While there is no "secret tool," there are a few common-sense ways to see a profile picture without compromising your security:
In short: There is no legitimate third-party "viewer" tool that can magically break Facebook’s encryption to show you private content. facebook private profile picture viewer online 2021
The Truth About Using a Facebook Private Profile Picture Viewer Online in 2021 While there is no "secret tool," there are
A fake loading bar appears to make it look like the site is "hacking" into Facebook’s database. Can You Really View Private Facebook Profile Pictures
But before you click that "Unlock" button, it is essential to understand how these tools work, the risks involved, and the reality of Facebook’s security. Can You Really View Private Facebook Profile Pictures?
Sometimes, even if a profile is private, the profile picture itself is set to "Public." You can often click the image to see it in full size—if the user hasn't restricted it.