> For AI agents: the complete documentation index is at [llms.txt](https://reflex.dev/docs/llms.txt). Markdown versions are available by appending `.md` or sending `Accept: text/markdown`.

# Configuration

Reflex apps can be configured using a configuration file, environment variables, and command line arguments.

## Configuration File

Running `uv run reflex init` will create an `rxconfig.py` file in your root directory.
You can pass keyword arguments to the `Config` class to configure your app.

For example:

```python
# rxconfig.py
import reflex as rx

config = rx.Config(
    app_name="my_app_name",
    # Connect to your own database.
    db_url="postgresql://user:password@localhost:5432/my_db",
    # Change the frontend port.
    frontend_port=3001,
)
```

See the [config reference](https://reflex.dev/docs/api-reference/config/) for all the parameters available.

## Environment Variables

You can override the configuration file by setting environment variables.
For example, to override the `frontend_port` setting, you can set the `FRONTEND_PORT` environment variable.

```bash
FRONTEND_PORT=3001 uv run reflex run
```

## Command Line Arguments

Finally, you can override the configuration file and environment variables by passing command line arguments to `uv run reflex run`.

```bash
uv run reflex run --frontend-port 3001
```

See the [CLI reference](/docs/api-reference/cli) for all the arguments available.

## Customizable App Data Directory

The `REFLEX_DIR` environment variable can be set, which allows users to set the location where Reflex writes helper tools like Bun and NodeJS.

By default we use Platform specific directories:

On windows, `C:/Users/<username>/AppData/Local/reflex` is used.

On macOS, `~/Library/Application Support/reflex` is used.

On linux, `~/.local/share/reflex` is used.