VivaldiFox - An add-on that allows colouring Firefox in a Vivaldi style fashion
Firefox Color - Build Beautiful Firefox Themes
automaticDark - Time-Based Theme Changer - Set Firefox to change the UI to a dark theme during the night and change back to a light theme during the day!
Night Mode for Instagram - Get the dark mode for Instagram on the web 🌚🖥️
Dark Reader - Reduce eye strain in your browser with this extension that provides a dark theme for browsing.
BrowserPage - The most intuitive Responsive Design Checker online tool for your Website.