# What is Google's UCP (Universal Commerce Protocol)? > What UCP (Universal Commerce Protocol) is, how a store publishes its capabilities at /.well-known/ucp, and what works today in AI Mode and Gemini. URL: https://clione.ai/glossary/ucp/ Lang: en UCP is the Universal Commerce Protocol, the standard Google wants [AI agents](/glossary/ai-agent/) to use to buy from stores without a separate integration for each one. Google introduced it on January 11, 2026, and **it is the piece behind the buy button in [Google AI Mode](/glossary/google-ai-mode/) and in [Gemini](/glossary/gemini/)**.[^google-ucp-launch] It matters to a store for two reasons: it defines what the store has to publish so an [AI agent](/glossary/ai-agent/) can buy from it, and its timeline says when each piece reaches each country. Its counterpart in ChatGPT is [ACP (Agentic Commerce Protocol)](/glossary/acp/). ## How it works Google describes it as an open standard for [agentic commerce](/glossary/agentic-commerce/) that covers the whole purchase journey, developed with Shopify, Etsy, Wayfair, Target and Walmart, endorsed by more than twenty companies, including Adyen, American Express, Mastercard, Stripe and Visa, and compatible with [A2A (agent-to-agent)](/glossary/a2a/), [AP2 (Agent Payments Protocol)](/glossary/ap2/) and [MCP (Model Context Protocol)](/glossary/mcp/).[^google-ucp-launch] Today the protocol's website lists Amazon, Microsoft, Meta, Salesforce and Stripe, among others, as co-developers, plus more than sixty endorsing organizations.[^ucp-home] The central mechanism is discovery. **Each store publishes a profile at `/.well-known/ucp`** with the services, capabilities and payment methods it supports, and the agent sends the address of its own profile with every request so both sides can negotiate what they can do together.[^ucp-overview] Google explains it as a standard JSON manifest that lets the agent discover features, endpoints and payment configurations without hand-written integrations.[^google-ucp-dev] The specification splits four roles: the business, which publishes its capabilities and serves requests; the platform, which is the agent or app doing the buying; the credential provider for payments; and the payment service provider. Each capability has a domain-style name, such as `dev.ucp.shopping.checkout`, and extensions add optional features to a capability. The transports are REST, MCP, A2A and a protocol for embedded experiences.[^ucp-overview] The published shopping capabilities are catalog, cart, checkout, identity linking with OAuth 2.0 and order; there is a draft for lodging and food delivery is announced.[^ucp-home] The current version of the specification is the one dated August 25, 2026.[^ucp-overview] ## What works today and what is announced | Date | What | Status as of October 6, 2026 | | ------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------- | | Jan. 11, 2026 | UCP introduced, with Google Pay checkout inside AI Mode and Gemini, at eligible US merchants; PayPal later | The merchant remains the seller[^google-ucp-launch] | | May 20, 2026 | Universal Cart: a cart that works across stores and Google services; payment with Google Pay or handoff to the merchant's site; Affirm and Klarna; hotels and food delivery | "Soon" and "in the coming months"; Canada and Australia, then the UK[^google-gml] | | Today | [Merchant Center](/glossary/google-merchant-center/) integration | Gradual rollout in the US; Australia and Canada, later[^google-mc-ucp] | To get in, Google asks you to prepare your [Google Merchant Center](/glossary/google-merchant-center/) account (shipping, returns and feed), join the waitlist, set up Google Pay as a payment method and publish the UCP profile; **Google has to approve the integration before it appears in AI Mode or Gemini**.[^google-ucp-guide] Shopify already works on UCP: agents authenticate, search its catalog, build carts and track orders using this protocol. The agent turns the cart into a checkout and sends the buyer to the store to pay; trusted agents can complete it directly.[^shopify-agents] ## In a store Here is what the profile of a **fictional example** store would look like at `https://coffee-makers-example.com/.well-known/ucp`, with the structure of the specification's own example: one shopping service over REST and the checkout capability.[^ucp-overview] The signing keys, which a real profile includes, are left out here. ```json { "ucp": { "version": "2026-08-25", "services": { "dev.ucp.shopping": [ { "version": "2026-08-25", "spec": "https://ucp.dev/2026-08-25/specification/overview/", "transport": "rest", "endpoint": "https://coffee-makers-example.com/ucp/v1", "schema": "https://ucp.dev/2026-08-25/services/shopping/rest.openapi.json" } ] }, "capabilities": { "dev.ucp.shopping.checkout": [ { "version": "2026-08-25", "spec": "https://ucp.dev/2026-08-25/specification/shopping/checkout", "schema": "https://ucp.dev/2026-08-25/schemas/shopping/checkout.json" } ] }, "payment_handlers": {} } } ``` What that file says is short: the store speaks UCP in its August 2026 version, serves requests over REST at a specific address and knows how to process a payment. An agent that reads it knows what it can ask for; one that does not find it has no way to know the store accepts agents. Thinking UCP replaces the Merchant Center feed. It is the other way around: **the first step in Google's guide is to have the Merchant Center account with shipping, returns and feed in order**,[^google-ucp-guide] and the protocol is built on top. A store without an up-to-date feed never gets to the UCP step. ## How to check 1. **Open `https://your-domain/.well-known/ucp`** in the browser. If it exists, look at the version, services and capabilities it declares.[^ucp-overview] 2. **Review Merchant Center**: feed without errors, shipping and returns configured. It is Google's first requirement.[^google-ucp-guide] 3. **If you sell in the United States**, complete the technical implementation and the interest form; Google lets you know when it selects you, and then onboarding opens in Merchant Center.[^google-mc-ucp] 4. **If you sell on Shopify**, check which UCP capabilities your platform already offers before building anything custom.[^shopify-agents] ## Related concept: ACP [ACP (Agentic Commerce Protocol)](/glossary/acp/) is OpenAI and Stripe's protocol for the same job: letting an agent discover and buy from a store. They are alike in the essentials, because both leave the merchant as the seller and both can use MCP as a transport.[^acp-site][^ucp-overview] They differ in who drives them and where they are used: UCP comes from Google with Shopify and large retail chains, and it is the one behind AI Mode and Gemini;[^google-ucp-launch] ACP is the one that powers ChatGPT. What sets UCP apart in its design is the public profile at `/.well-known/ucp` and the negotiation of capabilities on every request.[^ucp-overview] To go further, [agentic commerce](/glossary/agentic-commerce/) separates discovering, recommending and buying, and the [agentic commerce reading path](/learn/agentic-commerce/) puts the rest of the protocols in order.