works EXTREMELY well on FF 68 on desktop - better in fact that the built in mozilla dark theme (latter leaves elements unchanged e.g. window title bar stays system colour).

Everything except the actual webpage becomes dark: tabs, toolbar, bookmarks bar, title bar, etc. Fantastic.

Only 4 stars though because it does nothing on firefox for android - I actually wanted a theme change more for my mobile use.

EDIT: to Dev: yeah i did wonder in retrospect, as there was no mozilla light / dark themes for android. It's a shame though, as Google is proving able to roll out dark modes for its apps and i genuinely value them for being easier on my eyes.

Bumped to 5 to reflect your comments.

EDIT1: there are slivers of the FF window that don't change to black, when using your theme (left and right vertical edges of firefox window). Window buttons don't change either but perhaps they're protected by the OS.