Scott Cate's WebLog

Working with Fiddler on LocalHost

Developing ASP.NET AJAX (or any AJAX really) is tremendously easier if you can watch the traffic going across the wire. There are a lot of ways to accomplish this, but I think Fiddler is the most popular Windows application for ASP.NET developers. Sure there is Firebug, and probably a million others, but this post is about Fiddler).

Over the last few years, I've had a hard time getting Fiddler to work on local host. Actually until recently, it's just never worked.

Rumors online said to use http://127.0.0.1, instead of http://localhost and it'll work. Maybe for you, but not for me.

Then last month while speaking at Orlando ASPConnections, I was demoing some AJAX calls on stage, and an audience member told me that Fiddler will work on 127.0.0.1 with a trailing . on the IP address. So the address ends up like ...

• http://127.0.0.1. (Notice that extra out of place looking final period)

Or

• http://127.0.0.1.:45154 (Notice that extra out of place looking final period)

With a port number (if you're on Cassini).

Fiddler picks up this traffic and you're back in control of sniffing your own traffic.

Hope this helps others that didn't know the little nugget.