What Is ACP? The Agentic Commerce Protocol by OpenAI & Stripe (Complete Guide)
ChatGPT now has over 700 million weekly active users. And they are starting to shop.
What Is ACP? The Agentic Commerce Protocol by OpenAI & Stripe (Complete Guide)
Last updated: March 2026
ChatGPT now has over 700 million weekly active users. And they are starting to shop.
E-commerce referral traffic from ChatGPT grew 1,079% between January and December 2025, according to industry tracking data. ChatGPT referral visitors convert at 11.4%, more than double the 5.3% rate of traditional organic search (Similarweb). The question is no longer whether AI will reshape online commerce. It is how.
The answer, at least from the companies building the infrastructure, is the Agentic Commerce Protocol (ACP) – an open standard that defines how AI agents discover products, negotiate checkout details, and process payments on behalf of human buyers. If you sell online, ACP is the specification that will determine whether AI agents can find and sell your products.
This guide explains exactly what ACP is, how it works, who is behind it, and what ecommerce merchants need to know right now.
What Is ACP?
The Agentic Commerce Protocol is an open-source interaction model and API specification that enables AI agents – like ChatGPT, Microsoft Copilot, or any ACP-compatible system – to conduct end-to-end purchases on behalf of users. It was co-developed by OpenAI and Stripe and is licensed under Apache 2.0.
In practical terms, ACP is the language that lets an AI agent say to a merchant’s server: “My user wants to buy this product, ship it to this address, and here is a secure payment token.” The merchant’s system responds with pricing, tax, shipping options, and order confirmation – all without the buyer ever leaving the AI interface.
The protocol is defined at agenticcommerce.dev and maintained as an open-source project on GitHub.
ACP is not a marketplace. It is not an app. It is a set of rules that any AI agent and any merchant can implement to make commerce work programmatically.
Who Is Behind ACP?
ACP has two Founding Maintainers: OpenAI and Stripe. Their roles are distinct but complementary.
OpenAI provides the AI agent surface – ChatGPT, Operator (now ChatGPT Agent), and the broader ecosystem of 700 million+ weekly users who are already asking product questions and expecting purchase capabilities.
Stripe provides the payment infrastructure, including the SharedPaymentToken (SPT) primitive that makes secure agentic payments possible without exposing raw card data to AI agents.
The protocol is governed through a consensus-based model with provisions for transitioning to neutral foundation stewardship as the ecosystem matures. Contributions are accepted under a Contributor License Agreement, and the contact for protocol questions is [email protected].
Partner ecosystem
ACP has attracted significant early interest beyond its founders:
| Category | Partners |
|---|---|
| AI Platforms | Microsoft Copilot, Anthropic, Perplexity, Salesforce |
| Ecommerce Platforms | Shopify (1M+ merchants live), Wix, WooCommerce, BigCommerce, Squarespace, commercetools |
| Syndication Partners | Akeneo, Cymbio, Logicbroker, Mirakl, Pipe17, Rithum |
| Developer Tools | Vercel, Lovable, Replit, Bolt, Manus |
| Early Merchant Adopters | URBN (Anthropologie, Free People, Urban Outfitters), Etsy, Coach, Kate Spade, Revolve, Glossier, Vuori, Spanx, SKIMS, Ashley Furniture, Halara, Nectar |
The Four-Party Transaction Model
ACP introduces a four-party model that keeps the merchant in control while enabling AI-driven discovery and checkout:
| Party | Role |
|---|---|
| Buyer | Discovers products via AI, selects items, authorizes payment |
| AI Agent | Interfaces with the buyer, displays products and checkout UI, collects payment info, initiates checkout requests |
| Merchant | Receives checkout requests, remains merchant of record, controls products, pricing, fulfillment, and customer relationships |
| Payment Provider | Processes tokenized credentials, enforces spending controls, provides fraud detection signals |
The critical design choice: the merchant remains the merchant of record. The AI agent never takes ownership of inventory, pricing, or the customer relationship. This is what distinguishes ACP from a marketplace model.
The 5 API Endpoints Explained
ACP defines five RESTful endpoints that power the entire checkout lifecycle. Merchants host these endpoints on their own servers, and AI agents call them to conduct purchases.
1. Create Checkout Session
POST /checkout_sessions
The AI agent sends item IDs, buyer information, and optionally a shipping address. The merchant responds with authoritative pricing (item prices, tax, available shipping options). This is where the checkout begins.
2. Get Checkout Session
GET /checkout_sessions/:id
Retrieves the current state of a checkout session. The AI agent uses this to check whether the session is ready for payment, to refresh pricing, or to display updated information to the buyer.
3. Update Checkout Session
PUT /checkout_sessions/:id
Allows the agent to modify the session – updating the shipping address, selecting a fulfillment option, changing quantities, or applying discount codes. Each update triggers the merchant to recalculate totals.
4. Complete Checkout
POST /checkout_sessions/:id/complete
Finalizes the purchase. The agent sends a secure payment token (SharedPaymentToken) along with billing details. The merchant processes the payment, creates the order, and returns confirmation with tracking information.
5. Cancel Checkout
POST /checkout_sessions/:id/cancel
Cancels an in-progress checkout session. Includes an intent_trace field for structured cancellation context so merchants can understand why purchases were abandoned.
Status lifecycle
Every checkout session moves through a defined state machine:
not_ready_for_payment --> ready_for_payment --> in_progress --> completed or canceled
All requests require an API-Version header (date-based, e.g., 2026-01-30) and Bearer token authentication. Idempotency keys are supported for safe retries.
SharedPaymentToken: How Payments Work
The SharedPaymentToken (SPT) is the payment primitive that makes ACP secure. It solves a fundamental problem: how do you let an AI agent initiate a payment without giving it access to credit card numbers?
How SPTs work
- The buyer authorizes a payment through the AI agent’s interface (e.g., selecting a saved card in Stripe Link).
- Stripe issues a scoped, time-limited token – the SPT – to the AI agent.
- The agent passes the SPT to the merchant via the
/completeendpoint. - The merchant creates a Stripe PaymentIntent using the SPT and confirms the charge.
- Stripe clones the buyer’s payment method into a new one scoped exclusively to that seller.
At no point does the AI agent or the merchant see the raw card number, CVV, or any sensitive payment credential.
Security controls
| Control | Description |
|---|---|
| Per-seller scoping | Each SPT is granted to a single merchant account |
| Amount limits | max_amount caps the transaction value in cents |
| Time limits | expires_at sets automatic expiration |
| Revocability | Buyer or agent can revoke the token at any time |
| Fraud integration | Stripe Radar assesses risk for fraudulent disputes, card testing, stolen cards, and issuer declines |
| Network compatibility | Compatible with Mastercard Agent Pay and Visa Intelligent Commerce tokens |
SPTs also support Buy Now, Pay Later providers (Affirm and Klarna are rolling out), with Stripe handling the complexity of provisioning the appropriate token type behind the scenes.
How to Get Listed and Implement ACP
For merchants who want their products discoverable and purchasable by AI agents, the onboarding path depends on your existing setup.
If you already use Stripe
Stripe’s Agentic Commerce Suite lets existing Stripe merchants enable agentic commerce with minimal code changes – as little as one line of code, according to Stripe. From the Stripe Dashboard, you connect your product catalog, select which AI agents you want to sell through, and Stripe handles discovery, checkout, and payments.
If you use Shopify
Shopify merchants are already eligible for ChatGPT shopping integration. Over 1 million Shopify merchants (including Glossier, SKIMS, Spanx, and Vuori) are connected through the Shopify-Stripe-OpenAI pipeline.
Full custom integration
For merchants building from scratch, the process outlined at developers.openai.com involves five steps:
- Apply at
chatgpt.com/merchants - Provide a product feed (CSV or JSON with identifiers, descriptions, pricing, inventory, media, and fulfillment details)
- Build the five ACP checkout endpoints on your server
- Integrate payments via a Delegate Payment Spec-compliant provider (Stripe, or Adyen as a 3DS authentication provider)
- Certify with OpenAI for production access
ACP can also be implemented as an MCP server (Model Context Protocol) instead of REST endpoints, giving merchants flexibility in how they expose their commerce capabilities to AI agents.
Costs: What Merchants Pay
ACP itself is an open-source protocol – there is no licensing fee to implement it. However, the commerce transactions flowing through it carry costs:
- OpenAI commission: Approximately 2% affiliate commission on purchases made through ChatGPT, confirmed by Sam Altman. This applies when users discover products via ChatGPT and complete purchases.
- Stripe processing fees: Standard Stripe payment processing fees apply to all transactions settled through Stripe (typically 2.9% + $0.30 per transaction in the US).
- No price markup to buyers: End users pay the same price they would on the merchant’s website.
For merchants already on Stripe, the incremental cost is the OpenAI commission on sales that come through the ChatGPT channel. There is no additional ACP integration fee.
The March 2026 Pivot: From Checkout to Discovery
In early March 2026, OpenAI significantly scaled back its direct in-app checkout ambitions. This is a major strategic shift that every ecommerce merchant should understand.
What changed
| Before (2025) | After (March 2026) |
|---|---|
| Buy directly inside ChatGPT | Discover in ChatGPT, buy on merchant sites or apps |
| Instant Checkout as the flagship feature | Instant Checkout “moving to Apps” |
| OpenAI handles transactions | Merchants handle their own checkout |
| Unified checkout experience | Per-merchant ChatGPT app experiences (Target, Instacart, DoorDash) |
| Compete with retailers | Partner with retailers as a discovery layer |
Why the pivot happened
- Low merchant adoption: Only approximately 12 Shopify stores out of millions actually integrated Instant Checkout
- Browse-don’t-buy behavior: Users asked product questions but rarely completed in-app purchases
- Operational complexity: Inventory synchronization, tax calculation, dynamic pricing, fraud management, and refund processing proved too complex for a unified system
- Merchant resistance: Shopify President Harley Finkelstein emphasized that merchants need control over “subscriptions, inventory, shipping taxes” and proprietary data protection
- Catalog gaps: 83% of restaurants were invisible on ChatGPT compared to 14% on Google
What survives
ACP remains as connective infrastructure. Shopping Research (organic, unsponsored product recommendations) is the primary feature going forward. Dedicated merchant apps inside ChatGPT – like Target, Instacart, and DoorDash – are the new checkout paradigm. ChatGPT Agent (formerly Operator) can still autonomously browse and purchase on merchant websites.
OpenAI spokesperson: “We’re evolving how we approach commerce in ChatGPT to better meet merchants and users where they are.”
ACP Version History
ACP uses date-based versioning. Each version is a complete snapshot of the specification. Here is the full history:
| Version | Date | Key Changes |
|---|---|---|
| 2025-09-29 | September 2025 | Initial release. First Agentic Checkout and Delegate Payment specs. OpenAPI schemas and example JSON files. |
| 2025-12-12 | December 2025 | Breaking: fulfillment_address restructured to fulfillment_details. Multi-item fulfillment selection. Rich LineItem fields (images, descriptions, disclosures). Affiliate attribution extension. |
| 2026-01-16 | January 2026 | Authentication Provider model for 3DS. merchant_id made mandatory. Adyen added as a provider option. |
| 2026-01-30 | January 2026 (current stable) | Breaking: Payment Handlers Framework replaces simple payment identifiers. Capability Negotiation between agents and sellers. Extensions Framework for composable features. Discount Extension (code input, applied discounts, line-item allocations). |
The protocol has evolved rapidly – four versions in four months – reflecting the pace at which the agentic commerce ecosystem is developing. The API-Version header is required on all requests to ensure compatibility.
Key Stats
| Metric | Value | Source |
|---|---|---|
| ChatGPT weekly active users | 700 million+ | OpenAI |
| ChatGPT e-commerce referral traffic growth (2025) | 1,079% | Industry tracking |
| ChatGPT referral conversion rate | 11.4% | Similarweb |
| Traditional organic search conversion rate | 5.3% | Similarweb |
| Shopify merchants eligible via ChatGPT integration | 1 million+ | Stripe / Shopify |
| Shopify stores that actually integrated Instant Checkout | ~12 | The Information |
| OpenAI projected revenue by 2029 | $125 billion | OpenAI |
| Projected advertising/commerce share of OpenAI revenue | Up to 20% ($25B) | OpenAI |
| OpenAI affiliate commission rate | ~2% | Sam Altman (confirmed) |
| BNPL revenue increase on eligible sessions | Up to 14% | Stripe |
| ACP protocol versions released to date | 4 | agenticcommerce.dev |
Frequently Asked Questions
Is ACP the same as ChatGPT Instant Checkout?
No. ACP is the underlying protocol specification that defines how AI agents and merchants communicate during a purchase. ChatGPT Instant Checkout was a specific product built on top of ACP. As of March 2026, Instant Checkout is being deprioritized in favor of a discovery-and-redirect model, but ACP itself remains active as connective infrastructure.
Do I need Stripe to use ACP?
Stripe is the primary payment provider for ACP and the co-developer of the protocol. However, ACP supports a Delegate Payment specification that allows non-Stripe merchants to accept agentic payments. Adyen is already listed as a supported authentication provider. Merchants using other processors can use Stripe specifically for the agentic channel without migrating their entire payment stack.
Is ACP only for ChatGPT?
No. ACP is an open protocol licensed under Apache 2.0. Any AI agent can implement it. Microsoft Copilot, Anthropic, Perplexity, and Salesforce are all listed as partners. The “build once, distribute everywhere” principle means a merchant who implements ACP is discoverable by any compatible agent, not just ChatGPT.
What payment methods does ACP support?
Currently supported: Visa, Mastercard, American Express, Discover, Diners Club, JCB, UnionPay, eftpos, Interac, Apple Pay, Google Pay, and Link by Stripe. Buy Now, Pay Later through Affirm and Klarna is rolling out. Mastercard Agent Pay and Visa Intelligent Commerce network tokens are also supported.
How is ACP different from a product feed or shopping API?
Product feeds (Google Merchant Center, Meta Catalog, etc.) are one-directional – you push product data out. ACP is a bidirectional protocol that handles the entire checkout lifecycle: product selection, address collection, fulfillment negotiation, tax calculation, payment processing, order confirmation, and post-purchase updates via webhooks. It replaces the need for a human to navigate a checkout flow.
What happens to my customer data?
The merchant retains full control over customer relationships. ACP is designed so that the AI agent facilitates the transaction but never becomes the merchant of record. Customer data, order history, and post-purchase communication remain with the merchant. Webhook events (order_create, order_update) are sent from the merchant to the agent, not the other way around.
Can I use ACP for digital products or subscriptions?
Yes. ACP supports physical goods (with shipping fulfillment options), digital products (with digital fulfillment), and the protocol’s extensibility is designed to accommodate subscriptions, usage-based billing, and async “buy for me” flows. The Payment Handlers Framework introduced in version 2026-01-30 includes support for B2B payment terms (net 15, net 30, net 60, net 90).
Conclusion
The Agentic Commerce Protocol represents the first serious attempt to standardize how AI agents conduct commerce. Backed by OpenAI and Stripe, licensed under Apache 2.0, and already integrated with over one million Shopify merchants, ACP is the infrastructure layer that will determine which products AI agents can find and sell.
The March 2026 pivot away from in-app checkout does not diminish the protocol’s relevance – it clarifies the role. AI surfaces like ChatGPT are becoming the place where 700 million people decide what to buy. ACP ensures that when they decide, the transaction can happen programmatically, securely, and with the merchant in full control.
For ecommerce merchants, the immediate action is straightforward: if you are on Shopify or Stripe, you likely already have a path to ACP compatibility. If you are not, the protocol is open, documented at agenticcommerce.dev, and accepting integrations at chatgpt.com/merchants.
The merchants who show up first in AI agent results will capture the same early-mover advantage that the first Google-optimized stores captured two decades ago. The infrastructure is live. The question is whether you are listed.
Sources: agenticcommerce.dev, Stripe Agentic Commerce Documentation, OpenAI Commerce Developer Guide, ACP GitHub Repository, Digital Commerce 360, Similarweb, The Information.
Hexagon Team
Published March 8, 2026
