Two days after Amazon Web Services opened up its Agentic Shopping Assistant to outside retailers — a story we covered Wednesday — Google countered at Marketing Live on Thursday with something materially different in shape: not a hosted AI assistant that retailers bolt onto their own sites, but a shared cart that lives on Google's surfaces and is endorsed by most of the retailers Amazon would want for itself.
The launch came in two layers. The first is the Universal Cart, introduced last week at Google I/O and now getting its commerce-ecosystem build-out: a single cart that works across retailers and across Search, the Gemini app, YouTube and Gmail. Shoppers can add a pair of sneakers from Nike, a fragrance from Sephora, and a sofa from Wayfair into one persistent cart, then check out with Google Pay in a few taps — or transfer the items to the merchant's own site to complete the purchase there. The cart runs in the background, watching for price drops and back-in-stock alerts, powered by Gemini.
The second layer is the Universal Commerce Protocol (UCP), the open-source standard underneath it all. Google describes UCP as a common language between AI agents, merchants and payments infrastructure. It was co-developed with Shopify, Etsy, Wayfair, Target and Walmart, and — per Google's blog — has been endorsed by more than 20 others including Adyen, American Express, Best Buy, Flipkart, Macy's Inc., Mastercard, Stripe, The Home Depot, Visa and Zalando. Paired with it is the Agent Payments Protocol (AP2), which gives AI agents bounded authority to spend on the shopper's behalf.
The retailer roster is the part that should make Seattle nervous. As Retail Dive notes, checkout features will go live "soon" across Nike, Sephora, Target, Ulta Beauty, Walmart, Wayfair, and Shopify merchants such as Fenty and Steve Madden. That list reads as a who's-who of mid-funnel discovery brands that have spent the past three years quietly de-emphasizing Amazon as a sales channel. Search Engine Land reports that Google is also extending UCP into new industries — travel, restaurants, ticketing — so the cart isn't only for physical goods.
The strategic divergence between the two platforms is now sharp. Amazon's AWS play, as PYMNTS framed it, is an infrastructure-as-a-service move: retailers license Amazon's AI shopping technology to power their own sites, and Amazon collects the rent. Google's bet is the opposite — the cart and the protocol live on Google's surfaces, and the retailers participate as endpoints. Amazon wants to be inside the retailer's stack. Google wants the retailer to live inside Google's.
For retailers, the question is no longer whether to participate in agentic commerce. It's which agent's stack to make their inventory legible to. Joining UCP is comparatively cheap — it's an open protocol — and the early-mover retailers get prominent placement when Universal Cart starts shipping to U.S. shoppers this summer. Sitting it out means risking that Gemini, Search and YouTube simply route AI-driven traffic to whoever did show up.
That distinction also reframes what "agentic commerce" actually means competitively. As Digital Commerce 360 observed, AI models themselves are commoditizing quickly. The defensible moat is the commerce graph — the structured product feeds, merchant authentication, payment hooks and fulfillment integrations that make a checkout actually transact. Google is racing to lock those primitives in as an open standard before Amazon, Shopify or OpenAI lock them in as proprietary ones. Shopify, notably, is on both sides: it co-developed UCP, and it ships its own AI shopping integrations directly.
What changes for everyone selling on the open web is that the surface where the purchase decision happens just stopped being the merchant's site for a meaningful slice of shoppers. That has implications for SEO, for product-page conversion rate optimization, and for the entire 25-year-old assumption that ecommerce success comes from owning the destination. Universal Cart says the cart is portable now. The retailer's job is making sure the SKU shows up in it.