Cross-Origin Resource Sharing (CORS) is a security mechanism built into browsers that restricts web pages from making requests to a different domain than the one that served the page.

If you are building an API that needs to be accessed by a frontend app hosted on a different domain, you must configure CORS correctly or the browser will block the request.

Our native server proxy simulates a browser cross-origin request by injecting custom 'Origin' and 'Method' headers and checking if the target server responds with the correct 'Access-Control-Allow-Origin' headers.

Browsers actively enforce CORS. If a request is blocked, the browser hides the headers from JavaScript for security. Our backend proxy bypasses this to show you exactly what the server returned.

It means the API is completely public and allows requests from any website on the internet.

Yes, the CORS TESTER tool is completely free with no usage limits, sign-ups, or subscriptions required.

No. We do not store or log any of the URLs, domains, or passwords you check using our tools.

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