Networking - Proxy - PAC File - About PAC Files

A PAC (Proxy Auto-Configuration) file is a JavaScript function that determines whether web browser requests (HTTP, HTTPS, and FTP) go directly to the destination or are forwarded to a web proxy server.

The JavaScript function contained in the PAC file defines the function:

function FindProxyForURL(url, host) {
  // ...
}

NOTE: Parameters:

url: The URL being accessed.
- The path and query components of https:// URLs are stripped.
  - Different browsers may offer options to override or disable this.

host: The hostname extracted from the URL.
- This is only for convenience; it is the same string as between :// and the first : or / after that.
- The port number is not included in this parameter; It can be extracted from the URL when necessary.

References

https://developer.mozilla.org/en-US/docs/Web/HTTP/Proxy_servers_and_tunneling/Proxy_Auto-Configuration_PAC_file