CORS (Cross-Origin Resource Sharing) is a browser security mechanism that controls how web pages request resources from different origins. If the server doesn't set proper CORS headers, the browser blocks the request.

How is CORS test different from API test?

CORS test focuses on checking cross-origin headers (Access-Control-Allow-Origin etc.), while API test focuses on actual response data. This tool provides both: GET test and OPTIONS preflight.

What is a preflight request?

A preflight is an OPTIONS request the browser sends before certain cross-origin requests to check if the server permits them. This tool lets you manually send preflight requests.

What is a CORS proxy?

A CORS proxy is a middleman server that adds CORS headers when fetching APIs. Popular options: corsproxy.io, cors-anywhere. Note: your data passes through the proxy server.

Why do some APIs support CORS and others don't?

CORS support depends on the API server. Public APIs usually support CORS. Private/legacy systems may not. Server-side middleware (like the `cors` npm package) can enable it.

Online CORS Test Tool - Check Cross-Origin Support

Free online CORS test tool, pure client-side. Check if a URL supports cross-origin requests. Displays CORS response headers and preflight results to help debug cross-origin issues.

🔒 100% Client-Side

🌐 Target URL

🔒 Requests go directly from your browser. This tool does NOT log any data.