HDMI 2.1, often referred to informally as HDMI 4, is the latest version of the HDMI specification, released in 2017. It supports higher resolutions and refresh rates, including 8K at 60Hz and 4K at 120Hz, and features like Dynamic HDR, Enhanced Audio Return Channel (eARC), and Variable Refresh Rate (VRR). This version is designed to enhance the viewing experience for gaming and high-definition video playback.