Alibaba Cloud Certified Associate (ACA) 2025 – 400 Free Practice Questions to Pass the Exam

The "X-Forwarded-For" HTTP header is primarily used to identify the originating IP address of a client connecting to a web server through an HTTP proxy or load balancer. When a client makes a request to a server, the server typically sees the IP address of the proxy or load balancer. However, to preserve the original client's IP address, the proxy or load balancer adds the "X-Forwarded-For" header to the request.

This header can contain a list of IP addresses, which allows the origin server to determine the original client's IP address even when requests are routed through multiple proxies. This is particularly important for web applications that need to implement logging, geographical restrictions, or security measures based on the client's actual location.

The other options do not describe what is contained in the "X-Forwarded-For" header. Visitor's location, browser details, and session data are not typically conveyed through this header, as its main purpose is to pass along the client’s real IP address for accurate identification and logging in network communications.