Facebook Messenger brings new privacy features to allows iPhone and iPad users to lock the app with Face ID and Touch ID. The new App Lock in Facebook Messenger allows you to lock the app and all of your chats behind Face ID or Touch ID on iPhone or iPad devices. This feature also coming to Android in the next few months.
To enable App Lock in Facebook Messenger, open the Messenger app, and tap on your profile icon from the top left corner and choose privacy options. Under the privacy, option choose App Lock and toggle to on Touch ID or Face ID the confirmation pop-up will appear just click OK, and choose how soon the app lock after you leave the app.
Note: The annoying thing is, you can still reply to messages from the notification center on iPhone or iPad and answer calls while Messenger is a lock. This means if your device is in someone’s hands and a new message comes through, they can read, and also they can respond to it.