Facebook Messenger for iPhone comes with an “App lock” feature to lock the app.

You can enable this feature by following these steps:

Open the Facebook app.

Tap your profile picture in the top left.

Hit Privacy.

Tap App Lock.

Enable Require Face ID.

Tap OK on the pop-up.

These options are now available to you:

• After I leave Messenger

• 1 minute after leaving

• 15 minutes after leaving

• 1 hour after leaving

Select one of the options above to set when the app locks.

That’s all. Face ID or passcode will be required to unlock the app.

Note: You can turn off the app lock at any time by disabling the “Require Face ID.”