Does FastAPI Work With Auth0?
FastAPI and Auth0 integrate seamlessly for building secure APIs with enterprise-grade authentication and authorization.
Quick Facts
How FastAPI Works With Auth0
FastAPI works excellently with Auth0 through standard OpenID Connect and OAuth 2.0 protocols. You validate JWT tokens issued by Auth0 in FastAPI dependency injection, making authorization declarative and composable. The integration pattern is straightforward: Auth0 issues JWTs after user authentication, your FastAPI endpoint receives these tokens in the Authorization header, you verify the signature against Auth0's public keys, and extract claims for authorization logic.
Developers typically use the `python-jose` library to validate JWTs and the `fastapi-security` module for dependency injection. Auth0 provides standard endpoints for token validation and user metadata retrieval. The experience is clean because FastAPI's dependency system lets you create reusable security dependencies that automatically validate tokens and inject user context into handlers. Since Auth0 is an external identity provider, you're decoupled from session management—ideal for microservices and SPAs hitting your API from multiple clients.
Best Use Cases
Quick Setup
pip install fastapi python-jose[cryptography] pydantic python-dotenvfrom fastapi import FastAPI, Depends, HTTPException
from fastapi.security import HTTPBearer, HTTPAuthCredentials
from jose import jwt, JWTError
import os
app = FastAPI()
security = HTTPBearer()
AUTH0_DOMAIN = os.getenv("AUTH0_DOMAIN")
AUTH0_API_AUDIENCE = os.getenv("AUTH0_API_AUDIENCE")
ALGORITHMS = ["RS256"]
async def verify_token(credentials: HTTPAuthCredentials = Depends(security)):
try:
token = credentials.credentials
# In production, cache the JWKS and validate signature
payload = jwt.get_unverified_claims(token)
user_id = payload.get("sub")
if not user_id:
raise HTTPException(status_code=401, detail="Invalid token")
return payload
except JWTError:
raise HTTPException(status_code=401, detail="Invalid token")
@app.get("/protected")
async def protected_route(token: dict = Depends(verify_token)):
return {"message": f"Hello {token.get('sub')}"}Known Issues & Gotchas
JWT validation fails because Auth0 public keys change periodically and aren't cached
Fix: Use a library like `python-jose` with built-in key caching or implement caching with TTL for JWKS endpoint responses to avoid unnecessary HTTP calls
Token audience (aud) claim mismatch causes validation failure even with valid signature
Fix: Ensure your FastAPI app validates the 'aud' claim matches your API identifier configured in Auth0, and that your frontend requests tokens with the correct audience
CORS issues when frontend on different domain tries to send Authorization headers
Fix: Configure FastAPI's CORSMiddleware to allow Origin, Authorization headers, and use proper preflight handling
Expired tokens aren't automatically refreshed by FastAPI; client must handle refresh token rotation
Fix: Implement token refresh logic on the client side or add a refresh endpoint in FastAPI that validates refresh tokens from Auth0
Alternatives
- •Keycloak + FastAPI: Open-source identity provider with similar OAuth 2.0/OIDC support, better for self-hosted scenarios
- •Okta + FastAPI: Enterprise-focused identity platform similar to Auth0 with equivalent integration patterns
- •Firebase Authentication + FastAPI: Google-backed solution with simpler setup but less enterprise features than Auth0
Resources
Related Compatibility Guides
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