How do I get Fiddler to stop ignoring traffic to localhost?

To get Fiddler to capture traffic when you are debugging on local host, after you hit F5 to begin degugging change the address so that localhost has a "." after it.

For instance, you start debugging and the you have the following URL in the Address bar:

http://localhost:49573/Default.aspx

Change it to:

http://localhost.:49573/Default.aspx

Hit enter and Fidder will start picking up your traffic.

Fiddler's website addresses this question directly.

There are several suggested workarounds, but the most straightforward is simply to use the machine name rather than "localhost" or "127.0.0.1":

http://machinename/mytestpage.aspx

The correct answer is that it's not that Fiddler ignores traffic targeted at Localhost, but rather that most applications are hardcoded to bypass proxies (of which Fiddler is one) for requests targeted to localhost.

Hence, the various workarounds available: http://fiddler2.com/documentation/Configure-Fiddler/Tasks/MonitorLocalTraffic

Fiddler v4.5.1.0 will allow you to go to replace "localhost" with "localhost.fiddler", and present localhost as the host name for the receiving server running on your machine.

This avoids "host not recognised" errors when connecting to WCF services with the built in web server that visual studio uses.

i.e. Instead of http://localhost:51900/service.wcf you can use http://localhost.fiddler:51900/service.wcf