Why Aren't My FastAPI Cookies Reaching My React Frontend?

FastAPI Cookie Issues with React Frontend

Problem

FastAPI doesn't return cookies to the React frontend, despite executing a POST request and observing the cookie in the response headers using DevTools on Chrome.

Solution

To resolve the issue, follow these steps:

1. Verify Axios Request:

   Ensure that the Axios POST request is being performed successfully and not returning any errors. Additionally, check that the response includes 'status': 'success' with a 200 status code.

2. Set Credentials in Axios Request:

   Since the React frontend and FastAPI backend are using different ports, cross-origin requests are being made. To enable cookie transfer, set the withCredentials property to true in the Axios request:

   await axios.post(url, data, {withCredentials: true}))

3. Allow Credentials in FastAPI Middleware:

   For cross-origin requests, explicitly allow credentials in the FastAPI middleware using CORSMiddleware, setting allow_credentials=True. This sets the Access-Control-Allow-Credentials response header to true.

4. Specify Allowed Origins:

   Specify the allowed origins using ORIGINS, excluding the * wildcard. This ensures that only specific domains are allowed to send cookies.

5. Set Cookie HTTPOnly:

   In the FastAPI code, set the httponly parameter to True when setting the cookie. This prevents JavaScript from accessing the cookie, enhancing security.

6. Configure CORS Middleware:

   Add the CORSMiddleware to the FastAPI app and configure it to allow the origin used by the React frontend, allow credentials, and allow all methods and headers.

7. Check Browser Setting (For Localhost Testing Only):

   If accessing the React frontend via localhost, ensure that Axios POST requests use 'localhost' instead of '127.0.0.1' in the URL, as these are considered different domains.

By implementing these steps, FastAPI will correctly return cookies to the React frontend, enabling secure and authenticated communication between the frontend and backend.

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