Messenger From Facebook recently introduced an App Lock feature for iOS devices, which allows users to “lock” the Messenger application behind Face ID or Touch ID (depending on their device) when it’s not in use. App Lock will come to Android devices in the future. Our guide will show you how to turn on App Lock.Note: These screenshots were captured on an iPhone 11 Pro Max, which has the Face ID option.Step 1: Tap your profile picture in the top-left corner of the screen.Step 2: Tap “Privacy.”Step 3: Tap “App Lock.”Step 4: Tap the toggle to the right of “Face ID.”Step 5: If this is the first time you’ve turned on App Lock/Face ID within the Messenger app, your device will ask you if you want to allow Messenger to use the Face ID feature. Tap “OK” to give the app permission to do so.By default, Messenger will require Face ID any time you leave the app and then come back to it. However, you can choose from three different settings if you’d like. Tap “1 minute after leaving,” “15 minutes after leaving” or “1 hour after leaving” if you want to change this setting.