A 4K HDMI splitter can preserve VRR, ALLM, and 120Hz gaming, but only when every link in the chain: the source, the splitter, the cables, and both displays support that exact signal and negotiates it successfully. If any one piece falls short, the setup may settle for a lower shared mode or drop a feature while 120Hz continues working.
How Much Bandwidth Does 4K 120Hz Require?
To preserve 4K 120Hz gaming, match the splitter and the cable feeding it to the exact format you send, rather than relying on a 4K120 label. HDMI 2.1 raised the ceiling to 48Gbps and formally defined VRR and ALLM as part of the specification, as the HDMI Forum's HDMI 2.1 capability summary confirms. That number describes the standard's maximum capability, not a fixed requirement for every 4K 120Hz signal.
For a 4K HDMI splitter, the actual bandwidth a format needs changes with resolution, chroma subsampling, color depth, and whether compression is applied. According to the official HDMI format data-rate table, formats are grouped into cable and link tiers such as 24, 32, 40, and 48Gbps, and some higher-resolution or higher-bit-depth combinations are marked as exceeding even the top tier. A 4K 120Hz signal at reduced chroma or with visually lossless compression can fit a lower tier, while an uncompressed 10-bit 4:4:4 4K 120Hz signal needs the full 48Gbps ceiling.
| Target format (approximate) | Typical link tier | Practical result |
|---|---|---|
| 4K at 60Hz, 8-bit, standard chroma | 18 to 24Gbps class | Compare with the splitter's stated link tier |
| 4K at 120Hz with chroma subsampling or compression | 24 to 40Gbps class | Check the specific splitter and cable specifications |
| 4K at 120Hz, 10-bit, full 4:4:4, uncompressed | 48Gbps (Ultra High Speed) | Requires a splitter and cable rated for the target 48Gbps format |
| 8K at 60Hz and beyond | 48Gbps or over limit | May exceed even top-tier splitters and cables |
Before buying a 4K HDMI splitter, match the splitter’s rated link tier and the cable you use to your exact target format instead of trusting a 4K120 or HDMI 2.1 sticker alone. If you want a deeper side-by-side of what changed between generations, our breakdown of HDMI 2.0 vs. HDMI 2.1 covers the bandwidth and feature gap in more detail.
Can Both Displays Support the Same Features?
Both displays need to accept the exact mode you want on both outputs; if their capabilities differ, the source commonly negotiates down to whatever both screens can handle. A splitter cannot add capabilities that a display does not already have. If you want 4K at 120Hz with HDR, VRR, and ALLM on both a gaming TV and a monitor, both units must report support for that full combination.
Most home setups do not use two displays with identical specs. A newer gaming TV might support 4K 120Hz with VRR and ALLM, while a secondary monitor tops out at 4K 60Hz or lacks VRR entirely. When that happens, the source usually falls back to a mode both screens can accept, unless the specific splitter is designed to send different resolutions or refresh rates to each output independently.
Before buying, compare the desired resolution, refresh rate, HDR mode, VRR, and ALLM support on both displays rather than checking only your primary screen. Ignoring the second display’s specs is a common reason a dual-display setup looks worse than a single-display test.
How Do EDID Differences Affect Gaming?
EDID differences can make the source select a lower or different mode when the second display joins the path. The source uses this capability metadata to choose an output mode for the connected displays.
EDID Is the Capability Information the Source Uses
EDID stands for Extended Display Identification Data, and it is the metadata a display sends back to the source describing its identity, supported timings, and capabilities. Microsoft's driver documentation describes EDID as capability metadata that a graphics source uses to decide which display mode to output, including resolution and timing information.
When a splitter sits between one source and two displays, it has to relay or combine EDID information from both screens. If that information conflicts or is incomplete, the source may pick a mode that is safe for both displays rather than the best mode either one supports alone. This is one possible reason a console or PC drops to 1080p or 60Hz the moment a second display joins the signal path, even though the primary display alone handles 4K 120Hz without issue.
Use the One-Display Result as Your Baseline
Before troubleshooting a two-display setup, connect only your preferred display and record the resolution, refresh rate, and any HDR or VRR indicator the source reports. Then reconnect the splitter and second display and compare the result. If the mode changes, the drop usually points to EDID, bandwidth, or a cable—not a broken source or splitter.
Does a Splitter Preserve VRR and ALLM?
A splitter can preserve VRR and ALLM only when the source, splitter, cables, and both displays support and pass those features.
120Hz Is Not the Same as VRR or ALLM
VRR (Variable Refresh Rate) is different: it lets the display’s refresh rate follow the source’s frame output in real time. HDMI’s gaming guidance describes this as a way to reduce lag, judder, and tearing. ALLM, Auto Low Latency Mode, is a separate signal that automatically switches a display into its lowest-latency picture mode when a game console is active. Seeing "120Hz" on your display's info panel does not confirm that either feature is actually active.
Check the Complete Feature Path
For VRR or ALLM to pass through a splitter, the source, the splitter itself, the cables, and both displays all need to support and pass that specific signaling. Because splitter designs vary and this article does not test a specific model, treat VRR and ALLM support as conditional until you confirm it directly. If any link in that chain lacks support, the fixed 120Hz picture may keep working while VRR or ALLM quietly fails, which is why verification matters more than a spec sheet.
Does a Splitter Change Audio or ARC/eARC?
Audio has to be checked separately from video, including HDMI pass-through and any ARC/eARC return path. A splitter may preserve the picture while the audio format or routing changes.
Treat Audio as a Separate Compatibility Path
Video and audio use separate compatibility checks. The source, splitter, displays, receiver, or soundbar can each limit or change the audio format, even when the video signal works. A working 4K 120Hz picture with no sound issues on one display does not guarantee the same audio result once a second display and its own audio handling enter the chain.
Check the Return Channel Separately
If your setup relies on ARC or eARC to send audio from a TV back to a receiver or soundbar, check that path independently. The HDMI eARC audio capability guidance describes eARC as supporting high-bitrate and uncompressed formats up to 24-bit, 192kHz, and multichannel audio including Dolby Atmos and DTS:X, but it also notes that eARC is not defined as backward compatible with ARC. Do not assume your receiver or soundbar automatically gets the same audio format through a splitter that it received before; verify the actual output on your receiver's display or app.
How Can You Verify Gaming Performance?
A compliance label is not proof that your console, splitter, and two displays will work together as expected. The HDMI compliance-testing is a minimum standard, not a guarantee of interoperability. That is why hands-on verification matters more than a spec sheet once your hardware is in front of you.
- Connect only your preferred display and record the source's reported resolution, refresh rate, HDR status, and any VRR indicator as your baseline.
- Add the splitter and second display, then check the source's display settings again for any change in resolution or refresh rate.
- Open each display's on-screen information panel to confirm what mode it is actually receiving, not just what the source claims to send.
- Launch a game that supports VRR and ALLM and watch for tearing, stutter, or a menu indicator confirming each feature is active, rather than assuming a 120Hz readout covers both.
- Check your audio output on the receiver or soundbar display, then reconnect just one display to isolate whether the splitter, the second display, or a cable is the limiting factor.
If testing shows that your current hardware cannot deliver the resolution, refresh rate, or features you want, compare our HDMI splitter options or use our HDMI troubleshooting guide to narrow down a specific connection issue first.
FAQ about VRR, ALLM, and 120Hz Gaming with HDMI Splitters
Why Is 120Hz Unavailable After I Connect an HDMI Splitter?
This usually means the two-display path settled on a lower shared mode, the exact format you want exceeds the splitter or cable's link tier, or one display cannot accept 120Hz at all. Compare your one-display baseline result with the two-display result to see where the drop happens.
Why Does VRR Disappear Even Though 120Hz Still Works?
120Hz is a fixed refresh rate, while VRR is separate variable-refresh signaling that has to be supported and passed through the same chain. Confirm VRR is enabled at both the source and the display settings, then test with the second display disconnected to see if the setting returns.
Why Does Adding a Second Display Change My Resolution or Refresh Rate?
The source may be receiving conflicting or incomplete capability information from the two connected displays and choosing a mode both can accept. Check the source's selected mode with only one display connected, then compare it to the two-display result to confirm the change.
What Should I Check If Video Works but My Audio Format Changes?
Video and audio negotiate independently, so a working picture does not guarantee your preferred sound format survives. Check your receiver or soundbar's input display and confirm whether it is using ARC or eARC, since the two are not interchangeable by default.
