ACP vs x402: ChatGPT Product Discovery vs HTTP-Native Payments

Short answer: ACP and x402 operate at different points of the agentic stack. ACP, the Agentic Commerce Protocol (OpenAI and Stripe, 29 September 2025), powered the original Instant Checkout in ChatGPT; on 24 March 2026 OpenAI announced a focus on product discovery and merchant checkout. The current ChatGPT flow has merchant-side checkout or a ChatGPT app. x402, launched by Coinbase on 6 May 2025, is a lower-level payment primitive that revives the HTTP 402 status code to send native stablecoin payments per request, without accounts or API keys, settling on-chain through facilitators. ACP is commerce and discovery infrastructure; x402 is machine-to-machine settlement. Both are open source under Apache 2.0.

Criterion	ACP	x402
Author / steward	OpenAI and Stripe	Coinbase; spec now the x402 Foundation
Announced	29 Sep 2025	6 May 2025
Open-source status	Open source, Apache 2.0	Open source, Apache 2.0
What it is	Agent checkout / commerce protocol	HTTP-native payment protocol
Scope	Completing a purchase between buyer, agent and merchant	Pay-per-request payments for apps, APIs and agents over HTTP 402
Payment type	Card and existing processors (Stripe Shared Payment Token)	On-chain stablecoins via facilitators (exact scheme, EIP-3009)
Transport	HTTP (OpenAPI); MCP since 2026-04-17	HTTP 402 status code and payment headers; MCP and A2A representations
Primary use	Product discovery in ChatGPT; merchant-side checkout	Pay per API call autonomously, no accounts or keys
Notable adoption	OpenAI, Stripe, Etsy, Shopify (coming)	Coinbase, Circle, Anthropic, AWS, NEAR

Criterion

ACP

x402

Author / steward

OpenAI and Stripe

Coinbase; spec now the x402 Foundation

Announced

29 Sep 2025

6 May 2025

Open-source status

Open source, Apache 2.0

What it is

Agent checkout / commerce protocol

HTTP-native payment protocol

Scope

Completing a purchase between buyer, agent and merchant

Pay-per-request payments for apps, APIs and agents over HTTP 402

Payment type

Card and existing processors (Stripe Shared Payment Token)

On-chain stablecoins via facilitators (exact scheme, EIP-3009)

Transport

HTTP (OpenAPI); MCP since 2026-04-17

HTTP 402 status code and payment headers; MCP and A2A representations

Primary use

Product discovery in ChatGPT; merchant-side checkout

Pay per API call autonomously, no accounts or keys

Notable adoption

OpenAI, Stripe, Etsy, Shopify (coming)

Coinbase, Circle, Anthropic, AWS, NEAR

Frequently asked questions

Do ACP and x402 do the same thing?

No. ACP supports commerce integrations and the current ChatGPT product-discovery path; x402 sends native stablecoin payments over HTTP for pay-per-request use.

Does ACP use crypto like x402?

ACP and x402 address different layers. x402 settles on-chain stablecoins via facilitators; confirm the chosen ACP payment integration against the current provider documentation.

Which is older, ACP or x402?

x402 launched on 6 May 2025; ACP was announced on 29 September 2025.