Jan.ai Has a Free API: Open-Source ChatGPT Alternative Running 100% Offline

Jan is an open-source ChatGPT alternative that runs 100% offline on your computer. It provides an OpenAI-compatible API, a beautiful chat interface, and supports dozens of open-source models.

What Is Jan?

Jan is a desktop application that turns your computer into an AI server. It downloads and runs LLMs locally with full privacy — no data ever leaves your machine. It is fully open-source (AGPLv3) and works on Windows, Mac, and Linux.

Key Features:

• 100% offline, no cloud dependency
• OpenAI-compatible API server
• Beautiful chat UI with threads
• Supports GGUF models from Hugging Face
• GPU acceleration (CUDA, Metal, Vulkan)
• Extension system for plugins
• Local RAG with file uploads

Quick Start

1. Download Jan from jan.ai
2. Open the app and go to Model Hub
3. Download a model (e.g., Llama 3.2, Mistral, Phi-3)
4. Start chatting or enable the API server

Jan API: OpenAI-Compatible Local Server

Jan runs a local API server on port 1337 that is fully compatible with the OpenAI API:

from openai import OpenAI

client = OpenAI(
    base_url="http://localhost:1337/v1",
    api_key="jan"  # Any string works
)

# Chat completion
response = client.chat.completions.create(
    model="llama3.2-3b-instruct",
    messages=[
        {"role": "system", "content": "You are a senior developer."},
        {"role": "user", "content": "How do I set up a CI/CD pipeline with GitHub Actions?"}
    ],
    temperature=0.7,
    max_tokens=1000
)
print(response.choices[0].message.content)

Streaming Chat

stream = client.chat.completions.create(
    model="llama3.2-3b-instruct",
    messages=[{"role": "user", "content": "Explain microservices architecture"}],
    stream=True
)

for chunk in stream:
    content = chunk.choices[0].delta.content
    if content:
        print(content, end="", flush=True)

Using with JavaScript/TypeScript

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "http://localhost:1337/v1",
  apiKey: "jan"
});

async function chat(prompt: string) {
  const response = await client.chat.completions.create({
    model: "llama3.2-3b-instruct",
    messages: [{ role: "user", content: prompt }]
  });
  return response.choices[0].message.content;
}

const answer = await chat("What is WebAssembly?");
console.log(answer);

REST API Direct

# Chat completion
curl http://localhost:1337/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d x27{"model": "llama3.2-3b-instruct", "messages": [{"role": "user", "content": "Hello!"}]}x27

# List models
curl http://localhost:1337/v1/models

# Download a model
curl -X POST http://localhost:1337/v1/models/download \
  -H "Content-Type: application/json" \
  -d x27{"model": "mistral-7b-instruct"}x27

Jan vs LM Studio vs Ollama

Feature	Jan	LM Studio	Ollama
Open source	Yes (AGPL)	No	Yes (MIT)
GUI	Chat-focused	Model explorer	CLI
API port	1337	1234	11434
Extensions	Plugin system	No	No
Local RAG	Built-in	No	No
Model format	GGUF	GGUF	GGUF

Resources

• Jan.ai
• Jan GitHub — 26K+ stars
• Jan Discord

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