A:Answer All the HDMI ports on the LG CX 55 inch Class 4K Smart OLED TV w/ AI ThinQ® (54.6'' Diag), Model # OLED55CXPUA are HDMI 2.1 ports that all support 4K @ 120Hz when HDMI Ultra HD Deep Color is set to ON. They all support VRR (Variable Refresh Rate), ALLM (Auto Low Latency Mode) and HGiG HDR Gaming. The TV is an NVIDIA G-SYNC Compatible TV and it also supports FreeSync™.It has a really low input lag in 'Game' mode, and it's the lowest with VRR enabled, which is great for gaming. It also stays low with a 4k resolution, which makes it a good choice for Xbox One X or PS4 Pro owners. With an Xbox plugged in, it automatically enables the Auto Low Latency Mode and it turns on HDMI Deep Color Mode, but you have to enable Instant Game Response first for ALLM to work...^IFV