Shopping in Gemini and Google AI Mode: how UCP works, and what brands should do now

What is the Universal Commerce Protocol?

UCP is an open standard for how AI agents find products, build a basket and pay. Google launched it on 11 January 2026, developed with Shopify, Etsy, Wayfair and Target, and endorsed by more than 20 others, from Adyen and Mastercard to Visa and Zalando.

In practice a brand publishes a UCP profile on its own domain that says what its store supports: search, a cart, checkout. An agent that reads it can work with the catalog directly instead of scraping pages.

The same launch put a Buy button on eligible listings in AI Mode and the Gemini app, paid with Google Pay, and added a Business Agent: a Chat button in Search that answers product questions in a brand's own voice.

What changed in March, and since?

On 19 March 2026 Google added three optional parts to UCP. Cart lets an agent add several items from one store at once. Catalog lets it fetch live variants, stock and prices from a retailer's catalog when it needs them. Identity Linking gives a signed in shopper the member prices or free delivery they'd get on the retailer's own site. A UCP integration hub in Merchant Center followed in October, rolling out in the US.

In May Google said retailers in every market could add conversational attributes to their product descriptions in Merchant Center. Then on 15 October 2026 it launched the Universal Cart for US users across Search and the Gemini app. A shopper saves products from several retailers, gets alerts when prices drop or items come back in stock, and either pays with Google Pay in the cart or moves the items to the merchant's own cart to finish there.

Where can shoppers buy inside Gemini and AI Mode?

In the US, from merchants Google has selected. Google's Merchant Center help lists the US, Canada and Australia for eligible products, but its onboarding page says the integration hub reaches Australia and Canada next year. In May Google said the UK would follow later. There's no date for the UK or the EU.

Getting in is by invitation. A merchant does the technical work, fills in Google's interest form and waits to be selected. Google doesn't publish its criteria or a timeline. The names it has given are the big ones: Nike, Sephora, Target, Ulta Beauty, Walmart, Wayfair, and Shopify merchants such as Fenty and Steve Madden.

Google is clear on one point: “No matter which way you buy, the brand stays the merchant of record.” The brand ships, handles returns and keeps the customer.

What does Merchant Center ask for?

For checkout on Google, its developer guide asks for six things.

1. An account in good standing.With products approved for free listings.
2. Return policies in Merchant Center.The return cost, the return window and a link to the full policy, because the checkout screen shows them.
3. Customer support details.At least one of a support page, an email address or a phone number, for the Contact Merchant link on the order confirmation.
4. Matching product IDs.The id in your feed has to match the one your checkout expects.
5. The checkout attribute.Only products marked with native_commerce(checkout_eligibility) show the Buy button.
6. Google Pay.A Google Pay and Wallet Console account, and a payment provider that accepts Google Pay tokens.

How is it different from ChatGPT?

ChatGPT gave up checking out. OpenAI ended Instant Checkout as a standalone product in March 2026. Shoppers find products in ChatGPT, through OpenAI's Agentic Commerce Protocol (ACP), and pay on the retailer's own site. ChatGPT shopping is for US users only.

Google kept checkout and built it into a cart. In the US a shopper can pay without leaving Google, or be handed to the merchant's site. Our read: Google could keep it because it already held the cards. Google Pay and Wallet have them on file. OpenAI had to ask for them in a chat window.

For a brand the practical difference is the door. Google's is Merchant Center. If your feed is there and clean, you're halfway in already.

What should a brand do now?

Five things, wherever you sell. The US rules are the template for every market that follows.

1. Fix the Merchant Center feed.Titles, GTINs, prices, stock, shipping and every variant, accurate and current. The Universal Cart's price and stock alerts read this data. Write descriptions, and the conversational attributes, to answer questions.
2. Put returns and support in Merchant Center.Checkout requires them and they take an afternoon. Do it before you're asked.
3. Mark up your pages.schema.org Product and Offer on product pages, Organization on your homepage, so AI Mode reads facts instead of guessing them.
4. Publish a UCP profile.It tells any agent, Google's included, what your store supports. Google's onboarding starts with the technical work, so this comes first.
5. Ask your payment provider about Google Pay tokens.If it can't accept them, that's the slowest part to fix.

In the UK and the EU none of this buys you checkout this year. It decides whether you're found.

Where does Storefront fit?

Storefront gives a brand its own UCP profile and agent address (MCP), built from the Google Shopping feed it already sends to Merchant Center, live in minutes. Any agent that connects gets live price, stock, sizes and images, with links to the brand's own product pages.

To be plain about what it isn't: Storefront is not live in Gemini checkout, and nobody can get you selected by Google faster. Your UCP profile is ready for Gemini and AI Mode as Google opens merchant listings in each market, and we switch on checkout inside the agent as Google opens it where you sell. Until then agents hand the shopper to your product page, or to a hosted checkout on your own domain. You pay one flat monthly price, we take no cut of your sales, and it's built for brands that aren't on Shopify. Where each agent checks out today is in our comparison.

Where do you stand today?

Before you touch the feed, see what Google AI already says about you. The free score shows how the AI engines see your brand, Gemini included, and whether shopping agents can read your products, with the fixes ranked.