Universal Cart is Google's new shopping cart, built into Search and the Gemini app. A shopper can save products from different stores into one cart, get told when a price drops or an item is back in stock, then pay with Google Pay right there, or move the items across to the store's own cart and finish on its website. Either way, the store stays the seller of record.
In September, Google started emailing Shopify stores to say their products were eligible and there was “nothing for you to set up”. Every other store has to put its hand up and build the connection. This guide is for them.
Where it works right now
Universal Cart launched in the US on 15 October 2026, for products sold within the United States. Google says the Merchant Center side reaches Australia and Canada early next year.
Selling outside the US? Stage 1 is still worth doing now. It's Merchant Center work, and Google lists it as the first step for everyone.
- Get the Merchant Center basics right
- Pick your path and apply
- Checkout in Google: the extra prep
- Build, test and go live
- What to look for
Stage 1 of 4
Get the Merchant Center basics right
The cart is built on Google's Shopping Graph of product listings, and your listings get there through Merchant Center. Google's own advice is to keep that data “as robust and up to date as possible”. Harry rates Merchant Center S tier for any online store, because product feeds are no longer just a PPC asset handed to your ads team and forgotten: they're core search infrastructure. Our guide to Merchant Center for AI search covers the feed fields AI reads.
- 1Set up Merchant Center, with products approved for free listings. Both pathsGoogle's starting requirement is a Merchant Center account in good standing, with products approved for free listings. If your products aren't showing in free listings yet, fix that first.
- 2Keep price and stock in your feed accurate, and matching your product pages. Both pathsThe cart watches them for the shopper: it sends alerts when a price drops or an item comes back in stock. If your feed says one price and your product page says another, the shopper is working from the wrong one.
Stage 2 of 4
Pick your path and apply
Google offers two ways in, and they need different amounts of work. Decide this before you do any more prep, because some of the steps below only apply to one of them.
- 3Ask your ecommerce platform first. Both pathsIf a platform or provider runs your store, Google says to contact them directly about their UCP plans before you build anything yourself.
- 4Choose your path: checkout in Google, or cart transfer.Checkout in Google: the shopper pays with Google Pay without leaving Google, and your systems take the order. Cart transfer: the shopper's items move into your website's cart and they finish buying there. Google calls cart transfer its fast-track path: it “doesn't require full product feed setup, product warnings, or customer support information”. You can do both, but then you complete the checklist for both.
- 5Fill in Google's interest form. Both pathsIt's at support.google.com/merchants/contact/ucp_integration_interest. Google also calls it the waitlist. Checkout is open to select merchants while the program is in early access.
Stage 3 of 4
Checkout in Google: the extra prep
Only doing cart transfer? Skip to Stage 4. Checkout in Google needs all of this in Merchant Center before you build.
- 6Add your return policy in Merchant Center. Checkout in GoogleGoogle requires it and shows it on the checkout screen. Include the return cost, the return window and a link to your full policy. On an advanced account with sub-accounts, set it on each sub-account.
- 7Add your customer support details. Checkout in GoogleAt least one of: a customer service page, an email address or a phone number. Google uses it for the “Contact Merchant” link on the order confirmation page.
- 8Check which of your products can't use checkout. Checkout in GoogleGoogle excludes subscriptions, instalment plans, personalised items such as engraving, used, refurbished and final sale items, pre-orders, items that need a warranty or installation contract, freight or premium delivery, gifting with hidden prices, items that must be activated in store, age-restricted items such as alcohol and tobacco, anything Google Shopping policy blocks, services, rentals, virtual items, and products that need software installed first.
- 9Flag the products you want in checkout. Checkout in GoogleAdd the attribute
native_commerce(checkout_eligibility) set to TRUE. It defaults to FALSE, and only products with it set show the Buy now button. Google suggests adding it through a supplemental data source, so your main feed isn't touched. If your products need legal or safety warnings, add them with consumer_notice.
Stage 4 of 4
Build, test and go live
This is the developer part. Google's name for it is the Universal Commerce Protocol (UCP): an open standard that lets Google's AI and your store's systems talk to each other. Google has to approve your integration before you go live.
- 10Build it with your developer, from Google's UCP developer guide. Both pathsThe guide is at developers.google.com/merchant/ucp/guides. Both paths need a UCP profile, which is a file at
/.well-known/ucp on your site that tells Google what you support. Google doesn't require authentication on your endpoints, but supports API keys, OAuth 2.0 tokens and mutual TLS, so have your developer secure them. Cart transfer then needs the Cart API. Checkout in Google needs the checkout API with the Google Pay payment handler, order updates and a Google Pay & Wallet Console merchant account with production access (Google's prepare for production steps). If your feed's product IDs don't match the IDs your systems use, map them with merchant_item_id. Google says this build has to be done before you begin onboarding.
- 11Wait to be selected. Both pathsWhen Google selects you, it tells you, and the UCP integration hub opens in your Merchant Center account under Settings, then UCP integration.
- 12Test in the sandbox. Both pathsAdd your UCP profile location, plus a test API key if your test setup uses one, then run Google's test actions: create a cart for cart transfer, or create, update and complete a checkout. If you use API keys, use separate ones for testing and for the live site.
- 13Test what happens when something sells out. Checkout in GoogleIf an item goes out of stock during checkout, your system has to send back an
out_of_stock error, and Google shows the shopper a message. Find out how yours behaves before a real shopper does.
- 14Fix anything Merchant Center flags. Both pathsGoogle says Merchant Center will alert you if your feed attributes, returns or account settings need updating.
- 15Validate in production, then wait for Google to confirm you're live. Both pathsIn the hub, select your capabilities and publish your UCP profile. Its capabilities must exactly match the ones you selected. Then work through the checklist for your path. Cart transfer Confirm your product IDs match, and validate cart transfer. Checkout in Google Validate the three checkout endpoints, validate order status by setting up webhooks that send order updates to Google, and review and agree to the UCP Program Addendum. Google Support then reviews your integration. Wait for Google to confirm your account is live, or to tell you what needs fixing.
What to look for once you're live
- The Analytics tab in the UCP integration hub. Google's view of your checkout funnel across its AI buying flows.
- Orders arriving from Google. Google's requests carry a
UCP-Agent:Profile header and a User-Agent starting Google/UCP, so your developer can tell them apart from orders on your own site.
- Feed and site still agreeing. Price and stock in Merchant Center should match your product pages every day, not just on launch day.
- The trade-off. A shopper who buys inside Google may never see your website, so you may miss the upsell or the email signup. Weigh that against a sale you might not have got, and decide on purpose.
On Shopify? You may already be switched on
Google emailed Shopify stores in September: “Eligible products are automatically included. There's nothing for you to set up.” Shopify says direct checkout is on by default for eligible US-based stores selling to US customers. Eligible also means a valid Merchant Center account with your products in it, products eligible for Shopify Catalog, your store policies completed, and agreeing to Shopify's supplemental terms. See Shopify's full checklist.
To decide for yourself: in your Shopify admin, go to Sales channels, then Agentic. Turn off “Allow Shopify to manage for me”, click Google AI Mode and Gemini, turn Direct checkout on or off, then click Save. With it off, shoppers can still find your products in AI Mode and Gemini, but they're sent to your store to buy.
Get your feed ready first
The free Merchant Center Optimizer skill works through your feed for you: it triages disapprovals, rewrites feed titles to match what people search for, fills missing attributes and ranks every fix by revenue.
Get the Merchant Center Optimizer skill
