In this guide
Yes, HDMI 2.1 supports 4K at 120Hz, provided you use a certified Ultra High Speed HDMI cable and both your source and display fully implement the HDMI 2.1 standard.
- Cable is Ultra High Speed HDMI 2.1 certified for 48 Gbps
- Source (PS5, Xbox Series X, PC GPU) supports 4K@120Hz output
- Display has a true HDMI 2.1 port with 4K@120Hz support
- Cable is HDMI 2.0 or an uncertified “2.1” cable limited to 18 Gbps
- TV or monitor only partially implements HDMI 2.1 without full bandwidth
- Long cable run causes signal loss without an active or fiber optic cable
Why HDMI 2.1 Can Handle 4K 120Hz
HDMI 2.1 raises the maximum bandwidth from 18 Gbps (HDMI 2.0) to 48 Gbps. That extra headroom is what makes 4K at 120Hz possible. At 4:2:0 chroma subsampling the signal requires around 32 Gbps, comfortably within the 48 Gbps ceiling. For uncompressed 4:4:4 at 120Hz you need the full 48 Gbps, so cable quality matters even more. RTINGS has a detailed breakdown of HDMI 2.1 bandwidth requirements if you want the full numbers.
What You Actually Need
- Certified Ultra High Speed HDMI cable — look for the HDMI Forum certification label, not just “HDMI 2.1” printed on the box
- A compatible source — PS5, Xbox Series X, and recent Nvidia/AMD GPUs all output 4K@120Hz over HDMI 2.1
- A compatible display — confirm the specific port on your TV or monitor is rated for 4K@120Hz; some sets only have one true HDMI 2.1 port
Common Setups at a Glance
| Setup | Works? | Need | Note |
|---|---|---|---|
| PS5 → HDMI 2.1 TV | Yes | Certified 48 Gbps cable | Enable 4K 120Hz in PS5 display settings |
| PC GPU → HDMI 2.1 monitor | Yes | Certified 48 Gbps cable | Set refresh rate in OS display settings |
| Xbox Series X → HDMI 2.0 TV | No | HDMI 2.1 display | Capped at 4K@60Hz maximum |
| Any device → long passive cable | Maybe | Active or fiber optic cable | Signal loss likely beyond 3–5 m |
Extra Features HDMI 2.1 Unlocks
Beyond 4K@120Hz, a proper HDMI 2.1 connection also enables Variable Refresh Rate (VRR), Auto Low Latency Mode (ALLM), and Dynamic HDR — all useful for gaming. If you are connecting a laptop or device with a USB-C port, check out whether USB-C can connect to HDMI before buying an adapter, since bandwidth limits apply there too.
Running into no picture at all? The troubleshooting steps in our guide on why USB-C to HDMI is not working cover signal handshake issues that also apply to HDMI 2.1 setups.
Bottom line: HDMI 2.1 does support 4K at 120Hz, but the cable, source, and display all have to meet the standard. A certified Ultra High Speed HDMI cable is non-negotiable — an uncertified or older cable will silently cap your output at 4K@60Hz or lower.