What is HDMI 2.1?

HDMI 2.1 is the new standard in the world of connecting cables. Here's what it can bring to your TV or gaming setup.
A TV on an entertainment console, where you'll need to figure out what HDMI 2.1 is and why it matters.
HDMI 2.1 is the newest version of the port and cable that we use to plug our TVs in streaming devices, sound bars, game consoles, and more. Jens Kreuter / Unsplash

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HDMI 2.1 is the latest widely available version of HDMI, the high definition audio/video interface that’s been the gold standard for connecting media sources to your TV since the mid-2000s. Since then, there’s rarely been a need to upgrade your HDMI cables, but if you want to display the highest quality footage on your television as this technology advances, you might need to.

Although the HDMI port itself hasn’t physically changed over time, newer versions of the standard have been introduced, enhancing the connection’s ability to support higher resolutions and frame rates. So while the port is identical, a TV with HDMI 2.0 might not support the same features as one with HDMI 2.1. It can be confusing, because while you can find HDMI 2.1 ports on the latest and greatest televisions, A/V receivers, projectors, and video game consoles, companies don’t always distinguish which version of HDMI their device supports.

We’re here to clear up what HDMI 2.1 brings to the TV stand, to explain how to tell if you have it, and give you a basic understanding of the interface standard in general. 

HDMI basics

High-Definition Multimedia Interface (HDMI) is an audio/visual standard capable of transmitting audio and video through a single cable. Look behind your television, and chances are it has an HDMI port (or four). Since its introduction in 2002, HDMI has been a mainstay in households across the globe, with an estimated 10 billion HDMI devices sold (although it took some time to truly take off). 

Over the past 20-plus years, the amount of data that HDMI cables can transmit has steadily increased: The original version could only send up to 4.95 gigabits per second (Gbps), which allowed for 1080p video at 60Hz. Today, HDMI 2.1 can carry almost 10 times that amount.

HDMI 2.1 cable.
You probably can’t tell just by looking at it, but this is an HDMI 2.1 cable! Mike Epstein for Popular Science

What is HDMI 2.1?

In 2017, the HDMI Forum unveiled HDMI 2.1, which has a maximum data throughput of 48 Gbps. This allows it to support 4K, 5K, 8K, and 10K content at up to 120 frames per second. It’s the current high bar you’ll find in new TVs.

Colorwise, HDMI 2.1 supports 16-bit color and HDR, just like its predecessors HDMI 2.0a and HDMI 2.0b. But HDMI 2.1 offers significantly more support for dynamic HDR, where the color settings can be automatically adjusted on a scene-by-scene or even frame-by-frame basis to get the best possible color range. 

HDMI 2.1 also supports a number of other features that can improve your media viewing experience, including:

  • Quick media switching (QMS): This feature reduces the time it takes to swap between sources, eliminating a 1-to-3-second blackout that would otherwise occur when switching from one video source to another with a different frame rate.
  • Enhanced Audio Return Channel (eARC): The latest implementation of this feature allows for your TV to send higher quality audio directly to a sound bar or A/V receiver. All your connected devices can now communicate directly, making it easier to keep video signals and audio signals in sync. This is compatible with formats like Dolby Atmos and DTS:X.

Beyond that, HDMI 2.1 also offers a number of upgrades to your gaming experience:

  • Variable refresh rate (VRR): This feature allows for smoother transitions between different frame rates, so you are less likely to see any juddering or frame tearing if your frame rate changes as you play a video game.
  • Quick frame transport (QFT): Simply put, this reduces the time it takes for video footage to pass from a source to your display, which will also reduce lag when you’re gaming.
  • Auto low-latency mode (ALLM): If you’re using a gaming console or PC, ALLM can automatically turn off any picture processing to reduce lag even more.

Confusingly, just because a TV includes HDMI 2.1 doesn’t mean it supports every feature mentioned above. For example, a TV with an HDMI 2.1 port may support eARC, but not VRR. This inconsistency is not only frustrating for consumers, but could also make HDMI 2.1 adoption really messy.

When looking for an HDMI 2.1-equipped TV, pay close attention to the features it supports. Some manufacturers aren’t very transparent about this, so you may want to keep looking until you’re absolutely certain you know what’s included. Hopefully, as newer TVs are released, we’ll get more transparency, and more TVs with HDMI 2.1 will support many or all of the features introduced by the latest standard. 

What devices use HDMI 2.1 now?

HDMI 2.1 ports are available on most high-end TVs and A/V devices. 

The latest generation of video game consoles—the PlayStation 5, Xbox Series X, and Xbox Series S—support HDMI 2.1. They are one of the few widely available sources of the 4K, 120fps video that requires the bandwidth HDMI 2.1 offers.

So, while there’s no need to rush out and get a new TV, chances are that if you upgrade at some point in the next few years, it will have HDMI 2.1 as standard. And over time, as more high resolution, high-frame rate, HDR content becomes available, having a device with HDMI 2.1 will become more important.

Does HDMI 2.0 even matter anymore?

We’ve mentioned HDMI 2.0 a few times now, so let’s get this out of the way: This older version of the standard doesn’t have the bandwidth to support modern high-resolution, high-frame, HDR content.

HDMI 2.0 was released in 2013 and had a maximum data throughput of 18 Gbps, about 63 percent less capacity than HDMI 2.1. That was fast enough to support 4K resolution video at 60 frames per second or 8K resolution at 30 frames per second. HDMI 2.0a and HDMI 2.0b later added support for high dynamic range (HDR) video. Today, that’s not enough.

How to tell if your device supports HDMI 2.1

Checking to see what version of HDMI you have is, sadly, more complicated than it should be. As we explained above, manufacturers aren’t always clear about what version of HDMI is supported, and because the connector doesn’t physically look different, you can’t easily figure out what you have. As a general rule, though, unless you bought your TV within the last two or three years, chances are it supports HDMI 2.0—not HDMI 2.1.

First, check your device’s manual to see if it mentions support for HDMI 2.1. Some product listings on Amazon and other retailers will highlight HDMI 2.1, but it might only be supported in one or two ports out of the three or four your TV has. To check which specific ports are HDMI 2.1, look for some mention of “4K@120fps.” Even TVs with only HDMI 2.1 ports should note the distinction.

An HDMI 2.1 port on an LG C1 TV.
New TVs mark HDMI 2.1 ports, noting that they support “4K@120Hz.” LG

Do I need new HDMI cables?

If you have HDMI 2.0 cables, they won’t be sufficient for HDMI 2.1. To enjoy the enhanced picture and frame rate that HDMI 2.1 enables, you will need both an HDMI 2.1 TV and an HDMI 2.1 source device, as well as an HDMI 2.1 or ultra high-speed HDMI cable. 

These new cables come with the ultra high-speed HDMI logo printed on them as well as a holographic image and QR code that proves they are genuine and lists the exact HDMI 2.1 features it supports. If you need help choosing one, our gear and reviews team has curated a selection of the best HDMI cables currently available.

Thankfully, many devices that support high frame rate modes, including the PS5 and Xbox Series X, come with the proper cable, so you may not need to buy one after all.

Do I need a new TV?

HDMI 2.1 is a technology with its eye on the future. If you’re in the market for a new TV and want the best of the best, we recommend you get one with at least one HDMI 2.1 port, especially if you’re into gaming. This may cost a little more money, but we believe it will be a crucial feature for many of the ways we will use TVs going forward, particularly if you plan to connect any device other than a cable box to your TV.

That said, while we think it’s smart to prioritize the feature if you’re buying a new TV, there’s no need to rush out and replace the 4K TV you just bought to play some games in 4K at 120 Hz.

What about HDMI 2.1a?

HDMI 2.1 is still taking off, but HDMI 2.1a has already been announced. It adds support for source-based tone mapping (SBTM) which allows for HDR and standard dynamic range (SDR) footage to be displayed at the same time without issue. This comes in handy, for example, if you are watching a live stream with HDR video game footage and SDR picture-in-picture commentary

As of right now, though, HDMI 2.1a products are not widely available.

This story has been updated. It was originally published on March 19, 2022.