ACP (Stripe, OpenAI, Meta; launched September 2025) structures a purchase as three specs: a product feed, a checkout API, and a delegated payment token. It currently powers commerce in ChatGPT and Microsoft Copilot. UCP (Google, with Shopify and other retailers; launched January 2026) uses a single JSON manifest published at /.well-known/ucp and currently powers Google AI Mode. Most merchants serious about AI-driven sales will eventually need both, since each only reaches its own agents.
Origin and governance
| UCP | ACP | |
|---|---|---|
| Announced | January 11, 2026, at NRF | September 29, 2025 |
| Built by | Google, with Shopify, Etsy, Wayfair, Target, and Walmart | Stripe, OpenAI, and Meta |
| License | Open source | Apache 2.0 |
| Spec lives at | ucp.dev | agenticcommerce.dev |
| Named endorsers (beyond builders) | 20+, including Visa, Mastercard, Stripe, The Home Depot | 25+, including Salesforce and Squarespace |
Neither standard is a proprietary product you license. Both are open specifications any business, platform, or payment processor can implement without paying the companies that built them. The difference is who was in the room when each was designed, and which agents were built to speak it first.
How each one is actually structured
This is where the two genuinely diverge, not just in branding.
A single JSON file published at /.well-known/ucp, listing services, capabilities, payment handlers, and signing keys. One file, one location, checkable in one request.
A Product Feed Spec for the catalog, an Agentic Checkout Spec (a REST API for creating and completing a checkout session), and a Delegated Payment Spec (how an agent gets a scoped payment token). Three separate integrations, not one file.
Practically, this means checking UCP support is a single, fast lookup, which is what our checker and validator do. Checking ACP support is closer to auditing an integration than reading a file, since there's no single document that proves it end to end. For the full breakdown of what each actually requires, see our dedicated guides to UCP and ACP.
Where each one is actually live today
This is the part that matters most for deciding what to build first, and it changes as agents add support, so treat this as a snapshot rather than a permanent map.
Runs on ACP. Product discovery today; in-chat Instant Checkout existed from September 2025 to March 2026, when OpenAI retired it citing low adoption.
Runs on ACP too. Per Stripe's own newsroom, Copilot connects to sellers through Stripe, which in turn connects to the seller via ACP, using the same Shared Payment Token mechanism as ChatGPT.
Runs on UCP, the standard Google built specifically for its own AI shopping surfaces.
The practical read: right now, ACP has the wider agent surface (two major chat assistants), while UCP has the narrower but still significant one (Google's own AI Mode, which Google has been aggressively expanding). Neither has full coverage of the other's territory.
Full comparison
| UCP | ACP | |
|---|---|---|
| What a merchant checks/implements | One manifest at /.well-known/ucp | Three specs: feed, checkout API, payment token |
| Live agent surfaces today | Google AI Mode | ChatGPT, Microsoft Copilot |
| Payment mechanism | Handlers declared in the manifest | Delegated Payment Spec (e.g. Stripe's Shared Payment Token) |
| Merchant of record | The merchant | The merchant |
| Free to implement | Yes, open source | Yes, Apache 2.0 |
| Can a merchant support both? | Yes, they are not mutually exclusive | Yes, they are not mutually exclusive |
Which one should you actually build first?
Start with ACP if...
Broader chat coverage todayYour customers are more likely to be using ChatGPT or Copilot, or you already process payments with Stripe, PayPal, or Adyen, all of which have built ACP support into their existing infrastructure. See our guides on how Stripe, PayPal, and Adyen each frame that integration.
Start with UCP if...
Faster to check and implementYou're already deep in the Google ecosystem (Shopify's built-in Agentic storefronts channel handles UCP for you automatically), or you want the lower-lift path first: one manifest file is a smaller lift than three separate specs, even if it currently reaches fewer live agent surfaces.
Plan for both eventually
Realistic default for most merchantsSince the two don't overlap in which agents they reach, a merchant that only implements one is invisible to the other's entire agent ecosystem. Most businesses serious about AI-driven sales will end up doing both; the open question is just which to prioritize first given your specific customer base and existing payment stack.
Check where you actually stand today
Start with UCP, since it's the faster check: enter a domain to see whether it publishes a valid manifest.
Frequently asked questions
Yes. Neither standard is exclusive, and a business can implement one, the other, or both, depending on which AI agents its customers actually use.
It depends on your customers and existing stack. ACP currently reaches more chat-based agents (ChatGPT and Microsoft Copilot); UCP is a smaller, single-file lift and reaches Google AI Mode. If you already process payments with Stripe, PayPal, or Adyen, ACP support may already be closer than you think. If you're on Shopify, UCP is likely already handled for you.
ACP. Per Stripe's own newsroom, Copilot Checkout connects to sellers through Stripe, which connects to the merchant via the Agentic Commerce Protocol, the same mechanism ChatGPT uses.
No. Both are open specifications, UCP under an open source license and ACP under Apache 2.0, and neither requires paying the companies that built it to implement.
Yes, structurally. UCP support is a single manifest file at a fixed path, checkable in one request. ACP is three separate specs (a product feed, a checkout API, and a payment token flow), so there's no single document that proves support end to end the way a UCP manifest does.
Sources
- agenticcommerce.dev, the official ACP specification
- ucp.dev, the official UCP specification
- Stripe Newsroom, "Stripe helps power a new shopping experience in Microsoft Copilot"
- Google Developers Blog, "Under the Hood: Universal Commerce Protocol (UCP)"
- Stripe, "The three biggest agentic commerce trends from NRF 2026"
- Digital Commerce 360, "OpenAI shifts checkout plans in its agentic commerce strategy"