Right-click the profile picture and select
Facebook introduced "Profile Guard" and locked profiles to enhance privacy. When a profile is locked, clicking the picture usually does nothing. view facebook profile picture full size full
If the standard method doesn't work or you are on mobile, use Facebook's basic version which often bypasses certain viewing restrictions: verify a new contact’s identity
If the image is private or the user blocked you, no trick will work. view facebook profile picture full size full
Whether you want to see a friend’s vacation photo in detail, verify a new contact’s identity, or simply save a high-resolution image of a loved one, the default Facebook interface makes this unnecessarily difficult.
