HDMI 2.1
The HDMI version that enables 4K @ 120 Hz, 8K @ 60 Hz, VRR, and eARC. Required for full PS5/Xbox Series X output.
Spec released in 2017, first TVs around 2020. Uses FRL (Fixed Rate Link) instead of TMDS — 48 Gbps bandwidth vs HDMI 2.0's 18 Gbps. eARC: lossless audio from TV to receiver. VRR: variable refresh rate. ALLM: Auto Low Latency Mode (auto-enables game mode). Cable labelling is confusing — "Ultra High Speed" stamping on the cable is what you want. Worse, some TVs are marketed as "HDMI 2.1" but only support a subset of the spec.