Arco is a native macOS app that lets you send a single prompt to 400+ AI models simultaneously via OpenRouter and compare their answers side by side. Download free for Mac (macOS 13 Ventura or later, Apple Silicon).
What is Arco?
Arco is a native macOS app (requires macOS 13 Ventura or later, Apple Silicon) for chatting with and comparing AI models side by side. It takes a user prompt as input and displays responses from multiple models in parallel panes, with an optional AI-powered summary that highlights agreements and differences. Arco uses your own OpenRouter API key to access over 400 models including GPT-4o, Claude, Gemini, and Mistral. All data stays on your device—no servers store your conversations. It is developed by an independent team (contact: [email protected]).
Key Features
- Broadcast to all models — Type your prompt once and send it to every selected model simultaneously; no copying or pasting between chat sites.
- Fully private — Every conversation is stored locally on your Mac; no data is uploaded to Arco servers.
- AI-powered summary — Generate a structured comparison of all responses by having a judge model (pick any from your library) analyze where models agree and differ, streamed in real-time.
- 400+ models available — Access frontier and open-source models via OpenRouter with a single API key; add new models as they become available.
- Flexible layouts — Arrange model response panes in 1, 2, 3, or 4-column grids; hide or show panes as needed.
- Pay only for what you use — No subscription required; you pay OpenRouter's per-token rates directly with no markup.
- Perpetual license option — One-time payment of $49 for unlimited saved conversations and 1 year of updates and support.
Who is it for?
- Developers — Debug code and weigh architecture advice from multiple models to choose the approach that holds up.
- Writers — Generate multiple drafts, compare tone and style, and select the version that fits their voice.
- Researchers — Cross-check summaries across models to surface different perspectives and identify the strongest reasoning.
- Business teams — Draft reports and exec summaries, then pressure-test strategy ideas by comparing responses side by side.
What can you do with Arco?
- Compare model outputs for a single query — See how GPT-4o, Claude, Gemini, and others answer the same prompt in parallel panes.
- Generate a structured summary of disagreements — When models give conflicting answers, use the Summarize feature to get a breakdown of key differences and a recommended answer.
- Save and manage conversations — Free version stores up to 3 saved conversations; unlimited with the perpetual license.
How does Arco work?
- Sign up at OpenRouter.ai and obtain a free API key.
- In Arco, choose which models to include from the 400+ available.
- Type your question once and send it; all selected models answer in parallel. Optionally, use the Summarize feature with a judge model to get a comparison of all responses.
Pricing
Arco offers two tiers: a Free version with up to 3 saved conversations and access to all 400+ models, and an Unlimited perpetual license for $49 (one-time payment) that includes unlimited saved conversations, 1 year of updates and support, and works on one macOS device. No subscription required.
Pros
- All conversations stay local and private.
- Access to 400+ models through a single API key.
- No monthly subscription; pay only per-token usage to OpenRouter.
- Flexible layouts and real-time summary generation.
Cons
- Requires an OpenRouter account and API key (free to create).
- Only available for macOS 13+ on Apple Silicon.
- Free version limited to 3 saved conversations.
FAQ
What is Arco?
Arco is a native macOS app that lets you compare answers from 400+ AI models side by side using your own OpenRouter API key.
Do I need to pay for OpenRouter separately?
Yes. You pay OpenRouter directly for per-token usage. Arco does not charge any markup or subscription fee.
Where is my data stored?
All conversations are stored locally on your Mac. They are never uploaded to Arco servers or shared with third parties.
How many models can I compare at once?
There is no explicit limit; you can select any subset of the 400+ models available through OpenRouter.
Is Arco free?
Arco offers a free version with up to 3 saved conversations and an unlimited perpetual license for $49.
