FoxyProxy is an advanced proxy management tool that completely replaces Firefox's limited proxying capabilities. For a simpler tool and less advanced configuration options, please use FoxyProxy Basic.
Custom color schemes for all websites: night mode, dark themes, blue light filter, screen shader, high contrast, grayscale, etc.
Enables a special password-protected bookmark folder.
Prevent tabs opened by a hyperlink from hijacking the previous tab by adding the rel=noopener attribute to all hyperlinks (excluding same-domain hyperlinks).
Tons of features to improve your user experience on YouTube™.
Lets you fix annoying sound problems in YouTube videos and such. Like audio in one channel only, too quiet or too loud. (Unfortunately, doesn't work on many other websites because of cross-domain issues — but it does work on YouTube.com!)
YouTube High Definition is a powerful tool that will let you automatically play all YouTube videos in HD (High Definition), turn off annotations, change video player size, auto stop videos, auto mute videos, control embedded videos and much more.
Speed up, slow down, advance and rewind any HTML5 video with quick shortcuts.
Good old Wikipedia gets a great new look
Shows previews of linked articles on Wikipedia pages.
Search for highlighted text on Wikipedia via the context menu.
Redirects to a random unusual Wikipedia page when you open a new tab, because when you're opening a new tab you're looking for a distraction and that distraction might as well be a weird fact. Or show random Cognitive Bias, or Philosophical concept.
Show tabs like a tree.
New Tab Override brings back the ability to change the page which is shown when opening a new tab.
Automatically refresh tabs based on custom time intervals
OneTab - Too many tabs? Convert tabs to a list and reduce browser memory