Whatsapp has now introduced blue tick marks, which show users that their messages have been read.
Those who use the app will be familiar with the single, and the double ticks which show up under outgoing messages.
The first shows it has been sent successfully, while the second double ticks indicated that message had been received on the other phone. Now, the two ticks will turn blue once the message has been read.
Prior to the update, the way to work out if your friend had read your message was to use the "last seen" date and time stamp showing below their name. The new method is simpler, and more accurate.
WhatsApp has more than 600 million active users.