{ "id": "D07", "url": "https://cartforagents.com/guides/ucp-vs-acp", "title": "UCP vs ACP: compare contracts before choosing an integration", "description": "Compare protocol roles, discovery and execution boundaries with version notes, supported capabilities and unresolved interoperability questions.", "answer": "UCP and ACP are both open, date-versioned protocols for agent shopping, but they are different contracts: UCP has a business publish a profile that platforms read and negotiate against, and is the route Google documents for checkout in AI Mode and Gemini, while ACP, maintained by OpenAI and Stripe and still labelled beta, has merchants push product feeds to the agent and is the protocol behind ChatGPT's merchant program. Neither document says the two interoperate, so choose by the platform you need to reach and the contract that platform has documented, not by the protocol's name. As of October 27, 2026, a Shopify store selling in the US needs to build neither to be found in ChatGPT, because Shopify Catalog already supplies that data.", "take": "For a US Shopify store, neither protocol is a project for this quarter, because Shopify Catalog already supplies ChatGPT. Pick a protocol when a platform you need requires it.", "summary": "UCP and ACP both promise a common language for agent shopping, and both are open, dated and Apache-licensed. They are not interchangeable: they discover stores differently, move catalog data in opposite directions, and are backed by different platforms. Here is the side-by-side, with what each document says today and what nobody has documented yet.", "claims": [ { "text": "The UCP specification says businesses publish a profile at /.well-known/ucp, the platform selects one exact protocol version, and the business determines active capabilities from the versions both sides advertise.", "source_title": "Universal Commerce Protocol: Official Specification, Discovery, Governance, and Negotiation", "source_url": "https://ucp.dev/specification/overview/", "source_date": "2026-10-27", "method": "documented", "limitation": "Read on the version marked latest (2026-08-25)." }, { "text": "UCP lists dated versions 2026-01-11, 2026-01-23, 2026-04-08 and 2026-08-25 (latest), and its repository is licensed Apache 2.0.", "source_title": "Universal Commerce Protocol on GitHub: Releases", "source_url": "https://github.com/Universal-Commerce-Protocol/ucp/releases", "source_date": "2026-10-27", "method": "documented", "limitation": "A release is not evidence of adoption." }, { "text": "The ACP README says the specification is maintained by OpenAI and Stripe, is currently in beta, uses date-based versioning in YYYY-MM-DD format, and is licensed Apache 2.0.", "source_title": "Agentic Commerce Protocol on GitHub: README", "source_url": "https://github.com/agentic-commerce-protocol/agentic-commerce-protocol", "source_date": "2026-10-27", "method": "documented", "limitation": "The repository's MAINTAINERS.md now also lists Meta, a change recorded in the unreleased changelog; the README had not caught up on our check date." }, { "text": "ACP release 2026-04-17 deprecated 2026-01-30 and added a discovery document at /.well-known/acp.json, a cart capability, delegate authentication for 3DS2, and a Feed API in which merchants push catalog data to agent-hosted endpoints.", "source_title": "Agentic Commerce Protocol: Changelog, Version 2026-04-17", "source_url": "https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/blob/main/changelog/2026-04-17.md", "source_date": "2026-10-27", "method": "documented", "limitation": "Changelog for the protocol, not a statement of what ChatGPT has deployed." }, { "text": "The ACP website says implementing the protocol does not automatically list products with AI agents, that each platform manages its own participation process, and that businesses must apply to participate in ChatGPT.", "source_title": "Agentic Commerce Protocol website, FAQ", "source_url": "https://www.agenticcommerce.dev/", "source_date": "2026-10-27", "method": "documented", "limitation": "The same FAQ still says discovery mechanisms are being worked on, which the 2026-04-17 changelog has since added." }, { "text": "OpenAI's merchant page says ACP today supports product discovery and more accurate, personalized recommendations through shared product data, that OpenAI is moving away from a standalone Instant Checkout experience, and that purchases are completed on merchant-owned websites or apps.", "source_title": "OpenAI: ChatGPT merchants", "source_url": "https://chatgpt.com/merchants/", "source_date": "2026-10-27", "method": "documented", "limitation": "Marketing page with an FAQ; OpenAI's help article and developer docs still describe Instant Checkout." }, { "text": "OpenAI's help article says that for some eligible products and merchants, ChatGPT may show an Instant Checkout option, and that Shopify merchants' product data is already integrated into ChatGPT through Shopify Catalog with no additional work required.", "source_title": "OpenAI Help Center: Shopping with ChatGPT Search", "source_url": "https://help.openai.com/en/articles/11128490-shopping-with-chatgpt-search", "source_date": "2026-10-27", "method": "documented", "limitation": "Living help article; conflicts with the merchant page on checkout." }, { "text": "OpenAI's product feed reference says checkout requires a separately enabled integration and that setting is_eligible_checkout does not complete checkout onboarding.", "source_title": "OpenAI for Developers: Products (file upload)", "source_url": "https://developers.openai.com/commerce/specs/file-upload/products", "source_date": "2026-10-27", "method": "documented", "limitation": "Reference for approved partners; onboarding product feeds is limited to approved partners." }, { "text": "Google's Merchant Center help says that by integrating with UCP, merchants can implement a checkout button on eligible product listings in AI Mode in Google Search and on Gemini, and that the feature is available to select merchants.", "source_title": "Google Merchant Center Help: About the Universal Commerce Protocol (UCP) and UCP-powered checkout feature on Google", "source_url": "https://support.google.com/merchants/answer/16837055?hl=en", "source_date": "2026-10-27", "method": "documented", "limitation": "Market statements differ between Google pages; see our Google checkout guide." }, { "text": "Shopify's agent documentation says its MCP tools implement UCP across discovery, carts and checkout, and order monitoring.", "source_title": "Shopify: Agents, Understand how Shopify does UCP", "source_url": "https://shopify.dev/docs/agents", "source_date": "2026-10-27", "method": "documented", "limitation": "Shopify's implementation only." }, { "text": "Stripe's agentic commerce documentation lists Shared Payment Tokens among its concepts, while the ACP website names Stripe as the first ACP-compatible payment provider with its Shared Payment Token.", "source_title": "Stripe Docs: Agentic commerce", "source_url": "https://docs.stripe.com/agentic-commerce", "source_date": "2026-10-27", "method": "documented", "limitation": "An index page. We did not verify any other Stripe page, including any catalog-feed or UCP page, on 2026-10-27." }, { "text": "Shopify's ChatGPT channel help says ChatGPT is a product discovery channel, buyers are redirected to the store's online checkout, there is no ChatGPT direct checkout setting in the Shopify admin, and the store must sell to customers in the United States.", "source_title": "Shopify Help Center: ChatGPT (agentic storefronts)", "source_url": "https://help.shopify.com/en/manual/online-sales-channels/agentic-storefronts/chatgpt", "source_date": "2026-10-27", "method": "documented", "limitation": "Shopify's description of its channel; the store can be based outside the United States." }, { "text": "On October 27, 2026, the four Shopify sellers behind our humidifier catalog search each served a UCP profile at /.well-known/ucp (version 2026-08-25, checkout advertised) and returned HTTP 404 for /.well-known/acp.json.", "source_title": "Cart for Agents: discovery fetches, October 27, 2026 (How we checked, this page)", "source_url": "https://cartforagents.com/guides/ucp-vs-acp#how-we-checked", "source_date": "2026-10-27", "method": "observed", "limitation": "Four stores on one platform. A missing acp.json does not show that a store has no ACP integration; ChatGPT receives Shopify data through Shopify Catalog." } ], "sources": [ { "title": "Universal Commerce Protocol: Official Specification", "url": "https://ucp.dev/specification/overview/", "accessed": "2026-10-27" }, { "title": "Universal Commerce Protocol on GitHub: Releases", "url": "https://github.com/Universal-Commerce-Protocol/ucp/releases", "accessed": "2026-10-27" }, { "title": "Agentic Commerce Protocol on GitHub", "url": "https://github.com/agentic-commerce-protocol/agentic-commerce-protocol", "accessed": "2026-10-27" }, { "title": "Agentic Commerce Protocol: Changelog, Version 2026-04-17", "url": "https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/blob/main/changelog/2026-04-17.md", "accessed": "2026-10-27" }, { "title": "Agentic Commerce Protocol website", "url": "https://www.agenticcommerce.dev/", "accessed": "2026-10-27" }, { "title": "OpenAI: ChatGPT merchants", "url": "https://chatgpt.com/merchants/", "accessed": "2026-10-27" }, { "title": "OpenAI Help Center: Shopping with ChatGPT Search", "url": "https://help.openai.com/en/articles/11128490-shopping-with-chatgpt-search", "accessed": "2026-10-27" }, { "title": "OpenAI for Developers: Products (file upload)", "url": "https://developers.openai.com/commerce/specs/file-upload/products", "accessed": "2026-10-27" }, { "title": "OpenAI for Developers: Key concepts (Agentic Commerce)", "url": "https://developers.openai.com/commerce/guides/key-concepts", "accessed": "2026-10-27" }, { "title": "Google Merchant Center Help: About the Universal Commerce Protocol (UCP) and UCP-powered checkout feature on Google", "url": "https://support.google.com/merchants/answer/16837055?hl=en", "accessed": "2026-10-27" }, { "title": "Google Merchant Center Help: How to onboard to the UCP integration hub in Merchant Center", "url": "https://support.google.com/merchants/answer/16992327?hl=en", "accessed": "2026-10-27" }, { "title": "Google for Developers: Prepare your Merchant Center account (UCP guide)", "url": "https://developers.google.com/merchant/ucp/guides/merchant-center", "accessed": "2026-10-27" }, { "title": "Shopify: Agents", "url": "https://shopify.dev/docs/agents", "accessed": "2026-10-27" }, { "title": "Shopify Help Center: ChatGPT (agentic storefronts)", "url": "https://help.shopify.com/en/manual/online-sales-channels/agentic-storefronts/chatgpt", "accessed": "2026-10-27" }, { "title": "Stripe Docs: Agentic commerce", "url": "https://docs.stripe.com/agentic-commerce", "accessed": "2026-10-27" } ], "limitations": [ "Checked on 2026-10-27; re-check before acting. Both protocols ship dated versions several times a year, and platform programs change faster than the specs.", "This compares published contracts. We did not build either integration or see what any assistant shows shoppers.", "OpenAI's own pages disagree about Instant Checkout. We report each statement with its page rather than choosing one.", "The discovery check covers four Shopify stores, so it is not a sample of either protocol's adopters.", "The matrix is our reading of the documents for merchants. It is not an official comparison from either project.", "Store and brand names are withheld." ], "related": [ "https://cartforagents.com/guides/universal-commerce-protocol", "https://cartforagents.com/guides/agentic-commerce-protocol", "https://cartforagents.com/guides/shopify-agentic-storefronts", "https://cartforagents.com/guides/google-ucp-checkout", "https://cartforagents.com/guides/chatgpt-product-feed", "https://cartforagents.com/guides/how-to-rank-in-chatgpt" ], "published": "2026-10-27", "updated": "2026-10-27", "checked": "2026-10-27", "kind": "guide" }