Google is gradually rolling out a Merchant Center hub for its Universal Commerce Protocol to merchants in the United States, according to reports published on October 6, 2026, giving retailers three capabilities to choose from - cart transfer to their own website, native checkout on Google and identity linking - while Australia and Canada are now expected to follow next year.

In Short

Google has started giving some US online sellers a new settings area inside Merchant Center, its tool for product data, where they can decide how shoppers buy through Google's AI features: finish the purchase on Google, send the filled cart to the seller's own site, or sign in with a store account. It matters to retailers and advertisers because the choice decides where the sale is completed, and the tool is open only to merchants that Google selects. Australia and Canada are not due until next year, and Google's pages do not say how many merchants have been let in so far.

What appeared in Merchant Center

According to Search Engine Land, Google is gradually rolling out the Merchant Center Universal Commerce Protocol (UCP) integration hub to US merchants. PPC News Feed carried the same update on October 6, 2026, and credited Hana Kobzová with spotting it. Under the new arrangement, eligible merchants pick the UCP capabilities they want to support inside Merchant Center "rather than relying on a single checkout experience," according to Search Engine Land.

The documentation changed alongside the interface. Google renamed the relevant Merchant Center help page, which is now titled "How to onboard to the UCP integration hub in Merchant Center," and removed an earlier FAQ that discussed UCP-powered checkout for select US merchants, according to both outlets. With that FAQ gone, the page has a single subject: the hub as the route into UCP.

Google's help page describes UCP as "a new open standard for agentic commerce" that lets agents and systems work together across the commerce ecosystem. Merchants that integrate can place a checkout button on eligible product listings in AI Mode in Google Search and in Gemini, according to the same page.

The three capabilities

Cart transfer. Google's Cart API guide, last updated on October 5, 2026 (UTC), describes a capability named dev.ucp.shopping.cart. It moves a shopper's cart from a Google surface such as AI Mode in Google Search or Gemini to the merchant's website. The guide says the API supports Google's Universal Cart feature through a one-way population of the cart on the merchant's system, primarily via a CreateCart endpoint.

Native checkout. The purchase completes on Google. The Cart API guide describes native checkout as a distinct API, and states that it is not required for cart transfer. Payment handlers and order lifecycles are likewise not required for the cart route, according to the guide.

Identity linking. Shoppers sign in with their own account at the merchant's store, so loyalty benefits carry over, according to Zhao Hanbo, a commentator on LinkedIn. Google's developer guide places the next page after the Cart API under the title "Identity linking - OAuth 2.0." PPC Land's coverage of the January 11, 2026 protocol release described the same capability as OAuth 2.0-based connections between customer accounts and AI systems, allowing agents to reach order history, apply loyalty rewards and retrieve saved payment methods.

A mock-up in the help page illustrates the result. It shows a cart for a placeholder retailer called Everloom, with a "Buy now" button above a second button to check out on the retailer's own site, and a Google Wallet mark underneath. A label on the mock-up says it is a preview for reference only.

How merchants get in

The rollout is gradual, but it is not open enrolment. According to the help page, participation runs through three steps:

  1. Merchants complete the technical implementation described in the UCP developer guide, which is required before onboarding begins.
  2. Merchants fill out an interest form.
  3. Once Google selects a merchant, it sends a notification and opens the onboarding experience in Merchant Center.

That experience includes a sandbox environment for validating an integration, covering the UCP profile, cart transfer to a merchant site and the native checkout APIs, according to Google. Merchant Center also raises alerts when actions are needed on feed attributes, returns or account configuration. The mock-up of the onboarding flow shows three stages: selecting UCP capabilities, publishing a UCP profile and validating the implementation.

Merchants that rely on a third-party service provider or platform are told by Google to contact that provider directly for its UCP plans. The help page's list of related documents also includes a "Universal Commerce Protocol Checkout Terms of Service (US only)," a detail that confirms the United States-only scope of the checkout programme.

A source discrepancy sits in the wording. PPC News Feed says merchants using the hub "can now choose" capabilities, and Search Engine Land speaks of eligible merchants selecting them. Google's help page, however, makes selection by Google a precondition, and the navigation of the Cart API guide labels the Merchant Center material "Pilot - UCP integration in Merchant Center." The documents read together describe a controlled pilot that is widening, not a feature that every Merchant Center account can switch on.

Technical details of the cart route

The Cart API guide carries several specifics that the news reports do not repeat.

The Cart API is a new feature and is available only from UCP version 2026-04-08, according to Google. Merchants therefore need systems able to handle that version. They must also publish a UCP profile at /.well-known/ucp and include the dev.ucp.shopping.cart capability. The endpoint named in that profile - the guide uses https://business.example.com/ucp/v1 as an example - serves as the base URL for the API calls.

The initial release is deliberately narrow. It covers cart creation and transfer through the CreateCart method only. Updating, deleting or synchronising cart contents between Google and the merchant's system is not supported, according to the guide. In other words, the cart is populated once, from Google toward the merchant, and the two sides do not stay in step afterwards.

Authentication relies on supported methods that include API keys and OAuth 2.0, according to Google, which points to a separate Authentication and Security guide for details. The same guide frames the capability as "designed for basket building before the user has expressed explicit intent to check out" - a phrase that places cart transfer earlier in the shopping journey than native checkout.

Google lists benefits for both sides. Users get a transition from product discovery on Google to a prepopulated cart on the merchant's website. Merchants receive carts directly from Google, which simplifies the initial purchase steps and provides opportunities for upselling and cross-selling on their own site, according to the guide. The navigation of the same developer guide also lists BigQuery analytics, error codes, code samples and extended capabilities, though the attached pages do not describe those in detail.

Zhao Hanbo, co-founder of Nile, a company that describes itself as building a marketplace for agentic commerce, described cart transfer in a LinkedIn post as the lighter of the integrations, with a fast-track validation path. That characterisation does not appear in the Google pages reviewed for this report.

Australia and Canada slip to next year

On geography, the help page is explicit: the onboarding experience is rolling out gradually in the US, with Australia and Canada to follow next year. Search Engine Land reported that Google has shifted the timeline for other markets, and PPC News Feed described a shift in rollout timing.

The shift is measurable against earlier wording. An earlier version of the same help page, as indexed by search engines before the update, described a gradual rollout in the US, Canada and Australia in the coming months. Separately, PPC Land reported on May 20, 2026 that Google said UCP-powered checkout would roll out across Canada and Australia in the coming months, and to the UK later. The current help page names no date for the UK at all.

Two distinct things are therefore in play. The May statement concerned UCP-powered checkout reaching consumers in those markets. The October page concerns the Merchant Center onboarding experience that merchants use to configure and validate their integrations. The documents do not say whether the consumer-facing launch in Canada and Australia has moved as well.

Background from PPC Land

The hub is the latest step in a sequence that PPC Land has followed since January.

On January 11, 2026, Google presented the Universal Commerce Protocol, co-developed with Shopify, Etsy, Wayfair, Target and Walmart and endorsed by more than 20 further companies, among them Adyen, Mastercard, Stripe and Visa. The initial design centred on native checkout, embedded checkout and identity linking, with retailers staying merchant of record.

On March 2, 2026, Google published a Merchant Center help page for UCP-powered checkout. It set out the native_commerce attribute needed to show a Buy button, payments using funding primary account numbers stored in Google Wallet, and a requirement that payment service providers accept a Google Pay token. The page then applied to the United States and to selected merchants only. The same coverage cited a 2025 survey in which only 12% of consumers had used AI chatbots for product research, a figure that frames how early the consumer side remains.

On May 5, 2026, UCP checkout appeared in main Search results for the first time, with a Wayfair listing carrying a Buy button. That report also noted that shoppers without payment methods saved in Google Wallet cannot complete a UCP checkout through the interface.

On May 20, 2026, at Google Marketing Live, Google added multi-item carts and a cart-transfer option that lets shoppers move items from their Google cart to the merchant's own site. The same coverage recorded Google's figures of more than 60 billion product listings in the Shopping Graph (April 2026 internal data) and more than 1 billion monthly AI Mode users, as disclosed at Google I/O 2026. Retailers named as early participants in the cart features included Nike, Sephora, Target, Ulta Beauty, Walmart, Wayfair and Shopify merchants such as Fenty and Steve Madden.

Read against that history, the October 6 change moves cart transfer from a consumer-facing option into a configurable, testable merchant setting.

How the industry is reading it

Search Engine Land argued that a more integrated checkout infrastructure could reduce friction between product discovery and purchase, particularly as Google builds more AI-driven shopping experiences. It added that merchants connecting early may be better positioned for experiences in which AI agents help shoppers research products, build carts and complete transactions. Both points are the outlet's own analysis, and the Google pages reviewed for this report offer no figures to test them against.

Zhao Hanbo wrote that Google is "quietly turning Merchant Center into the operating layer for AI shopping." He framed the change as a progression: a product feed feeding Google Shopping before; product data plus APIs, identity and checkout feeding AI shopping now; and, next, a place where brands manage how agents discover, understand and buy their products. The last step is his projection, and nothing in Google's documents commits to it.

Two comments under the same LinkedIn post added further claims. Tony Chan, an AI discovery strategist, distinguished between transaction readiness, which determines whether an agent can complete a journey, and decision readiness. Toma Adamia, who describes himself as CTO and co-founder of UCP Fluent, wrote that Google's UCP guide makes a consumer_notice field mandatory for items carrying regulatory warnings such as California Proposition 65. PPC Land could not locate that requirement in the Google pages reviewed for this report, so it remains an unverified claim from a commenter with a commercial interest in UCP product data.

Zhao Hanbo also wrote that checkout inside Google's AI surfaces is already switched on by default for Shopify merchants, a switch that sits in the Shopify admin. Google's help page does not mention Shopify, and it directs merchants working with platforms to contact those platforms directly. The statement is therefore attributed to him alone.

What the documents leave open

Several facts that a merchant, agency or ad tech vendor would want are absent from the material:

  • The number of merchants already selected, and the criteria Google applies when choosing among interest forms.
  • The time between submitting the interest form and receiving access.
  • Whether the sandbox and production validation results feed any visibility or eligibility decision in AI Mode and Gemini.
  • Whether analytics in the hub, hinted at by the BigQuery analytics entry in Google's developer navigation, will report on cart-transfer volumes separately from native checkout.
  • A date for the UK, and any statement on whether the consumer-facing checkout in Canada and Australia has moved alongside the Merchant Center onboarding.

Why it matters for the marketing community

The hub gives a concrete interface to a question that has run through PPC Land's UCP coverage since January: where the sale finishes. In the cart-transfer path, the filled cart arrives on the merchant's site and the final purchase experience stays there, according to Zhao Hanbo and consistent with Google's Cart API guide. In native checkout, the transaction completes on Google. The difference determines which party records the conversion and what data the merchant keeps - an inference drawn from the two flows described, not a figure either side has published.

For advertisers running Shopping and Performance Max campaigns on product feeds, Merchant Center's role is widening from feed management to capability validation. Google's own wording in the help page stresses that Merchant Center remains the central hub for preparing product data used to show ads and listings on Google surfaces. The new alerts on feed attributes, returns and account configuration extend that role into operational territory that used to sit with engineering and payments teams.

The staging also matters. A US-first, selection-based rollout means that merchants outside the United States have no hub access yet, and that agencies serving Canadian and Australian clients face a documented 2027 horizon for onboarding. For merchants inside the United States, the open questions listed above - selection criteria, timing, reporting - bear on how quickly the hub translates into measurable sales.

Timeline

Summary

Who: Google, which operates Merchant Center and the Universal Commerce Protocol; US merchants selected for the programme; and merchants in Australia and Canada, who are now expected to follow next year. Search Engine Land and PPC News Feed reported the change, and commentators including Zhao Hanbo of Nile offered analysis.

What: A Merchant Center UCP integration hub that lets eligible merchants choose among cart transfer to their own website, native checkout on Google and identity linking. It includes a sandbox for validating the UCP profile, cart transfer and native checkout APIs, plus alerts on feed attributes, returns and account configuration. Google renamed the help page and removed a previous FAQ about UCP-powered checkout for select US merchants.

When: Reported on October 6, 2026. Google's Cart API guide was last updated on October 5, 2026 (UTC). Australia and Canada are expected next year.

Where: Inside Merchant Center, for merchants in the United States first, with checkout surfaces in AI Mode in Google Search and in Gemini.

Why: Google is building out the merchant-side tooling for agentic commerce, moving UCP from a limited checkout capability toward a configurable layer in Merchant Center. Search Engine Land cites reduced friction between discovery and purchase and better positioning for AI-agent shopping; the documents themselves leave open how many merchants are in the programme and how selection works.