Have you ever want to know what exactly happens during view a web page? If you are a web programmer, system programmer, or even hacker, you must have ever seen something being transmitted out of your machine and their responses. I am talking about the basic part to debug a web application. Basically, there are 2 basic choices to request a web page; GET and POST. Then data in your machine are encoded and sent to the web server via these request and get response, the web page, back. However, today technology is not as easy as I stated earlier. There are something about headers, cookies, content-type, and many more. You might get strange behavior due to incorrectly set cookie or assign wrong content-type. In this situation, you will be so happy if you know what are sent and received during the session. It is very useful information for all of us.

If you are a hardcore hacker, you may use a kind of sniffer to sniff all packets and resemble them into web request/response. Ethereal is the first candidate in my mind. However, it is over acting to use a powerful sniffer for just sniffing HTTP protocol. Fortunately, I found Fiddler.

Fiddler is a HTTP Debugging Proxy which logs all HTTP traffic between
your computer and the Internet. Fiddler allows you to inspect all HTTP
Traffic, set breakpoints, and "fiddle" with incoming or outgoing data.
Fiddler is designed to be much simpler than using NetMon or Achilles,
and includes a simple but powerful Jscript.NET event-based scripting
subsystem.

It is very simple and powerful HTTP debugging proxy. Since it is just a proxy, you can tell browser to pass all requests through Fiddler without touching system configuration. All data in the protocol are decoded and display in various formats including image. In addition, you are able to debug the session, spoof request, set breakpoint, and lots more. Give it a try and you will love it.

Most of all, it is totally free of charge.

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