HDMI 2.1 explained: what it does, and why PS5 and Xbox owners want it on their next TV

Here’s why you want your next gaming TV to have HDMI 2.1

HDMI 2.1 explained
(Image credit: Future)

The arrival of the PlayStation 5 and Xbox Series X has added a stack of new things to think about when you’re shopping for the best gaming TV. The most important of which is the presence of HDMI 2.1… but what does HDMI 2.1 actually do? It’s all well and good to see jargon like VRR, ALLM, and 4K 120Hz floating around as essential HDMI 2.1 features, but it’s important to know what each of these means. 

While the next-gen consoles arrived late last year, not all TV manufacturers were totally on the HDMI 2.1 train in time for that. Right now, you have to specifically seek out TVs with HDMI 2.1, but soon it'll be normal across the best TVs and best OLED TVs once the 2021 models arrive. 

It will remain rarer on the best TVs under £1000 and the best TVs under $1000, though there are some great choices already. And don't expect to see it on the best TVs under £500, for now.

Here we’ll break down what HDMI 2.1 offers, why it’ll make your eyes happy while gaming, and bust some of those 8K myths at the same time.

What is HDMI 2.1?

HDMI 2.1: Sony XR TV

The Sony 2021 Bravia XR range includes widespread HDMI 2.1 support.

(Image credit: Sony )

HDMI, or High Definition Multimedia Interface as only its mother would call it, has been gradually upgraded over the last 15 years or so as we all happily ditched SCART connections and those ludicrous multi-pin offerings. The comparatively slick HDMI connector is now the main display technology between our consoles and TVs.

HDMI 2.1 is the new standard of this technology, capable of higher video resolutions up to 10K and higher refresh rates than regular HDMI 2.0. These include being able to display 4K at 120Hz and 8K at 60Hz. 'Hz' measures the refresh rate which, put simply, is the number of times the screen updates per second. It's roughly equivalent to 'fps' or frames per second in gaming (which means how many images the console can create per second), and having a higher refresh rate means images should appears clearer and smoother because you're getting more information to your eyes. 

In the past, TVs could only receive 60Hz input over HDMI (meaning they could show a maximum of 60 frames per second), but with PCs and consoles now capable of outputting up to 120 frames per second, we need a connection capable of 120Hz support. That's HDMI 2.1.

Basically, the advantage of HDMI 2.1 is bandwidth – it can transfer more data at once. This can used for more higher resolution (as with 8K video) or more frames at the same resolution (as with 120Hz video), as well as greater colour depth.

Understandably, this requires not just a compatible console and screen but also a better cable to match. An HDMI 2.1 cable known as an Ultra High Speed HDMI Cable supports dynamic HDR formats and has a high bandwidth capacity of 48Gbps. This cable is fully backwards compatible so you can plug the ones that come with the new consoles into an HDMI 2.0 port and they will work perfectly. To make the most of HDMI 2.1 then, you’ll need a compatible output such as a PS5, a high speed cable, and a television with an HDMI 2.1 port. 

The cables aren't expensive mercifully (and many devices, such as the PS5, come with one) – but if you buy a cheap one, you'll need to double check it will work with HDMI 2.1. If it says it supports 8K, it should be fine.

HDMI 2.1 and new-gen consoles

HDMI 2.1: PS5

The PS5 includes HDMI 2.1, though some feature are yet to be enabled.

(Image credit: Sony & PlayStation 5 images courtesy Sony; image edited by Future)

HDMI 2.1 supports three very attractive features for those who own PS5 and Xbox Series X consoles. These are Variable Refresh Rate (VRR), Auto Low Latency Mode (ALLM), and 120Hz gaming at 4K. You’ll still need to read the small print to make sure that these are supported on a TV, but generally speaker HDMI 2.1 means you’ll have compatibility with them. 

VRR means that the screen adjusts and regulates the refresh rate on the fly to keeps your TV in sync with the current frames per second that the console is outputting. Without it, a TV always refreshes at a set rate (say, 60Hz, or 60 times per second). The console is also trying to create 60 frames per second, meaning everything is synced perfectly. But a big bit of action in a game might cause the console to have to lower its fps a bit, because it's working harder – to 50 fps, let's say. Now the two are out of sync, and the TV is refreshing when the console is only partway through building a frame, so you end up seeing two mis-aligned halves of a frame on the screen. This is called 'screen tearing'. VRR fixes this, but making sure that the TV only shows a new frame when the consoles tells it one is ready.

This means that whether your console is mid fight scene with multiple enemies on screen at once, or a more serene slow walk through the woods, you will always see the smoothest possible visuals. Currently the Xbox Series X is capable of VRR but the PS5 is awaiting an update to enable it. Sony’s ‘PlayStation 5 Ready’ XH90/X900H TV is also waiting for an all-important VRR compatibility update. 

ALLM is all about low latency and preventing lag. Lag is the delay between you pressing a button on the controller and the action taking place on screen. Lag is most noticeable when playing games that require faster reaction times, such as first-person shooters and racing games. ALLM creates a signal that means a TV knows that it needs to enter a gaming low latency mode. We’re not saying it means you’ll be better at Warzone, but being in a gaming mode automatically can definitely help. ALLM is currently not supported by the PS5 (again, it's due in an update), but is available on the Xbox Series X. 

And then there’s the not-so-small matter of gaming at 120Hz in 4K. Both the PS5 and Xbox Series X are capable of possibly the most exciting feature of HDMI 2.1. It’s currently available on only a small number of games but 4K gaming at 120 frames per second means ultra-fast refresh rates at resolutions only made possible by the new generation hardware. Not only is this far easier on the eye as everything runs smoothly, it also minimises lag – with double the frames per second, you see the results of a button press twice as fast as you would before.

HDMI 2.1 and 8K gaming

HDMI 2.1 explained: Samsung Q800T

The Samsung Q800T is an 8K TV with HDMI 2.1 features.

(Image credit: Samsung )

The increased bandwidth and refresh rates of HDMI 2.1 means technically that resolutions up to 10K are possible. This meant that before launch both the PS5 and Xbox Series X were lauded as being capable of 8K gaming – in fact, Sony puts '8K' right on the box. 

The word here to focus on is ‘capable’ because that’s technically what HDMI 2.1 allows. Truthfully though, the big goal for both Sony and Microsoft’s consoles is 4K gaming and currently only a relatively small number of games can even make the most of that. 

8K gaming isn’t even possible on some of the beefiest PC gaming rigs, making this a serious pipe dream for this generation of consoles. The budget restraints on PS5 and Xbox Series X hardware mean that 4K gaming will continue to be the aim for both boxes for the foreseeable future. 

It is important to note, though that it’s still not a bad idea to check out the best 8K TVs. They are gradually becoming cheaper, and they're also the best way to make sure that your 4K games or videos look their best, because they include all of the most advanced image technology. You’ll just need to make sure there’s an HDMI 2.1 port so you can make the most of VRR, ALLM, and 4K gaming at 120Hz.