There are a whole lot of apps are available for online messaging services around, but WhatsApp has a collection of features that makes it widely used.
The Facebook-owned app claims to have over two billion users worldwide, which is pretty unbelievable.
Mark chats as unread
Ever been out and about, read a chat, and then completely forgot to reply? We do it all the time on WhatsApp.
There is a way to mark important chats with dot to remind you to go back to it though.
iOS: Chats > Swipe left to right > Mark as Unread.
Android: Long press chat > Open Menu > Mark as Unread.