I tried Darkreader (along with a basically all the other dark theme addons available on AMO) and found those "hangs" really annoying. The one I've been using is

I tried Darkreader (along with a basically all the other dark theme addons available on AMO) and found those "hangs" really annoying. The one I've been using is this one: https://addons.mozilla.org/en-US/firefox/addon/dark-background-light-text https://addons.mozilla.org/en-US/firefox/addon/dark-backgrou.... It doesn't hang, works on pretty much any site and has customizable colors.