Why Aren't My FastAPI Cookies Showing Up in My React Frontend?

FastAPI: Handling Cookies in React Frontend

Overview

FastAPI enables cookie handling for backend development. However, sending and receiving cookies in React frontends may require specific configurations to ensure proper functionality.

Why Cookies Are Not Returned to React Frontend

If your FastAPI backend is not returning cookies to your React app, several factors may contribute to this issue:

1. Invalid Axios Request:

• Ensure that your Axios request is correctly sending credentials by setting the withCredentials property to true.
• Verify that the Axios request URL matches the domain of your FastAPI backend. Using localhost and 127.0.0.1 as different domains can disrupt cookie creation.

2. CORS Restrictions:

• Due to cross-origin requests, you need to explicitly configure CORS settings in your FastAPI application.
• Specify the allowed origins using the CORSMiddleware with allow_credentials=True to enable cross-origin cookie usage.

3. Cookie Settings in FastAPI:

• Ensure that you correctly set cookies in your FastAPI routes using the response.set_cookie() method.
• Verify that the httponly parameter is set to True to prevent client-side access to cookies.

4. SameSite Attribute:

• The SameSite attribute of the cookie can impact its availability across different domains.
• Set it to SameSite=Lax or SameSite=Strict to control cookie accessibility and prevent cross-site attacks.

Sample FastAPI Cookie Setting:

from fastapi import FastAPI, Response

app = FastAPI()

@app.get('/')
def main(response: Response):
    response.set_cookie(
        key='token',
        value='some-token-value', 
        httponly=True,
        samesite='Lax'  # or 'Strict'
    ) 
    return {'status': 'success'}

Sample Axios Request with Credentials:

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

Important Note:

• Remember that using wildcards (*) for Access-Control-Allow-Origin may limit the types of communication and prevent cookies and authorization headers from being sent.
• Ensure that the frontend domain is explicitly included in the allowed origins and that allow_credentials=True is set for proper cookie handling.

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