Fiddler – The free web debugging proxy for any browser, system or platform

Fiddler is free web debugging proxy for any browser, system or platform.  Edit web sessions easily: just set a breakpoint to pause the processing of the session and permit alteration of the request/response. Compose your own HTTP requests and run them through Fiddler.
Fiddler lets you see the “total page weight,” HTTP caching and compression at a glance. Isolate performance bottlenecks with rules such as “Flag any uncompressed responses larger than 25kb.”
Benefit from a rich extensibility model, ranging from simple FiddlerScript to powerful extensions which can be developed using any .NET language.
Decrypt HTTPS traffic and display and modify web application requests using a man-in-the-middle decryption technique. Configure Fiddler to decrypt all traffic, or only specific sessions.
Use Fiddler to log all HTTP(S) traffic between your computer and the Internet. Debug traffic from virtually any application that supports a proxy (IE, Chrome, Safari, Firefox, Opera and more).
Debug traffic from PC, Mac or Linux systems and mobile (iOS and Android) devices. Ensure the proper cookies, headers and cache directives are transferred between the client and server. Supports any framework, including .NET, Java, Ruby, etc.