Universal Commerce Protocol (UCP): the Google and Shopify standard.

What is the Google and Shopify UCP protocol?

The Universal Commerce Protocol (UCP) is an open agentic commerce standard announced by Google on January 11, 2026 at the National Retail Federation (NRF), and co-developed with Shopify. It establishes a common language so AI agents and merchant systems can operate together across the whole shopping journey, from discovery to buying to post-purchase. The goal: avoid forcing merchants to build a different connection for every agent. Established

Who is behind UCP?

UCP is led by Google in collaboration with Shopify, Etsy, Wayfair, Target and Walmart, and endorsed by more than 20 ecosystem players: Adyen, American Express, Best Buy, Flipkart, Macy's, Mastercard, Stripe, The Home Depot, Visa, Zalando and others. It is an open-source project, described as neutral and vendor-agnostic by its authors. Established

How does UCP work?

UCP standardizes commerce operations (catalog, cart, checkout, order, post-purchase) behind an agent-usable interface. It is designed to be compatible with existing protocols: Agent2Agent (A2A) for agent-to-agent communication, Agent Payments Protocol (AP2) for payment authorization, and Model Context Protocol (MCP) for tool and data access.

First concrete application: Google built a reference implementation that powers native checkout in AI Mode (Search) and the Gemini app. Shoppers pay with Google Pay (and soon PayPal), and the merchant remains the seller of record. To take part on the Google side, a merchant uses a Merchant Center account with checkout-eligible products. Established

Under the hood: discovery, capabilities, payments

Technically, a UCP merchant publishes a discovery manifest at the standardized address /.well-known/ucp: a JSON document declaring supported services (e.g. dev.ucp.shopping), exposed capabilities (checkout, discounts, fulfillment, plus identity linking and order management) and accepted payment handlers (Google Pay, Shop Pay...). A compatible agent can thus dynamically discover what the merchant supports, without bespoke integration. The protocol separates payment instruments (what the buyer uses) from handlers (who processes), and every authorization is backed by cryptographic proof of user consent. Exchanges run over REST APIs, MCP or A2A. Established

The step-by-step merchant playbook (Merchant Center, manifest, SDK) is detailed in the UCP implementation guide.

What changed at Google Marketing Live (May 2026)

On May 20, 2026, Google announced a major expansion of UCP-powered features. Established

• Universal Cart expands: a multi-retailer cart where shoppers save products across merchants and pay via Google Pay or the retailer's checkout. Announced brands: Nike, Sephora, Target, Walmart, Wayfair, and Shopify merchants such as Fenty and Steve Madden.
• Buy now, pay later: Affirm and Klarna integrations directly inside Google Pay.
• New surfaces: UCP integrates with Direct Offers, Demand Gen campaigns, AI Mode shopping experiences and Shopping ads on YouTube.
• New verticals announced: hotel booking from AI Mode and food ordering from Google Maps. Emerging
• Merchant tooling: AI Performance Insights and Conversational Attributes in Merchant Center, Ask Advisor integration.

Availability-wise, these features are rolling out in the United States first, with announced expansions to Canada and Australia, then the United Kingdom. Established

Milestones

Page updated June 10, 2026. This timeline is maintained as the standard evolves.

UCP vs ACP: the two transaction-layer standards

UCP and the Agentic Commerce Protocol (ACP) from OpenAI and Stripe target the same layer, but with opposite philosophies.

In practice, many merchants will implement both to maximize distribution, much like listing on several marketplaces. Emerging The full dimension-by-dimension comparison lives on the UCP vs ACP page.

What it changes for a merchant

Being present on UCP requires an offer that is readable and actionable by a machine: structured product data, explicit policies, an agent endpoint. It is the same groundwork as agentic commerce in general. The implementation guide details the concrete steps, and the readiness audit methodology assesses this state layer by layer.

Frequently asked questions