Telerik Fiddler is an HTTP debugging proxy server application is used to debug any kind of application. It is build on .Net Framework. It is fast and accurate in finding the issue. It is open source software.
The tool enables you to inspect incoming and outgoing data to monitor and modify requests and responses before the browser receives them. Fiddler also includes a powerful event-based scripting subsystem, which you can extend by using any .NET Framework language.
FiddlerCore is the core proxy engine used by Fiddler to intercept and modify web traffic. You can integrate FiddlerCore into your .NET applications to provide unprecedented functionality.
Debug traffic from PC, Mac or Linux systems and mobile devices. Ensure the proper cookies, headers and cache directives are transferred between the client and server. Supports any framework, including .NET, Java, Ruby, etc.
Fiddler is a free web debugging proxy which logs all HTTP(s) traffic between your computer and the Internet. Use it to debug traffic from virtually any application that supports a proxy like IE, Chrome, Safari, Firefox, Opera and more.