CORS Header Generator

CORS Header Builder

Generate Access-Control-Allow-* headers for common cross-origin scenarios. Detect wildcard and credentials conflicts early.

Generated Result

CORS Checklist

1. If using cookies or Authorization credentials, browsers do not accept * as Allow-Origin.

2. Preflight requests typically also require the server to correctly respond to OPTIONS.

3. Frontend can only see non-simple response headers that are exposed via Access-Control-Expose-Headers.

JSON Preview

{
  "headers": [
    {
      "name": "Access-Control-Allow-Origin",
      "value": "https://app.geekformat.com"
    },
    {
      "name": "Access-Control-Allow-Methods",
      "value": "GET, POST, PATCH, DELETE, OPTIONS"
    },
    {
      "name": "Access-Control-Allow-Headers",
      "value": "Content-Type, Authorization, X-Request-Id"
    },
    {
      "name": "Access-Control-Expose-Headers",
      "value": "ETag, X-Trace-Id"
    },
    {
      "name": "Access-Control-Allow-Credentials",
      "value": "true"
    },
    {
      "name": "Access-Control-Max-Age",
      "value": "600"
    }
  ],
  "warnings": []
}

Configure CORS headers online, avoid cross-origin pitfalls.

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Use Cases

  • Generate a standard CORS header set first during frontend-backend integration to quickly verify if it's a configuration issue
  • Locate Allow-Origin and Credentials conflicts through warning prompts when debugging browser cross-origin errors
  • Generate directly copyable cross-origin configuration blocks for Nginx, gateways, or backend services
  • Verify Methods, Headers, and Max-Age correctness when handling OPTIONS preflight request configuration

How to Use

  1. Enter allowed origins, request methods, request headers, exposed headers, and whether to include credentials
  2. Tool automatically generates standard CORS response header blocks and displays conflict warnings
  3. Review the CORS checklist to confirm configuration is reasonable
  4. Copy the generated response header block for server configuration or API debugging

Features

  • Direct CORS header generation: Origin, Methods, Headers, Credentials all configured at once
  • Ready for deployment: Nginx, gateways, and backend services get fewer mistakes
  • Preflight-friendly: Perfect for OPTIONS requests, API debugging, and browser cross-origin error troubleshooting
  • Generate and copy: Output is clear and standardized, ready for gateway, proxy, and backend service configuration

FAQ

How to quickly generate correct CORS response headers?

Enter allowed origins, methods, request headers, and whether to include credentials first, then generate corresponding response headers. This is more reliable than manual typing and helps avoid wildcard-credential conflicts.

Why can't Access-Control-Allow-Origin use wildcard with Credentials?

When credentials are allowed, browsers don't accept wildcard origins. This tool helps you identify such common conflicts early, reducing cross-origin errors during integration.

Is it suitable for preflight OPTIONS request configuration?

Yes. It helps generate Methods, Headers, Max-Age, and other common preflight-related fields, suitable for frontend-backend cross-origin debugging and gateway configuration.

Can I copy the output directly into server configuration?

Yes. Generated results are suitable for copying into Nginx, Express, Spring Boot, gateway rules, or other server-side configurations, saving time on manual header writing.