What does HDMI 2.1 Mean?

Virtually all current video monitors and TVs leave the factory with at least one HDMI port. But this type of connection is not a single standard: to meet the growing demand for high-resolution video and high-quality audio, the industry improves HDMI from time to time. One such improvement is HDMI 2.1.

HDMI 2.1

HDMI 2.1 maintains the same connectors as previous versions, but brings several small innovations that, together, considerably improve the experience of using a TV or video monitor.

Before, what is HDMI?

According to AbbreviationFinder, HDMI stands for High-Definition Multimedia Interface , HDMI consists of a connection standard for transmitting video and audio over a single cable.

In other words, with HDMI you can connect cameras, cell phones, computers, video games, TV receivers, Blu-ray players and other devices to your TV, video monitor or projector using a cable that transmits both image and audio – in previous standards, it was necessary to have a cable for each thing.

Also take into account that HDMI is a standard focused on high definition, which means that the transmitted content can have excellent image and sound quality. This is where HDMI 2.1 starts to make a difference.

What is HDMI 2.1?

The first version of HDMI, 1.0, appeared in 2002. Since then, the technology has undergone several revisions, always with the aim of bringing improvements. HDMI 2.1 is one of them.

This version was announced at the beginning of 2017, including one of the highlights of the Consumer Electronics Show (CES) that year. The reason for this is its attributes: HDMI 2.1 allows, for example, the transmission of videos in very high resolutions, such as 4K and 8K .

In addition, HDMI 2.1 has a high bandwidth: up to 48 Gb/s (gigabits per second). Just to make a comparison, the previous version, HDMI 2.0 , handles up to 18 Gb/s.

But these are just some of the characteristics. We will know more details about HDMI 2.1 in the next topics, starting with the supported resolutions.

HDMI 2.1 resolutions: up to 10K

When this text was being written, resolutions HD (720p), full HD (1080p) and 4K were quite common in TVs and video monitors. While these standards are expected to remain the mainstay in the market for quite some time, the industry is already paving the way for even more generous resolutions.

HDMI 2.1 is capable of meeting this demand. Here are the main resolutions of the technology, according to the HDMI Licensing Administrator (lower resolutions than these are also supported, of course):

  • 4K50/60
  • 4K100/120
  • 5K50/60
  • 5K100/120
  • 8K50/60
  • 8K100/120
  • 10K50/60
  • 10K100/120

If you didn’t understand any of these numbers, here’s a quick explanation using the 8K50/60 resolution as an example: it indicates that the technology is compatible with 8K transmissions, but with frequencies that can range from 50 to 60 Hz, which means that the screen displays 50 or 60 images (also called frames) per second.

Likewise, 10K100/120 resolution indicates that the transmission supports 10K resolution at frequencies of 100 and 120 Hz per second.

HDMI eARC (enhanced ARC)

As you already know, HDMI is also capable of transmitting audio. Thanks to this, you do not need to have one cable for video and another for sound only, as in old transmission technologies. EARC (enhanced ARC) is related to this capability.

First, we need to know what ARC is. It is an acronym for Audio Return Channel or, in free translation, Audio Return Channel . With this technology, TVs, signal receivers, video games and the like can share sound equipment via HDMI.

Suppose, for example, that you have a Nintendo Switch and a soundbar connected to your TV. Thanks to HDMI ARC, you can make the video game sound play on the soundbar instead of over the television’s speakers.

All you have to do is connect the audio equipment to the HDMI ARC connection on the TV. The most interesting thing is that this standard is compatible with high quality audio provided by standards such as Dolby Digital 5.1 and DTS .

But what about HDMI eARC? ARC came up with HDMI 1.4 . EARC appeared on HDMI 2.1 as an extension of the technology. Basically, what it does is it supports even more advanced audio standards, including those that are not compressed or that generate 3D effect (as if the sound originated in the environment you are in).

Standards compatible with eARC include Dolby TrueHD and DTS-HD Master Audio.

VRR (Variable Refresh Rate)

HDMI 2.1 is compatible with VRR (Variable Refresh Rate), a subject that mainly interests players on duty. It is not difficult to understand why.

As was made clear in the topic on resolutions, video monitors and TVs can work with different frame rates (or frames) per second. However, it is common for the frame rate to fluctuate considerably in games, especially in the heavier ones.

Well, VRR is a generic term for a type of technique that allows the screen to work with dynamic frame rates per second. With that, the rates generated by the video card for running the game are now synchronized with the rates on the screen, which helps to avoid visual discomfort for the player and makes the game experience more fluid, so to speak.

ALLM (Auto Low Latency Mode)

Imagine that you installed a video game on your TV, such as Xbox One. When you execute a command to, for example, access a game setup menu, there will be a time lag between sending this information through the console and playing it on the screen. Well, this interval is what is known as latency , basically.

The lower the latency, the better. What ALLM (Auto Low Latency Mode) does is allow the TV or monitor to be automatically configured to enter a low latency mode which, as such, will reduce the delay in displaying the content as much as possible.

The TV or monitor must support HDMI 2.1 to have ALLM, but this specification must also be present on the device that sends the content to the screen.

QFT (Quick Frame Transport)

QFT (Quick Frame Transport) is another technique that aims to decrease latency, being useful mainly for games, therefore. This is done, essentially, through a faster transmission of the frames (or frames) from the device emitting the image (such as a video game) to the screen.

In addition to games, QFT is very useful to prevent loss of fluidity in virtual reality applications.

QMS (Quick Media Switching)

QMS (Quick Media Switching) is useful to avoid those black or white screens that appear before the content is displayed. This problem can occur when you switch between different videos on a streaming service, for example.

Under these circumstances, each video may have been made available with different refresh rates. Thus, when switching between one video and another, the TV or monitor needs to perform a new synchronization, which makes the device not display any content for a few moments.

Basically, QMS triggers VRR to eliminate this problem.

What is dynamic HDR?

Several TV models support High Dynamic Range or, simply, HDR. HDMI 2.1 equipment can go a little further by supporting Dynamic HDR or Dynamic HDR.

To know what we are talking about, first, you need to understand what HDR is. Well, in comparison with conventional screens, this is a pattern that reproduces a wider range of brightness and colors, in addition to more marked contrast. This means that HDR images are more vivid than videos that do not have this feature (that is, SDR – Standard Dynamic Range videos).

Just to give you an idea, HDR can allow bright spots in images to become even more intense, which contributes to a greater perception of depth. In addition, shades of colors such as blue, red and green take on such vibrant shades that they often look real.

But what about Dynamic HDR? This pattern follows the same principles, but more precisely. In a video, HDR parameters are not always applied properly, which makes certain scenes look excessively dark, for example.

With Dynamic HDR, it is possible to apply these parameters practically frame by frame with the right settings for each one, which further increases the sense of realism.

Dynamic HDR is supported by standards such as Dolby Vision and HDR10 +.

Ultra High Speed ​​HDMI Cable (48G)

At this point in the text, you already know that HDMI 2.1 supports very high resolutions, HDR streams and advanced audio standards. However, to take advantage of all of this, it is important to use an HDMI cable that is known to be compatible with these features.

These cables were named Ultra High Speed , but are also identified as 48G , a term that alludes to HDMI’s 48 Gb/s capacity.

Of course, you can use 48G cables on devices that have previous versions of HDMI (not least because the connectors have not changed from one version to another), but they were developed in accordance with the HDMI 2.1 definitions precisely to ensure that the connection on that standard works properly with the most different types of equipment.

As a rule, Ultra High Speed ​​cables are more expensive than less advanced cables, but they are usually worthwhile for those who have, for example, a 4K TV based on HDMI 2.1.


Despite being announced in 2017, HDMI 2.1 only started to appear consistently in devices released in mid-2019, which is not surprising: the industry takes some time to adopt new technologies.

In any case, HDMI 2.1 brings such significant advances over previous versions that, when established, it should remain a market standard for a long time.

It is not a mere whim: the growing demand for 4K TVs and the increase in high definition video streaming services are among the factors that, above all, make HDMI 2.1 a necessity.