Telerik's Fiddler is a very popular tracing tool for web traffic. It is very powerful but still extremely easy to use. Fiddler an invaluable tool for all web developers to review how a web site works, troubleshoot problems, and do performance evaluations. It is highly extensible using FiddlerScript or by creating .NET extensions. The customizations include additions to the Fiddler UI as well as automatically adjusting traffic before it is sent to the web server or before the response is sent to the client. The features can also be embedded into your own .NET application via FiddlerCore. The FiddlerCap utility provides an easy way for users or customers to capture web traces to identify problems. It is not limited to just Windows, as it can also be configured to capture traces for smartphones, tablets, and non-Windows platforms.