What is CORS and Why Does It Exist?

Short summary

CORS (Cross-Origin Resource Sharing) is a browser-side security mechanism that prevents JavaScript from reading responses from a different Origin unless the server explicitly allows it. A common misconception is that a CORS error means the request never reached the server — in reality the request succeeds but the browser blocks the response. Fixing CORS is typically a backend configuration task involving Access-Control-Allow-Origin headers.

• •CORS is a browser security mechanism, not a server one; the request usually reaches the server even when CORS fails
• •Servers must return Access-Control-Allow-Origin matching the requesting Origin for JavaScript to access responses
• •Wildcard origins (*) should only be used for public resources, never for authenticated or sensitive APIs

Generated with AI, which can make mistakes.