CORS Tester

Test Cross-Origin Resource Sharing configuration and security

corscross-originsecurityapitestconfigurationheaders

CORS Configuration Tester

Test and validate Cross-Origin Resource Sharing (CORS) policies to ensure secure cross-domain requests. This tool simulates CORS behavior and provides security recommendations.

Note: This tool simulates CORS testing. Real browser CORS testing requires a backend proxy.

Quick Start Presets

Select a common configuration to get started quickly

Test Configuration

Configure your CORS test parameters

The API endpoint you want to test CORS against
The origin making the request (your website URL)

Simple methods (GET, HEAD, POST) don't trigger preflight requests

Headers that will be sent with the request
Quick add:

Common CORS Configurations

Examples of typical CORS headers and their security implications

Allow All Origins

HIGH RISK
Access-Control-Allow-Origin: *

Allows any website to access the resource

Security warning: Use with caution

Specific Origin

LOW RISK
Access-Control-Allow-Origin: https://example.com

Only allows specific origin

With Credentials

MEDIUM RISK
Access-Control-Allow-Credentials: true

Allows sending cookies and auth headers

Preflight Cache

LOW RISK
Access-Control-Max-Age: 86400

Caches preflight response for 24 hours

CORS Security Best Practices

Essential guidelines for secure CORS implementation

Configuration Guidelines

  • Never use wildcard (*) with credentials

    This combination is blocked by browsers for security

  • Specify exact origins, not wildcards

    Use an allowlist of trusted domains

  • Validate origin against allowlist

    Dynamically check Origin header server-side

  • Limit allowed methods and headers

    Only allow what's necessary for your API

Security Measures

  • Use HTTPS for all CORS requests

    Prevents man-in-the-middle attacks

  • Implement proper authentication

    Don't rely on CORS alone for security

  • Regularly audit CORS policies

    Review and update as your API evolves

  • Use environment-specific configs

    Different policies for dev, staging, prod