Track HTTP traffic in Firefox with FiddlerHook

Eric Lawrence, the creator of Fiddler (his side project since 8 years) & an Internet Explorer Program Manager at MS, presented an interesting session titled "Advanced Web Debugging with Fiddler" at MIX10. I have gone through the half-hour breezy presentation and also downloaded it (.WMV version is 68.2MB) so that I can watch it again to digest & try out the many tips discussed in it. I plan to blog about the tips that Eric shared in his presentation with my own observations, starting with this one. I agree with him when he says "people are using Fiddler in a shallow way" as I'm one among them (having started using it on & off since 2005). Although the documentation is pretty good, I guess there should be more ways of creating awareness. I found that Fiddler now has a dedicated blog on MSDN & a Discussion Group.

While current versions of Internet Explorer, Google Chrome, Apple Safari, and Opera all automatically use Fiddler when Fiddler is configured to capture HTTP traffic, Firefox is the only browser which does not use the System Proxy settings by default. So you can manually configure Firefox to point at Fiddler or better still, take advantage of the FiddlerHook Firefox add-on that lets you toggle Fiddler use with Firefox.

When you install Fiddler, FiddlerHook add-on gets installed as well. When I installed the latest version of Fiddler (v 2.2.9.4 beta) on a PC with Vista & Firefox 3.0, I did not see FiddlerHook in the menu under Tools or in the Firefox Add-ons/Extensions list. I suspected this could have been because I had already opened Firefox while installing Fiddler. I also wondered about what Firefox versions this Extension works on. My suspicion was confirmed when I re-installed Fiddler without having Firefox open and bingo...the Extension appears! Eric mentions in his talk that FiddlerHook works on Firefox 3.0 & above.


Whenever you need to debug HTTP traffic in Firefox, you can adjust your FiddlerHook preferences in the status bar or from the Tools > Monitor with Fiddler menu option. For easier access, you can add the "Launch Fiddler" button to your toolbar by right-clicking the Firefox toolbar, choosing Customize & dragging the Fiddler icon in the dialog box that appears to a preferred position in the toolbar.

Also see:
Web Performance Analysis & Optimization tools

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