Public vs. private: what a video downloader can (and can't) touch

It's a fair question: if a downloader can pull a video from a public post, why can't it grab one from a private account or a members-only group with the same link format?

The short answer is that 'public' and 'private' aren't cosmetic labels — they're access controls enforced by the platform itself, usually tied to whether you're logged in and what your account is allowed to see. A public video's file location is something anyone, logged in or not, can be handed by the platform. A private one is only served to sessions that pass an authentication check first.

A tool that only reads publicly available data never needs to touch that authentication layer at all — it just asks for what's already being offered to any visitor. Getting past a login wall, a paywall, or a 'friends only' restriction would mean impersonating a logged-in session or otherwise working around a deliberate access control, which is a fundamentally different (and much riskier) thing to build.

That's why a responsibly built downloader draws a hard line at public content: it's not a technical ceiling that a smarter tool could push past, it's a boundary that exists on purpose, on the platform's side, for good reasons.