Firefox OS (Advanced)
by Ahmad Salah
9 Add-ons in this Collection
Firebug by Joe Hewitt, Jan Odvarko, others
Greasemonkey by Anthony Lieuallen, Aaron Boodman, 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.
Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...
Help make Firefox better. The Add-on Compatibility Reporter enables you to report if the Firefox add-ons that you're using are working properly.
Pixel Perfect by Mike Buckley, Lorne Markham, others
Pixel Perfect is a Firefox extension that allows web developers and designers to easily overlay a web composition with semi-transparent layers (images). These layers can be consequently used for per pixel comparison between the page and a layer.