Snapchat recently released a new feature called Story Replies that aims to facilitate further interaction between users. This tutorial will teach you how to use Story Replies to respond to individual snaps in a user's story.
Reply to a Snapchat Story in Private Messaging
In order to take advantage of this feature, you must be currently viewing a user's snap story.
When the image or video of interest appears in a user's story, simply swipe your finger upwards on your screen. This will start a conversation with the user.