Jan
FreeAn open-source ChatGPT alternative that runs 100% offline on your own machine
An Apache 2.0 desktop LLM client positioned as a fully offline ChatGPT alternative. Model downloads and chat happen in one window — no command line, no account. Its installer is the smallest of its class at 55 MB on Windows.
Why we picked it
One thing worth clearing up first: GitHub reports Jan's licence as NOASSERTION, which makes it look unclear. Open the LICENSE file and it is a standard Apache 2.0 — GitHub's auto-detection simply fails on an extra attribution line at the end.
It is the same class of thing as LM Studio — a desktop app you open and chat in — except it is open source and much smaller: 55 MB on Windows and 97.8 MB on macOS, against Ollama's 1492 MB and 174.6 MB.
Its weakness is scale. At 43,996 stars it is the smallest of this group, and community, tutorials and third-party integrations all trail Ollama. But if what you want is an open-source chat window that works offline, this is the most direct answer.