Winhttp Web Proxy Auto-Discovery Service
To help the connectivity of proxy settings. Winhttp 5.1 implements the Winhttp web proxy auto-discovery (WPAD) service, also known as the auto proxy.
It helps user applications and components to use win HTTP to resend the HTTP request to ensure proxy configuration to set correctly. What its working is very simple. It gets the PAC FILE from client server and the PAC file executed when each HTTP was requested.
The winHttp expects a PAC script code contains a function called find proxy for URL.