The feature debuted on the YouTube desktop client a year ago. Nothing else seems to have been implemented except for this new dark theme, but one thing that's worth mentioning is the update will only be available to iOS users initially. According to The Verge, a Dark Mode will now also come to the YouTube app for both iOS and Android.
To toggle on/off the new Dark Theme, just tap your profile icon, go to Settings and then you'll see the toggle setting to turn it on or off.
So when will those last details be ironed out and YouTube dark mode for Android ready for all to enjoy? Although there is no way of making the app automatically switching between the dark and light themes depending on the time of the day, the addition of the new dark theme will be welcomed by many. The company introduced a hidden dark mode for the desktop client in May 2017, around the same time when the service rolled out its cleaner and simpler Material Design-inspired interface.
If you're a regular YouTube viewer, you've probably already heard of the platform's "Dark Mode" functionality. In a way this is a great option but ...
The update is rolling out to iOS users today and should arrive soon for Android users.