Firefox plugins

I love Firefox add-ons. Love em, perhaps to a fault*. Here are a few of my favorites that I've used on load and performance testing projects.

* Ironically (for a discussion about using add-ons to enhance performance testing), add-ons can degrade Firefox's own performance. Having many add-ons active can turn Firefox into a remorseless memory-sucking monster. I've tried using a number of workarounds for keeping Firefox memory usage under control, but the best solution is to disable or uninstall as many add-ons as possible.

Firebug

https://addons.mozilla.org/en-US/firefox/addon/1843

This is THE essential web developer tool that does detailed analysis web pages and page transactions. What do you mean you don't have it? Go on, off with you - stop reading this and get it now!

HttpFox

https://addons.mozilla.org/en-US/firefox/addon/6647

A slightly lighter weight tool than Firebug that focuses on transactions without the deep analysis of page content.

YSlow

https://addons.mozilla.org/en-US/firefox/addon/5369

Analyzes web page content for potential performance optimizations, based on a number of criteria used by Yahoo to rate their own pages (formerly an in-house Yahoo tool that they released for public use). Note that this uses a Russian nesting doll architecture of sorts in that it is an add-on to Firebug (itself an add-on to Firefox).

Xpath Checker

https://addons.mozilla.org/en-US/firefox/addon/1095

Displays Xpath value of a selected object on a web page.

Toggle Proxy

https://addons.mozilla.org/en-US/firefox/addon/51740

Greatly simplifies enabling/disabling a web proxy. This is HUGE benefit if you're recording web tests with a tool like Jmeter or Grinder that acts as a proxy in front of the browser to capture transaction data for test cases.

IE Tab 2

https://addons.mozilla.org/en-US/firefox/addon/92382

The follow up to the original, great IE Tab, which is no longer active and thus unsupported in Firefox 3.6+. This plugin allows you to view a page in IE from within Firefox, so you don't have to open a separate IE session.

What are some other Firefox add-ons that you have used for load and performance testing web apps?

~ Justin