CORS (Cross-Origin Resource Sharing) Overview CORS controls which websites can call your API from a browser. Without proper CORS headers, browsers block cross-origin requests. Misconfigured CORS is either too restrictive (breaks your frontend) or too permissive (security risk). This skill covers correct configuration for common setups. Instructions Step 1: Express Step 2: Next.js API Routes Step 3: Manual Headers (Any Framework) Guidelines - NEVER use with — browsers reject this. - origin is only safe for truly public APIs with no authentication. - Always set to cache preflight responses (red…