Cross-Origin Intelligence

Simulate and audit Cross-Origin Resource Sharing (CORS) handshake logic. Test preflight (OPTIONS) requests and cross-domain access headers.

Request Allowed
Simulated Server Response HTTP/1.1 200 OK
Access-Control-Allow-Origin: *

Content-Type: application/json

Understanding CORS

CORS (Cross-Origin Resource Sharing) is a system consisting of transmitting HTTP headers, that determines whether browsers block frontend JavaScript code from accessing responses for cross-origin requests.


The Preflight Logic: For "complex" requests (like those with PUT/DELETE or custom headers), the browser first sends an OPTIONS request. The server must respond with the appropriate `Access-Control-Allow-Methods` and `Access-Control-Allow-Headers` before the actual request can proceed.

Security Pitfall: Using `Access-Control-Allow-Origin: *` while also setting `Access-Control-Allow-Credentials: true` is strictly prohibited by browsers for security reasons. You must specify an explicit origin when allowing credentials.

? How to Use CORS Policy Debugger Lab

  1. Open the networking tool in your browser.
  2. Enter the IP address, domain, subnet, or network data.
  3. Select the calculation or lookup type you need.
  4. Click the action button to get instant results.
  5. Copy or export the network information for your records.

✓ Why Use This Tool

  • 100% Free — No account, subscription, or payment required.
  • Privacy First — All processing happens in your browser. Your files never leave your device.
  • No Installation — Works directly in any modern browser on any device.
  • Instant Results — Get your output in seconds without waiting for server processing.

Frequently Asked Questions

Can I use these networking tools without installing any software?

Yes. All IT and networking tools run directly in your browser. There is nothing to install, no configuration required, and they work on any operating system.

How accurate is the network diagnostic information?

The tools query live DNS resolvers and use your browser's network APIs for real-time data. Results reflect your actual network conditions at the time of the query.

Can IT professionals use these tools for client network diagnostics?

Yes. These tools are designed for professional use and provide accurate, real-time network information suitable for diagnosing DNS misconfigurations, IP conflicts, and connectivity issues.