When we need something more than Firebug

Us web developers in our quest to build something unique will eventually come upon a wall that looks insurmountable with our current set of debugging tools like Firebug and Chrome's or IE's developer tools. Sometimes you just need something that can work at the HTTP protocol. This is where Fiddler2 comes in. Fiddler is a web debugging proxy for any browser, system or platform. Which makes it quite handy if you're doing AJAX stuff on a lot of different platforms from Java to Node.js.

What's really special with Fiddler is the composer feature which allows to make AJAX verb (GET, DELETE, PUT, HEAD, etc.) calls to your server side API. It then allows you to look at the response headers, cookies, the raw results and a bunch of other values to help you debugged that code.

Use this with Mozilla Firefox to get the most mileage out of it since it does integrate into it quite nicely. Chrome doesn't do it because of that new rule that you can't install a plugin that's not found in the Chrome store.

It also has a nice set of add-ons which is just icing on cake. I like StresStimulus add-on which allows you to do load testing with your web apps.

Another thing is this thing is free and will run on Linux boxes (needs Mono though).

Add this to your toolbox.