Because Manycam creates a "Virtual Camera," other programs see it as a real webcam.

ManyCam serves as a "virtual webcam," meaning once it is installed and configured, it appears as a selectable camera source in other applications.

: You can switch between up to 12 different sources (on desktop) during a live session. This includes your webcam, pre-recorded videos, your desktop screen, or even a YouTube video URL Virtual Backgrounds