What is Proxy Auto-Config file (PAC)?

Ordinarily, when you configure Web browsers to surf through a proxy server , you directly enter the IP address of the proxy server into each browser's "manual proxy configuration" window. If you later want to change the proxy's IP address, you have to manually re-configure each browser - a tedious task at best. A Proxy Auto Config file tells the browser to load its proxy configuration information from a remote JavaScript file, rather than from static information you enter directly.

In this file you can specify which proxies you can use and for every URL you can specify different proxy.

How to use PAC files?

Additional information about PAC files you can get here:
http://developer.netscape.com/docs/manuals/proxy/adminux/autoconf.htm

Format of Proxy Auto-Config files

Detailed desription of PAC files format see here:

http://home.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html

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