If you see a YouTube video, a blog post, or a “hacker tool” offering to view locked profile cover photos:
Here are some possible methods to view locked profile cover photos:
Even friends see a slightly limited view, but the main restriction applies to people not on the friend list.
claim to show full-size images by pulling the image's unique ID. However, Facebook frequently updates its API to block these "loopholes." Search Engine Cache
Facebook’s engineers have built a system that prevents external client-side manipulation.