Active HDMI and Passive HDMI cables differ primarily in their ability to transmit signals over long distances without compromising signal quality.
Passive HDMI Cables: These are standard HDMI cables that can transmit data in both directions. They are typically used for short distances, up to about 20 or 30 feet for HDMI 2.0 signals. Beyond this length, signal attenuation can occur, resulting in a loss of picture quality. For HDMI 2.1 signals, the optimal cable length is even less, around 10 feet.
Active HDMI Cables: These cables come with an onboard processor to amplify the signal over long distances. This allows you to enjoy the full 48Gbps bandwidth of HDMI 2.1 for as long as 25 feet without any loss of quality. For much longer distances, you can use HDMI 2.1 active optical cables made of fiber optic, which can support distances of up to 30 feet.