CORS: Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true

Cover Image for CORS: Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true
Matheus Mello
Matheus Mello
published a few days ago. updated a few hours ago

šŸŒšŸ”— CORS: Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true

šŸ‘‹ Hey there, tech enthusiasts! Today, let's tackle a common issue that many developers face when dealing with Cross-Origin Resource Sharing (CORS).

šŸ”’ The problem: You might have encountered the error message "Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true" while making Ajax calls from your web application to a backend server. This error occurs when you have set the "credentials" flag to true and are trying to use a wildcard (*) in the "Access-Control-Allow-Origin" header.

šŸš€ Let's dive into the setup: In this scenario, we have a frontend server running on Node.js (domain: localhost:3000) communicating with a backend server built with Django and Ajax (domain: localhost:8000). The web application is served by Node.js, and the browser interacts with Django through Ajax.

šŸ’” Solution breakdown:

  1. The Node.js setup:

In your Node.js server code, make sure to set the "Access-Control-Allow-Origin" header to the exact URL of your backend server (http://localhost:8000/) instead of using a wildcard (*) when the "credentials" flag is set to true. Here's an example code snippet:

var allowCrossDomain = function(req, res, next) {
    res.header('Access-Control-Allow-Origin', 'http://localhost:8000/');
    res.header('Access-Control-Allow-Credentials', true);
    res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    next();
};
  1. Django configuration:

To configure CORS properly in Django, you can use the 'django-cors-headers' library. Set the following options in your Django settings:

CORS_ORIGIN_ALLOW_ALL = False
CORS_ALLOW_CREDENTIALS = True
CORS_ORIGIN_WHITELIST = (
    'http://localhost:3000' # Replace with the exact URL of your frontend server
)

šŸŽÆ That's it! With these changes, you should be able to resolve the "Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true" error.

šŸ” Troubleshooting tips:

  • Double-check that you are using the correct URLs in your Node.js setup and Django configuration.

  • Make sure you have installed the 'django-cors-headers' library and included it in your Django project.

šŸ’¬ Have questions or feedback? Feel free to leave a comment below if you have any questions or need further assistance with CORS. I'd love to help you out! šŸ˜Š

šŸš€ Keep coding and building amazing web applications! Happy CORS troubleshooting! šŸ‘©ā€šŸ’»šŸ‘Øā€šŸ’»


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