Analyze Cross-Origin Resource Sharing headers and generate secure Express/Node.js middleware.
Execution runs 100% locally inside the browser sandbox using HTML5 Canvas, Web Cryptography Subtle API, and Web Workers. Zero egress.
Zero network latency. Operates completely offline with zero dependencies on third-party backend servers or cloud services.
Built according to official RFC specifications, cryptographic test vectors, and enterprise-grade data transformation standards.
Specify your allowed domain origins or wildcard.
Enable cookie credentials and customize allowed HTTP methods.
Copy the hardened Express CORS middleware snippet into your API server.
Browsers reject Access-Control-Allow-Origin: * when Access-Control-Allow-Credentials: true is set to prevent cross-origin credential leakage.
86400 seconds (24 hours) is recommended to cache preflight OPTIONS responses and reduce server load.
Zero-egress companion tools in the Security & Network suite
Measure cryptographic randomness, Shannon entropy (0-8 bits/byte), Chi-square test, and byte distributions.
Brute-force all 256 single-byte XOR keys with automated English frequency & chi-squared scoring.
Audit CSP, HSTS, X-Frame-Options, and security headers with OWASP grading (A+ to F).
Compare memory hardness, GPU ASIC resistance, and security parameters across KDF standards.
