Some tech-savvy users suggest using your browser’s “Inspect Element” or “View Page Source” tool to find the hidden URL of the full-size profile picture. Historically, this worked occasionally because Facebook served the full image in a hidden div container. Today, if the profile is private, the page source only contains the low-resolution thumbnail URL. No amount of digging in your browser console will summon a high-res image that the server never sent to you.