If that all sounds like too much work for you, there are already Chrome extensions like ImprovedTube that will add something similar to this mode. Once that's done, all you'll need to do is reload the page, click your avatar, and dark mode should load up. To check if it is, follow the steps given below.
Reddit user /u/_paul- discovered the feature and provided instructions for enabling it on PC.
How to Enable YouTube Dark Mode on macOS?
Press the keyboard combination shortcut Option + Command + I to open the developer tools sidebar.
The final steps are to close that developer window, refresh the browser then you'll have a toggle switch for dark mode in the main settings on the top right.
Just like before, toggle it on or off depending on your choosing. Once a user activates the hidden dark mode, which seems better for night-time viewing, it applies to the rest of the website regardless of whether you're browsing the homepage or visiting a specific channel.
Did you enjoy this guide?
YouTube is yet to announce the feature, but it's easy to enable in the latest version of Google's own Chrome browser (v57 and up).