You don't absolutely need HDMI 2.1 to reach 120Hz or even 144Hz refresh rates, but it is important for supporting both high refresh rates and high resolution at the same time.
HDMI 2.1 allows for higher resolutions like 8K and higher frame rates of up to 120 frames per second (fps). Resolution improves the clarity and sharpness of the picture, which means you can simply see more details, and have less distance to the screen or a bigger screen without noticing any pixels.
It is only necessary that the PS5 and the TV support HDMI 2.1. There is also a labeling problem here on the part of the technology. It would be easier for everyone if HDMI cables had the same name as the technology they support, starting from something as basic as that the standard has always been backward compatible.
Games in 4K 60Hz with HDR work perfectly on premium HDMI (HDMI 2.0), with room to spare. Note that the PS5/Xbox Series X|S ship with an ultra high speed HDMI cable (HDMI 2.1), so if you have that, use it. All HDMI versions are backward compatible.
To be able to read the signal from either the PS5 or Xbox Series X/S, you need at least HDMI 2.0 connectivity (for 1080p at 120fps). Whereas, HDMI 2.1 is mandatory for 4K at 120fps. As we've said above, the consoles won't be pushing 120fps at maximum resolutions that often - not initially anyway.
The firmware on all three consoles continues to improve and offers smart bandwidth detection. If you force a PS5/ Xbox Series X|S to connect to a fast 1080p 120Hz projector using high speed HDMI (HDMI 1.4), the console will simply not make 1080p 120Hz available and will limit you to 1080p 60Hz.
While HDMI 2.0 does support 1080p 120Hz and even 1440p 120Hz in theory, the PS5 is designed with HDMI 2.1 in mind and therefore any lower bandwidth version of HDMI will produce unexpected results.
HDMI 2.1a Dynamic HDR
Does Dynamic HDR require the new Ultra High Speed HDMI Cable? No, but it will be necessary to enable 4K120 and 8K60 video with HDR due to the high bandwidth required by these resolutions and refresh rates.
Assuming we're talking from strictly a PS5 perspective, HDMI 2.1, while not something that can be easily dismissed, it is not important.
An HDMI 2.1 connection essentially allows for 120fps at 4K, or 8K at 60fps, while an HDMI 2.0 connection can allow for 120fps, but at either 1080p or 1440p. HDMI 2.0 connections also allow for 4K at 60hz, which has been enjoyed for some time thanks to consoles like the PS4 Pro and Xbox One X.
The HDMI 2.0 standard was phased out by the group in 2017, and display manufacturers should continue to use HDMI 2.1 in the future — even if it lacks some of the essential features of the newer standard.
HDMI 2.1 monitors are so expensive because HDMI 2.1 is a relatively new technology in the market and it's reserved for high-end gaming displays. Like with 4K monitors, the prices will soon go down as the technology becomes mainstream and more manufacturers make HDMI 2.1 monitors.
Standard HDMI: Up to 720p or 1080i resolution at a 30Hz refresh rate. High Speed HDMI: Up to 4K resolution (including 1080p) at a 30Hz refresh rate. Premium High Speed HDMI: Up to 4K resolution with high dynamic range (HDR) at up to 60Hz refresh rate.
In short, you need an HDMI cable with at least 18 Gbps in order to transport the 4k HDR video signal.
To successfully stream 4K Ultra HD (4K) or High Dynamic Range (HDR) content, all devices connected via HDMI® to your compatible Roku® streaming player must support HDCP 2.2. This includes your TV, an audio/video receiver (AVR), and any other devices connected in between.
Bridging the gap between 1080p and 4K, 1440p, or '2K' hits the sweet spot – significantly boosting your gaming visuals without pushing your hardware to the brink. Getting a 1440p monitor also means getting a 120Hz refresh rate display without burning a hole into your pocket.
PS5 1440p output does not support ultra-wide screen formats. So, the traditional 16:9 display ratio is a must. If your monitor is not ultra-wide, then the problem must be a lack of native support for 1440p resolution.
For 144Hz at 1440p, you will need at least HDMI 2.0 or DisplayPort 1.2 while for 4K 144Hz you are going to need HDMI 2.1 or alternatively, DisplayPort 1.4 with DSC 1.2.
The PS5 console supports the HDMI 2.1 specification, and it also supports 4K 120Hz video output. As this emerging technology isn't fully supported in the market, Sony Interactive Entertainment is working with TV manufacturers to improve performance and bring the best experience to console users.
The HDMI cable that's included with your PS5 is the recommended one you use. But if you need a new one or want another one, use any Ultra High Speed HDMI Cable that supports HDMI 2.1. A standard HDMI cable works but isn't ideal, especially if you want to future proof.
HDMI 1.4 can deliver 10.2 Gbps and its bandwidth is large enough to provide 24 & 30 frames per second think of it as the entry level with the ability to have a dabble with any content such as 4K.
When it comes down to 4K TV, you do not need to pick up special HDMI cables. The HDMI cable standard can impact color and resolution, but newer versions are not required for 4K TV.
If you are wondering about whether your existing HDMI cable will work, it is possible that you will not need to upgrade to one that is “4K-compatible.” Any HDMI cable up to five meters in length labeled “high speed” should be able to handle the increased bandwidth of 4K signals.
HDMI 2.1 comes with quick frame transport or QFT technology. It allows sources to deliver active video signals over the HDMI cable. As a result, gamers can experience a reduction in input lag.