HDMI (High-Definition Multimedia Interface) is a common digital standard for sending video, and often audio, from a computer or embedded device to a display. It carries tightly timed electrical signals that a monitor must interpret correctly, which is why a board that can generate HDMI-compatible output can drive modern screens even if it is not a full PC.
In cyber security, HDMI matters because display ports can be part of both attack and defense surfaces. Attackers may use HDMI-connected devices, adapters, or capture hardware to observe what a system is showing, or to move data through unexpected output paths in constrained environments. Defenders care because secure workstations, kiosks, and embedded systems may still leak sensitive information through the screen channel. Testing HDMI behavior helps verify that a device only outputs what it should, at the expected resolution and timing.