agnostic identifiers and a "Bazaar" discovery layer. Cloudflare will integrate x402 and co-launch the x402 Foundation, while Google Cloud's Agent Payments Protocol uses x402 for on-chain settlement. Solana and Base are the production networks. The protocol's complexity lies in the facilitator, which monitors blockchain networks and verifies payments.