CORSszabályokat

CORSszabályokat, or Cross-Origin Resource Sharing rules, are a mechanism that uses additional HTTP headers to tell a browser that a web application running at one origin is permitted to request resources from another origin. The origin is defined as the combination of protocol, domain, and port. By default, browsers implement a "same-origin policy" which restricts web pages from making requests to a different origin than the one that served the web page. This security measure prevents malicious scripts from accessing sensitive data from other domains.

CORSszabályokat allow servers to explicitly indicate which origins are allowed to access their resources. When a browser makes a cross-origin request, it sends an `Origin` header that specifies the origin of the requesting page. The server, if it supports CORS, will then examine this header and, if the origin is permitted, include specific CORS headers in its response. The most common CORS header is `Access-Control-Allow-Origin`, which specifies the allowed origin(s). Other headers like `Access-Control-Allow-Methods` and `Access-Control-Allow-Headers` can further refine the allowed HTTP methods and headers for the request.

If the server does not include the appropriate CORS headers in its response, or if the requesting origin is not listed in the `Access-Control-Allow-Origin` header, the browser will block the request and return an error, typically visible in the browser's developer console. Web developers must configure their servers to correctly set these CORSszabályokat to enable legitimate cross-origin interactions, such as fetching data from an API hosted on a different domain or subdomain.