Recently, many application is rolling out the Dark Mode feature. Now, it seems WhatsApp is also working on the Dark Mode feature. At this moment, we are not sure yet on when it will be available to all the users. However, according to WABetaInfo, this feature will be rolling out to the Android devices first. WABetaInfo also stated that Facebook is currently fixing a few bugs before they roll out the feature as part of the 2.19.82 update.
As part of the leak, WABetaInfo also states that WhatsApp might implement the dark grey scheme instead of the black which most of the application has. As for now, apart from WhatsApp, Facebook Messenger, Telegram, Viber, and Windows 10 mail app has rolled out the Dark Mode feature. The main purpose of having this feature is to prevent eye strains to the users when they using the app. Moreover, the Dark Mode feature is also able to reduce screen glare. This will allow users to use the application in the low light.
If you want to join as the beta tester of WhatsApp you can click on this link here. You have to also note that, when you register as the beta tester, you will get the testing version of the WhatsApp which may be unstable.
In conclusion, we believe with this feature, soon all the apps will roll out this dark mode feature too to reduce users eye strain.