The Facebook-owned app, WhatsApp, has introduced a new small but useful feature, read receipts. Previously WhatsApp would show double check marks if a sent message had been received. The first check mark was for sent and the other one for received. Now the app goes one step further and turns those check marks blue if the message has been read.
You don’t need to download an updated version of WhatsApp in order to take benefit of this new feature. It has been pushed over the web and is available to all users. So it means that it is applicable to all devices running WhatsApp.
You can read more about it at WhatsApp’s office FAQ.