Google recently added functionality allowing users to darken the appearance of YouTube when viewed through a web browser. While it’s unlikely to make a big difference for most if Night Light or Night Shift is enabled, every bit counts!
The dark theme functionality can be enabled by first selecting your user icon in the top right corner of the webpage.
Once the user icon is selected you will be presented with several options, one of which is to enable the dark theme.
Then, select “dark theme: off” to bring up the toggle allowing you to enable the dark theme.
Once enabled the dark theme will replace most white areas with black and invert the color of fonts allowing them to remain visible.
For best results, enable dark theme and activate full-screen mode on your browser. That way the light appearance of the top of your web browser will be temporarily hidden. For Chrome and Edge users simply press the F11 key to active full-screen mode and the same to deactivate it.