x402
Cardano & ADATechnical
An open web standard reviving HTTP 402 ("Payment Required") for autonomous AI agents and machine-to-machine micropayments. Officially supported on Cardano via the @x402/cardano SDK, enabling clients and agents to pay for web APIs, compute, and digital resources per request in ADA, USDM, or native tokens without accounts or API keys.
Also known as: HTTP 402, x402 standard, 402 Payment Required, @x402/cardano, agentic payments
Official standard maintained under the Linux Foundationx402 Specification