Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
The first and only download manager/accelerator built inside Firefox!
Download all the links, movies and audio clips of a page at the maximum speed with a single click, using the most popular, lightweight and reliable external download managers.
The Web Developer extension adds various web developer tools to the 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!
Advanced Eyedropper, Color Picker, Gradient Generator and other colorful goodies...
HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen on the form of an icon
For Firefox 23+, you need 0.958 (under review)
NewTongWenTang is a tool to switch display Chinese content between traditional and simplified glyphs (中文繁簡體互轉工具)
Extends the function of the drag-and-drop mouse gesture so that it can be used to load URLs, do a web search of selected text on a page, or save an image on a page. The successor to Super DragAndGo.
PHP code formatters for Selenium IDE.
Created by Adam Goucher.
Detects Duplicate Bookmarks when bookmarks are added and specify where is the previous URL. You can also search and delete duplicates URL already in your Bookmarks.
Firefox 13 support is available from http://bookmarkdd.mozdev.org in version 1.1.1.
Collections are groups of related add-ons that anyone can create and share.Explore Collections