Google leads. Launch partners include Shopify, Etsy, Wayfair, Target, Walmart, and approximately twenty other commerce platforms and brands. The announcement was published on the Google Developers Blog on January 11, 2026. The current spec version is 2026-04-08, with 2026-01-23 still supported during the early-access window.

Glossary

UCP: Universal Commerce Protocol

Q: Where does AP2 fit in?

AP2 (Agent Payments Protocol) is Google's sister protocol to UCP and handles secure agent-led payments. UCP orchestrates the broader purchase lifecycle and AP2 handles the payment layer specifically. The two are designed to work together in Google's agentic commerce stack.

Google's open commerce protocol, announced January 11, 2026 with Shopify, Etsy, Wayfair, Target, Walmart, and roughly twenty partners. Often misidentified as "Unified Content Protocol" in early third-party coverage.

Spec 2026-04-08 · 2026-01-23 also supported · Last updated 2026-06-03

The naming confusion

UCP stands for Universal Commerce Protocol, not Unified Content Protocol. Several third-party publications used the wrong expansion in the week after Google's January 11, 2026 announcement, and the mistaken name has cycled through some vendor decks. The canonical name on ucp.dev and developers.google.com/merchant/ucp is Universal Commerce Protocol.

In detail

A UCP-ready merchant publishes a JSON profile at /.well-known/ucp (no auth, minimum 60-second cache TTL, includes ucp and signing_keys objects) and exposes five native checkout REST endpoints at a merchant-declared base, conventionally /ucp/v1: POST /checkout-sessions, GET /checkout-sessions/{id}, PUT /checkout-sessions/{id}, POST /checkout-sessions/{id}/complete, POST /checkout-sessions/{id}/cancel.

The SLOs are aggressive. POST /checkout-sessions must hit ≥95% availability, P50 ≤1s, P95 ≤4s. POST /complete must hit P50 ≤6s, P95 ≤10s. Most Shopify storefronts need an edge layer to clear those targets reliably.

Webhooks flow from the merchant TO Google at shoppingdataintegration.googleapis.com (not the reverse). Three events are mandatory: Order Created (status: processing, fired immediately), Order Shipped, and Order Delivered. Webhook signing uses RFC 9421 in 2026-04-08, or HMAC/detached-JWT per RFC 7797 in 2026-01-23. Identity linking uses OAuth 2.0 with PKCE-S256 recommended; Google Streamlined Linking is optional for in-Google account-link UI. Compatible transports include REST, MCP, A2A, and Embedded Protocol (EP). The Google Pay handler is com.google.pay at v2026-01-23.

The three new product-feed attributes

UCP introduces three attributes on the Merchant Center product feed:

native_commerce — a SKU-level boolean opt-in. Recommended via a supplemental feed rather than modifying the primary feed. Without it the SKU is not eligible for UCP checkout, even if the merchant is otherwise UCP-ready.
consumer_notice — required for regulated products. Contains a notice_type enum value and a notice_message string.
merchant_item_id — optional. Maps a GMC product ID to a merchant's internal UCP ID.

Ineligible categories per Google's documentation: subscriptions, installments, personalized goods, pre-order, bundled, age-restricted, services, rentals, virtual items, and software-dependent goods.

Why it matters

UCP is the answer to a question Shopify brands have been asking: how do you participate in Google AI Mode and Gemini commerce without rebuilding checkout? UCP defines the contract; Shopify ships the integration through Shopify Agentic Storefronts. Pilot eligibility as of 2026-06-03 is US, Canada, and Australia.

Related terms

ACP (Agentic Commerce Protocol) — the OpenAI/Stripe/Meta counterpart that powers ChatGPT Instant Checkout.
Shopify Agentic Storefronts — Shopify's channel for AI-driven commerce; wraps UCP for Shopify merchants.
AP2 (Agent Payments Protocol) — Google's sister protocol for secure agent-led payments.
Agentic commerce — the umbrella term.
Product schema — the structured data UCP attaches to.

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Frequently asked questions

What is the difference between UCP and Unified Content Protocol?

UCP stands for Universal Commerce Protocol, not Unified Content Protocol. The Unified Content Protocol name appears in some third-party coverage but is incorrect. Canonical sources are developers.google.com/merchant/ucp and ucp.dev.

Who maintains UCP?

Google leads. Launch partners include Shopify, Etsy, Wayfair, Target, Walmart, and approximately twenty others. Announced on the Google Developers Blog January 11, 2026.

Where does AP2 fit in?

AP2 (Agent Payments Protocol) is Google's payments-layer sister protocol to UCP. UCP orchestrates the lifecycle; AP2 handles secure agent-led payments.

Related guides

Score your store's UCP and ACP readiness in 60 seconds with the free Agentic Readiness Grader.