CORS Headers Configuration Builder
Processed in your browser
Configure Cross-Origin Resource Sharing (Access-Control-Allow-Origin, Methods, Headers, Max-Age) and generate drop-in server configurations.
CORS Policy Parameters
Config Snippet
⚡
Direct In-Browser Handoff
HTTP API & Protocol Diagnostics Suite
Chain this tool with complementary private browser utilities for a complete zero-server workflow:
Helpful Examples
Public REST API
Origin: *, GET/POST/OPTIONS
*How to Use the CORS Headers Configuration Builder
Client-side CORS (Cross-Origin Resource Sharing) rule builder. Generate secure, production-tested HTTP response headers for Nginx, Apache, Node.js Express, and PHP APIs. Control origins, allowed HTTP methods, credentials, and preflight OPTIONS caching without CORS errors.
Privacy & Data Processing Notice
No user data leaves your browser. Computation is executed entirely on your device. We do not store, view, or transmit your inputs over our network. Your computation remains on your personal machine.
Frequently Asked Questions
What causes a CORS error in the browser?
When frontend JavaScript requests resources from a different origin (domain, protocol, or port), the browser sends a preflight OPTIONS request. If the server does not return the proper `Access-Control-Allow-Origin` header, the browser blocks the response.
Can I use wildcard * with Access-Control-Allow-Credentials?
No. The Fetch/CORS specification explicitly forbids `Access-Control-Allow-Origin: *` when `Access-Control-Allow-Credentials: true` is set. You must specify the exact requesting origin.
Related Utilities
Frequently paired browser tools in Network & Internet Tools