Microsoft's Fiddler2 is a Web Debugging Proxy utility that lets you "fiddle" with incoming or outgoing HTTP data. It logs all HTTP traffic between your PC and the Internet. You can use it to inspect two-way HTTP activity, set breakpoints, and more.
Fiddler2 is one of Microsoft's nifty Power Toys, a class of plain but useful system tools and other small utilities that greatly expand users' control over the Windows environment as well as their PC's software and hardware. Fiddler2's interface is typical of the type, businesslike and efficient but lacking the stylish elements of recent Windows applications. The Help file links to a Web site, unusual for a Microsoft product and of questionable utility if the connection it's debugging isn't working. Inexperienced users can get into trouble with Power Toys if they don't know what they're doing before they do it, and while Fiddler2 can't do much harm, it's a complex tool for users who need it, not a tweak anyone can "fiddle" with. However, for system administrators and others who know how to make good use of Fiddler2's capabilities, it's essential.
Fiddler2 is a free utility from Microsoft that is certified for versions of Windows up to Vista, but we installed and tested it in Windows 7 and it worked just fine. It requires a recent version of Microsoft's Internet Explorer and .NET Framework V.2 or higher to do its thing, and it installs a quick access icon on the IE toolbar in addition to the Start Menu and Command Line options.