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(Pocket-lint) - Do you want to be extra sure that no one is peeping your Facebook Messenger chats when you're away from your iPhone, iPad or Android device?

Luckily Facebook allows you to enable an extra layer of security. The app itself can be locked down when you close it, requiring you to use Face IDTouch ID or a biometric authentification to open it back up.

Here's everything you need to know about this privacy feature, including how to enable it on your mobile device.

How to lock the Facebook Messenger app on your device

Have you ever been in a situation where you unlocked your phone and let a friend or family member borrow it, and immediately regretted that decision, fearing the person would be able to access your Facebook Messenger chats?

Don't worry, Facebook has a feature called App Lock for iPhone, iPad users, as well as some Android users. Keep in mind that you have to set up a face or fingerprint ID and passcode on your mobile device before the app lock can work - check out Apple's support page for help if you're running an iPhone or iPad.

Once you have either authentication method set up, you can immediately enable it for use in the Facebook Messenger app. To turn the app lock on or off for Messenger:

  1. Open the latest version of the Facebook Messenger app.
  2. Tap your profile picture in the top left.
  3. Tap Privacy > App Lock.
  4. Tap Require Face ID or Require Touch ID / Unlock with biometrics to turn on and off.
  5. Select when to lock Messenger after leaving the app.

When you want to respond to messages or calls from Messenger, tap on the notification, and App Lock will ask for your fingerprint or Face ID. You can still see message notifications and calls from Messenger when it's locked, though you can turn off previews for Messenger.

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You can also set up your device to let you reply to locked notifications without providing an ID.

Is App Lock coming to Facebook Messenger for Android?

App Lock is supposed to be available on Android devices running Android 9 and Android 10. We don't have the option on our devices strangely, but if you do, you can access it using the steps detailed above.

Writing by Maggie Tillman. Editing by Britta O'Boyle.