Coinbase releases x402, an open protocol for stablecoin payments over HTTP

Coinbase/Base

On May 6, 2025, Coinbase launched x402, an open standard that embeds stablecoin payments in HTTP requests using the long-unused HTTP 402 'Payment Required' status code. APIs, apps, and AI agents can pay per request without accounts or cards. AWS, Anthropic, Circle, and NEAR contributed to the launch.

• Server returns 402 with payment terms; client signs token-transfer authorization and retries with payment header.
• Enables machine-to-machine settlement; minimal code integration for both humans and AI agents.
• Unlocks automated internet economy for AI agents, APIs, and applications requiring seamless value exchange.
• Coinbase open-sourced x402 in May 2025; later (April 2026) donated to x402 Foundation at Linux Foundation.