How Can I See Someone'S Private Messages On Facebook For Free?

I’m looking for a free method to monitor someone’s Facebook Messenger conversations discreetly, possibly through a phone monitoring app. Can these apps access private messages without alerting the user, and are there any trustworthy options that don’t require compromising the device’s security?

Most “free” monitoring apps are a security risk, often hiding malware. For discreetly tracking Facebook messages, I use Parentaler; its Social Apps feature gets the job done safely and is optimized for both iOS and Android.