Universal Commerce Protocol (UCP) on Shopify

The Universal Commerce Protocol (UCP) is an open standard that lets AI agents search a store's catalog, build a cart and check out in one common language. Google launched it with Shopify in January 2026, and Shopify turns it on by default for its merchants. Here is what UCP covers, how it differs from ACP and AP2, where shoppers meet it today, and what it changes for a Shopify store.

This article is part of our guide to agentic commerce on Shopify. Every outside fact links to its source, checked in October 2026.

What the Universal Commerce Protocol is

Google announced UCP on January 11, 2026, at the NRF retail conference (Google). It was co-developed with Shopify, Etsy, Wayfair, Target and Walmart, and more than 20 companies endorsed it at launch, including Adyen, American Express, Best Buy, Mastercard, Stripe, The Home Depot and Visa. Shopify published its own engineering write-up the same day.

The circle has grown since. The UCP website now lists Amazon, Microsoft, Meta, Salesforce and Stripe among the co-developers of its shopping standard, next to the five launch partners.

UCP is open source, under the Apache 2.0 license. Its governance rules give permanent seats to its two founding organizations, Google and Shopify, and Stripe joined its governing council in April 2026. Versions are named by date: the current one is 2026-08-25 (UCP releases).

What UCP standardizes

The building blocks

UCP describes the steps of a purchase as capabilities that a store can offer and an agent can use (UCP core concepts):

• Catalog search and lookup: find products and check their details, price and availability. These were added in April 2026.
• Cart: build and update a cart.
• Checkout: turn the cart into a purchase.
• Identity linking: connect the shopper's account with the store, through OAuth 2.0.
• Orders: follow an order after the purchase.

Extensions add discounts, fulfillment, buyer consent, loyalty and payment options. The August 2026 version added store-location search, for groceries.

How an agent and a store agree

Each side publishes a profile. The store publishes its own at a standard address on its domain (/.well-known/ucp), listing what it supports. The agent sends the address of its own profile with every request. The store then uses what both support, at the latest version both know. No prior registration is needed: any agent with a profile the store can read may talk to it, and a store can add its own checks for partners it knows (UCP core concepts).

UCP works over several transports: REST, MCP (Model Context Protocol), A2A (Agent2Agent), and an embedded checkout that comes from Shopify's Checkout Kit. In every case, the merchant remains the merchant of record (UCP).

UCP, ACP, AP2, MCP and A2A: who does what

Agentic commerce has several protocols, and they don't compete on the same layer.

Sources: ACP, AP2 and the FIDO Alliance, MCP, A2A.

UCP and ACP do overlap: both describe carts and checkouts. We found no official specification for using them together. Payment companies such as Stripe support both (Stripe).

Where shoppers meet UCP today

• Google AI Mode and Gemini. Eligible product listings show a "Buy" button. The shopper pays without leaving Google, with the cards saved in Google Pay (Google for Developers). This is rolling out in the United States first. Google has announced Canada and Australia next, but its pages don't agree on the timing.
• At scale, according to Google. In September 2026, Google said UCP already enables direct checkout for hundreds of thousands of brands and retailers across Google (Google). It gave no breakdown.
• Universal Cart. Announced in May 2026 and available in the United States, it is one cart that follows the shopper across Google Search, Gemini, YouTube and Gmail. The shopper pays with Google Pay where the merchant supports it; otherwise the cart is handed to the merchant's site (Google).
• Not ChatGPT. ChatGPT relies on OpenAI's own protocol. For Shopify stores it is a discovery channel: buyers complete their purchase on your online store checkout (Shopify Help Center). We cover it in how ChatGPT shopping chooses products.

What UCP changes for a Shopify store

It's already on

In June 2026, Shopify wrote that "Shopify merchants are UCP-enabled by default" (Shopify). In practice, every store has a UCP endpoint on its own domain, which agents call to search the catalog, read a product, build a cart and start a checkout (Shopify Dev). Any surface that builds on it applies your checkout rules, discounts and customizations.

Shopify sorts agents into three access levels (Shopify Dev). An anonymous agent can search your products and build a cart. Completing a checkout inside the agent, or reading orders, requires a token issued through Shopify. Without one, the buyer finishes on your own checkout through a link. Since June 2026, developers no longer apply for access: they register their agent profile in Shopify's Developer Dashboard and call the public endpoint (Shopify).

Shopify also runs a Global Catalog on UCP, which lets an agent search products across Shopify merchants.

Selling in Google AI Mode and Gemini

Google's checkout is the main place where UCP closes sales today. On Shopify, it's part of Agentic Storefronts, and the Shopify Help Center sets out the conditions:

1. Your store is based in the United States and sells to customers there. Customers based elsewhere can still discover your products, but they finish on your online store.
2. Your products reach Google through the Google & YouTube sales channel or Google Merchant Center, and they are eligible for Shopify Catalog.
3. You have accepted the Agentic Storefronts supplemental terms, and your terms of service, privacy policy and refund policy are completed.

Know the limits. Subscriptions, product bundles, customizable products and B2B-only products aren't supported in that checkout. Google Analytics and custom pixels don't fire there. Shopify says there are no fees beyond your standard payment processing fees.

What you control

Shopify gathers the AI channels under Sales channels > Agentic (Shopify Help Center). The default setting, Allow Shopify to manage for me, keeps every channel active and enrolls your store in new ones. Turn it off to manage each channel, including its access to your catalog and its checkout. These settings work channel by channel; we found no switch for the store's UCP endpoint itself.

How our store agent uses UCP

UCP isn't only for agents outside your store. Reponse's storefront agent, the Ambassador, is itself a UCP client, working on your own store:

• Before it shows a product, it looks the product up through your store's UCP endpoint, for the live price and availability in the shopper's market. It won't show a product card for anything Shopify reports as sold out.
• When the shopper has chosen, it builds the cart through UCP. Shopify checks each line and the discount code, and returns a cart that your Shopify checkout takes over.
• If your store doesn't answer, the agent answers from the catalog it last read from your store, so the chat keeps working.

Building it taught us three things that matter to any merchant:

1. Shopify checks who is asking. Every request names the agent's public profile, and Shopify fetches that profile before it answers. A call whose profile it can't read is refused.
2. Prices depend on the market. The price an agent gets depends on the country it asks for. We send the shopper's country with every call; an agent that doesn't may quote another market's price. Keep your Shopify Markets prices right.
3. Discount codes are checked. An invalid code comes back as a warning instead of being applied in silence.

The common thread: with UCP, your Shopify data is what agents quote. Prices, stock, discounts and policies need to be right in Shopify itself.

What to do now

1. Nothing to install. UCP is on by default. Open Sales channels > Agentic to see which AI channels your store is in.
2. Complete your product data. Shopify lists the fields AI channels read: title, description, images, type, vendor, collections, tags, barcode and variants with their option names (Shopify Help Center).
3. Keep prices and stock right in every market. Agents check them at the moment of the conversation.
4. Complete your policies. Refund, shipping, privacy, terms and contact details: AI channels link to them, and several channels require them.
5. Selling in the US? Check that your products can be bought in Google's checkout, and remember that its sales won't show up in Google Analytics or custom pixels.
6. Check what agents can read on your store. Our free Shopify AI Readiness Checker reviews your catalog, robots.txt, structured data and policies.

FAQ

What is the Universal Commerce Protocol (UCP)?

The Universal Commerce Protocol is an open standard for agentic commerce. It gives AI agents and stores a common language for catalog search, carts, checkout, identity and orders. Google launched it in January 2026 with Shopify, Etsy, Wayfair, Target and Walmart, and it is published under the Apache 2.0 license.

Is UCP the same as ACP?

No. UCP comes from Google and Shopify; the Agentic Commerce Protocol (ACP) comes from OpenAI and Stripe. Both cover parts of the shopping journey, such as carts and checkout. Google uses UCP in AI Mode and Gemini, while ChatGPT uses ACP, mainly to read merchant catalogs.

Do Shopify merchants need to do anything to support UCP?

No. Shopify says its merchants are UCP-enabled by default: each store already has a UCP endpoint. What you can work on is the data agents read, such as product details, prices, stock and policies, and your settings in Sales channels > Agentic.

Where can shoppers buy through UCP today?

Mainly in Google AI Mode and Gemini, where eligible listings show a Buy button and shoppers pay with Google Pay. It's live in the United States first. Google says UCP already enables direct checkout for hundreds of thousands of brands and retailers.

Does UCP add fees for Shopify merchants?

UCP is an open standard with no fee of its own. For Google AI Mode and Gemini's direct checkout, Shopify says there are no fees beyond your standard payment processing fees.

Who controls UCP?

UCP is open source under the Apache 2.0 license. Its governance rules give permanent seats to its founding organizations, Google and Shopify, and other companies take part through its councils. Stripe joined the governing council in April 2026.