Why We Built UCPList and Open-Sourced the Data
The story behind UCPList: why a developer side project became the most comprehensive UCP directory, and why we made all the data open source.
The Gap Nobody Was Filling
UCP launched on January 11, 2026. Shopify and Google announced it together. Within days there were blog posts, GitHub repos, SDK experiments, and Shopify merchants toggling the new checkout setting. Real stuff was happening.
But if you wanted to find all of it in one place? Good luck.
The official spec at ucp.dev is solid for understanding the protocol. checkout.directory lists some merchants. Various GitHub orgs had scattered repos. But there was no single resource that showed you the full picture: who's building what, which merchants are actually live, what tools exist, and what the ecosystem looks like as a whole.
I kept running into the same problem. I'd be looking at a Shopify store trying to figure out if their UCP endpoint was live, then I'd want to check what SDKs existed, then I'd want to know which payment handlers were on board. Every answer required a different search, a different source, a different level of trust.
So I started a spreadsheet.
From Spreadsheet to Directory
The spreadsheet grew fast. Within a week I had 30+ entries across merchants, platforms, SDKs, and validators. It was already the most complete list I'd seen anywhere, which honestly said more about the gap than about my research skills.
Turning it into a website was the natural next step. A spreadsheet is fine for one person. A website is useful for an ecosystem.
We built UCPList with Next.js, pulled in the shadcn/ui component library, and deployed to Vercel. Nothing fancy. The directory launched with about 40 listings and a basic category system: merchants, platforms, payment handlers, developer tools, and agent integrations.
Today we track 77 listings and counting.
Why Open Source Matters Here
Early on we made a decision that shaped everything else: the listing data goes in a public GitHub repo.
All of it. Every merchant, every tool, every status designation. It lives at Full-Vibe/ucp-ecosystem and anyone can see it, use it, fork it, or submit PRs.
This matters for a few reasons:
Trust. When a directory tells you a merchant is "verified live," you should be able to see what that means. Our verification is in the open. You can see when we last checked an endpoint, what we found, and how we categorized it.
Reuse. If you're building an agent that needs a list of UCP-enabled merchants, you shouldn't have to scrape our site. Just pull the data. It's structured, it's typed, it's yours.
Accuracy. An ecosystem directory maintained by one small team will always have blind spots. Open-sourcing the data means anyone in the ecosystem can fix mistakes, add missing entries, or update stale information. The directory gets better every time someone opens a PR.
Protocol alignment. UCP itself is an open protocol. A closed, proprietary directory tracking an open protocol would be weird. The data layer should match the protocol's values.
What We Actually Learned
Building this taught us things that aren't obvious from just reading the UCP spec:
Most live UCP merchants are Shopify stores. This makes sense. Shopify built UCP support directly into their platform, so enabling it is a toggle. The 47 merchants we've verified with live endpoints are overwhelmingly on Shopify. Allbirds, Glossier, Pura Vida, and dozens more. The big announced merchants (Target, Walmart, Wayfair) don't have working endpoints yet.
The ecosystem is nascent. There's no way around this. UCP is less than three months old. The tooling is early. The merchant count is small relative to total e-commerce. Most payment handler integrations are announced, not shipped. That's fine. Every protocol starts somewhere.
Developer tools are surprisingly good. The UCP conformance test suite is real and useful. The spec is well-documented. The UCP Schema provides solid type definitions. If you want to build something, the foundation is there.
Nobody was tracking the full picture. checkout.directory tracks merchants. GitHub has the official repos. But nobody was connecting the dots between platforms, payment handlers, developer tools, and agent integrations. That cross-cutting view is what UCPList provides.
What's Next
We're adding more data every week. We built a UCP Validator that checks merchant endpoints in real time. We built a manifest generator for merchants who want to create their own UCP configuration. We're working on automated monitoring so the directory stays fresh without manual checking.
The goal hasn't changed: if you need to find something in the UCP ecosystem, you should be able to find it here in under five minutes.
If you're building something with UCP and it's not listed, submit it or open a PR. The directory is only as good as the community behind it.
Read next
UCP launched in January 2026 and the ecosystem fragmented fast. There was no map. So we built one.
UCPList is the directory that helps AI agents, developers, and merchants find every piece of the UCP ecosystem in one place. Here is what we built, why, and what is in it.
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