FastAPI applications require secret keys for JWT token signing, session management, and OAuth2 flows. A strong, unpredictable secret key is essential for maintaining application security.
What is FastAPI SECRET_KEY?
In FastAPI, secret keys are used primarily for JWT (JSON Web Token) signing and verification, OAuth2 flows, and session-based authentication via Starlette middleware. The key ensures that tokens cannot be forged and sessions remain secure.
Key Requirements
- At least 32 characters for adequate security
- URL-safe characters recommended for compatibility
- Cryptographically random generation
- Unique per application and environment
How to Use
Use the generated key with FastAPI's security utilities:
```python
from fastapi import FastAPI
import os
SECRET_KEY = os.getenv('SECRET_KEY')
ALGORITHM = 'HS256'
# For JWT tokens
from jose import jwt
token = jwt.encode(payload, SECRET_KEY, algorithm=ALGORITHM)
```Best Practices
- Store in environment variables, not in code
- Use python-dotenv for local development
- Consider using Pydantic Settings for configuration
- Use HS256 or RS256 algorithms for JWT signing
- Implement token refresh mechanisms
Common Mistakes to Avoid
- ✗Using weak or predictable keys
- ✗Hardcoding secrets in source code
- ✗Not validating token expiration
- ✗Using the same key for different purposes (signing vs encryption)