What I mostly use
30 Add-ons in this Collection
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 easy way to download and convert Web videos from hundreds of YouTube-like sites.
DownThemAll! by Nils Maier, Federico Parodi, others
The first and only download manager/accelerator built inside Firefox!
Greasemonkey by Anthony Lieuallen, Aaron Boodman, others
The best security you can get in a web browser!
Allow active content to run only from sites you trust, and protect yourself against XSS and Clickjacking attacks.
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.
Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager.
United States English Spellchecker for Firefox, Thunderbird and SeaMonkey by Kevin Atkinson and Geoff Kuenning.
To enable, right-click in a multi-line text box, select "Languages", then "English (United States)".
This extension allows you to export your saved passwords and disabled login hosts using XML or CSV files that can be imported later.
Draw a ruler across any webpage to check the width, height, or alignment of page elements in pixels.
Allows the download manager to also open in a tab or sidebar, and adds some optional display changes.
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