Checkout inside ChatGPT (ACP) is liveThe protocol race →
Every vendor says their protocol is winning. AgentCheckout.org is the independent reference: how agent-led checkout actually works, which standards are really shipping, and what it means if you sell things online.
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Agentic payments · AP2 · ACP · UCP · x402
Tracking the names building the rails
Pillar guide · Last updated July 2026 · Maintained monthly
How AI agents pay, the six competing protocols, and what merchants should do about it. Definition, step-by-step flow, the neutral comparison table nobody else publishes, and the merchant playbook.
Read the guideSix protocols are competing to become the rails of agent-led checkout. Here is the short version.
| Protocol | Backer(s) | Lane | Status (Jul 2026) |
|---|---|---|---|
| AP2 | Google + 60+ partners | Open trust layer — signed mandates | Donated to FIDO Alliance |
| ACP | Stripe + OpenAI | Checkout inside ChatGPT | Live |
| UCP | Google + Shopify, Walmart, Target… | Full shopping journey | Live in Google AI Mode (US) |
| x402 | Coinbase | HTTP-native machine-to-machine payments | De-facto web3 rail |
| Visa TAP | Visa | Agent identity on Visa rails | Pilots |
| Agent Pay | Mastercard | Agentic tokens on Mastercard rails | Live pilots EU + India |
The full neutral comparison lives in the guide: see the protocol table →
The reference is built guide by guide. Coming next:
The pillar — definition, flow, protocols, merchant playbook.
Mandates, verifiable credentials, and the FIDO donation.
The revived 402 status code and machine-to-machine micropayments.
The neutral head-to-head the SERP is missing.
Paid by Agents is our monthly briefing: every launch, pilot and standards move across AP2, ACP, UCP and x402 — what shipped vs. what was press-released, plus the merchant angle everyone else skips.