CORS Configuration Tester
Test Cross-Origin Resource Sharing (CORS) headers and verify Access-Control-Allow-Origin configurations.
How to Use CORS Configuration Tester
Enter API endpoint URL and test origin.
Inspect CORS headers returned by the server.
Detect dangerous wildcard origins with credentials allowed.
CORS Configuration Tester runs 100% client-side in your web browser. Your data, passwords, keys, and files are processed using the Web Crypto API and never transmitted to any server. Zero telemetry, zero storage, zero cloud processing.
Frequently Asked Questions
What is a dangerous CORS configuration?
Reflecting any origin with Access-Control-Allow-Credentials: true allows malicious websites to steal authenticated user data.
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