These tools often request your Facebook login (never provide it), or they use your session to scrape data. I ran a test in a sandbox environment, and the tool attempted to access my friend list and basic info. That’s a privacy nightmare waiting to happen.
or specialized services allow you to paste a profile URL to retrieve the full-size image. Manual Inspection fb profile picture viewer
If you are friends with the user, simply click on their profile picture. Facebook will open the full-size image in a lightbox. From there, you can right-click (or long-press on mobile) to save it. No tool needed. The Truth About "FB Profile Picture Viewer" Tools: