CORS Security Guide
Same-Origin Policy (SOP)
Browsers block cross-origin requests by default. Two URLs have the same origin if their protocol, host, and port all match.
CORS Headers Reference
Access-Control-Allow-Origin | Specify allowed origin(s). Never use * with credentials. |
Access-Control-Allow-Methods | List allowed HTTP methods |
Access-Control-Allow-Headers | List allowed request headers |
Access-Control-Allow-Credentials | Set true only when credentials (cookies) needed |
Access-Control-Max-Age | Cache preflight response (seconds) |