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://ubifytools.com' 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://ubifytools.com' 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;
}Cross-Origin Resource Sharing (CORS) Configuration Guide
CORS is a browser security protocol that restricts HTTP requests made from scripts running on a different domain. When client-side fetch calls include custom headers such as Authorization or non-simple HTTP verbs like PUT or DELETE, the browser sends an automatic preflight OPTIONS request before issuing the real payload.
Preflight Handling (HTTP 204)
Configuring server endpoints to return HTTP 204 No Content for OPTIONS requests satisfies preflight checks immediately without routing through heavy application logic.
Credentials and Wildcards
When sending cookies or authorization headers (Access-Control-Allow-Credentials: true), browsers explicitly prohibit wildcard origins (*). An explicit origin list is required.
Preflight Caching (Max-Age)
Setting Access-Control-Max-Age: 86400 tells browsers to cache the preflight handshake for up to 24 hours, reducing redundant OPTIONS roundtrips on subsequent requests.
Ubify Core Engineering Team
SOFTWARE ENGINEERS & SYSTEMS ARCHITECTS