Google introduced the Universal Commerce Protocol (UCP) at the National Retail Federation show on January 11, 2026. It was built with Shopify, with Etsy, Wayfair, Target and Walmart as founding partners and more than 20 other backers at launch, including Visa, Mastercard, Stripe, American Express, Best Buy and The Home Depot.
Our earlier article covered the basics: what UCP is for, how a purchase works, and how to get ready. Almost nine months later, a lot has changed. The protocol has shipped four spec releases, added new features, set up a formal governance structure that includes some of Google’s biggest rivals, and started moving into grocery, food delivery and travel. This post brings the picture up to date.
What UCP is, in short
UCP is an open standard that sets out how AI shopping agents talk to online stores. It is published on GitHub under the Apache 2.0 license, so any developer can build on it for free.
The problem it solves is simple. Without a shared standard, every store would need a separate integration for every AI assistant. With UCP, a store publishes one machine-readable profile at a standard web address (/.well-known/ucp). Any agent that follows the protocol can read that profile and learn what the store supports.
One principle has not changed since launch: the retailer stays the merchant of record. The store keeps its own checkout rules, its customer relationship, its transaction data and everything that happens after the sale. The AI agent passes the order along; it does not take the store’s place.
How a UCP purchase works
The basic flow is the same as at launch, with more detail filled in at each stage:
- Discovery. The agent reads the store’s profile and searches its catalog. Since March, it can ask live questions about price, stock and sizes instead of relying on a feed that updates on a schedule.
- Negotiation. The agent and the store agree on what is supported, such as payment methods and checkout options. The store’s server makes the final call.
- Checkout. The agent builds a cart and starts checkout. Payment runs through Google Pay today and works with the Agent Payments Protocol (AP2), which attaches proof that the shopper approved the purchase.
- After the sale. Order status, returns and customer service run through the store’s own systems.
Stores can offer these features through a standard REST API, a Model Context Protocol (MCP) server, or the Agent2Agent (A2A) protocol, depending on what fits their setup.
What has changed in 2026
UCP has changed something about once every three weeks since launch. The chart shows each milestone by date and type.
The March update did the most to change how UCP works in practice. Before it, an agent could only check out one item per session. Cart support lets it hold several items, Catalog lets it look up live prices and stock, and Identity Linking lets shoppers keep their loyalty perks when an agent buys for them.
In May, Google added Universal Cart, which lets a shopper combine items from different retailers in one checkout. It also added Affirm and Klarna as buy now, pay later options inside Google Pay, and brought UCP checkout to YouTube Shopping ads.
Who steers UCP now
UCP is no longer run mainly by Google and Shopify. It now has five councils, and three of them, for food, lodging and payments, were set up between July and September.
The April changes matter most for trust in the standard. Amazon, Meta and Microsoft, all of which compete with Google in AI, now sit on the Tech Council that shapes the spec. The industry councils bring in companies that already run those markets, such as DoorDash and Uber Eats for food, and Expedia and Marriott for hotels.
Beyond retail: grocery, food and travel
The August 25 release (v2026-08-25) is the clearest sign of where UCP is heading. It adds features for grocery shopping: agents can find physical stores with their addresses, opening hours and map locations, and can order items by weight.
It also updates payments. The spec now supports 3D Secure 2 checks, payment plans with deposits and installments, and splitting one order across more than one payment method. The spec has been split into Shopping, Payment and Common sections so the payment parts can serve other industries too.
Food ordering and hotel booking specs are still being written. The release lays the groundwork, but it does not mean you can order groceries or book a hotel through an AI assistant today.
If you have already built on UCP, read the breaking changes first. Fulfillment schemas have a new structure, buyer consent has moved to a flexible map, and signing keys now sit in a single JWK Set. Stores can keep supporting older versions while they update.
How UCP compares with ACP
UCP is not the only protocol for AI shopping. OpenAI and Stripe released the Agentic Commerce Protocol (ACP) in September 2025, and it powered Instant Checkout inside ChatGPT. In March 2026, OpenAI ended Instant Checkout and began sending shoppers to retailer apps and websites to finish their purchases. ACP itself is still an open spec, and Stripe continues to support it.
| UCP | ACP | |
|---|---|---|
| Built by | Google and Shopify | OpenAI and Stripe |
| Announced | January 2026 | September 2025 |
| Covers | Discovery, cart, checkout, after the sale | Product feed, cart, checkout, payment |
| Main checkout today | Live in Google AI Mode and Gemini (US) | Instant Checkout ended March 2026 |
The gap is about live checkout, not about which spec is better on paper. Many merchants may end up supporting both.
What merchants should do now
UCP checkout on Google is live for eligible US retailers. Google has said Canada and Australia come next, with the UK after that.
- Check your product data. Agents now ask live questions about stock, sizes, prices and compatibility. Missing or out-of-date details mean an agent may skip your product or give the shopper a wrong answer.
- Use your platform if you can. Shopify opened UCP to every developer in June. Salesforce, Stripe and Commerce Inc. are adding support, and WooCommerce stores can use a free plugin.
- Start in Merchant Center. Google made UCP sign-up simpler there in March, and your existing product feeds are the starting point.
- Track versions. UCP versions are named by date, such as v2026-08-25. Review the release notes each time, since some releases include breaking changes.
The bottom line
In January, UCP was a checkout spec for one item at a time, run mostly by Google and Shopify. Today it handles carts, live catalogs and loyalty accounts, is steered by councils that include Amazon, Meta, Microsoft, PayPal and Stripe, and is expanding into grocery, food and travel. Some of that is still on paper, and wider country rollout is not finished. For most retailers, the practical steps are the same as before: keep product data complete and current, lean on your commerce platform, and keep an eye on each new release.