ACP vs x402: Agent Checkout vs Pay-per-Request
ACP, the Agentic Commerce Protocol from OpenAI and Stripe, standardises checkout between AI agents and merchants, typically paid with card credentials scoped through Shared Payment Tokens. x402 standardises paying for individual HTTP requests, typically in stablecoins such as USDC on Base. Use ACP for agent shopping with merchants and x402 for per-call APIs, data, and machine services.
The job each protocol does
ACP covers the purchase of goods or services from a merchant: building a cart, getting totals, and completing checkout. x402 covers access to a resource behind a paywall: the server quotes a price for a request and releases the response once paid. One is a shopping flow; the other is a metered access flow.
Payment instruments
ACP launched with Stripe's Shared Payment Tokens, which scope a buyer's card to one merchant and amount. x402 settles onchain, most commonly with USDC, and its V2 specification added hooks for other rails. Each choice reflects its main use: consumer purchases versus machine payments.
Payment size and frequency
Card payments carry minimum amounts and fees that make very small charges uneconomic. x402 on a low-fee network such as Base makes payments of fractions of a dollar practical, which is essential for per-call pricing where an agent may pay many times a minute.
Who integrates
ACP is implemented by agent platforms and merchants or their commerce platforms. x402 is implemented by API and resource providers through server middleware, and by agents through client libraries that handle 402 responses automatically.
Trust model
In ACP, the merchant remains merchant of record and the token's scope limits exposure. In x402, payment is verified before the resource is served, usually through a facilitator, so the provider is paid upfront and the agent's wallet limits bound its exposure.
Who governs ACP vs x402
ACP is open source under Apache 2.0 with OpenAI and Stripe as founding maintainers. x402 is governed by the x402 Foundation under the Linux Foundation, with members including payment networks, cloud providers, and crypto companies.
Choosing
If your agent buys products from merchants for a user, ACP or similar checkout protocols fit. If your agent pays for APIs, data, or compute, or your service charges agents per request, x402 fits. Stripe supports both, so merchants on Stripe can accept either.
A worked comparison
A travel assistant booking a hotel for a user fits ACP: there is a merchant, a cart, a total, taxes, and a confirmation the user may want to review. The same assistant checking live prices across a paid aggregator API many times fits x402: each lookup is small, frequent, and needs no checkout, only a payment and a response.
Developer experience
ACP integration involves checkout endpoints, product feeds, tax and shipping logic, and token handling, often through a commerce platform or Stripe. x402 integration involves wrapping endpoints with middleware that declares a price and verifying payment through a facilitator, and on the agent side a client that pays 402 responses automatically.
Limits and safety
Both protocols need payer-side limits. With ACP, scoped tokens cap each purchase, and platforms often require user confirmation above thresholds. With x402, the agent's wallet should enforce per-request price checks, period caps, and allowlists, since an agent may make many payments without human review.
Where each is heading
ACP continues to evolve through dated releases focused on merchant checkout. x402's V2 specification added multi-chain support and hooks for legacy rails, broadening where it applies. The overlap may grow at the edges, but the core split between checkout and metered access is likely to remain.
| Aspect | ACP | x402 |
|---|---|---|
| Purpose | Agent checkout with merchants | Pay per HTTP request |
| Typical payment | Scoped card token | USDC onchain |
| Typical size | Retail order amounts | Fractions of a dollar upward |
| Created by | OpenAI and Stripe, Sept 2025 | Coinbase, 2025 |
| Governance | Founding maintainers, Apache 2.0 | x402 Foundation, Linux Foundation |
Frequently asked questions
- What is the difference between ACP and x402?
- ACP standardises checkout between AI agents and merchants, usually with scoped card tokens, and keeps the merchant as merchant of record. x402 standardises paying for individual HTTP requests, usually in stablecoins, so APIs and services can charge agents per call without accounts or subscriptions.
- Can a merchant support both ACP and x402?
- Yes. They address different flows, so a business can offer agent checkout for products through ACP and per-request access to APIs or data through x402. Stripe supports both, which lets merchants on Stripe accept agent orders and machine payments from one account.
- Which protocol is better for AI agents paying for APIs?
- x402, or a similar HTTP 402 protocol. It lets an agent pay small amounts per request in stablecoins without signing up, and payments are verified before the response is returned. ACP targets shopping checkout rather than metered access to APIs and data.