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Feature checklists make every tool look equivalent. This table leads with the three things that actually differ — what it costs you before it works, whether your files leave your device, and where the free version stops.
| WebLLM Chatchat.webllm.ai | Arenaarena.ai | ChatGPTchatgpt.com | Claudeclaude.ai | |
|---|---|---|---|---|
| What it does | Runs an open language model inside your browser, nothing sent to a server | Put one prompt to two anonymous models and vote for the better answer | The general assistant most people mean when they say they used AI | Anthropic's assistant, strongest on long documents and careful writing |
| What it costs you | No sign-upWorks the moment the page loads. No account, no email, no trial. | No sign-upWorks the moment the page loads. No account, no email, no trial. | Free tierA genuinely usable free tier with paid plans for volume or team features. | Free tierA genuinely usable free tier with paid plans for volume or team features. |
| Your files | Runs on your device | Runs on their server | Runs on their server | Runs on their server |
| Where it stops | The first run downloads gigabytes of model weights and it will not start at all without WebGPU. | Prompts and votes are collected for research and can end up in public datasets. | Free accounts are rate-limited on the best model and get downgraded to a smaller one mid-session without warning. | Free usage is capped per rolling window, and the cap tightens at busy times of day. |
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| Category | AI Assistants & Generators | AI Assistants & Generators | AI Assistants & Generators | AI Assistants & Generators |
| Last checked | 2026-07-29 | 2026-07-29 | 2026-07-29 | 2026-07-29 |
| Open the site | Open | Open | Open | Open |
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