How long can an HDMI cable be? Active vs passive

Passive cables and their limits

A passive HDMI cable has no electronics inside - it is just copper with connectors. At short runs (under 3m) passive cables carry HDMI 2.1 at full bandwidth. At longer runs signal attenuation reduces the usable bandwidth, so a cable rated for HDMI 2.1 may only carry HDMI 2.0 or lower at 5-10m. At 10m and above, a passive cable struggles to carry 4K reliably.

What an active cable does

An active HDMI cable has a small receiver chip built into one connector. It amplifies and regenerates the signal so 4K at 60Hz arrives intact at 15m, 20m and beyond. The cable is directional: the end with the chip marked SOURCE goes into your player or PC; the DISPLAY end goes into the screen. Plugging it in backwards gives no picture.

When you need an active cable

Use an active cable when your run is over 10m and you need 4K at 60Hz or above. For 1080p signals, passive cables can reach 15m and sometimes further. The Cable Finder automatically restricts to active cables when you select a length above 10m.