XUL Add-ons, as browsers with their support, provide to user more freedom in creation and extension of browsers features. XUL has so many features that many addons are impossible to realize in browsers without XUL support.
This add-on is a downloader that lets you easily download videos from sites like Youtube, Facebook, Metacafe, Dailymotion, Break, VKontakte and music for example from SoundCloud, Grooveshark and from many other sites...
Personas (now known as lightweight themes) are free, easy-to-install "skins" for Firefox. Personas Plus extends that built-in functionality to give you even more control and easier access to new, popular, and your own favorite themes.
Qwant is the European search engine that does not track you. This extension makes Qwant your default search engine and homepage as well as allowing you to easily extend Firefox Tracking Protection to the whole Web.