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 includes a powerful event-based scripting subsystem, and can be extended using any .NET language.
Fiddler is freeware and can debug traffic from virtually any application, including Internet Explorer, Mozilla Firefox, Opera, and thousands more.
What's new in Version
Protocol Violation list
New layout option (View > Layout)
Enhanced Fiddler Options dialog