x402

Definition

An HTTP 402 payment protocol in which a server states its price, the client pays (usually in stablecoins) and retries; governed by the x402 Foundation.

Example

The x402 Foundation launched operations on 14 Jul 2026 with 40 members. x402.org, read 4 Nov 2026.

Where it appears in the sourced facts

• The initial version supports pull payments such as cards; real-time bank push payments (UPI, PIX) are roadmap items; x402 samples exist through the A2A x402 extension. ap2-protocol.org, read 4 Nov 2026. In Agent Payments Protocol (AP2).
• The June release cites open standards like x402 and "Machine Payments Protocol compatibility". mastercard.com, read 4 Nov 2026. In Mastercard Agent Pay for Machines (AP4M).
• On 20 Oct 2026 at Cloudflare Connect, Mastercard said AP4M builds on x402 and opened Early Access with buyer- and seller-side APIs, a toolkit, sandbox and documentation. mastercard.com, read 4 Nov 2026. In Mastercard Agent Pay for Machines (AP4M).
• American Express is a premier member of the x402 Foundation (operational launch 14 Jul 2026). x402.org, read 4 Nov 2026. In American Express Agentic Commerce Experiences (ACE).
• x402.org says a server responds with HTTP 402 when a request arrives without payment, prompting the client to pay and retry; it lists zero protocol fees. x402.org, read 4 Nov 2026. In x402.

Nearby terms

• HTTP 402 Payment Required
• Facilitator
• SD-JWT
• All terms