UCP vs ACP: what Shopify merchants need to know

If you’ve read anything about agentic commerce this year, you’ve run into two acronyms: UCP and ACP. Both are open standards for AI agents that find and buy products. Both have large companies behind them. If you sell on Shopify, you don’t have to implement either one. It’s still worth knowing what they are, because they decide what an AI agent can see and do with your store.

The short version

	UCP	ACP
Full name	Universal Commerce Protocol	Agentic Commerce Protocol
Who built it	Shopify and Google, with retailers	OpenAI and Stripe
Announced	January 11, 2026	September 29, 2025
Scope	Discovery through checkout and orders	Commerce flows between buyer, agent and business, starting with checkout
Where it shows up	Shopify Catalog, Google AI Mode and Gemini checkout	ChatGPT shopping; Microsoft says it’s adopting ACP for Copilot Checkout
License	Open standard	Apache 2.0

UCP: Universal Commerce Protocol

Shopify announced UCP on January 11, 2026 as “a new open standard co-developed with Google to bring commerce to agents at scale” (Shopify news). Google’s announcement the same day says it “was co-developed with industry leaders including Shopify, Etsy, Wayfair, Target and Walmart, and endorsed by more than 20 others across the ecosystem” (Google).

The spec site calls it “the common language for platforms, agents, and businesses” (ucp.dev). Shopify’s engineering team describes the scope: UCP “defines the discovery and negotiation mechanisms between agent and merchant, as well as the core capabilities that make commerce programmable” (Shopify Engineering). In plain terms, it covers the whole trip: searching a catalog, building a cart, checking out and following an order. It works alongside other agent standards, including Model Context Protocol (MCP), Agent2Agent (A2A) and the Agent Payments Protocol (AP2).

Where you already use it

Two places, whether you knew it or not:

• Shopify Catalog. Shopify’s developer docs say both its Global Catalog, which searches across all Shopify stores, and its Storefront Catalog, scoped to a single store, “implement the UCP Catalog capability” (Shopify Catalog docs). When an agent searches for products through Shopify, it’s speaking UCP. We explain the catalog itself in What is Shopify Catalog?
• Google checkout. Google said UCP would “power a new checkout feature on eligible Google product listings in AI Mode in Search and the Gemini app.” By September 2026 Google said “UCP already enables direct checkout for hundreds of thousands of brands and retailers across Google” (Google, Sep 16, 2026).

ACP: Agentic Commerce Protocol

OpenAI introduced ACP on September 29, 2025, alongside Instant Checkout in ChatGPT, “powered by the Agentic Commerce Protocol, built with Stripe” (OpenAI). The spec site describes it as “an open standard for programmatic commerce flows between buyers, AI agents, and businesses,” released under the Apache 2.0 license (agenticcommerce.dev).

ACP started narrower than UCP. Its first job was checkout: letting an agent start a purchase with a business, pass payment details securely, and leave the business as merchant of record. It isn’t only OpenAI’s: when Microsoft announced Copilot Checkout in January 2026, it said it “is adopting open standards like the Agentic Commerce Protocol (ACP)” (Microsoft Advertising blog).

What happened to Instant Checkout

In March 2026, OpenAI stepped back from its own checkout, while keeping ACP. The same post describes new shopping experiences in ChatGPT “powered by the Agentic Commerce Protocol,” and explains the checkout change: “We’ve found 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” (OpenAI, Mar 24, 2026).

For Shopify stores, ChatGPT is now “a discovery-focused referrer platform,” and shoppers pay on your own checkout in an in-app browser (Selling on ChatGPT). ACP still sits behind ChatGPT’s shopping, but for a Shopify store the connection runs through Shopify Catalog, and there’s nothing to set up on your side. We cover the current setup in Selling on ChatGPT with Shopify.

Is it UCP or ACP?

For a Shopify merchant, it isn’t a choice. Shopify decides which protocols it supports and connects your store to the channels on your behalf through agentic storefronts. You don’t write code for either one.

What you do control is the same for both: the product data the protocols carry. Whatever standard an agent uses, it’s passing along your titles, prices, availability, and a description that Shopify’s catalog may have “generated or enriched” with AI (Global Catalog docs). A protocol moves data accurately. It doesn’t check whether the data is right.

When the protocols matter to you

A few cases where it’s worth knowing more:

• You also sell outside Shopify. Google’s Merchant Center has its own UCP setup for checkout, with requirements that apply to your feed (Google Merchant Center help).
• You’re building a custom agent or app. Shopify’s catalog docs cover the UCP endpoints, including a per-store endpoint at your own domain.
• You’re evaluating an “agent-ready” tool. Several apps offer to generate UCP manifests or agent files. For a Shopify store, check what Shopify already provides before paying for it. Shopify serves agent discovery files automatically (Shopify Catalog and product discovery), and its catalog already speaks UCP.

Common questions

Do I need to enable UCP on my Shopify store?

No. If your products meet the Shopify Catalog requirements, they’re available to agents through Shopify’s catalog, which implements UCP. Channel settings live under Sales channels > Agentic (Shopify agentic storefronts: a settings guide).

Is one protocol better for sales?

There’s no public data comparing them, and for a Shopify store the question doesn’t come up. What affects whether an agent recommends your product is covered in How AI shopping agents choose which products to show.

Will these standards change?

Almost certainly. Both are young, and the ChatGPT checkout change shows how quickly the products built on them shift. The spec sites list versions, and ucp.dev already has a draft for lodging.

Whatever the protocol, the thing you can check is what the data says. Hearsay reads what Shopify’s catalog tells AI agents about each of your products and flags claims that contradict your copy. The free scan runs on 5 products.