====== Networking - Proxy - PAC File - About PAC Files ======

A **PAC** [[https://en.wikipedia.org/wiki/Proxy_auto-config|(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:

<code javascript>
function FindProxyForURL(url, host) {
  // ...
}
</code>

<WRAP info>
**NOTE:**  Parameters:

  * **url**:  The URL being accessed.
    * The path and query components of **<nowiki>https://</nowiki>** 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 **<nowiki>://</nowiki>** and the first **<nowiki>:</nowiki>** or **<nowiki>/</nowiki>** after that.
    * The port number is not included in this parameter; It can be extracted from the URL when necessary.

</WRAP>

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===== References =====

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