The feature, which appears to only be available to users with the latest version of Chrome (version 57 or better), was discovered by Reddit user _Paul-, and has yet to be officially acknowledged by YouTube. Accessing it requires a few fairly technical steps, but follow these directions and you'll be all good to try it out:
- Step one: Head to YouTube.com in Chrome and access the Developer Tools window. To do this on a Mac, press Option + Command +I. Windows users, press Ctrl + Shift + I.
- Step two: Select the Console tab and paste the following text: document.cookie="VISITOR_INFO1_LIVE=fPQ4jCL6EiE; path=/"
- Step three: Hit Enter, close the Developer Tools window, and refresh the YouTube page.
- Step four: Tap the settings menu in the upper right hand corner. You should see a "Dark Mode" panel at the bottom. Turn it on and boom: all black (most) everything.