4K 120Hz not working: ports, cables and settings to check

To run 4K at 120Hz, three things must line up: the TV (port and panel), the cable and the source. One weak link caps the whole chain at 60Hz or drops the picture.

Step 1: Use the right HDMI port

Many TVs give 4K120 on only some of their HDMI inputs. Examples from our catalog:

• The Sony Bravia 8 II has two inputs that support 4K 120Hz and VRR, and the others are slower.
• The TCL QM7L supports 4K at 144Hz on HDMI 1 and 2, and 4K at 60Hz on HDMI 3 and 4.
• The Hisense U6 Series limits HDMI 2.1 to two of its four inputs.
• On LG C5 all four inputs are listed for 4K 120Hz, VRR and ALLM.

Move the console to a port your TV's spec says supports 4K120, and select that input on the TV. Check the manual or the port labels on the TV. Samsung adds that a device in the wrong HDMI port can stop game mode from being switched on.

Step 2: Confirm the panel is 120Hz

A TV can have HDMI 2.1 labels and still show 60Hz. Our catalog notes that the Roku Plus Series has a 60Hz panel despite its HDMI 2.1 ports. If your set is a 60Hz panel, 4K120 is not available.

Step 3: Use a certified Ultra High Speed cable

Engadget says to shop by cable category. Premium High Speed cables are certified for 18Gbps and Ultra High Speed cables for 48Gbps. Ultra High Speed is the category it connects with 4K120 gaming. The HDMI Forum says certified Ultra High Speed cables carry a label on the packaging and the cable name on the jacket. Sony, for PS5, recommends the cable that came with the console or an Ultra High Speed cable, Engadget reports. A catalog example is the Belkin Ultra HD HDMI 2.1 cable.

Keep the run short while you test. Engadget says longer passive cables become unreliable as bandwidth rises, and that a cable fine at 4K60 can fail at 4K120. See HDMI handshake problems.

Step 4: Check the TV's settings

1. Enable game mode for the input. On 2025 Samsung models, Samsung Australia puts Game Mode inside Game Mode Settings, under Advanced Features. Older Samsung models use the Connection or General menus.
2. Confirm the input is selected on the TV and not a different port.
3. Check whether your TV has a per-input setting that must be switched on for full-speed HDMI. It is not universal, so look in your manual.

Step 5: Check the source device

1. Open the console or PC video output settings and confirm 120Hz is allowed. Menu names vary by system version, and this guide could not verify the current console paths, so check the maker's support page.
2. Confirm the game supports 120Hz. Not every game does.
3. Make sure HDMI Device Link or CEC options are not interfering. Engadget notes CEC can cause unexpected input changes.

Step 6: Test one change at a time

1. Short certified cable to a supported port, no switches or receivers in between.
2. Try the game again.
3. Add back the soundbar or receiver and test again. Engadget lists switches, couplers and receivers as extra failure points.

Related: PS5 and Xbox TV settings. Our TV finder can filter by gaming features.