Web Development
Intermediate
What is CORS Headers?
HTTP headers that control cross-origin resource sharing between different domains, specifying allowed origins, methods, and headers.
Key CORS headers: Access-Control-Allow-Origin (which domains can access), Access-Control-Allow-Methods (allowed HTTP methods), Access-Control-Allow-Headers (allowed request headers), Access-Control-Allow-Credentials (allow cookies), Access-Control-Max-Age (preflight cache duration).
Common configuration: Allow-Origin: * (any domain, no credentials) or Allow-Origin: https://app.example.com (specific domain). Wildcards cannot be used with credentials. CORS errors are the most common frontend development issue when connecting to APIs.