What's an easy way to see what AJAX calls are being made?

Question

I'm looking for something (preferably a Firefox extension) which will allow me to see all AJAX subrequests. Basically, anytime an XMLHTTPRequest() is made, I want to know what URL was being requested and what (if any) GET and POST vars were passed along with it.

Unless I'm missing it, I don't see anything quite like this in Firebug or Web Developer Toolbar.

(In case you're curious, the main reason for wanting this is that I want to scrape a local copy of a site that is using JS to load all its contents, and I don't want to spend hours digging through their JS code when I could just see the subrequests being made.)

Answer 1

Firebug should show it in the Net panel.

EDIT: Also, if Firebug slows down your Firefox in a way that makes it unusable, like it does for me sometimes, WireShark (formerly Ethereal) will analyze all network traffic on your system, including HTTP and AJAX requests.

Answer 2

Fiddler 2 is a great tool for watching HTTP traffic.

* 2014 Update *

Since my original post, both Internet Explorer and Chrome have added built-in developer tools that are quite useful. While I still support and use Fiddler for non-web related http monitoring or when I need to really dig in deep and modify requests in transit, these days I find myself pretty much using IE or Chrome's built in tools as they are sufficient for 99% of my needs. They both have a networking tab, where you can monitor http requests, plus other nifty features for debugging webpages.

• Internet Explorer F12 Tools Introduction
• Documentation for Chrome's F12 Tools
• FireBug, which is mentioned above is also a good tool if you're using FireFox.