106 Add-ons in this Collection
Firebug by Joe Hewitt, Jan Odvarko, others
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
The Web Developer extension adds various web developer tools to the browser.
FirePath is a Firebug extension that adds a development tool to edit, inspect and generate XPath 1.0 expressions, CSS 3 selectors and JQuery selectors (Sizzle selector engine).
Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
Advanced Eyedropper, Color Picker, Gradient Generator and other colorful goodies...
View HTTP headers of a page and while browsing.
Accelerate your SEO efforts on the fly. SEOquake is a free plugin for browsers that provides you with key SEO metrics for a specific page, along with other useful tools such as SEO Audit and many others.
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
A plugin for Selenium-IDE to have favorite test suites and open and execute the test suites with a single click