Facebook does not show who viewed a profile, and no third-party tool can reveal it. Every "anonymous Facebook viewer" is either a scraper returning public data you could see yourself, a survey funnel, or malware — there is no hidden viewer list to expose.
What is real. Public profiles and Pages can be read without logging in, which is what those tools are actually doing. Facebook's own privacy checkup (Settings → Privacy → Who can see what you share) shows your exposure. If someone is impersonating a family member, the report flow (Profile → Report → Pretending to be someone) is the only mechanism that removes a fake account.
For a child's account, the parent-side options are inside the app: supervised accounts for teens (Family Center on Instagram, Supervision on Facebook), which show who they follow and who follows them, time spent, and let you set limits — not the content of private messages.
Where our app fits. Ultimate Phone Spy runs on Android 4.0+, Windows and macOS (social media monitoring). On an Android device it captures Facebook notifications and messages as they arrive, with the child's knowledge. On iPhone we do not operate, so the supervised-account route above is the honest answer.
The line not to cross. Watching an adult's profile activity through a workaround is not "anonymous" in any legal sense — in the EU the processing needs a lawful basis whether or not the person notices.