Retailers using Google's AI shopping infrastructure now have access to multi-item cart management, live product catalogue queries, and loyalty program portability, capabilities absent when the Universal Commerce Protocol first launched two months ago. On March 19, 2026, Google published an update to the Universal Commerce Protocol (UCP) introducing three new optional capabilities, Cart, Catalogue, and Identity Linking, and separately announced a simplified onboarding path through Google Merchant Center.
What UCP Is and Where It Stands
The Universal Commerce Protocol is an open-source standard designed to power the next generation of agentic commerce, establishing a common language and functional primitives that enable seamless commerce journeys between consumer surfaces, businesses, and payment providers. UCP was co-developed with industry leaders, including Shopify, Etsy, Wayfair, Target, and Walmart, and endorsed by more than 20 others across the ecosystem, including Adyen, American Express, Best Buy, Flipkart, Macy's Inc., Mastercard, Stripe, The Home Depot, Visa, and Zalando.
Google announced UCP on January 11, 2026, at the National Retail Federation conference. At launch, UCP's checkout capability was limited to a single-item guest checkout, a meaningful first step, but one that made the protocol feel more like a proof of concept than a mature commerce standard. The March 19 update is the first since that initial launch.
Three New Capabilities
Cart
Cart lets agents save or add multiple items to a shopping basket from a single store. According to the UCP specification, Cart is designed for pre-purchase exploration, allowing agents to build baskets before a shopper commits to a purchase. Those baskets can then convert to checkout sessions when the shopper is ready. Cart is published as a draft specification.
Catalogue
Catalogue enables agents to retrieve real-time product details from a retailer's inventory, including variants, pricing, and stock availability. The Catalogue specification supports both search and direct product lookups. Unlike existing Google Shopping product feeds, which are static snapshots updated periodically, agents can now query live catalogue data rather than relying solely on product feeds. Catalogue is also currently a draft specification.
Identity Linking
Building on existing standards, UCP supports Identity Linking, which allows shoppers on UCP-integrated platforms to receive the same loyalty or member benefits they would on a retailer's site when logged in, such as pricing or free shipping, making shopping more connected across the web. Identity Linking allows shoppers to connect their retailer accounts to UCP-integrated platforms using OAuth 2.0. Identity Linking was included in the latest stable version of the UCP specification at the time of the March 2026 announcement, rather than as a draft.
UCP adopters can customize the experience they provide by selecting which capabilities to support.
Merchant Center Onboarding
Google confirmed it will continue to bring relevant UCP capabilities to shopping experiences in AI Mode in Search, the Gemini app, and beyond, and is actively working to onboard more retailers of all sizes to agentic experiences on Google with a simplified UCP onboarding process in Merchant Center, rolling out over the coming months.
Only product listings using the `native_commerce` product attribute will display the checkout button in Google AI Mode and the Gemini app. Google's Merchant Center help page lists the checkout feature as currently available to selected merchants, with an interest form for those who want to participate.
UCP-powered checkout is currently available to eligible U.S.-based merchants, with global expansion planned throughout 2026.
Platform Partners
Partners, including Commerce Inc, Salesforce, and Stripe, will implement UCP on their platforms in the near future. Three platform partners announced plans to implement UCP, with Commerce Inc, Salesforce, and Stripe each publishing separate announcements.
Salesforce's position is notable in the context of the broader agentic commerce landscape. The company previously announced support for OpenAI and Stripe's competing Agentic Commerce Protocol (ACP), meaning the space is becoming multi-protocol and ecosystem-driven, with Salesforce Commerce Cloud merchants positioned to serve agents on both Google's and OpenAI's surfaces from a single platform.
What This Means for Retailers
Retailers already managing product data through Google Merchant Center are the primary target for the simplified onboarding path. Google's stated goal is to bring in "more retailers of all sizes," acknowledging that UCP's earlier adoption required fairly heavy technical investment.
For e-commerce brands with loyalty programs, Identity Linking introduces a concrete operational question. Identity Linking addresses the specific and commercially important problem of whether a loyal customer who has accumulated points, earns member pricing, or qualifies for free shipping on a retailer's website will still receive those benefits when completing a purchase through a UCP-powered AI surface instead.
Retailers evaluating UCP adoption should note that Cart and Catalogue remain draft specifications, meaning their technical details may change as the open-source community contributes feedback before finalization. Brands with accurate, well-structured product feeds and real-time inventory systems are better positioned to take advantage of the Catalogue capability than those dependent on periodically refreshed data snapshots. Merchants on Salesforce, Stripe, or Commerce Inc platforms may be able to access UCP onboarding through their existing platform rather than through a direct integration.
Google published the UCP update on March 19, 2026. The announcement came from Ashish Gupta, VP/GM Merchant Shopping at Google, on the official Google blog.
