I saw the majority of a talk by Eric Lawrence, creator of Fiddler, on Fiddler at Austin Code Camp.

"All problems in computer science can be solved by another level of indirection."
- David Wheeler

Well, with that is mind Mr. Lawrence gave us Fiddler, now owned by Telerik, which is a proxy that http traffic (requests to and stuff being returned from the world beyond one's browser) bottleneck through. Fiddler has come up in talks by both Shawn Weisfeld and Ryan Vice on ASP.NET Web API, and I have certainly used it some myself in trying to understand ASP.NET Web API. The meaty meat of this talk was on how to use Fiddler to juggle huge amounts of traffic without having what is reported back by Fiddler become just noise. I have largely worked around this problem myself by just opening Fiddler just before I use it and then closing out the one browser I have open after Fiddler sniffs whatever act I hope it will sniff so that more activity does not build up in its reporting. I thus won't go into the management tricks for heavy use stuff, however other things touched upon of interest were:

• Fiddler may be chained to another proxy upstream of it so if your company requires that you bottleneck through a different proxy to get out into the wild, this does not mean Fiddler is out as an option.
• Fiddler may be used as a reverse proxy! If you run a web site on a random port such as port 81 and then send web traffic to Fiddler on port 80, you may then route the port 80 pings into port 81 from wherein a signal back may roundtrip back through Fiddler.
• Telerik is working on making a Mac-friendly version of Fiddler.
• FiddlerHook is a Firefox plugin that will let you toggle Fiddler on and off. It ended up both installed and disabled when I installed Fiddler itself. To use the plugin you just have to enable it.
• SPDY/HTTP 2.0 or "Speedy" uses binary transfer of data (not plain text ASCII) and is a new hypertext transfer protocol. Internet Explorer 11, coming at year's end with Windows 8.1, will support it and the latest versions of Chrome and Firefox already support it. Fiddler is ready for this. Bring it.
• Charles is a rival to Fiddler.
• Regarding the interface: In Fiddler, clicking in the black bar (or pressing Alt+Q to get there) gives one a spot to type in command line commands. Also, the "Stream" button may be toggled on and off. When it is on there will be no buffering (Fiddler otherwise catches and then rethrows) and this setting is much more friendly to SignalR than the alternative.