ACP and UCP are two open standards that let an AI agent buy on a shopper's behalf. ACP, the Agentic Commerce Protocol, was published by OpenAI and Stripe on 29 September 2025 alongside Instant Checkout in ChatGPT. UCP, the Universal Commerce Protocol, was announced by Google on 11 January 2026, co-developed with Shopify, Etsy, Wayfair, Target and Walmart, and covers the whole journey from discovery to post-purchase support. Both solve the transaction. Neither decides whether an agent picks your product in the first place. That decision is made on your product content, and it is the half of the story almost nobody writes about.
What problem do both standards solve?
Before these protocols, an agent buying for a shopper had to deal with a different checkout at every merchant. A protocol replaces that with a shared language, and the payment goes through without the shopper leaving the conversation.
Stripe described ACP as "a shared language between businesses and AI agents" that lets a merchant sell through multiple AI platforms with a single integration. UCP's launch announcement from Google makes the same promise from the other side: one standard for consumer surfaces, businesses and payment providers.
ACP: what it is, who shipped it, when
ACP is a joint standard from OpenAI and Stripe. Stripe's newsroom announced it on 29 September 2025 together with Instant Checkout, which lets ChatGPT users in the United States buy directly inside a conversation.
At launch the announcement named US Etsy sellers as live and over one million Shopify merchants as coming soon. ChatGPT acts as the buyer's AI agent, "just as a personal shopper would," in Stripe's words.
ACP also has a catalog side. OpenAI's developer documentation says product feeds give ChatGPT "the catalog data it needs to index your products, understand core attributes, and present accurate product information." As of October 2026, OpenAI states that onboarding product feeds is available to approved partners only, by application.
UCP: what it is, who shipped it, when
UCP is an open-source standard published by Google on 11 January 2026. Google's Developers Blog says it was co-developed with Shopify, Etsy, Wayfair, Target and Walmart, and endorsed by more than 20 others, including Visa, Mastercard, Stripe, American Express, Best Buy, The Home Depot and Zalando.
The scope is wider than checkout. Google's announcement describes a standard that works "across the entire shopping journey" and runs "from discovery and buying to post-purchase support." The Developers Blog lists discovery, consideration, purchase and order management.
Google says UCP is compatible with the Agent Payments Protocol (AP2) for payments.
Google's checkout feature is more limited than the standard. Google Merchant Center Help says UCP checkout applies only to products eligible in the United States, Canada and Australia, for participating merchants, and that only listings carrying the native_commerce(checkout_eligibility) attribute show the Buy button.
Side by side: scope, backers, what each covers
The criteria below are the ones a seller cares about: who is behind it, how far it reaches, where the shopper sees it, and what the seller supplies.
| Criterion | ACP | UCP |
|---|---|---|
| Published by | OpenAI and Stripe | Google, co-developed with Shopify, Etsy, Wayfair, Target, Walmart |
| Date | 29 September 2025 | 11 January 2026 |
| Scope | Agent-to-merchant checkout, plus product feeds for ChatGPT | Discovery, consideration, purchase and order management |
| Where shoppers see it | Instant Checkout in ChatGPT | Checkout on eligible listings in Google AI Mode and the Gemini app |
| Merchant data | Product feed, approved partners by application | Merchant Center data and attributes |
What ACP does better: it shipped first, and it is tied to one very large consumer surface. A seller who connects once is in ChatGPT.
What UCP does better: it has a wider scope and a wider list of retail backers. It covers more of the journey than checkout alone, and it is built to work with Google's AP2 payments standard.
So they are not strict rivals. Stripe appears on both lists. The sensible reading is two entry points to the same shift, each backed by the platform that owns a major AI shopping surface.
What neither of them does
Neither protocol chooses your product.
A protocol tells an agent how to complete a purchase once it has decided what to buy. The decision comes earlier, when the agent reads product content and judges which product answers the shopper's request. Content that is thin, contradictory or missing key facts loses at that step, and no protocol can fix it.
Google's own announcement points the same way. It introduced "dozens of new data attributes in Merchant Center designed for easy discovery in the conversational commerce era," which "go beyond traditional keywords to include things like answers to common product questions, compatible accessories or substitutes." That is a standards body telling merchants that answers and compatibility facts are now part of the product record.
What does a seller actually have to do?
Most sellers do not implement either protocol. Their platform does.
→ On Shopify or Etsy, both named in the ACP and UCP announcements, the platform is the integration point. Your job is the data it passes on.
→ On Amazon, the assistant is Amazon's own, Alexa for Shopping (formerly Rufus), and it reads your listing. The principle is identical: the agent selects on content before anything else happens.
→ With your own checkout, you may need to build to a protocol, or to use a processor or platform that has. This is where a developer earns their fee.
For everyone, the work is the same and it is a data problem.
→ Identity: brand, model, GTIN, title.
→ Price and availability: accurate, and the same everywhere.
→ Shipping and returns: stated plainly.
→ Answers: the facts shoppers ask about, written as facts.
The failure mode is contradiction. When your marketplace listing says one thing, your website another and your feed a third, an agent cannot tell which is true. The safe move for the agent is to skip you.
Be honest about where Cosmy fits. Cosmy does not implement ACP or UCP, build feeds or run checkout. If you run your own store, a platform or payment provider is the right answer for that part. Cosmy covers the content side for Amazon: it runs an Alexa for Shopping analysis on your listing and returns a gap report of the buyer questions the listing cannot answer.
Do you need to care yet?
Care about the data now. Care about the protocols when your platform asks you to.
Both standards are rolling out in stages. UCP checkout is limited to three countries and to participating merchants. ACP's feed onboarding is by application. Waiting for the dust to settle is a reasonable position on implementation.
It is not a reasonable position on content. A listing that answers shopper questions with specific facts is selectable under either standard, on any surface, and costs nothing to improve.
What to do next
- Check whether your platform supports either standard. Most sellers inherit support rather than build it.
- Treat protocol readiness as a data problem. Identity, price, availability and shipping, accurate and consistent.
- Fix contradictions between your marketplace listing, your site and your feed.
- Do not build to a protocol directly unless you run your own checkout.
Where to start
The fastest way to see what an AI agent cannot answer about your product is to look at the gaps directly. A free Cosmy account at cosmy.ai runs an Alexa for Shopping analysis on one of your ASINs and returns a gap report.
