If you are a Whatsapp user, you will notice your double check marks turn Blue. It means that the message sent has been read by the recipient. In a group chat or broadcast message, the double checkmarks will turn blue when every participant has read your message. This is a new update by Whatsapp and will soon appear on Whatsapp FAQ’s.
The double checkmarks simply notifies the sender that the message has been received by recipient; the new blue checkmark update adds a third layer of information, as an updated FAQ will confirm.
Another way to check if it was read was by long pressing on the sent message to access a ‘Message Info‘ screen, detailing the times when the message was received, read or played. This can also be done in messages sent on group chat or broadcast message.
Of course, one could use ‘last seen’ indicators on the top left of a conversation to know when a contact was last in the app, but the blue checkmarks are more direct. It would have been nice to see this added in as an on opt-out feature though – some users may not be so fond of the additional information.