UCP vs ACP: The Full Comparison
Google's Universal Commerce Protocol vs OpenAI/Stripe's Agentic Commerce Protocol \u2014 how they differ on scope, fees, payment, platform reach, and which to implement first.
Quick answer
ACP (Agentic Commerce Protocol) by OpenAI and Stripe is open source, focused on checkout, uses Stripe payments, and powers ChatGPT and Microsoft Copilot. UCP (Universal Commerce Protocol) by Google is proprietary, covers both discovery and checkout, uses Google Pay (no transaction fee), and powers Google AI Mode, Gemini, Shopify, Walmart, Wayfair, and Target. Most retailers should plan to implement both because they reach different agent ecosystems.
Side-by-side
The two protocols at a glance
Universal Commerce Protocol
By Google · Proprietary · January 2026
- Covers product discovery and checkout
- No transaction fee (per Google)
- Native Shopify support
- Reaches Google AI Mode + Gemini
- Implementation: publish a manifest at
/.well-known/ucp.json
Best for: Shopify merchants and brands chasing Google ecosystem reach.
Agentic Commerce Protocol
By OpenAI + Stripe · Apache 2.0 · September 2025
- Open source spec, public auditing
- Stripe Shared Payment Tokens \u2014 cards never seen by AI
- Reaches ChatGPT (800M+ weekly users) + Copilot
- Native: WooCommerce, BigCommerce, Squarespace, Wix, Etsy
- Implementation: 4 REST endpoints (Create / Update / Complete / Cancel Checkout)
Best for: WooCommerce / BigCommerce / Wix merchants chasing OpenAI + Microsoft reach.
UCP vs ACP feature-by-feature
Which one should you implement first?
You sell on Shopify
Start with UCP — it's already native in Shopify admin. Enable it and you're live with Google AI Mode, Gemini, and Shopify Merchant Search. Add ACP next via a Shopify app or Brambles.ai.
You sell on WooCommerce, BigCommerce, Squarespace, Wix, or Etsy
Start with ACP — those platforms ship native ACP support, which unlocks ChatGPT (800M+ weekly users) and Microsoft Copilot. Add UCP next via Brambles.ai or Google's manifest spec.
You're a publisher (not a retailer)
You don't directly implement ACP or UCP — you embed Brambles.ai. The platform represents your shoppable content to both protocol ecosystems automatically.
You want maximum AI agent reach with zero engineering effort
Use Brambles.ai. The platform is compatible with both ACP and UCP, so your products and content appear across ChatGPT, Copilot, Gemini, Google AI Mode, and more without you implementing either spec yourself.
Common questions
What is the difference between UCP and ACP?
UCP (Universal Commerce Protocol) by Google and ACP (Agentic Commerce Protocol) by OpenAI and Stripe are two competing standards for AI agents to complete commerce transactions. ACP is open source under Apache 2.0, focuses purely on checkout, uses Stripe Shared Payment Tokens, and powers ChatGPT Instant Checkout and Microsoft Copilot. UCP is proprietary, covers both discovery and checkout, uses Google Pay (with no transaction fee), and powers Google AI Mode, Gemini, Shopify, Walmart, Wayfair, and Target.
UCP vs ACP — which one should retailers implement first?
If you're a Shopify merchant, UCP is already native — enable it from the Shopify admin and you're live with Google AI Mode and Gemini. If you're on WooCommerce, BigCommerce, Squarespace, Wix, or Etsy, ACP is your priority since those platforms ship native ACP support and unlock ChatGPT and Microsoft Copilot. For maximum reach, support both. Brambles.ai is compatible with both protocols so you don't have to choose.
Does ACP charge a transaction fee?
Reports indicate ACP transactions through ChatGPT carry roughly a 4% fee for Shopify merchants (paid to OpenAI/Stripe). Google has publicly stated UCP has no transaction fee — they intend to monetize via ads and Google Pay processing margins instead.
Is UCP open source like ACP?
No. ACP is published under Apache 2.0 — anyone can read, audit, and contribute to the spec. UCP is a proprietary Google standard. Merchants implement UCP by creating a manifest at /.well-known/ucp.json per Google's published documentation, but the protocol itself is not open source.
Will ACP and UCP merge into a single standard?
No public roadmap suggests they'll merge. The two protocols solve overlapping but different problems: ACP is purely a checkout protocol, while UCP also covers product discovery and availability. Most analysts expect both to coexist for the foreseeable future, similar to how multiple payment standards coexist today.
Skip the protocol implementation
Brambles.ai handles ACP and UCP compatibility for you. One integration, both ecosystems, every agent.