---

title: PAC

slug: Glossary/PAC

page-type: glossary-definition

---

{{GlossarySidebar}}

A Proxy Auto-Configuration file (**PAC file**) is a file which contains a function, `FindProxyForURL()`, which is used by the browser to determine whether requests (including HTTP, HTTPS, and FTP) should go directly to the destination or if they need to be forwarded through a web proxy server.

```js

function FindProxyForURL(url, host) {

// …

}

ret = FindProxyForURL(url, host);

```

See [Proxy Auto-Configuration (PAC) file](/en-US/docs/Web/HTTP/Proxy_servers_and_tunneling/Proxy_Auto-Configuration_PAC_file) for details about how these are used and how to create new ones.

## See also