If you use WhatsApp frequently you must have noticed the usual two grey check marks which normally appears when a message is sent now turns blue after a while. This could be to indicate that a message has been read by the recipient.
This new feature has been added without you needing to update your WhatsApp. It seems like the new feature is still under construction as it’s no longer available on my phone.
If you have experienced this new feature on your WhatsApp, feel free to drop your thoughts.