It's been a long time coming, but Facebook has finally announced that it's rolling out a dark mode for WhatsApp to all users on both Android and iOS. The feature was first discovered all the way back in September 2018 and finally showed up in beta versions of the app earlier this year.
As you'd expect, one of the biggest benefits of dark mode is that of reduced eye strain when you look at the app in poorly lit environments. It could also prevent the temporary blindness that comes when you turn your phone on when you're in bed at night.
Facebook says it designed the dark mode for WhatsApp with two things in mind - readability and information hierarchy. For that, it tried to use colors close to the system defaults on each operating system and used colors to prioritize the most relevant information on the screen.
Naturally, the app will follow the system-wide setting for dark mode on both iOS 13 and Android 10. If you're on Android 9 or lower, you can manually enable dark mode in Settings -> Chats -> Theme. It looks like you're out of luck if you're on any version of iOS prior to iOS 13, but that shouldn't be as much of a problem given that Apple tends to support devices for much longer.