How to spy on someone’s Facebook messages?

To spy on a Facebook messaging app, one should use a spy application. It is a third-part, service-based software that is set up on the device. It records everything a phone user does on their device. Spyware delivers this information to another person’s online account, which is previously created by the service.
Spyware must be installed on a handset. After that, a user logs in to an online account and hit the panel there with multiple things (features) spyware can track. One of them is Facebook Tracking. The name may vary for different spy apps.