Since Snapchat changed its chat interface about a month ago, you may have been wondering what's up with the tiny blue dot that occasionally appears at the end of a conversation.
Sometimes a smiley face emoji appears instead of the blue dot.
The blue dot means that the person you're messaging is currently in the conversation with you. The smiley emoji means that they just opened the chat window.
So the blue dot and smiley emoji are kind of like read receipts, except they indicate when two people are active in the same conversation. Mystery solved!
