Hueshift от Ƒorkle

Hueshift is a lightweight extension that reduces eye strain by forcing a clean, consistent dark mode onto the web pages you visit as well as the Firefox UI. It features a variety of built-in dark color palettes so you can easily switch up your look, injecting your chosen stylesheet directly into active tabs as you browse. Built with privacy in mind, everything runs entirely local to your browser with zero data collection or tracking.

Required permissions explained:
Access your data for all websites: Required so Hueshift can inject the themes CSS into the pages you visit. Hueshift runs 100% locally in your browser. There is no tracking, no telemetry, and zero data leaves your machine.

Hueshift is in early beta stages and will likely have many visual bugs during normal browsing. These issues will hopefully be ironed out along the way however if you find any bugs please share the domain with the developer to help identify what needs to be fixed, thank you.