Proxy Configuration Via "proxy.pac"


Many modern User Agents implement a method of configuring proxy servers based on the Netscape-designed "proxy.pac" feature, also known as Automatic Proxy Configuration (APC). This utilises the javascript engine to provide administrators with a method of allowing the User Agent to selectively uses proxy servers based on certain criteria.


  • Internet Explorer Caching - Microsoft Internet Explorer's automatic proxy caching; how it can interfere with proxy.pac load balancing and failover


Most modern graphical Web Browsers implement APC, including the current releases of Firefox, Internet Explorer, Netscape, Opera, and Safari.

Sun's Java Web Start (JWS) has limited support for APC.

Manu Garg has written a PAC-parser library with python bindings, available at

Further Reading

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Technology/ProxyPac (last edited 2008-05-18 19:38:57 by localhost)