Facebook’s Graph API (Application Programming Interface) gives developers controlled access to public data. For locked profiles, the API simply returns a null value for the large-sized profile picture URL. There is no hidden parameter or "secret key" to bypass this.
Some tools may ask you to download software or browser extensions that can infect your device with viruses or spyware. fb locked profile dp viewer
: Non-friends see only a small, low-resolution thumbnail of the profile picture and cover photo. why they exist
Here is a blog post covering how these "viewers" work, why they exist, and the safest ways to navigate this privacy feature. fb locked profile dp viewer
: The primary draw is accessing the original, uncropped version of the profile picture that is otherwise hidden. Anonymous Viewing