UCP, the Universal Commerce Protocol, is the open standard Shopify co-developed with Google in January 2026. ACP, the Agentic Commerce Protocol, is the open standard OpenAI and Stripe released in September 2025. Both keep the merchant as merchant of record. They differ on who governs them, how much of the purchase they cover, and which AI surfaces use them.
- A Shopify merchant implements neither protocol directly: the Agentic Storefronts channel connects the store to AI surfaces from the admin.
- UCP covers catalog, cart, checkout, identity linking and orders. ACP began with checkout and delegated payment and added cart, feeds and orders in its 2026-04-17 version.
- OpenAI scaled back in-chat Instant Checkout in March 2026. Shopify purchases from ChatGPT complete on the merchant's own checkout.
Sell on Shopify, or build apps for the people who do, and two acronyms keep turning up: UCP and ACP. Shopify's Universal Commerce Protocol and OpenAI's Agentic Commerce Protocol are both open standards for letting an AI agent find a product and buy it on someone's behalf. They overlap far more than the "protocol war" coverage suggests, and the differences that matter to a merchant are few.
The comparison table comes first, followed by what each protocol is, who controls it, what a merchant has to do, what changes for app builders, and a short list of what to do about it.
| Dimension | UCP (Shopify and Google) | ACP (OpenAI and Stripe) |
|---|---|---|
Released | 11 January 2026 | 29 September 2025 |
Who governs the spec | Domain tech councils; the shopping council includes Google, Shopify, Etsy, Meta, Amazon, Microsoft, Stripe, Salesforce, Target and Wayfair | OpenAI and Stripe as founding maintainers, with Meta also listed as a lead maintainer |
Status | Dated releases; v2026-08-25 is the most recent | Labelled beta; stable version 2026-04-17 |
Scope | Catalog search, cart, checkout, identity linking, orders; lodging and food drafts | Checkout, delegated payment, cart, product feed, orders, authentication |
Merchant of record | The merchant | The merchant |
Payments | Payment handlers negotiated per merchant, any processor; supports Google's AP2 | A scoped payment token passed to the merchant's own processor |
Transports | REST, JSON-RPC, MCP, A2A | REST (OpenAPI) and MCP |
Where it runs | Google AI Mode and Gemini checkout; Shopify's agent tools and Catalog | ChatGPT commerce flows; reference implementations from OpenAI and Stripe |
What a Shopify merchant builds | Nothing: Agentic Storefronts handles it | Nothing: Shopify connects the store to ChatGPT through its Catalog |
Sources: ucp.dev, the UCP release notes and maintainers list, the ACP repository (README, MAINTAINERS and changelog), and Shopify's 24 March 2026 announcement. All retrieved 29 September 2026.
What is Shopify's
Universal Commerce
Protocol?
The Universal Commerce Protocol is an open standard co-developed by Shopify and Google and announced on 11 January 2026. It defines how an AI agent searches a merchant's catalog, builds a cart, checks out, links a buyer's account and tracks the order. The spec is Apache 2.0 licensed, and the merchant stays merchant of record.
UCP works by negotiation. A merchant publishes a profile at a well-known URL listing the capabilities it supports (checkout, fulfillment, discounts) and the payment handlers it accepts. The agent publishes its own profile, and the protocol settles the overlap, so nobody writes a custom integration per store. Shopify's UCP page lists discounts, loyalty programs, subscriptions and fulfillment options as supported.
It runs over REST, JSON-RPC, MCP and Google's Agent2Agent protocol, and supports Google's Agent Payments Protocol (AP2) for payment. Versions are dated. The 25 August 2026 release added 3DS2 authentication, deposits and installment schedules, and the groundwork for grocery, food and lodging. On the Shopify side, the developer docs describe the agent layer as a set of UCP-compliant MCP servers.
What is OpenAI's
Agentic Commerce
Protocol?
The Agentic Commerce Protocol is an open standard that OpenAI and Stripe released on 29 September 2025 so ChatGPT and other agents can complete purchases with merchants. Its core is a checkout API plus a delegated payment spec. The agent hands the merchant a narrowly scoped payment token, and the merchant charges it through its own processor as merchant of record.
Stripe's version of that token is the Shared Payment Token, scoped to one merchant and one basket total. Merchants can process it through Stripe or through another provider. The agent never becomes the seller, which the spec's own README states in as many words.
ACP is labelled beta and ships dated versions too. The 2026-04-17 release added a cart, a product feed API that merchants push to the agent, order updates, authentication and MCP support. A protocol that started as checkout plus payment has grown toward the same lifecycle UCP covers.
Who controls
UCP and ACP?
Neither protocol belongs to one company, but their origins still show. ACP's founding maintainers are OpenAI and Stripe, and its maintainers file adds Meta as a lead maintainer. UCP runs through domain tech councils, and its shopping council seats people from Google, Shopify, Etsy, Meta, Amazon, Microsoft, Stripe, Salesforce, Target and Wayfair.
Two names sit on both lists. Stripe maintains ACP and holds a seat on UCP's shopping council, and Meta appears in both governance files. That overlap tells you where this is heading. Payment companies and large platforms are hedging across both standards, because neither standard owns every surface a buyer uses.
The more useful question is which surfaces use which standard. AI Mode in Google Search and the Gemini app sell through UCP. OpenAI's developer docs present ACP as the protocol behind ChatGPT's commerce flows, including checkout and product feeds. Shopify connects its merchants to both kinds of surface from one admin, which is why the choice rarely lands on a Shopify merchant's desk.
What does a Shopify
merchant have
to do?
Very little on the protocol side. Shopify's Agentic Storefronts sales channel is active by default for eligible stores. It connects products to ChatGPT, Microsoft Copilot, AI Mode in Google Search and the Gemini app, and you manage it under Sales channels > Agentic in the admin. You never implement UCP or ACP yourself.
Where the purchase finishes depends on the surface. Shopify's help center says ChatGPT shoppers pay on your online store checkout, inside ChatGPT's in-app browser or in a new tab. Other channels can use a Shopify-powered direct checkout if you switch it on. Shopify's March 2026 announcement adds that the ChatGPT route carries no transaction fees beyond standard processing, tags orders with ChatGPT referral attribution, and leaves you as merchant of record.
Under either protocol, the work that moves results is product data. Agents read titles, variants, attributes, prices and inventory from Shopify Catalog, so a gap there is a gap in every AI channel at once. I cover the data side in how products get picked, or ignored, in ChatGPT, and the channel setup in the Agentic Storefronts explainer.
Brands that do not run their store on Shopify can still list in Shopify Catalog through Shopify's Agentic plan, which opened to every brand in January 2026 and became publicly available that March.
If you are deciding which AI channels to keep on, or how your app should show up in them, I can save you a few wrong turns. The form takes two minutes.
What happened to
checkout inside
ChatGPT?
OpenAI launched Instant Checkout, the first ACP product, in ChatGPT on 29 September 2025, starting with US Etsy sellers and Shopify merchants billed as coming soon. By March 2026 OpenAI had changed course. It said the first version lacked the flexibility it wanted, let merchants use their own checkout, and turned its effort to product discovery (CNBC, 24 March 2026).
That was a product decision about one checkout, and the protocol carried on: ACP shipped its 2026-04-17 version afterwards, and OpenAI pointed merchants toward product feeds and ChatGPT apps for deeper integrations. The dated story of who sells inside which assistant belongs in the AI checkout tracker. For why it stalled, read the Instant Checkout postmortem; for the app route, ChatGPT's second swing at shopping.
What do UCP and ACP
mean for Shopify
app developers?
For most Shopify apps, UCP is the protocol that reaches your merchants, because it is what Shopify's agent layer speaks. Since the Spring '26 Edition, any developer can build on it without approval. You register an agent profile, call the public MCP endpoint, and work from catalog search through cart, checkout and order tracking.
Access is tiered. Shopify's docs describe agents building a cart and handing the buyer to the merchant's checkout, with higher trust tiers allowed to complete checkouts directly. Order events come back as UCP-shaped webhooks covering fulfillment, refunds, returns, exchanges and cancellations.
The practical test for an app is whether its value survives a buyer who never sees the storefront theme. Features that live in data travel: reviews, product attributes, subscription terms, loyalty balances, discount logic. Features that exist only as theme UI do not travel on their own. I work through that split category by category in which app categories get bypassed when agents do the buying.
On the merchant side, the surface for apps is Sidekick. Sidekick App Extensions let an app expose its data and actions inside Sidekick conversations, and the launch partners included Klaviyo, Judge.me, Loop, Smile and Yotpo. More in Sidekick versus your app stack.
Founders building their own shopping agent face a real choice. UCP reaches Shopify's catalog and Google's surfaces, while ACP's reference implementations come from OpenAI and Stripe. Check each spec's capability list against the flows you need before you commit engineering time to either.
What should merchants
and app founders
do about it?
Merchants should confirm which AI channels are on, fix product data, and read AI orders by their referral attribution. App founders should map each feature to a UCP capability or extension and decide whether Sidekick is their merchant-facing surface. Neither group needs to pick a protocol.
For merchants
Open Sales channels > Agentic and decide which channels stay on, since eligible stores start with the channel switched on. Audit variant attributes, identifiers, images, prices and inventory accuracy. Report AI-referred orders on their own line and judge them on incremental margin, the way you would any new channel. Test your checkout inside a mobile in-app browser, since that is where ChatGPT buyers pay.
For app founders
List which of your features are data and which are theme UI, then check the data ones against UCP's capabilities and extensions. If you build agents, register an agent profile and prototype against Shopify's MCP endpoints. Watch both spec repositories: a new dated version is when capabilities change, and it is a better signal than any launch post.
I helped build and scale the Partner Program at Shopify, and later ran brands on the platform. The pattern I saw repeat with every new channel is that merchants overinvest in the integration story and underinvest in the data, and in agentic channels the data is the part the agent reads. For the wider merchant strategy, read agentic commerce for Shopify brands, and for which app categories gain or lose, the 2026 ecosystem value map.
What people ask
about UCP
and ACP.
Q: What is the difference between UCP and ACP?
UCP, the Universal Commerce Protocol, was co-developed by Shopify and Google and covers catalog, cart, checkout, identity linking and orders. ACP, the Agentic Commerce Protocol, was released by OpenAI and Stripe and centres on checkout and delegated payment, later adding cart, feeds and orders. Both keep the merchant as merchant of record. They differ mainly in governance and in which AI surfaces use them.
Q: Does Shopify use the Agentic Commerce Protocol?
Shopify's agent tooling is built on UCP, which it co-developed. For ChatGPT, Shopify connects merchants through Shopify Catalog and Agentic Storefronts, and buyers pay on the merchant's own checkout. Shopify's March 2026 announcement of that ChatGPT connection does not name ACP, so a Shopify merchant has nothing ACP-specific to set up.
Q: What is OpenAI's agentic commerce strategy?
OpenAI released ACP with Stripe in September 2025 and launched Instant Checkout in ChatGPT the same day. In March 2026 it scaled that back, letting merchants use their own checkout while ChatGPT concentrates on product discovery, merchant product feeds and retailer apps. ACP itself kept evolving, with a stable version dated 2026-04-17.
Q: Do Shopify merchants need to do anything to sell through AI agents?
Not on the protocol side. Agentic Storefronts is active by default for eligible stores and is managed under Sales channels > Agentic in the Shopify admin. The useful work is product data quality, choosing which AI channels to keep on, and tracking AI-referred orders separately so you can judge them on margin.
Q: Who is the merchant of record under UCP and ACP?
The merchant, under both. UCP's documentation says businesses remain the merchant of record and own the customer relationship, and ACP's specification describes agents transacting without becoming merchant of record. Payment tokens pass to the merchant, who charges them through its own processor, so tax, refunds and liability stay with the merchant.
Pick the channels that keep your customer yours.
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