> ## Content Index
> Fetch the complete content index at: https://stablecoininsider.org/llms.txt
> Use this file to discover other available public pages before exploring further.

# ACP vs UCP: Agentic Commerce Protocols Compared (2026)
- URL: https://stablecoininsider.org/acp-vs-ucp/
- Published: 2026-11-11T07:14:27.000Z
- Updated: 2026-11-11T07:14:29.000Z
- Description: ACP vs UCP compared from the specs: OpenAI and Stripe's Agentic Commerce Protocol against Google and Shopify's Universal Commerce Protocol on checkout, payment tokens, live surfaces, merchant build, release cadence and the stablecoin rails that sit beside both.
- Author: Alexandra
- Tags: AI, AI Agents, payments, Stablecoin Payments

ACP vs UCP comes down to who runs the shopping surface. The Agentic Commerce Protocol (ACP), from OpenAI and Stripe, now mainly feeds product data into ChatGPT, where buyers finish on the merchant's own site; the Universal Commerce Protocol (UCP), led by Google and Shopify, runs checkout inside Google AI Mode and the Gemini app ([OpenAI merchants](https://chatgpt.com/merchants/), [Google UCP guide](https://developers.google.com/merchant/ucp)).

Both are open source under Apache 2.0, both keep the merchant as seller of record, and both hand the merchant a scoped payment credential instead of a raw card number ([agenticcommerce.dev](https://www.agenticcommerce.dev/), [UCP specification](https://ucp.dev/latest/specification/overview/)). The differences are in scope, discovery, payment plumbing and where each one is actually live.

This guide compares the two from their specifications and launch documents, not from vendor marketing. It extends our earlier comparisons of the payment layer underneath, [x402 vs AP2 vs ACK-Pay](https://stablecoininsider.org/x402-vs-ap2-vs-ack-pay/), and of the card networks' agent programs, [Visa Intelligent Commerce vs Mastercard Agent Pay](https://stablecoininsider.org/visa-intelligent-commerce-vs-mastercard-agent-pay/).

Stablecoin Insider's take: most ranking pages treat ACP and UCP as a standards war. In practice the bigger news of 2026 is that OpenAI pulled back from in-chat checkout while Google pushed checkout into its own surfaces, so the two protocols now solve different problems for a merchant. Neither one moves stablecoins natively, which matters for anyone hoping agent commerce runs on USDC.

## Key Takeaways

- ACP launched with ChatGPT Instant Checkout on 29 September 2025, and in March 2026 OpenAI moved purchases back to merchant-owned sites while ACP shifted to product discovery ([OpenAI](https://chatgpt.com/merchants/)).
- UCP launched on 11 January 2026, co-developed with Shopify, Etsy, Wayfair, Target and Walmart and endorsed by more than 20 firms including Adyen, Mastercard, Stripe and Visa ([Google](https://blog.google/products/ads-commerce/agentic-commerce-ai-tools-protocol-retailers-platforms/)).
- UCP covers catalog, cart, checkout, identity linking and orders over REST, MCP, A2A or embedded transports; its latest tagged release is 2026-08-25 ([UCP releases](https://github.com/Universal-Commerce-Protocol/ucp/releases)).
- ACP has five dated spec versions, the latest 2026-04-17, and now lists OpenAI, Stripe and Meta as lead maintainers ([ACP maintainers](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/blob/main/MAINTAINERS.md)).
- Neither protocol has a native stablecoin rail; Stripe routes agent stablecoin payments through MPP and x402 instead, with a 0.01 USDC minimum ([Stripe machine payments](https://docs.stripe.com/payments/machine)).

## What is the difference between ACP and UCP?

ACP is a platform-mediated standard: merchants send product feeds to an AI platform and expose checkout endpoints that the platform calls. UCP is a merchant-hosted standard: each business publishes a profile at /.well-known/ucp, and any agent that speaks the protocol negotiates capabilities with it directly ([ACP](https://www.agenticcommerce.dev/), [UCP spec](https://ucp.dev/latest/specification/overview/)).

| Dimension          | ACP (Agentic Commerce Protocol)                                                                                                                                   | UCP (Universal Commerce Protocol)                                                                                                                                                                                                                            |
| ------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Started by         | OpenAI and Stripe, 29 September 2025 ([OpenAI](https://openai.com/index/buy-it-in-chatgpt/))                                                                      | Google, 11 January 2026 ([Google](https://blog.google/products/ads-commerce/agentic-commerce-ai-tools-protocol-retailers-platforms/))                                                                                                                        |
| Maintainers        | OpenAI, Stripe and Meta ([MAINTAINERS.md](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/blob/main/MAINTAINERS.md))                       | UCP governing body for the dev.ucp namespace; vendors publish their own extensions ([spec](https://ucp.dev/latest/specification/overview/))                                                                                                                  |
| License            | Apache 2.0 ([repo](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol))                                                                       | Apache 2.0 ([repo](https://github.com/Universal-Commerce-Protocol/ucp))                                                                                                                                                                                      |
| Spec versions      | 2025-09-29, 2025-12-12, 2026-01-16, 2026-01-30, 2026-04-17 ([spec folder](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/tree/main/spec)) | 2026-01-11, 2026-01-23, 2026-04-08, 2026-08-25 ([releases](https://github.com/Universal-Commerce-Protocol/ucp/releases))                                                                                                                                     |
| Discovery          | Merchant product feed sent to each AI platform; per-platform application                                                                                          | Agent reads the merchant's /.well-known/ucp profile and negotiates capabilities                                                                                                                                                                              |
| Scope              | Product feed, checkout sessions, order webhooks, delegated payment                                                                                                | Ask, cart, checkout, identity linking, order, plus extensions such as discounts and fulfillment                                                                                                                                                              |
| Transports         | REST and MCP ([ACP](https://www.agenticcommerce.dev/))                                                                                                            | REST, MCP, A2A and embedded ([spec](https://ucp.dev/latest/specification/overview/))                                                                                                                                                                         |
| Payment credential | Delegated payment token; Stripe Shared Payment Token was the first compatible one ([ACP FAQ](https://www.agenticcommerce.dev/))                                   | Payment handlers declared by the merchant (Google Pay, Shop Pay, PSP tokenizers), optional AP2 mandates                                                                                                                                                      |
| Main live surface  | ChatGPT shopping in the U.S., discovery only ([OpenAI](https://chatgpt.com/merchants/))                                                                           | Checkout in AI Mode and the Gemini app, U.S. and now Canada ([Google Canada](https://blog.google/intl/en-ca/products/explore-get-answers/a-new-way-to-shop-introducing-a-more-intuitive-agentic-shopping-experience-for-consumers-and-retailers-in-canada/)) |
| Seller of record   | The merchant                                                                                                                                                      | The merchant                                                                                                                                                                                                                                                 |

GitHub activity hints at the gap in community pull: on 11 November 2026 the UCP repository showed about 3,490 stars against about 1,600 for the ACP repository ([UCP repo](https://github.com/Universal-Commerce-Protocol/ucp), [ACP repo](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol)). Stars measure developer attention, not merchant revenue, so treat this as a soft signal only.

## What is ACP and what changed in 2026?

ACP is the open standard OpenAI and Stripe released to let an AI agent run a checkout against a merchant's own backend and pay with a scoped token. It powered Instant Checkout in ChatGPT at launch, starting with U.S. Etsy sellers ([OpenAI launch post](https://openai.com/index/buy-it-in-chatgpt/)).

The protocol defines a product feed, a set of checkout session endpoints the merchant hosts, order webhooks, and a delegated payment step where the agent passes a token rather than card details. Any compatible payment provider can implement the payment side, and Stripe's Shared Payment Token was the first ([agenticcommerce.dev](https://www.agenticcommerce.dev/)).

The big change came on 24 March 2026\. OpenAI said the first version of Instant Checkout did not offer the flexibility it wanted, let merchants use their own checkout, and expanded ACP to carry product feeds and promotions for discovery. Target, Sephora, Nordstrom, Lowe's, Best Buy, The Home Depot and Wayfair were named as integrated for discovery ([OpenAI](https://openai.com/index/powering-product-discovery-in-chatgpt/)).

OpenAI's merchant page now says it is "moving away from a standalone Instant Checkout experience," that purchases are completed on merchant-owned websites or apps, that there are no fees on purchases that start in ChatGPT, and that Shopify and Etsy catalogs are already integrated ([ChatGPT merchants](https://chatgpt.com/merchants/)). Other merchants apply and join a waitlist.

Stablecoin Insider's take: ACP did not die, it changed jobs. Today it is mostly a catalog pipe into ChatGPT, with checkout handed back to the merchant. The checkout and delegated payment parts of the spec still exist, so any other AI platform could run in-chat checkout on ACP, but the largest one has chosen not to for now.

## What is UCP and how does it work?

UCP is an open commerce standard that lets any agent discover what a business supports and then search, build a cart, check out and track orders against that business's own endpoints. Google announced it on 11 January 2026 and uses it for checkout on eligible listings in AI Mode and Gemini, paid with Google Pay, with PayPal named as coming ([Google](https://blog.google/products/ads-commerce/agentic-commerce-ai-tools-protocol-retailers-platforms/)).

A business publishes a machine-readable profile at /.well-known/ucp listing its services, capabilities, payment handlers and public signing keys. The platform advertises its own profile on every request, and the business computes the intersection of capabilities both sides support at a shared version ([UCP specification](https://ucp.dev/latest/specification/overview/)). Capability names use reverse-domain namespaces, so a vendor can publish an extension such as com.example.installments without a central registry.

The standard capabilities are Ask, Cart, Checkout, Identity Linking and Order. The 2026-04-08 release added the cart capability, catalog search and lookup, and request and response signing; 2026-08-25 added 3DS2 authentication, split payments across instruments, deposit and installment schedules, location search for grocery and a loyalty extension ([UCP releases](https://github.com/Universal-Commerce-Protocol/ucp/releases)).

On Google's side, REST is the recommended transport for Native Checkout and Cart because Merchant Center validation only tests REST; MCP is early access and needs per-account enablement after integration testing ([Google MCP transport guide](https://developers.google.com/merchant/ucp/guides/overview/mcp-transport)).

## How do checkout and payment differ between ACP and UCP?

In ACP the agent platform calls the merchant's checkout endpoints and passes a delegated payment token scoped to one merchant, amount and time window; in UCP the merchant advertises payment handlers, the platform gets an opaque credential from the payment provider, then submits it to the merchant to complete ([Stripe SPT docs](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens), [UCP spec](https://ucp.dev/latest/specification/overview/)).

| Step                 | ACP                                                                                                                                                        | UCP                                                                                                                                         |
| -------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- |
| 1\. Find the product | Platform ranks items from the merchant's feed                                                                                                              | Agent queries the merchant's catalog capability or a platform index such as Merchant Center                                                 |
| 2\. Build the order  | Platform creates a checkout session on the merchant's endpoint                                                                                             | Agent creates a cart or checkout session after capability negotiation                                                                       |
| 3\. Get a credential | Agent issues a scoped token; Stripe SPTs carry usage and expiry limits ([Stripe](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens)) | Platform runs the merchant-declared handler, such as Google Pay or a PSP tokenizer ([spec](https://ucp.dev/latest/specification/overview/)) |
| 4\. Prove consent    | Buyer confirms in the platform interface                                                                                                                   | Optional AP2 mandates give signed proof of checkout terms ([AP2 extension](https://ucp.dev/latest/specification/overview/))                 |
| 5\. Complete         | Merchant charges through its processor                                                                                                                     | Merchant captures through its backend; one instrument per order unless split payments is active                                             |
| 6\. After the sale   | Order webhooks back to the platform                                                                                                                        | Order capability pushes shipping, delivery and return updates                                                                               |

UCP is stricter about credentials. Credentials flow only from platform to business, businesses must not echo them back, and a handler\_id tells the business which provider key to use, which is meant to keep platforms out of PCI-DSS scope ([UCP payment architecture](https://ucp.dev/latest/specification/overview/)). ACP reaches the same goal through the token itself: Stripe can return a card credential type of fpan, dpan or agentic\_token depending on account setup ([Stripe SPT docs](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens)).

For autonomous purchases, UCP leans on AP2\. Google donated AP2 to the FIDO Alliance on 28 April 2026 and released version 0.2 with support for purchases where the shopper is not present at the moment of payment ([Google](https://blog.google/products-and-platforms/platforms/google-pay/agent-payments-protocol-fido-alliance/)). ACP has no separate signed-mandate layer; it limits the delegated token itself, scoping it to one merchant with a maximum amount and an expiry, and leaves buyer confirmation to the platform interface the shopper is using ([ACP specification](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/tree/main/spec)).

## Where are ACP and UCP live in November 2026?

UCP checkout is live in Google AI Mode and Gemini for eligible U.S. retailers and, since 4 November 2026, Canadian shoppers buying from lululemon, select Shopify merchants, Shoppers Drug Mart and Simons. ACP powers shopping discovery for ChatGPT users in the U.S. ([Google Canada](https://blog.google/intl/en-ca/products/explore-get-answers/a-new-way-to-shop-introducing-a-more-intuitive-agentic-shopping-experience-for-consumers-and-retailers-in-canada/), [OpenAI](https://chatgpt.com/merchants/)).

| Surface or program                  | Protocol               | What a buyer can do                                                       | Source                                                                                                                                                                                         |
| ----------------------------------- | ---------------------- | ------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| ChatGPT shopping (U.S.)             | ACP                    | Discover and compare products, then buy on the merchant's site or app     | [OpenAI](https://chatgpt.com/merchants/)                                                                                                                                                       |
| ChatGPT apps (for example Walmart)  | Apps, not ACP checkout | Account linking, loyalty and merchant payments inside an app              | [OpenAI](https://openai.com/index/powering-product-discovery-in-chatgpt/)                                                                                                                      |
| Google AI Mode and Gemini (U.S.)    | UCP                    | Native checkout with Google Pay, retailer stays seller of record          | [Google](https://blog.google/products/ads-commerce/agentic-commerce-ai-tools-protocol-retailers-platforms/)                                                                                    |
| Google AI Mode and Gemini (Canada)  | UCP                    | Direct checkout from four launch partners and merchant groups             | [Google Canada](https://blog.google/intl/en-ca/products/explore-get-answers/a-new-way-to-shop-introducing-a-more-intuitive-agentic-shopping-experience-for-consumers-and-retailers-in-canada/) |
| Merchant Center UCP integration hub | UCP                    | Onboard, test in sandbox, validate and go live from Merchant Center       | [Google help](https://support.google.com/merchants/answer/16992327?hl=en)                                                                                                                      |
| Stripe Agentic Commerce Suite       | ACP and UCP            | One Stripe integration for discovery, checkout and payments across agents | [Stripe Sessions](https://stripe.com/blog/everything-we-announced-at-sessions-2026)                                                                                                            |

Stripe sits on both sides. It co-wrote ACP, appears among UCP's launch endorsers, and announced at Sessions 2026 that customers would be able to buy merchants' products in AI Mode and the Gemini app through UCP via a Stripe and Google partnership ([Stripe](https://stripe.com/blog/everything-we-announced-at-sessions-2026)). Its agentic commerce docs list UCP next to Shared Payment Tokens and the catalog feed ([Stripe docs](https://docs.stripe.com/agentic-commerce)).

## What does a merchant have to build for ACP vs UCP?

For ACP a merchant needs a product feed, the checkout session endpoints in the spec and order webhooks, but most merchants today only need the feed because ChatGPT sends buyers to their own checkout. For UCP a merchant needs a /.well-known/ucp profile plus live endpoints for every capability it declares ([ACP](https://www.agenticcommerce.dev/), [UCP spec](https://ucp.dev/latest/specification/overview/)).

| Build item                | ACP                                                                  | UCP                                                                                         |
| ------------------------- | -------------------------------------------------------------------- | ------------------------------------------------------------------------------------------- |
| Catalog data              | Feed pushed to each platform (SFTP, API or a provider)               | Catalog capability on your endpoint, or Merchant Center data for Google                     |
| Checkout API              | Checkout session endpoints per the spec (optional for ChatGPT today) | Checkout capability, plus cart if you want pre-checkout baskets                             |
| Payments                  | A compatible PSP that accepts delegated tokens                       | One or more payment handlers in your profile; PSP tokenization keeps raw cards off your API |
| Identity                  | Handled by the platform                                              | Optional OAuth 2.0 identity linking for accounts and loyalty                                |
| Security                  | Token scope and expiry from the PSP                                  | Published signing keys, HTTP message signatures, signed webhooks                            |
| Who often does it for you | Shopify and Etsy (already integrated), Stripe, Salesforce            | Shopify, Stripe, Google Merchant Center                                                     |

OpenAI says merchants on Shopify or Etsy need no application or setup, and that a self-serve merchant platform is planned ([OpenAI](https://chatgpt.com/merchants/)). Google says simplified UCP integration will arrive directly inside Merchant Center starting next year ([Google Canada](https://blog.google/intl/en-ca/products/explore-get-answers/a-new-way-to-shop-introducing-a-more-intuitive-agentic-shopping-experience-for-consumers-and-retailers-in-canada/)).

[x402 vs AP2 vs ACK-Pay: Which Agent Payment Standard Should You Build On?How the payment and authorization standards under agent checkout compare, from HTTP 402 stablecoin payments to AP2 mandates.![](https://stablecoininsider.org/favicon.ico)Stablecoin Insider](https://stablecoininsider.org/x402-vs-ap2-vs-ack-pay/)

## Where do stablecoins fit in ACP and UCP?

Neither ACP nor UCP ships a native stablecoin payment method today; both settle through whatever the merchant's payment provider accepts, which in live deployments means cards and wallets. Stablecoins enter through separate machine-payment protocols such as x402 and Stripe's Machine Payments Protocol (MPP) ([Stripe machine payments](https://docs.stripe.com/payments/machine), [x402](https://www.x402.org/)).

| Rail on Stripe                | Protocol   | Network       | Asset  | Minimum                                                        |
| ----------------------------- | ---------- | ------------- | ------ | -------------------------------------------------------------- |
| Card via Shared Payment Token | ACP or MPP | Card networks | Fiat   | 0.50 USD ([Stripe](https://docs.stripe.com/payments/machine))  |
| Stablecoin                    | MPP        | Tempo         | USDC.e | 0.01 USDC ([Stripe](https://docs.stripe.com/payments/machine)) |
| Stablecoin                    | MPP        | Solana        | USDC   | 0.01 USDC ([Stripe](https://docs.stripe.com/payments/machine)) |
| Stablecoin                    | x402       | Base          | USDC   | 0.01 USDC ([Stripe](https://docs.stripe.com/payments/machine)) |

Stripe says these stablecoin payments are available to businesses in all U.S. states except New York, with access in 30+ other countries on request, and that funds land in the Stripe balance and settle in fiat ([Stripe](https://docs.stripe.com/payments/machine)). Shared Payment Tokens themselves are in public preview for agents, customers and sellers in the U.S., Canada and select European countries ([Stripe SPT docs](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens)).

UCP's design leaves a door open. Because payment handlers are named by reverse-domain and bound to the domain that serves their schema, a stablecoin provider could publish its own handler, for example under its own domain, and any merchant could list it in a profile without asking a central body ([UCP authority binding](https://ucp.dev/latest/specification/overview/)). No such handler appears among the spec's examples, which use Google Pay, Shop Pay and generic card tokenizers.

Stablecoin Insider's take: the agent stack is splitting into a shopping layer (ACP, UCP) and a money layer (cards via tokens, stablecoins via x402 or MPP). For a stablecoin issuer or wallet, the fastest route into agent checkout is probably a UCP payment handler or a PSP that already accepts USDC, not waiting for either shopping protocol to add a crypto field.

If you want to accept the money layer directly today, our guides to [accepting Stripe MPP payments in USDC](https://stablecoininsider.org/how-to-accept-stripe-mpp-payments-in-usdc/) and to the [best x402 facilitators](https://stablecoininsider.org/best-x402-facilitators-compared/) cover the setup.

## ACP vs UCP: which should you implement first?

Most retailers should start with UCP if they want agents to complete purchases, because it is the protocol with live in-agent checkout at scale, and with an ACP product feed if ChatGPT discovery matters to them, because that is now ACP's main job. Many will end up running both through their platform or PSP ([Google](https://blog.google/intl/en-ca/products/explore-get-answers/a-new-way-to-shop-introducing-a-more-intuitive-agentic-shopping-experience-for-consumers-and-retailers-in-canada/), [OpenAI](https://chatgpt.com/merchants/)).

| Your situation                                 | Start with                                              | Why                                                                              |
| ---------------------------------------------- | ------------------------------------------------------- | -------------------------------------------------------------------------------- |
| Shopify or Etsy merchant                       | Nothing new for ChatGPT; check UCP status in your admin | Catalogs already reach ChatGPT, and Shopify co-developed UCP                     |
| Retailer with strong Google Shopping traffic   | UCP via Merchant Center                                 | Checkout happens inside AI Mode and Gemini, where that intent already is         |
| Brand that depends on conversational discovery | ACP product feed                                        | ChatGPT ranks products from shared feeds, then sends buyers to your checkout     |
| Stripe merchant                                | Stripe Agentic Commerce Suite                           | One integration covers ACP feeds, SPTs and the Stripe and Google UCP partnership |
| Platform building its own shopping agent       | UCP as client, ACP checkout as option                   | UCP gives permissionless discovery; ACP checkout is still in the spec            |
| API or data seller paid per call               | Neither; use x402 or MPP                                | Shopping protocols target carts and orders, not per-request billing              |

Stablecoin Insider's take: the choice is less about which protocol wins and more about which surface your buyers use. A merchant that only builds for one is betting on one assistant. Because both protocols keep the merchant as seller of record and neither charges a license fee, the cost of supporting both is mostly engineering and data quality.

[Compare agentic commerce infrastructure](https://stablecoininsider.org/best-infrastructure-agentic-commerce-2026/)

## How do ACP and UCP relate to AP2, MPP, x402 and the card networks?

ACP and UCP are shopping protocols, AP2 is an authorization layer, x402 and MPP are payment rails, and Visa and Mastercard run their own agent token programs underneath. A single agent purchase can touch several of them at once ([AP2](https://blog.google/products-and-platforms/platforms/google-pay/agent-payments-protocol-fido-alliance/), [x402](https://www.x402.org/), [Stripe MPP](https://docs.stripe.com/payments/machine)).

- Shopping layer: ACP and UCP describe catalog, cart, checkout and orders between agent and merchant.
- Consent layer: AP2 mandates sign what the buyer approved; UCP has an AP2 extension built in ([UCP spec](https://ucp.dev/latest/specification/overview/)).
- Credential layer: Stripe Shared Payment Tokens, Google Pay tokens and network agent tokens; see [Visa Intelligent Commerce vs Mastercard Agent Pay](https://stablecoininsider.org/visa-intelligent-commerce-vs-mastercard-agent-pay/).
- Rail layer: cards for retail checkout today; stablecoins over x402 or MPP for machine payments, covered in [x402 vs AP2 vs ACK-Pay](https://stablecoininsider.org/x402-vs-ap2-vs-ack-pay/).

## Conclusion

ACP and UCP started as rivals and have drifted into different roles. ACP is now the feed that gets products into ChatGPT answers, with checkout back on the merchant's site. UCP is the protocol that actually closes sales inside an AI assistant today, in Google's AI Mode and Gemini, and it is the more complete spec, with cart, identity linking, orders and an AP2 consent layer ([UCP spec](https://ucp.dev/latest/specification/overview/), [OpenAI](https://chatgpt.com/merchants/)).

For the stablecoin market the key point is that neither protocol carries USDC natively. Stablecoin payments reach agents through x402 and MPP, and the most likely bridge into retail agent checkout is a UCP payment handler or a PSP such as Stripe that already accepts both. For the rails under these protocols, start with [x402 vs AP2 vs ACK-Pay](https://stablecoininsider.org/x402-vs-ap2-vs-ack-pay/) and our list of [agentic commerce infrastructure](https://stablecoininsider.org/best-infrastructure-agentic-commerce-2026/).

## FAQ

#### What is the main difference between ACP and UCP?

ACP, from OpenAI and Stripe, is platform-mediated: merchants send feeds to an AI platform, which today uses them for discovery in ChatGPT. UCP, from Google and Shopify, is merchant-hosted: each business publishes a /.well-known/ucp profile and agents check out against its own endpoints, live in AI Mode and Gemini ([OpenAI](https://chatgpt.com/merchants/), [UCP spec](https://ucp.dev/latest/specification/overview/)).

#### Is ChatGPT Instant Checkout still available?

Not as a standalone feature. OpenAI says it is moving away from standalone Instant Checkout and that purchases are completed on merchant-owned websites or apps ([OpenAI](https://chatgpt.com/merchants/)).

#### Who created UCP?

Google launched UCP on 11 January 2026, co-developed with Shopify, Etsy, Wayfair, Target and Walmart and endorsed by firms including Adyen, American Express, Mastercard, Stripe and Visa ([Google](https://blog.google/products/ads-commerce/agentic-commerce-ai-tools-protocol-retailers-platforms/)).

#### Do ACP or UCP support stablecoin payments?

Not natively. Both use the merchant's payment provider. Stripe accepts agent stablecoin payments over MPP and x402 in USDC on Tempo, Solana and Base ([Stripe](https://docs.stripe.com/payments/machine)), and UCP lets any provider publish its own payment handler ([UCP spec](https://ucp.dev/latest/specification/overview/)).

#### Do merchants pay fees to use ACP or UCP?

Neither protocol charges a license fee; both are Apache 2.0\. OpenAI says there are no fees on purchases that start in ChatGPT ([OpenAI](https://chatgpt.com/merchants/)). Normal payment processing fees still apply.

#### Can a merchant support both ACP and UCP?

Yes. They do not exclude each other, and providers such as Stripe offer both through one integration ([Stripe](https://stripe.com/blog/everything-we-announced-at-sessions-2026)).

Sources: [agenticcommerce.dev](https://www.agenticcommerce.dev/), [ACP specification](https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/tree/main/spec), [ChatGPT merchants](https://chatgpt.com/merchants/), [OpenAI product discovery](https://openai.com/index/powering-product-discovery-in-chatgpt/), [UCP specification](https://ucp.dev/latest/specification/overview/), [UCP releases](https://github.com/Universal-Commerce-Protocol/ucp/releases), [Google UCP launch](https://blog.google/products/ads-commerce/agentic-commerce-ai-tools-protocol-retailers-platforms/), [Google Canada](https://blog.google/intl/en-ca/products/explore-get-answers/a-new-way-to-shop-introducing-a-more-intuitive-agentic-shopping-experience-for-consumers-and-retailers-in-canada/), [Google UCP MCP guide](https://developers.google.com/merchant/ucp/guides/overview/mcp-transport), [Google AP2 donation](https://blog.google/products-and-platforms/platforms/google-pay/agent-payments-protocol-fido-alliance/), [Stripe Shared Payment Tokens](https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens), [Stripe machine payments](https://docs.stripe.com/payments/machine) and [Stripe Sessions 2026](https://stripe.com/blog/everything-we-announced-at-sessions-2026), read on 11 November 2026.

This article is for informational and educational purposes only and isn't financial, investment, legal or technical advice. Protocol versions, partner lists and availability change often; every fact here was read from the linked specification, company page or documentation on 11 November 2026\. It isn't advice to buy or sell USDC or any other digital asset, and it isn't a recommendation to adopt ACP, UCP, Stripe, Google or any other product. Check the current specification and your payment provider's terms before you build.