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.

CORS Builder

CORS Builder is a free, client-side tool designed to help developers with build cors headers visually with express, nginx, apache, and cloudflare worker output..

How to Use

  1. Input your data into the primary editor or upload a file.
  2. Adjust any necessary configuration options.
  3. View the output in real-time or click the action button to process.
  4. Copy or download the results securely.

Privacy First

All processing happens directly in your browser. We never send your sensitive data to our servers.

Frequently asked

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