Before understanding the "private viewer," one must understand the platform's architecture.

There are portable trojans (e.g., RedLine, Raccoon Stealer) that steal browser cookies. If a user uploads private videos and you infect their computer, you can steal their session cookie and paste it into your browser, giving you access to their private videos. However:

Some sites do not give you software at all. They force you through an endless loop of human verification tests, spam surveys, or ad clicks to "unlock" the viewer, generating revenue for the scammer while wasting your time. Safe and Legitimate Ways to Access Media

Allows viewing on public or shared workstations. The Appeal of "Portable" Software

Portable applications (.exe or script-based) are highly valued in the niche community of media consumption for several reasons: