Jan

Jan is an open-source desktop application that serves as a fully offline alternative to ChatGPT. It runs large language models entirely on your local hardware with no data leaving your machine, providing a privacy-first AI chat experience across Windows, macOS, and Linux. For users seeking a free, open-source desktop AI assistant that works without an internet connection, Jan is one of the leading choices.

Key Features

Offline-first architecture. Jan is designed from the ground up to work without an internet connection. All model inference happens locally using your CPU or GPU. No telemetry, no cloud dependencies, and no account required. Your conversations stay on your device.

Built-in model hub. Jan includes a curated catalog of popular open-weight models in GGUF format. Browse, download, and manage models directly within the app. It supports models from the Hugging Face ecosystem and lets you import custom GGUF files from disk.

Extension ecosystem. Jan’s plugin architecture allows community-built extensions to add functionality. Extensions can provide new inference backends, integrate remote API providers as fallbacks, add tools, and customize the interface. The extension system makes Jan adaptable to diverse workflows.

Local API server. Jan exposes an OpenAI-compatible API server, turning your desktop into a local inference endpoint. Applications, scripts, and development tools that support the OpenAI format can connect to Jan without modification.

Cross-platform with GPU acceleration. Jan supports NVIDIA GPUs via CUDA, AMD GPUs via Vulkan, and Apple Silicon via Metal. It automatically detects available hardware and configures layer offloading for optimal performance.

When to Use Jan

Choose Jan when you want a fully offline, open-source ChatGPT replacement with no vendor lock-in. It is well-suited for privacy-conscious users, developers who want an extensible local AI platform, and anyone who prefers an open-source alternative to proprietary desktop apps like LM Studio.

Ecosystem Role

Jan occupies the open-source desktop UI tier alongside LM Studio and GPT4All. It uses llama.cpp-based inference engines under the hood and reads standard GGUF model files. Its extension system differentiates it from simpler desktop clients, while its offline-first philosophy appeals to users who prioritize data sovereignty. For web-based multi-user deployments, consider Open WebUI instead.