Millions of users use Snapchat on a daily basis. If you know about Snapchat, then you are also aware that when a person takes a screenshot of any snap on Snapchat, Snapchat alerts the user, and they come to know about it. Unfortunately, you cannot turn off the screenshot notifications; it is a built-in feature.
So if you think about how to screenshot on Snapchat without them knowing, then you can try this method. You can use any other phone and open the camera. Now, launch Snapchat on your phone and watch the videos and snaps on your phone. You have to capture this process on your phone.