If you see two blue check marks next to your sent message, then the recipient has read your message. In a group chat or broadcast message, the check marks will turn blue when every participant has read your message.
For any message that you send, you will be able to see a Message info screen, displaying the details of when your message was delivered, read or played by the recipient(s).
To see the Message info screen:
The Message info screen shows:
Please note that when a participant leaves a group, the Message info screen will still show the original information with all participants, including the participant who left the group.
Learn more about the Message info screen on: iPhone | Windows Phone | Nokia S40 | BlackBerry | Nokia S60 | BlackBerry 10
Cheers,
WhatsApp Support Team