Each time you receive a new message in the Facebook Messenger mobile app, a small notification with the contact's picture — called a Chat Head — is displayed on your screen. Chat heads allow you to view and reply to your messages from the current screen without needing to open Facebook Messenger. While many users find this feature useful, others don't.
This tutorial explains how to turn off chat heads in the Facebook Messenger mobile app. The procedure is the same for the various versions of the app (Android, iOS, and Windows Phone).
Turn Off Chat Heads in Messenger
Open the Facebook Messenger app. Click Settings (small cog icon) > Chat heads.