Arco is a native Mac app for chatting with and comparing AI models side by side. You type one question, and several models answer at once in the same window. No more bouncing between ChatGPT, Claude, Gemini, and a pile of browser tabs just to figure out which answer you actually trust. And no more settling for comparison tools that only give you a short list of models, and keep your chats on their servers.
Why bother comparing models?
Every model has a different personality. One is great at code, another at writing, another at careful reasoning. Trusting a single reply is fine for small stuff. For anything that matters, comparing a few answers side by side usually gets you somewhere better.
Arco makes that comparison the default, not a chore.
What's actually in it
Ask once, see every answer. Broadcast the same question to multiple models and watch the replies come in together.
Pick from 400+ models. Access the full OpenRouter catalog, from frontier models to open-source options, with one API key.
Bring your own key. Plug in your OpenRouter key and talk to providers directly from your Mac.
Keep chats on your device. Conversations stay local. Arco doesn't store your chats on its servers.
Summarize the noise. When several models reply, Summarize sends those responses to a judge model you choose and gives you a clear breakdown: where they agree, where they differ, and which answer looks strongest.
Who's it for?
Developers comparing code suggestions. Writers weighing tone and drafts. Researchers cross-checking summaries. Prompt engineers testing the same idea across models. Anyone who wants better answers without juggling five tabs or handing their chats to another cloud product.
Getting started is pretty simple
1. Grab an OpenRouter API key.
2. Drop it into Arco and pick the models you want.
3. Ask anything, compare the replies, and move on with the answer that holds up.
That's it. You're usually comparing models within a few minutes.
A lot of online multi-model tools only give you a short list of models, keep your chats on their servers, and make you wait when a new model comes out. They feel built for people who use AI all day, not for the times you just need a quick comparison.
If you've been stuck switching tabs, or tried a comparison tool that never quite clicked, Arco is that workflow cleaned up for your Mac.
