CORS Header Generator & Config Builder
Visual generator for Cross-Origin Resource Sharing (CORS) headers. Prevent browser preflight errors and build hardened configs for NGINX, Express.js, Cloudflare Workers, and Apache.
CORS Policy Parameters
# NGINX Reverse Proxy CORS Configuration
location /api/ {
if ($request_method = 'OPTIONS') {
add_header 'Access-Control-Allow-Origin' 'https://ubify.app, https://tools.ubify.app' always;
add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
add_header 'Access-Control-Allow-Headers' 'Content-Type, Authorization, X-Requested-With' always;
add_header 'Access-Control-Allow-Credentials' 'true' always;
add_header 'Access-Control-Max-Age' 86400;
add_header 'Content-Type' 'text/plain; charset=utf-8';
add_header 'Content-Length' 0;
return 204;
}
add_header 'Access-Control-Allow-Origin' 'https://ubify.app, https://tools.ubify.app' always;
add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
add_header 'Access-Control-Allow-Headers' 'Content-Type, Authorization, X-Requested-With' always;
add_header 'Access-Control-Allow-Credentials' 'true' always;
add_header 'Access-Control-Expose-Headers' 'Content-Length, X-Total-Count' always;
proxy_pass http://backend_upstream;
}Mastering Cross-Origin Resource Sharing (CORS)
CORS is a browser security mechanism that restricts HTTP requests initiated from scripts outside the origin domain. When web applications perform cross-origin AJAX or Fetch calls with custom headers (such as Authorization) or non-simple HTTP methods (such as PUT or DELETE), browsers issue an automatic OPTIONS preflight request.
Preflight Handling (HTTP 204)
Responds immediately to incoming HTTP OPTIONS requests with status 204 No Content, avoiding unnecessary backend execution and eliminating browser CORS console exceptions.
Credentials & Wildcards
Enforcing credentials requires explicit origin matching. If Access-Control-Allow-Credentials: true is sent, browsers reject wildcards (*) for security.
Preflight Caching (Max-Age)
Configuring Access-Control-Max-Age: 86400 instructs clients to cache the preflight handshake for 24 hours, slashing API roundtrips in half.
Ubify Core Engineering Team
SOFTWARE ENGINEERS & SYSTEMS ARCHITECTS