If you have a legitimate reason, send a request with a polite message explaining who you are. Many people accept if they recognize you.
or a violation of privacy laws. Respecting boundaries is a fundamental part of digital citizenship. 4. The Only Legitimate Way
To understand why no "best free viewer" exists, you need to understand how Facebook works.
While you cannot break Facebook’s security, you can use and OSINT (Open Source Intelligence) techniques. These are 100% legal (though ethically gray) and completely free.
Facebook's privacy settings are designed to protect users' personal information. When a user makes their profile private, it means that only their approved friends can see their posts, photos, and other information. Facebook's algorithms and security measures are in place to prevent unauthorized access to private profiles.
When a friend tags the private user in a public post or a friend-of-friend post, that image becomes visible depending on the friend’s privacy settings. You can often gather significant information from these tagged images without ever seeing the user’s uploaded content.