The Web Developer extension adds various web developer tools to the browser.
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
FirePHP enables you to log to your Firebug Console using a simple PHP method call.
Not using Firebug 1.9+ on Firefox 8+? See http://firephp.org/
Statusbar button to turn the proxy on and off with a single click.
An extension that allows for the use of dynamic commands in Firefox.
A maintained version can be installed via: https://bitbucket.org/satyr/ubiquity/downloads/tip.xpi
Collections are groups of related add-ons that anyone can create and share.Explore Collections