HDMI 2.1 is not just a spec sheet number — it is the difference between your monitor keeping up with your setup and quietly bottlenecking it. The jump from HDMI 2.0 to 2.1 unlocks significantly higher bandwidth, which means 4K at 120Hz or 144Hz over a single HDMI cable without compression, and full compatibility with PS5 and Xbox Series X at their maximum output. If you are running a current-gen console or a high-end GPU and pushing high resolutions at high refresh rates, HDMI 2.0 will hold you back whether you realise it or not.
The problem is that HDMI 2.1 is still not standard across the mid-range monitor market in 2026. Plenty of monitors are sold as “4K gaming” screens with only HDMI 2.0 ports, which means you cannot actually hit 4K at high refresh rates over HDMI — you need DisplayPort instead. I flag this clearly in every relevant analysis so you know exactly what you are connecting before you buy.