We know you're all about that dark mode life, thus, we will show you how to activate the same on YouTube in your browser.
The text in the setting suggests you might use this feature when enjoying YouTube at night, but there's more than a few people out there interested in using it like this all the time.
YouTube is testing a new Dark Mode that can be enabled by following some simple instructions. If you have the most recent download of Google Chrome, hit control + shift + I (Windows) or option + command + I (Mac). I personally appreciate this move since the darker theme will make the viewing experience less stressful on the eyes when you're watching content for hours. Those signed in can click their profile icon and scroll down to "Dark Mode".
Close the console, hit Enter, reload YouTube.com and click your avatar.
To enable dark mode, open the console while you're visiting YouTube and paste the following: document.cookie="VISITOR_INFO1_LIVE=fPQ4jCL6EiE". While this is just a UI that YouTube has created for YouTube Gaming, adding "gaming" as a subdomain to the URL works on any of YouTube's videos.