Test cross-origin request settings
Cross-Origin Resource Sharing decides whether a web page on one origin may call an API on another. Misconfigured CORS is a common source of frustrating "blocked by CORS" errors during development. This tool helps you check how an endpoint responds to cross-origin requests, so you can see what it allows and fix the configuration.
How to use it
- Enter the endpoint and the request details.
- Inspect the CORS headers the server returns.
- Compare them with what your page's origin needs.
Where it helps
- Diagnosing a request blocked by the browser's CORS rules.
- Confirming an API allows your site's origin.
- Understanding preflight behaviour for non-simple requests.
Questions people ask
Why does the browser block my request even though the API works in a tool? CORS is enforced by the browser, not the server — a direct request succeeds, but a browser request needs the right permission headers.
Is my input uploaded? The request goes to the endpoint you specify; the tool itself doesn't store it.