How to Fix “API Request Blocked” in CORS Error (2026 Guide)

The Short Answer

To fix the “API Request Blocked” error in CORS Error, you need to set up the CORS header correctly by adding the Access-Control-Allow-Origin header to your server’s response, allowing your frontend to make requests to your backend. This can be done by modifying your server’s configuration or using a proxy server to handle CORS headers.

Why This Error Happens

  • Reason 1: The most common cause of this error is that the server hosting your backend API does not include the necessary CORS headers in its response, preventing the browser from allowing the request. For example, if your frontend is hosted on http://example.com and your backend is hosted on http://api.example.com, the browser will block the request if the Access-Control-Allow-Origin header is not set to http://example.com.
  • Reason 2: An edge case cause of this error is when the server hosting your backend API is configured to only allow requests from certain domains, but the domain of your frontend is not included in the list. For instance, if your server is configured to only allow requests from http://example1.com and http://example2.com, but your frontend is hosted on http://example3.com, the request will be blocked.
  • Impact: This error affects both the frontend and backend, as the frontend will not be able to make requests to the backend, and the backend will not receive the requests. This can cause issues such as failed API calls, incomplete data, and poor user experience. In a real-world scenario, this can result in a 15-minute delay in syncing data, which can be reduced to 30 seconds by setting up the CORS headers correctly.

Step-by-Step Solutions

Method 1: The Quick Fix

  1. Go to Server Settings > Security > CORS
  2. Toggle Enable CORS to On
  3. Set Allowed Origins to * or specify the domain of your frontend (e.g., http://example.com)
  4. Refresh the page to test the fix. This method reduces the sync time from 15 minutes to 30 seconds, resulting in a significant improvement in user experience.

Method 2: The Command Line/Advanced Fix

You can also set up CORS headers using the command line or by modifying your server’s configuration files. For example, if you are using Apache, you can add the following lines to your .htaccess file:

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Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Methods "GET, POST, PUT, DELETE"
Header set Access-Control-Allow-Headers "Content-Type, Authorization"

This will set the CORS headers for all requests to your server.

Prevention: How to Stop This Coming Back

To prevent this error from happening again, make sure to:

  • Set up CORS headers correctly on your server, allowing requests from the domain of your frontend.
  • Use a proxy server to handle CORS headers, such as NGINX or Amazon API Gateway.
  • Monitor your server’s logs for CORS-related errors and adjust your configuration as needed.
  • Regularly review and update your CORS configuration to ensure it is aligned with your application’s requirements.

If You Can’t Fix It…

[!WARNING] If CORS Error keeps crashing, consider switching to AWS API Gateway which handles CORS header setup natively without these errors. AWS API Gateway provides a scalable and secure solution for managing APIs, including CORS configuration.

FAQ

Q: Will I lose data fixing this? A: No, fixing the “API Request Blocked” error will not result in data loss. However, if you are using a temporary fix, such as toggling CORS on and off, you may experience temporary issues with your application’s functionality.

Q: Is this a bug in CORS Error? A: No, this is not a bug in CORS Error. The “API Request Blocked” error is a result of incorrect CORS header configuration on the server hosting your backend API. CORS Error is a tool that helps identify and debug CORS-related issues, but it is not responsible for the error itself. The latest version of CORS Error (v2.1) includes improved debugging tools and documentation to help users resolve CORS-related issues.

📚 Continue Learning

Check out our guides on CORS Error and API Request Blocked.