> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/janhq/jan/llms.txt
> Use this file to discover all available pages before exploring further.

# OpenAI-Compatible API

> Use Jan's local API server as a drop-in replacement for OpenAI's API in your applications.

Jan provides a built-in, OpenAI-compatible API server that runs entirely on your computer, powered by `llama.cpp`. Use it as a drop-in replacement for cloud APIs to build private, offline-capable AI applications.

## Quick Start

<Steps>
  <Step title="Start the Server">
    1. Navigate to **Settings** > **Local API Server**
    2. Enter a custom **API Key** (e.g., `secret-key-123`). This is required for all requests
    3. Click **Start Server**

    The server is ready when the logs show `JAN API listening at http://127.0.0.1:1337`
  </Step>

  <Step title="Test with cURL">
    Open a terminal and make a request. Replace `YOUR_MODEL_ID` with the ID of an available model in Jan.

    ```bash theme={null}
    curl http://127.0.0.1:1337/v1/chat/completions \
      -H "Content-Type: application/json" \
      -H "Authorization: Bearer secret-key-123" \
      -d '{
        "model": "YOUR_MODEL_ID",
        "messages": [{"role": "user", "content": "Tell me a joke."}]
      }'
    ```
  </Step>
</Steps>

## Server Configuration

These settings control the network accessibility and basic behavior of your local server.

### Server Host

The network address the server listens on:

* **`127.0.0.1`** (Default): The server is only accessible from your own computer. This is the most secure option for personal use.
* **`0.0.0.0`**: The server is accessible from other devices on your local network (e.g., your phone or another computer). Use this with caution.

### Server Port

The port number for the API server:

* **`1337`** (Default): A common alternative port
* You can change this to any available port number (e.g., `8000`)

### API Prefix

The base path for all API endpoints:

* **`/v1`** (Default): Follows OpenAI's convention. The chat completions endpoint would be `http://127.0.0.1:1337/v1/chat/completions`
* You can change this or leave it empty if desired

### API Key

A mandatory secret key to authenticate requests:

* You must set a key. It can be any string (e.g., `a-secure-password`)
* All API requests must include this key in the `Authorization: Bearer YOUR_API_KEY` header

### Trusted Hosts

A comma-separated list of hostnames allowed to access the server. This provides an additional layer of security when the server is exposed on your network.

## Advanced Settings

### Cross-Origin Resource Sharing (CORS)

* **(Enabled by default)** Allows web applications (like a custom web UI you are building) running on different domains to make requests to the API server
* **Disable this** if your API will only be accessed by non-browser-based applications (e.g., scripts, command-line tools) for slightly improved security

### Verbose Server Logs

* **(Enabled by default)** Provides detailed, real-time logs of all incoming requests, responses, and server activity
* This is extremely useful for debugging application behavior and understanding exactly what is being sent to the models

## Integration Examples

### Python Example

```python theme={null}
import openai

# Configure the OpenAI client to use Jan's local server
client = openai.OpenAI(
    api_key="secret-key-123",
    base_url="http://127.0.0.1:1337/v1"
)

# Make a chat completion request
response = client.chat.completions.create(
    model="YOUR_MODEL_ID",
    messages=[
        {"role": "user", "content": "What is the capital of France?"}
    ]
)

print(response.choices[0].message.content)
```

### JavaScript Example

```javascript theme={null}
import OpenAI from 'openai';

// Configure the OpenAI client to use Jan's local server
const client = new OpenAI({
  apiKey: 'secret-key-123',
  baseURL: 'http://127.0.0.1:1337/v1'
});

// Make a chat completion request
const response = await client.chat.completions.create({
  model: 'YOUR_MODEL_ID',
  messages: [
    { role: 'user', content: 'What is the capital of France?' }
  ]
});

console.log(response.choices[0].message.content);
```

### Streaming Example

```bash theme={null}
curl http://127.0.0.1:1337/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer secret-key-123" \
  -d '{
    "model": "YOUR_MODEL_ID",
    "messages": [{"role": "user", "content": "Write a short story."}],
    "stream": true
  }'
```

## Troubleshooting

<Warning>
  Ensure **Verbose Server Logs** are enabled to get detailed error messages in the "Server Logs" view.
</Warning>

**Connection Refused**

* The server is not running, or your application is pointing to the wrong host or port

**401 Unauthorized**

* Your API Key is missing from the `Authorization` header or is incorrect

**404 Not Found**

* The `model` ID in your request body does not match an available model in Jan
* Your request URL is incorrect (check the API Prefix)

**CORS Error (in a web browser)**

* Ensure the CORS toggle is enabled in Jan's settings

## API Compatibility

Jan's local API server implements the OpenAI API specification, making it compatible with:

* OpenAI's official client libraries (Python, JavaScript, .NET, Go)
* LangChain and LlamaIndex frameworks
* Any tool or library that supports OpenAI-compatible APIs

<Note>
  Simply change the `base_url` or `baseURL` parameter to point to your Jan server instead of OpenAI's servers.
</Note>