Using Fiddler to intercept .NET - Visual Studio 2013/2015 traffic

When running, by default Fiddler adjusts user's system proxy to point at localhost:8888, where it is listening for traffic. In most cases this is enough.

To debug network traffic running in localhost with a different account (eg is a web service running in iis), you need to configure .NET to send traffic through Fiddler's proxy.

Go to the path
C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config

or, if you are using a 64bit configuration the path is
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config

Open with an admin-level privileges the machine.config and add the following to the end of file or -if already exists one- merge the <system.net>

 <system.net>
      <defaultProxy enabled = "true" useDefaultCredentials = "true">
           <proxy autoDetect="false" bypassonlocal="false"
                  proxyaddress="http://127.0.0.1:8888" 
                  usesystemdefault="false" />
      </defaultProxy>
 </system.net>

Reboot the system.

- Once you finish remember to revert the machine.config file


NOTE: these paths are valid for .NET4+. Set the path according to the version you are using