It is open source under Apache 2.0, maintained by OpenAI and Stripe.

How many stores support ACP?

ARC does not measure this yet and labels it 'not measured', which is not the same as zero.

Is ACP the same as UCP?

No. Both cover checkout, but they come from different backers and differ in scope.

What is ACP (Agentic Commerce Protocol)?

ACP (Agentic Commerce Protocol) is an open-source standard (Apache 2.0) maintained by OpenAI and Stripe. It defines how an AI agent and a merchant create and complete a checkout. ARC lists ACP on its Protocol Matrix but does not yet measure ACP adoption, so any count you see elsewhere isn't from ARC.

ACP in one paragraph

ACP is the checkout handshake published by OpenAI and Stripe. An agent and a merchant create a checkout and can hand over a delegated payment token. The merchant stays merchant of record. The spec is Apache 2.0 at agentic-commerce-protocol and agenticcommerce.dev.

Who maintains it

OpenAI and Stripe maintain the open-source spec. That is from the project, not an ARC count of merchants.

What it covers

Creating and completing a checkout between an agent and a merchant. It does not, by itself, tell ARC where a store's ACP endpoint is.

How it differs from UCP

UCP is a public profile at /.well-known/ucp plus catalog and cart tools. ACP is a checkout handshake agreed between a merchant and an agent platform. See UCP vs ACP.

Why ARC marks it not measured

ARC saved checks, accessed 2026-10-13

Declared: Not measuredNot measuredNo public discovery marker to check

Valid: Not measuredNot measuredNot checked

Usable: Not measuredNot measuredNot checked

Transacts: Not measuredNot measuredNot checked

There is no public discovery file ARC can fetch, so a blank is not zero stores. Any ACP count published somewhere else is not an ARC figure.

What stores can do

Read the spec and the merchant docs from OpenAI and Stripe if you want to join that checkout. ARC can still check the public UCP profile and the browser cart, which are different questions.

Frequently asked questions

What is ACP (Agentic Commerce Protocol)?: ACP (Agentic Commerce Protocol) is an open-source standard (Apache 2.0) maintained by OpenAI and Stripe. It defines how an AI agent and a merchant create and complete a checkout. ARC lists ACP on its Protocol Matrix but does not yet measure ACP adoption, so any count you see elsewhere isn't from ARC.
Who owns ACP?: It is open source under Apache 2.0, maintained by OpenAI and Stripe.
How many stores support ACP?: ARC does not measure this yet and labels it 'not measured', which is not the same as zero.
Is ACP the same as UCP?: No. Both cover checkout, but they come from different backers and differ in scope.

On ARC

Cite this: ARC, arcreport.ai, accessed 2026-10-13, CC-BY-4.0. Protocol figures: ARC saved checks, accessed 2026-10-13 (13 October 2026). Index browser figures: ARC open dataset snapshot 2026-10-12. Platform figures: ARC saved checks, accessed 2026-10-13.

Every figure is labelled Measured, Inferred or Not measured. Not measured is not zero. A missing result is not a mark against a store. ARC stops before payment.