head to head · open source
Open WebUI vs sim
Open WebUI has 152,394 GitHub stars, 22,296 forks, 294 open issues and last shipped yesterday. sim has 29,655 stars, 3,837 forks, 336 open issues and last shipped yesterday. Open WebUI leads on adoption by 414% (152,394 vs 29,655 stars). Open WebUI is written in Python under a custom or non-standard licence; sim is written in TypeScript under Apache-2.0. Open WebUI has attracted 15% as many forks as stars, sim 13%. sim was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (ai), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| Open WebUI | sim | |
|---|---|---|
| GitHub stars | ★ 152K | ★ 30K |
| License | Custom / other | Apache-2.0 |
| Written in | Python | TypeScript |
| Last push | 2026-09-17 | 2026-09-17 |
| Forks | ⑂ 22K | ⑂ 3.8K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Open WebUI if
- You weight community size — 152K stars and counting
- You want the Custom / other license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick sim if
- You want the sim feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches TypeScript
- You evaluated both and sim fits your workflow better
About Open WebUI
Open WebUI is a self hosted, open source AI interface that unifies access to local and cloud based large language models. It runs entirely in a web browser and supports Ollama for local model hosting alongside any OpenAI compatible API, including services like LMStudio, GroqCloud, Mistral, and OpenRouter. Built in Python, it functions as a drop in replacement for proprietary AI platforms, giving users full control over their model infrastructure and data.
read the full Open WebUI overview →
About sim
Sim is an open source collaborative workspace for building, deploying, and monitoring AI agents and workflows. It lives in the TypeScript ecosystem and is distributed under the Apache 2.0 license, with a repository that has accumulated roughly 29,600 stars and 3,800 forks over its two year history. The project positions itself as a single surface where chat, workflows, tables, files, and knowledge coexist, whether accessed through a browser or a desktop application for macOS.
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Frequently asked questions
Is Open WebUI or sim more popular?
Open WebUI has 152,394 GitHub stars and sim has 29,655. Open WebUI has the larger community by that measure.
Are Open WebUI and sim free?
Both are open source. Open WebUI has no licence declared in this registry, and sim is licensed under Apache-2.0. Both are free to self-host.
What is the difference between Open WebUI and sim?
Open WebUI is written in Python and sim in TypeScript. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Open WebUI or sim?
Choose Open WebUI if you want the larger community (152,394 stars) or its Custom / other licence terms. Choose sim if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.