By information hierarchy, the Facebook owned company means using colours and design elements “to make sure the most important information stands out.” By readability, it means using colours that are closer to the system defaults on both platforms, iOS and Android. The WhatsApp team shared the details of this update on their blog where they mentioned that the focus for implementing Dark Mode was readability and information hierarchy. Alternatively, you can go to the Control Centre and tap on Dark Mode.Tap on Dark to enable system wide Dark Mode.Next, go to Settings on the phone and find the Display & Brightness option.Visit App Store on you iPhone and download the latest version of WhatsApp (2.20.30).WhatsApp Dark Mode: How to enable it on iPhone And, iPhone users who do not have iOS 13 will not be able to experience WhatsApp's Dark Mode. This manual method is not available for iOS 13 users. You will also find a System default option when you tap on Theme which will automatically switch between light and dark mode according to the default system settings.