---
title: "x402, defined | Agent Ready Checkout"
description: "x402: 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."
canonical: https://agentreadycheckout.com/glossary/x402
site: "Agent Ready Checkout"
last_updated: 2026-11-04
section: "Glossary"
---

# x402, defined | Agent Ready Checkout

> x402: 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.

Source: https://agentreadycheckout.com/glossary/x402
Site: Agent Ready Checkout
Last reviewed: 2026-11-04

Glossary

# x402

In short

x402: 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. x402 appears in 23 sourced facts on this site, the first in Agent Payments Protocol (AP2). Example: The x402 Foundation launched operations on 14 Jul 2026 with 40 members.

## 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](https://x402.org/linux-foundation-announces-operational-launch-of-x402-foundation-to-standardize-internet-native-payments-for-ai-agents-and-applications/), 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](https://ap2-protocol.org/), read 4 Nov 2026. In [Agent Payments Protocol (AP2)](https://agentreadycheckout.com/protocols/ap2).
-   The June release cites open standards like x402 and "Machine Payments Protocol compatibility". [mastercard.com](https://www.mastercard.com/us/en/news-and-trends/press/2026/june/mastercard-launches-agent-pay-for-machines.html), read 4 Nov 2026. In [Mastercard Agent Pay for Machines (AP4M)](https://agentreadycheckout.com/protocols/agent-pay-for-machines).
-   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](https://www.mastercard.com/global/en/news-and-trends/press/2026/october/Mastercard-Agent-Pay-for-Machines-in-action.html), read 4 Nov 2026. In [Mastercard Agent Pay for Machines (AP4M)](https://agentreadycheckout.com/protocols/agent-pay-for-machines).
-   American Express is a premier member of the x402 Foundation (operational launch 14 Jul 2026). [x402.org](https://x402.org/linux-foundation-announces-operational-launch-of-x402-foundation-to-standardize-internet-native-payments-for-ai-agents-and-applications/), read 4 Nov 2026. In [American Express Agentic Commerce Experiences (ACE)](https://agentreadycheckout.com/protocols/amex-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](https://www.x402.org/), read 4 Nov 2026. In [x402](https://agentreadycheckout.com/protocols/x402).

## Nearby terms

-   [HTTP 402 Payment Required](https://agentreadycheckout.com/glossary/http-402-payment-required)
-   [Facilitator](https://agentreadycheckout.com/glossary/facilitator)
-   [SD-JWT](https://agentreadycheckout.com/glossary/sd-jwt)
-   [All terms](https://agentreadycheckout.com/glossary)

## Sources

1.  [x402 Foundation operational launch](https://x402.org/linux-foundation-announces-operational-launch-of-x402-foundation-to-standardize-internet-native-payments-for-ai-agents-and-applications/), read 4 Nov 2026
2.  [AP2 protocol site](https://ap2-protocol.org/), read 4 Nov 2026
3.  [Mastercard launches Agent Pay for Machines](https://www.mastercard.com/us/en/news-and-trends/press/2026/june/mastercard-launches-agent-pay-for-machines.html), read 4 Nov 2026
4.  [Watch Mastercard Agent Pay for Machines in action](https://www.mastercard.com/global/en/news-and-trends/press/2026/october/Mastercard-Agent-Pay-for-Machines-in-action.html), read 4 Nov 2026
5.  [x402.org](https://www.x402.org/), read 4 Nov 2026

Last reviewed 4 Nov 2026

## Edition

Matrix edition of 4 Nov 2026.

Reviewed 4 Nov 2026, [5 sources](#sources-h).

## Method

[How cells, sources and read dates are defined](https://agentreadycheckout.com/method)