DisplayPort Alt Mode

DisplayPort Alt Mode is the standard that lets a USB-C port carry a video signal to a dock or monitor. It is the feature that makes docking possible, and it is not universal — some ports and some cheap cables do not support it, which is why a handheld sometimes refuses to output through a hub that works fine for data and power. When docking matters, confirm both the device’s port and the cable support Alt Mode, because a video-incapable port is a silent, confusing failure.