Comparison
UCP vs ACP: two standards, two philosophies.
The Universal Commerce Protocol (Google, Shopify) and the Agentic Commerce Protocol (OpenAI, Stripe) both structure the agentic transaction. Here is what actually separates them, dimension by dimension, from primary sources.
The 30-second summary
- UCP (Google/Shopify, Jan. 2026): decentralized, the merchant publishes its capabilities, purchases happen in AI Mode and Gemini.
- ACP (OpenAI/Stripe, Sept. 2025): platform-mediated. OpenAI scaled back its native ChatGPT checkout in 2026 and partnered with Visa for payments (June 2026).
- In both cases: the merchant remains the merchant of record.
- In practice: the two stack, like distribution channels.
The dimension-by-dimension comparison
| Dimension | UCP (Google/Shopify) | ACP (OpenAI/Stripe) |
|---|---|---|
| Backers | Google and Shopify, with Etsy, Wayfair, Target, Walmart and 20+ partners | OpenAI and Stripe |
| Announced | January 2026 (NRF) | September 2025 |
| Model | Decentralized: the merchant publishes its capabilities, any compatible agent can transact | Platform-mediated: the merchant sends data to OpenAI |
| Discovery | Standardized /.well-known/ucp manifest read dynamically by the agent | Product feed sent to the platform |
| Buying surface | Google AI Mode, Gemini app (and any compatible surface) | ChatGPT and third-party apps. The native Instant Checkout was scaled back in 2026 |
| Payment | Modular handlers: Google Pay, Shop Pay... (PayPal announced). Affirm/Klarna BNPL via Google Pay since May 2026 | Single-use token via Stripe; OpenAI payments via Visa Intelligent Commerce since the June 2026 partnership |
| Merchant of record | The merchant | The merchant |
| Protocol compatibility | A2A, AP2, MCP; REST, MCP, A2A or embedded transports | REST specification; OpenAI ecosystem |
| Code | Open source: spec, Python SDK, samples on GitHub | Open specification on GitHub |
What changed in June 2026
The agentic transaction layer reorganized in a matter of days. Four moves qualify the table above. Established
- OpenAI leans on Visa. At the Visa Payments Forum on June 10, 2026, OpenAI and Visa announced the integration of Visa Intelligent Commerce into OpenAI experiences: tokenized Visa credentials, real-time authorization, and user-defined guardrails (spend cap, merchant categories, human approval). It is another path into commerce after the native ChatGPT checkout was scaled back.
- ACP's native checkout was scaled back. Launched in September 2025 (first with Etsy), Instant Checkout was moved into third-party apps during 2026. ACP remains OpenAI's standard, mainly for discovery and product feeds.
- Mastercard extends Agent Pay. On June 10, 2026, Mastercard launched Agent Pay for Machines (AP4M) for agent-to-agent transactions, with Checkout.com, Cloudflare, Coinbase, Ripple and Stripe.
- AP2 changes governance. The mandate-based payment authorization protocol is now stewarded by the FIDO Alliance and claims 120+ partners.
In Europe, Worldline, ING and Mastercard completed a first end-to-end agentic payment in live conditions, a sign these rails are leaving the lab. Emerging
The real dividing line: who owns discovery
The structuring difference is not technical, it is topological. With UCP, discovery belongs to
the merchant: it publishes a manifest at a standardized address (/.well-known/ucp), and any
compatible agent can read it, with no bilateral agreement. With ACP, discovery belongs to the
platform: the merchant sends its data to OpenAI, which decides what gets exposed in ChatGPT. Established
Consequence for a merchant: UCP behaves like an infrastructure standard (like publishing a sitemap), ACP behaves like a distribution channel (like listing on a marketplace). Both logics can coexist within one strategy. Emerging
What the two share
- The merchant remains the merchant of record: legal responsibility, customer relationship and business logic stay with the merchant.
- The prerequisite is identical: a structured catalog, accurate prices and stock, explicit policies. A protocol never compensates for poor data.
- Open source as an adoption strategy: public specifications on GitHub on both sides.
To prepare that shared foundation, the readiness audit methodology scores your state layer by layer, and the UCP implementation guide details the path on the Google/Shopify side.
Frequently asked questions
01 Are UCP and ACP competitors?
Are UCP and ACP competitors?
They target the same transactional layer of agentic commerce, but on different surfaces: UCP powers purchases on the Google side (AI Mode, Gemini), ACP on the ChatGPT side (Instant Checkout). For a merchant, the question is not picking a side but covering the surfaces where your buyers are.
02 What is the philosophical difference between UCP and ACP?
What is the philosophical difference between UCP and ACP?
UCP is decentralized: the merchant publishes a capabilities manifest (/.well-known/ucp) that any compatible agent can discover and invoke. ACP is platform-mediated: the merchant sends its data to OpenAI and checkout happens inside ChatGPT. In both cases the merchant remains the merchant of record.
03 Should you implement UCP, ACP, or both?
Should you implement UCP, ACP, or both?
Many merchants will implement both, much like listing on several marketplaces. The groundwork is largely shared: structured catalog, explicit policies, accurate data. Readiness is the durable investment; the protocols are its distribution.
04 Who else structures the agentic transaction layer?
Who else structures the agentic transaction layer?
Around these two standards: AP2 (Agent Payments Protocol, now stewarded by the FIDO Alliance, 120+ partners) for payment authorization via cryptographic mandates, Visa Intelligent Commerce (integrated into OpenAI experiences since June 2026) and Mastercard Agent Pay, extended by Agent Pay for Machines (AP4M) for agent-to-agent transactions, on the network side, and x402 (Coinbase) for stablecoin settlement. See the glossary for definitions.
05 Did OpenAI abandon checkout in ChatGPT?
Did OpenAI abandon checkout in ChatGPT?
Not commerce, but the native checkout. Instant Checkout, launched in September 2025 (first with Etsy), was scaled back during 2026 and moved into third-party apps. On June 10, 2026, OpenAI partnered with Visa (Visa Intelligent Commerce) to process agent purchases beyond a single checkout flow. ACP remains OpenAI's standard, mainly for discovery and product feeds.
Primary sources
- Google Developers Blog, "Under the Hood: UCP".
- UCP specification (GitHub) and ucp.dev.
- Stripe, "Developing an open standard for agentic commerce" (ACP).
- ACP specification (GitHub).
- Google, UCP expansions at Google Marketing Live (May 2026).
- Visa, announcements at the Visa Payments Forum (OpenAI partnership, June 10, 2026).
- Fortune, Mastercard Agent Pay for Machines (June 10, 2026).
Go further
The full standard reference, the implementation guide, and the agentic commerce context.