by far the most polished dark mode addon, for most people this is the one you want to use. unfortunately for mobile users who prefer to browse x.com (formerly twitter) with adblock instead of through the android x app, this extension will slow your phone to a crawl after a few hours of browsing, forcing you to clear data and quit firefox. long story short: this is a great extension, but it's not updated regularly enough for anyone to consider donating, it's clearly abandonded. check out "Dark Background and Light Text" by Mikhail Khvoinitsky for an alternative darkmode extension on Firefox