These are not "free viewers" but paid parental control or monitoring apps. They require physical installation on the target device and do not "hack" Facebook servers; instead, they capture what is displayed on the device's screen. Warning: Scams and Security Risks
If someone has set their profile to private, they have explicitly expressed a desire for that content not to be seen by the general public or specific individuals. Attempting to violate that boundary is a form of digital trespassing. It undermines the very concept of consent. facebook private profile photo viewer free
To maintain your online safety and protect your personal data: These are not "free viewers" but paid parental