Instead of "hacking" Facebook, they are installed on a target device and capture activity (messages, stories, likes) directly from the operating system.
If you are looking for free ways to see what is available, use "Open Source Intelligence" (OSINT) techniques: facebook private profile viewer best free
Directly bypassing Facebook's security to view a truly "private" profile is generally through legitimate means. Facebook’s privacy architecture is robust, and third-party apps cannot force access to content hidden by a user's explicit settings. Instead of "hacking" Facebook, they are installed on