While I was checking some news, I bumped into one about Youtube testing a "dark" interface, much like the Adobe Suite so your eyes don't get sore with all those white backgrounds. It's not public yet but you can already test via the browser console. Just tested it and it works just fine (after refreshing the youtube you might need to manually enable it in the youtube options left to the "connexion" button):

http://www.theverge.com/2017/4/14/15299552/youtube-dark-mode-how-to-activate

Note: works the same in Firefox. Be wary that if you aren't connected to your youtube account, it will reset your default cookie so you'll have the "standard" suggestions on the homepage. And the overall youtube layout will be different too.

Is this means i don't need this ?

https://addons.mozilla.org/en-US/firefox/addon/dark-youtube-theme/

Guess you won't need it anymore...

I've attached screenshots from my netbook. The cool thing is that once the new interface is enabled, you can easily switch it on/off as you like (pic 2 & 3). The problem with add-ons based on youtube in general is that youtube is constantly evolving and sometimes the casual updates break the code upon which add-ons are written and if the devs aren't reactive enough, you're stuck.

the gaming mode in youtube is even better. Its dark and it also stretches the videos better.
to use, just change prepend "gaming" to "youtube.com" like "gaming.youtube.com", leave the tail as is.

But it still contains total and utter drivel does it not?

Yeah, I've been using for a bit. Is it actually launching now?

Yeah, but now you can watch it for longer without hurting your eyes! ;)

I checked the gaming layout only once when it was launched (two years ago I think) and totally forgot about it. Now that you brought that up, I re-tested it and quite like the fact that the comments are browsable in the right column so it's quite convenient to read conversations while watching the video at the same time. Thanks for the tip ;) No official and widespread launch yet.

I didn't realize this was a problem, but then I keep my screen brightness normally minimum anyway, to save my eyes. I might sometimes brighten it a bit if sun is shining outside directly to the room, or if I play Team Fortress 2 and want to see the dark corners better.

On GOG I have selected the "light" mode where everything is light grey.

So your brain will hurt even more.

I use Magic Actions and it has that function along with disabling comments, related videos, no auto-play etc..

I use a Chrome add-on called "Deluminate", give that a try :P