CORS (Cross-Origin Resource Sharing) is a security mechanism that allows resources on a web page to be requested from another domain. It's essential for APIs to control access between different origins.

Key Concepts 🔍

  • Origin: The domain, protocol, and port of the request source
  • CORS Headers:
    • Access-Control-Allow-Origin (required)
    • Access-Control-Allow-Methods
    • Access-Control-Allow-Headers
    • Access-Control-Allow-Credentials
  • Preflight Requests: OPTIONS requests sent before actual API calls

Configuration Example ⚙️

GET /api/data HTTP/1.1
Host: yourdomain.com
Origin: https://example.com

HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, PUT, DELETE
Access-Control-Allow-Headers: Content-Type, Authorization

Best Practices 🛡️

  1. Use specific origin values instead of * in production
  2. Always set Access-Control-Allow-Credentials when needing cookie authentication
  3. Validate request origins server-side
  4. Monitor CORS-related security vulnerabilities regularly

For more details about API documentation structure, visit API Docs to explore other technical guides.

CORS_Policy
HTTP_Headers