Fiddler is a great tool for logging HTTP/HTTPS traffic in the client side. However, you may see that no traffic is logged if you would like to debug your web site by browsing http://localhost or http://127.0.0.1. If this is your case then you can try to browse the web site with http://ipv4.fiddler or http://ipv6.fiddler URLs. These URLs would be mapped to 127.0.0.1 or ::1 and you will have the HTTP packet details in Fiddler.
Why don't I see traffic sent to http://localhost or http://127.0.0.1?
PS: Latest version of the Fiddler will log the traffic for http://localhost or http://127.0.0.1 if you use Internet Explorer 9.0 or later.