# ACP Explained: The Agentic Commerce Protocol A neutral guide to the Agentic Commerce Protocol (ACP): what it is, who maintains it, how payment flows through a Shared Payment Token, what is actually live, and how it relates to AP2, MCP, and UCP. URL: https://agenticcommerceatlas.com/learn/acp-explained/ Author: Andrew McPherson | Publisher: Agentic Commerce Atlas Updated: 2026-10-31 --- The Agentic Commerce Protocol (ACP) is an open standard for letting an AI agent complete a purchase with a merchant. Its purpose is narrow and practical: give agents and stores a shared language for checkout so a merchant builds one integration instead of a different one for every AI platform. ## Who is behind it ACP was launched on 29 September 2025 by **OpenAI and Stripe**, and it powered the original "buy it in ChatGPT" Instant Checkout experience. The project's README describes **OpenAI and Stripe** as the founding maintainers that jointly govern the project, while `MAINTAINERS.md` lists **OpenAI, Stripe, and Meta** as lead maintainers. Stripe's own ACP documentation now also describes the standard as created by Stripe, OpenAI, and Meta, which is the clearest first-party confirmation of Meta's role. **Meta** is also a member of the rival UCP Tech Council, so it remains tied to both commerce-layer efforts. ACP is licensed under **Apache 2.0**, requires a contributor license agreement, and is governed through a public proposal process, with a stated future path of "neutral foundation stewardship as ecosystem matures." ## What ACP actually does ACP standardizes the checkout conversation between a buyer's agent and a merchant. The specification covers agentic checkout (creating, updating, and completing a checkout session), cart and product feed, delegated payment, delegated authentication via OAuth 2.0, and orders and webhooks for confirmation, shipping, delivery, and refunds. Crucially, the merchant stays in control. They remain the merchant of record and keep the customer relationship, fulfillment, returns, tax, and support. ACP is the handshake at the checkout, not a takeover of the store. It is just as important to be clear about what ACP is **not**. It is not a tool-discovery protocol, that job belongs to MCP. It is not an agent-identity or attestation layer. And it is not a crypto-settlement protocol. ACP describes itself as compatible with both plain REST and MCP, and it deliberately leaves those adjacent layers to other standards. ## How payment flows This is the part most people get wrong, so it is worth being precise. When a buyer checks out, the payment service provider (Stripe in the reference implementation) issues a **Shared Payment Token**: a credential scoped to one specific seller, under usage limits that carry a maximum chargeable amount, a currency, and an expiry. For a one-time purchase it is single-use; Stripe's documentation now also describes recurring SPTs, which carry a recurring interval in their usage limits and can be charged again by the same seller within those limits. OpenAI's own description is that it "prepares a one-time delegated payment request and sets a maximum chargeable amount and expiry based on what the user has selected to buy," so in practice the ceiling is set to the cart the buyer approved rather than bound by the protocol to an exact total. The agent, for example ChatGPT, passes that token to the merchant through the ACP interface, and the merchant charges it through their own processor. Stripe's Shared Payment Token is the first Delegated Payment Spec-compatible implementation and is available in the US, Canada, and select European countries; OpenAI says more payment service providers are coming. The point of the design is that the agent never sees the buyer's actual card details, and the token cannot be reused for a different amount or a different merchant. Merchants already on Stripe can enable it with minimal code; merchants on other processors can adopt it through the Shared Payment Token API or the protocol's Delegated Payments specification.
  1. 1BuyerPay

    The buyer pays through the inline checkout.

  2. 2ProviderTokenize

    The payment provider issues a token, scoped to one merchant and one total.

  3. 3AgentHand off

    The agent passes the token on, never the card.

  4. 4MerchantCharge

    The merchant charges it; the token cannot be reused.

A single-use token moves instead of the card, locked to one merchant and one amount.
## What is actually live Here the gap between announcement and reality matters, and it is the single most misreported part of ACP's story. **Etsy** was genuinely live from day one for US buyers. **Walmart** announced a partnership with OpenAI on 14 October 2025 under which customers and Sam's Club members would "soon" be able to shop Walmart through ChatGPT using Instant Checkout. **PayPal** announced on 28 October 2025 that it would adopt ACP to bring its merchant network into ChatGPT, using the delegated payments API. Note that both were announcements of intent, not confirmations of a live integration. The widely repeated claim that "over a million Shopify merchants" went live is not accurate. Both OpenAI's and Stripe's launch announcements described those merchants as "coming soon," and only a small number of Shopify merchants actually integrated. What happened next is widely reported in a stronger form than OpenAI's own words support, so it is worth separating the two. In its own post of **24 March 2026**, OpenAI said that "the initial version of Instant Checkout did not offer the level of flexibility that we aspire to provide, so we're allowing merchants to use their own checkout experiences while we focus our efforts on product discovery," that merchants wanting deeper native experiences "continue to have the option to develop ChatGPT apps" (OpenAI now calls these **plugins**), and that it was "expanding the Agentic Commerce Protocol (ACP) to support product discovery." The flatter line widely quoted in trade press, that "Instant Checkout is moving to Apps," came from an OpenAI spokesperson rather than that post, and reads as more of a migration than OpenAI described. Two things follow. The center of gravity in ChatGPT did move from in-chat buying to discovery that hands the shopper to the merchant's own checkout. But **Instant Checkout was not retired**: OpenAI's current developer documentation states that "Instant Checkout in ChatGPT is currently available to approved partners," still documents a checkout experience "embedded in ChatGPT's UI," and carries an application form for merchants, with no published merchant or region list. The lesson is that adoption of a standard depends as much on the host surface promoting it as on the standard itself. The specification is officially in **beta**. ACP uses date-based versioning, and the latest stable version is **2026-04-17**. The released versions to date are `2025-09-29` (initial release), `2025-12-12` (fulfillment enhancements), `2026-01-16` (capability negotiation), `2026-01-30` (extensions, discounts, payment handlers), and `2026-04-17` (cart, feed, orders, authentication, and MCP), with current work staged in an `unreleased` directory. Note that ACP's own documentation site has not always kept pace with the repository, so the `spec/` directory on GitHub is the authoritative record of what is current. ## Where it sits in the wider landscape ACP is the checkout layer. Around it sit several other standards that mostly compose with it rather than replace it: [AP2](/learn/ap2-explained/) handles payment authorization and trust, MCP handles discovery, and x402 handles machine-native stablecoin settlement. The one genuine rival at the commerce-semantics layer is Google's **Universal Commerce Protocol (UCP)**, launched in January 2026 with backers including Shopify, Etsy, Target, Wayfair, and Walmart, which aims at the broader shopping journey rather than checkout alone. In April 2026 its Tech Council (now the Shopping Tech Council) expanded to sixteen seats across ten companies as Amazon, Meta, Microsoft, Salesforce, and Stripe joined, and on 28 April 2026 Stripe also joined UCP's Governing Council alongside permanent members Google and Shopify. So Stripe now co-maintains ACP and sits on UCP's Governing Council, its Shopping Tech Council and its Payments Tech Council (seated 2 September 2026), and Meta is a lead maintainer of ACP and a member of UCP's Shopping Tech Council. That is a clear sign the standards are still settling and that the largest players are hedging rather than picking a side. For a side-by-side, see [ACP vs UCP](/learn/acp-vs-ucp/); for the full map, see [the protocol stack](/learn/agentic-commerce-protocol-stack/). ## What it means for you If you are a merchant, ACP is one of the two checkout-layer standards worth tracking, alongside UCP. Adopting it is what makes your products buyable from an agent surface that supports it; for a step-by-step integration, see [how to implement ACP](/learn/implement-acp/). If you are a builder, treat ACP as the checkout handshake and pair it with a discovery layer and a payment-authorization layer rather than expecting it to do everything. And whatever you read about adoption numbers, check whether a partner is actually live or merely announced. ## Frequently asked questions ### Who maintains ACP? ACP's README describes OpenAI and Stripe as the founding maintainers that jointly govern the project, while MAINTAINERS.md lists OpenAI, Stripe, and Meta as lead maintainers. Meta also sits on the rival UCP Tech Council, so it remains tied to both commerce-layer efforts. ACP is licensed under Apache 2.0, with a stated path toward broader community governance. ### Did a million Shopify merchants go live on ACP? No. The 'over a million Shopify merchants' line was described as 'coming soon' in both the OpenAI and Stripe launch announcements, not as a live fact. Only a small number of Shopify merchants integrated, and on 24 March 2026 OpenAI said the first version of Instant Checkout had not offered the flexibility it wanted, so it would let merchants use their own checkout experiences while OpenAI focused on product discovery, and it expanded ACP to cover discovery. Etsy was genuinely live from launch. Note that Instant Checkout itself was not retired: OpenAI's developer documentation still describes it as available to approved partners. ### How does payment work in ACP without sharing card details? The buyer pays through an inline checkout and the payment service provider issues a Shared Payment Token scoped to one specific merchant and one cart total. The agent passes that token to the merchant, who charges it. The raw card credentials are never exposed to the agent. ## Primary sources - OpenAI: Buy it in ChatGPT: https://openai.com/index/buy-it-in-chatgpt/ - Stripe and OpenAI launch Instant Checkout: https://stripe.com/newsroom/news/stripe-openai-instant-checkout - Agentic Commerce Protocol documentation: https://docs.stripe.com/agentic-commerce/acp - Agentic Commerce Protocol specification: https://github.com/agentic-commerce-protocol/agentic-commerce-protocol - OpenAI and PayPal team up for Instant Checkout: https://newsroom.paypal-corp.com/2025-10-28-OpenAI-and-PayPal-Team-Up-to-Power-Instant-Checkout-and-Agentic-Commerce-in-ChatGPT - OpenAI retreats on Instant Checkout: https://www.modernretail.co/technology/shopify-says-purchases-are-coming-inside-chatgpt-through-agentic-storefronts-as-openai-retreats-on-instant-checkout/ - Amazon, Meta, Microsoft, Salesforce, and Stripe join the UCP Tech Council: https://www.newsfilecorp.com/release/294133/Amazon-Meta-Microsoft-Salesforce-and-Stripe-Join-the-Universal-Commerce-Protocol-Tech-Council - ACP MAINTAINERS.md (lead maintainers): https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/blob/main/MAINTAINERS.md - Walmart partners with OpenAI to create AI-first shopping experiences: https://corporate.walmart.com/news/2025/10/14/walmart-partners-with-openai-to-create-ai-first-shopping-experiences - UCP announcements (Tech Council and Governing Council): https://ucp.dev/documentation/announcements/ - Agentic Commerce key concepts (Instant Checkout availability, Delegated Payment Spec): https://developers.openai.com/commerce/guides/key-concepts - Shared payment tokens: https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens - Powering Product Discovery in ChatGPT: https://openai.com/index/powering-product-discovery-in-chatgpt/