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HDMI 2.1 TV: why the new cable standard matters

The end of an HDMI 2.1 cable
(Image credit: Shutterstock)

HDMI 2.1 is a new standard of HDMI. That might not sound exciting, but the implications are huge and HDMI 2.1 is already impacting the way many people watch movies, TV shows and play games. 

Until recently, very few TVs and displays had HDMI 2.1 capability. But fast-forward to 2021 and HDMI 2.1 has well and truly arrived. Importantly, you won’t find it everywhere. But HMDI 2.1 ports are now built-in to many of the best 2021 TVs.

HDMI 2.1 is a game-changer because it works by letting more information pass between games consoles, AV receivers, TVs and other devices. What that means for you is you'll see a significant upgrade in the resolution and refresh rate of your TV or display. Pictures will be more detailed, images will be sharper and games will look better in every way. This is why many people (us included) think HDMI 2.1 is going to truly transform entertainment.

But although HMDI 2.1 is a huge deal for all kinds of entertainment, including your favorite TV shows and movies, you’ll notice the biggest difference in gaming. Especially now that the next-gen Xbox Series X and PS5 consoles are available (if you can get your hands on one, that is). 

PS5 console in white with controller

(Image credit: Sony)

Both of these next-gen games consoles need an HMDI 2.1 connection to support frame rates up to 120 frames per second (fps). This is far higher than the usual 60fps and 30fps frame rates you’ll see on past games consoles. This is why many TV companies are currently scrambling to bring out new displays that are built for the future of gaming.

When High Definition Multimedia Interface (or HDMI) first arrived, it shook up the AV industry in a similar way. Everyone rejoiced at no longer having to use bulky SCART connectors, or confusing component video cables. Instead, HDMI offered high definition video with a connector that was only a little bigger than a standard USB.

There have been many improvements to HDMI over the years. Extra features are added as the needs of TVs have changed and HDMI 2.1 is the next big step.

The headline feature for HDMI 2.1 is support for 8K content at 60fps. However, there are many smaller features that add up to a much more capable standard, including support for Variable Refresh Rate (VRR), Dynamic HDR, and Quick Media Switching, which should make it faster than ever to change between the devices attached to your television.

Here's our guide to everything you need to know about HDMI 2.1 and all of the changes that have arrived with this new HDMI standard. 

HDMI 2.1 resolution and refresh rates

A close up of an HDMI 2.1 connection

HDMI 2.1 'lays the pipe' for the TV and VR industries

The new HDMI 2.1 cables allow faster refresh rates. This includes 8K resolution video at 60 frames per second and 4K at 120 frames per second – and it's that second feature that's a real selling point for both gamers and home cinema geeks who want content to look as good as it possibly can.

"We've increased resolutions and frame rates significantly," Jeff Park, Director of Marketing at HDMI Licensing, told TechRadar, adding that "NHK [Japan's national public broadcaster] is going to push 8K120 as an actual broadcast stream, and many consumer electronics manufacturers want to hit that target, so we're laying the pipe to give the industry flexibility. It's practical stuff."

HDMI 2.1 can go even further, supporting resolutions as high as 10K at 120Hz – though that kind of capability isn't here yet and isn't supported on commercial sets.

HDMI 2.1: a saviour for gaming?

A pair of hands holding an Xbox controller

(Image credit: Shutterstock/Miguel Lagoa)

HDMI 2.1 might have the biggest impact on the world of gaming. Especially if you have a next-gen games console, like the PS5 or Xbox Series X. Both of these new consoles must have a TV that supports HDMI 2.1 to work properly.

That's because HDMI 2.1 covers a number of technologies, including capability for 4K gaming at 120Hz, or 8K gaming at 60Hz – both of which are visually impressive if you have the hardware and cables to support them.

8K gaming is a while off still, but HDMI 2.1 means you soon won't have to choose between 4K resolution and high refresh rates, being able to experience both together.

HDMI 2.1 also enabled VRR (variable refresh rate), which helps to keep games looking smooth by switching up the refresh rate on the fly to best suit how much is happening onscreen. That means less image lag, stutter and frame tearing similar to the effect achieved by FreeSync and G-Sync.

This is great news for gamers, because HDMI 2.1 enables a 3D graphics processor to render and display images in real time, which will result in more fluid gameplay and greater detail.

HDMI 2.1: what is eARC?

It's not all about TVs, either; soundbars, AV amplifiers and other audio equipment also benefit from HDMI 2.1 – though it will mean upgrading all of your equipment.

For the last few generations, HDMI cables have had an Audio Return Channel (ARC), which means audio can be sent both ways between a TV and audio gear. This essentially enables a display to send its own audio – perhaps from a built-in Netflix app – to a soundbar or surround sound system, bypassing its own speakers.

AV amplifiers and other audio equipment will also benefit from HDMI 2.1 – although it will mean upgrading all of your equipment.

Enhanced Audio Return Channel (eARC) is nothing more than a simple update to keep pace with changes in audio codecs, specifically to include the new object-based audio codecs, Dolby Atmos and DTS:X.

"eARC ups the bandwidth significantly,” says Park. “Previously you were limited to two-channel PCM or legacy Dolby Digital or DTS audio, but with eARC that reverse channel can now support much higher bandwidth audio including Dolby True HD, DTS HD, Dolby Atmos, DTS:X and other object-based audio at much higher bandwidths."

HDMI 2.1: what is a 48G cable? 

An HDMI 2.1 cable being put into the side of a laptop

Incoming HDMI 2.1 cables will cope with 48Gbps (Image credit: Shutterstock)

This is about defining a new specification of a HDMI cable's speed, with so-called 48G cables (for now just a working title) offering 48Gbps bandwidth for sending uncompressed 8K video, with HDR, over a HDMI 2.1 cable.

So why do we need a 48G-rated cable? "Because we're carrying so much data now – we've gone from 18Gbps in HDMI 2.0 to 48Gbps in HDMI 2.1," says Park. "Today we have 'standard speed' and 'high speed' HDMI cables, and 48G will be related to that."

Ditto the compliance tests that each HDMI 2.1 cable will have to pass in order to be labelled as such. Backwards-compatible with earlier versions of the HDMI specification, and able to be used with existing HDMI devices.

HDMI 2.0 cables are all really the same, despite what some manufacturers will try to tell you with their branding – but an HDMI 2.1 cable with 48Gbps will be necessary to experience the technology's capabilities, and you'll need a compatible HDMI 2.1 port on any connecting hardware (TVs, soundbars) too.

HDMI 2.1 TV: what screens are out there?

The Sony AG8 OLED TV in a grey room

(Image credit: Sony)

2021 is the year that HDMI 2.1 went mainstream. The standard only received piecemeal support last year on a handful of high-end sets, often with only one HDMI 2.1 port with two or three HDMI 2.0 ports alongside.

That's still the case with some manufacturers (the Sony A90J OLED features a mix of 2.1 and 2.0 inputs), while others are going all-in on HDMI 2.1 ports on their premium TV ranges. Both LG and Samsung are in this latter camp, and you can expect up to four HDMI 2.1 ports on select sets.

Sony was surprisingly slow to incorporate the standard, given it was also behind the PS5 consoles, only bringing HDMI 2.1 to two Sony TVs last year – through an over-the-air firmware update. But now there are some solid options from Sony if you're looking for HDMI 2.1 ports, like the Sony X90J, a native 120Hz TV with two full-spec HDMI 2.1 ports for the Xbox Series X and PS5.

LG was a big early adopter, with the LG CX OLED featuring four HDMI 2.1 ports – though at 10-bit 4K/120Hz passthrough rather than the full 12-bit. This shouldn't really affect your picture onscreen, given that the CX only has a 10-bit panel anyway. 

Although the best TV that's set to come out of 2021 from LG – and one of the best overall, too – is the LG C1 OLED TV, with four HDMI 2.1 ports that support 4K at 144Hz, plus you’ve got three USBs, RF tuner, Wi-Fi, Bluetooth and optical digital audio output. Last but not least, one of the HDMI ports supports eARC/ARC, which is great for folks with an AVR or soundbar who don’t like to have more than one remote in use. There are other LG TVs that support the full 12-bit HDMI too, such as the ZX OLED.

When it comes to Samsung, you'll find HMDI 2.1 in a handful of sets from 2019 to the newest ones from the brand. This includes the Samsung QN85A, and Samsung QN90A Neo QLED TV that both came out in 2021. 

Other brands have HDMI 2.1 options as well, including the TCL 6-Series 2021 8K QLED TV and the Vizio P-Series Quantum X.

Jamie Carter originally contributed to this article.

Henry St Leger

Henry is TechRadar's News & Features Editor, covering the stories of the day with verve, moxie, and aplomb. He's spent the past three years reporting on TVs, projectors and smart speakers as well as gaming and VR – including a stint as the website's Home Cinema Editor – and has been interviewed live on both BBC World News and Channel News Asia, discussing the future of transport and 4K resolution televisions respectively. As a graduate of English Literature and persistent theatre enthusiast, he'll usually be found forcing Shakespeare puns into his technology articles, which he thinks is what the Bard would have wanted. Bylines include Edge, T3, and Little White Lies.