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CORS Tester

Test CORS (Cross-Origin Resource Sharing) headers for any URL. Check Access-Control-Allow-Origin, methods, headers, and credentials support.

Free Online CORS Tester

Enter a URL and an origin to test CORS (Cross-Origin Resource Sharing) headers. This tool sends an actual HTTP request from your browser to check if the target server allows cross-origin requests from the specified origin.

How to Test CORS Headers

  1. Enter the URL you want to test
  2. Set the Origin header (the domain making the request)
  3. Choose the HTTP method for the test
  4. Click "Test CORS" or "Send Preflight" to check headers

Features

  • Test any URL for CORS header support
  • Send preflight OPTIONS requests
  • View Access-Control-Allow-Origin, Methods, Headers
  • Check credentials and max-age support
  • Real browser-based CORS testing

Frequently Asked Questions

What is CORS?
CORS (Cross-Origin Resource Sharing) is a security mechanism that allows a web page from one domain to request resources from another domain. Servers must include specific HTTP headers to allow cross-origin requests.
What is a preflight request?
A preflight request is an OPTIONS request sent by the browser before certain cross-origin requests. It checks whether the actual request is safe to send by verifying the allowed methods, headers, and origin.
What does Access-Control-Allow-Origin mean?
This header specifies which origins are allowed to access the resource. It can be a specific origin (e.g., https://example.com) or a wildcard (*) to allow any origin.
Why is my CORS request blocked?
CORS requests are blocked when the server does not include the proper Access-Control-Allow-Origin header matching your origin, or when required methods/headers are not allowed in the preflight response.
Can I test CORS from the browser?
Yes. This tool sends requests directly from your browser, so it accurately reflects how your browser would handle CORS for the given URL and origin combination.

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