On the Facebook mobile app (iOS/Android), when you view a locked profile, the cover photo is visible, albeit tiny. You can pinch-to-zoom. You won't get high resolution, but you can often see the general composition (e.g., "Is that a beach?" or "Are they holding a child?").
: Strangers cannot engage with hidden content or scroll through personal updates. fb locked profile cover photo viewer exclusive
When someone locks their profile, Facebook applies a "limited view" for anyone not on their friends list: On the Facebook mobile app (iOS/Android), when you