UCP
Universal Commerce Protocol
A universal power socket for shopping. Any assistant plugs into any store without a custom adapter.
Reality check
In production, and the most real of the twelve. An independent checker counts more than 15,000 verified storefronts, mostly through Shopify. One catch, the August release made 17 breaking changes, so "supports UCP" doesn't tell you which version.
How it works
UCP defines the common steps of buying (catalog, cart, checkout, order) and carries them over ordinary web APIs or the plugs agents already use (MCP, A2A). A store describes what it supports at /.well-known/ucp.
Ask Google's AI Mode for waterproof hiking boots under $150, and it compares several shops and checks out right in the chat, while the retailer stays the "merchant of record," the legal seller who handles returns and customer data.
Who's behind it
Google launched it with Shopify on January 11, 2026, co-developed with Etsy, Wayfair, Target and Walmart. A Governing Council has Google and Shopify as permanent members, and Stripe joined on April 28; a technical council added Amazon, Meta, Microsoft, Salesforce and Stripe in April, and industry councils for food, lodging and payments followed over the summer. A council seat isn't a storefront: Amazon being at the table doesn't mean Amazon sells through UCP.
The current release, v2026-08-25, added support for more industries and stronger card security.