Google’s Universal Cart launched in the US on October 15 across Search and the Gemini app. But a new analysis of the developer documentation by e-commerce SEO consultant and data engineer Brandon Lazovic found a gap that matters more than the consumer announcement: retailers do not see a saved item until the shopper transfers the cart.
One request, at the end
According to Lazovic’s October 16 analysis, Google’s Cart API reference states the platform “accumulates those items locally” and does not fire multiple API calls as items are added. The merchant’s cart endpoint receives a single request carrying every saved item at once, and only when the shopper clicks transfer.
That has a direct commercial consequence. As Lazovic puts it: “Until then, the save-to-cart moment your abandoned-cart emails depend on stays with Google.” A product saved on Monday and transferred on Friday arrives, in his description, as a Friday visitor with a full cart. A save that never transfers appears in no report the retailer can open.
No updates, no sync
The initial release is limited to cart creation and transfer. Google’s overview says updating, deleting, or synchronizing cart contents between Google and the merchant’s system are not supported. The merchant responds to the one request with a continue_url that points to a pre-filled cart on the merchant’s own site.
This makes the data flow one-way. Google can send a cart; the retailer cannot push changes back or reconcile its own cart with Google’s. Merchant Center reporting exists, but the first metric is “Clicks to Buy” – not saves. Lazovic reports the Merchant API alpha report adds cart_transfers, average cart value and average items per cart, but neither counts a product saved to the cart.
What retail teams should do
The most practical fix is small and within merchant control. Because the merchant’s server writes the continue_url, it controls the parameters. Lazovic recommends adding a parameter that marks the session as a Universal Cart transfer. Without one, a shopper arriving from Google with a full cart lands in analytics as ordinary Google or direct traffic.
The other dependency is feed freshness. Price-drop and restock alerts are generated from Google’s copy of merchant data, its Shopping Graph of 60+ billion product listings, so an out-of-date feed can create alerts that send shoppers to a different price than the notification implied.
For teams assessing the integration, keep three facts front and centre:
- Saves stay with Google until transfer, so abandoned-cart email triggers do not fire at the save moment.
- Merchant reports start at Clicks to Buy, filtering out shoppers who never transfer.
- Tag the continue_url now; an untagged transfer cannot be told apart afterward.
Launch partners raise a verification question
Lazovic also fetched the public UCP profile at /.well-known/ucp for eight merchants named in Google’s posts. Two Shopify stores, Steve Madden and Fenty Beauty, returned a profile with 11 capabilities. The other six, including Nike, Target and Walmart, returned a 404. He cautions that a 404 means only that no file sits at that path from his connection, not that the retailer is not integrated. Still, Google’s own guide tells merchants to publish the profile there, making the misses worth a second look.
The bottom line: Universal Cart shifts upper-funnel intent data inside Google. Retailers keep the conversion-adjacent end of the journey, but the saves, the modern add-to-cart signal, are not visible yet. Plan attribution and abandoned-cart flows accordingly.
Source: PPC Land
