CORS Header Builder — Visual Cross-Origin Config
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CORS Header Builder

Configure cross-origin policy visually and copy ready-to-use headers, middleware, or worker code.

*
Quick add:
HTTP methods
Content-Type
Quick add:
Quick add:
Configuration checks
Wildcard origin (`*`) allows any site to call your API. Restrict to known origins for production.
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, HEAD, POST
Access-Control-Allow-Headers: Content-Type
Access-Control-Max-Age: 86400

About CORS

Cross-Origin Resource Sharing (CORS) is a browser security mechanism that lets servers opt into receiving requests from origins other than their own. This builder generates the correct Access-Control-* headers for the most common stacks — raw HTTP, Express, Fastify, Nginx, Apache, and Cloudflare Workers — without sending your config anywhere. Everything runs in your browser.

Common pitfalls

  • credentials: true with origin * is rejected by browsers — list explicit origins.
  • Access-Control-Allow-Headers: * does not work with credentials either.
  • Most browsers cap Access-Control-Max-Age at 86400 seconds (24 hours).
  • When you echo specific origins back, always set Vary: Origin to keep caches honest.