Night Eye is a browser extension that enables dark mode on almost all websites, including Facebook, Google, Quora, Github, Stackoverflow, and Wikipedia, among others. It is available for Google Chrome, Mozilla Firefox, Opera, Vivaldi, Yandex, and Microsoft Edge . The extension offers three different modes: Dark, Filtered, and Dynamic .
According to user reviews, Night Eye is an excellent dark mode extension that is highly customizable and has bonus features that help make some websites more compatible with dark mode 1. However, one of the downsides is that it requires a paid subscription or a initial payment to purchase a lifetime license for multiple browsers. 
Night Eye is also known for reducing eye strain and promoting overall eye health by minimizing blue light exposure and in my opinion is doing the best job in this field.