> ## Documentation Index
> Fetch the complete documentation index at: https://fastapi.codewithsiva.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Environment Variables & Configuration

> Store configurations in .env files, secure database credentials, and manage settings with pydantic-settings

## 1. Environment Variables (.env)

An **environment variable** is a dynamic-named value that can affect the way running processes will behave on a computer. In backend development, we use them to store:

* API Keys and secrets
* Database connection strings (URLs)
* Application ports and modes (e.g., debug vs. production)

### The `.env` File

Instead of hardcoding configurations in our code, we save them in a local text file named `.env`:

```env theme={null}
# .env
DATABASE_URL=postgresql://user:pass@localhost:5432/mydb
SECRET_KEY=supersecretjwttokenkey
DEBUG=True
PORT=8000
```

> \[!CAUTION]
> **Never commit your `.env` file to Git!** It contains sensitive credentials. Always add `.env` to your `.gitignore` file. Instead, commit a `.env.example` file that lists the keys but leaves the values blank.

***

## 2. Managing Settings with Pydantic Settings

While you can access environment variables using Python's built-in `os.environ.get()`, it does not validate data types or check if required fields are missing.

The industry-standard way to manage configuration in FastAPI is using **`pydantic-settings`**.

### Installation

```bash theme={null}
pip install pydantic-settings
# or with uv
uv pip install pydantic-settings
```

### Creating a Settings Config

Inherit from `pydantic_settings.BaseSettings`. Pydantic will automatically load fields from environment variables (case-insensitive) and validate their types.

```python theme={null}
# app/config.py
from pydantic_settings import BaseSettings, SettingsConfigDict

class Settings(BaseSettings):
    # Automatically loaded from env or defaults to local
    DATABASE_URL: str = "sqlite:///./local.db"
    SECRET_KEY: str
    DEBUG: bool = False
    PORT: int = 8000

    # Configures settings behaviour to load from a .env file
    model_config = SettingsConfigDict(env_file=".env", extra="ignore")

# Instantiate settings
settings = Settings()
```

### Accessing Settings in Your App

Now, import `settings` anywhere in your application:

```python theme={null}
# app/main.py
from fastapi import FastAPI
from app.config import settings

app = FastAPI(debug=settings.DEBUG)

@app.get("/")
def read_root():
    return {"status": "ok", "db": settings.DATABASE_URL}
```