I have spent seven years designing, deploying and supporting proxies and corresponding PAC files in a Fortune 100 company. In those years, I have learned a number of hard lessons and gradually refined my PAC files to become (what I feel to be) well organized and highly efficient. I always had to create my PAC file structures by hand and never had any documents to refer to beyond the basic docs provided by a few vendors.   One of the things that frustrated me most was the lack of good, practical advice online.  There is a lot of basic material out there, but nothing that was written with a practical, engineering-focused mindset.  

This guide is an attempt to wrap up many of the things that I’ve learned to make it easier for others responsable for designing, deploying and maintaining PAC files.  

The content of this site is designed to expand upon the original guide published by Netscape and provide some more advanced examples and some fairly critical warnings. It is assumed that the serious reader has first read through the Netscape document and understands the basic functions listed there before trying to process the content here. There are a lot of functions listed that I don’t use, simply because I haven’t ever had the need. (i.e. time-based calculations), but I do use a lot of them, plus a few other tips and tricks from JavaScript that I’ve picked up over the years.  

JavaScript is, of course, a complex programming language.  It is tremendously flexible and can provide a lot of functionality.   I am, however, NOT a JavaScript developer and won’t ever be.   The target audience of this guide are engineers like myself with little or no formal development background.  If you’re a JavaScript developer you might find some useful tricks and tips here on interaction with proxies but you probably won’t be very interested in the sections that are more focused on the language itself.  

July 28th, 2009 Update - New Forums

As I've been working on the site I've found that the Comments module that I put in place isn't working the way I hoped it would.    In the interest of providing more flexibility and collaboration I've replaced it with a new Forums system.   You can access it at the link below and on the menu to the left. 

The goal of the forums is to provide a place to discuss topics related to PAC files.  Got an idea to throw out there and see what people think? Put it in a post.  Have a question you can't get answered anywhere else?  Try to post it here.  Found a great new tool that you're using that others might like?  Put it in a post.    

ReturnProxy Forums

 July 31st, 2009 Update - New section on Proxy Load Balancing in a PAC file

I've done some reformatting and editing on the PAC File Tips and Tricks to clean it up and made some edits to improve things while I was at it.    The other day, I found a great article on proxy load balancing and, with permission from the author (Thanks Shaun!) I took some ideas from it and put them in a new section on load balancing between two proxies in a PAC file.    I also created a new sample PAC file with load balancing for a real-world example.