HDMI cable 4K guide - Which cable do you really need?

It wasn't too long ago that HDMI 2.0 was announced. Shortly thereafter, the HDMI 2.0a, HDMI 2.0b and HDMI 2.1 versions followed. What confusion had settled in the past regarding the HDMI standard is now boiling up again - more complicated than ever. So: what should you know about these connections now? Let's try to explain it in simple terms:

HDMI 2.0, HDMI 2.0a, or HDMI 2.0b - simply explained!

What is the relevance of new HDMI versions in general?
HDMI versions were and are basically designed as internal version designations for manufacturers of HDMI compatible devices and should not really matter to the end user. The HDMI Licensing Org. itself has pointed out several times that the use of version designations is more likely to irritate consumers than help them. TV manufacturers have recognized this and are often very reluctant to provide detailed version designations for HDMI inputs. Cable manufacturers, on the other hand, often just flaunt supported HDMI versions.

So why should you care?
The arms race started at the latest when Apple announced the first Mac Pros with quadruple 4K Ultra HD support. Today, an entire industry has jumped on the trend, offering 4K displays for home theater and computers. And once again, the industry is faster than the market. Many users are still asking themselves? What is 4K anyway? Why do we need it? And most importantly? What new hardware is required? For example, are there special HDMI cables 4k?

4K - Technical hurdles for HDMI cables
It doesn't matter if it's 4k, 4K2K, 4K Ultra HD or 2160p. All of these essentially mean the same thing: super high-definition television. Those who always thought HD was the measure of all things are now being taught better with 4K.

Attention alphabet soup: 4K, 4K2K, Ultra High Definition, Ultra HD, UHD, Quad Full HD, QFD, 2160p - All this means essentially the same thing: Namely, the next generation of HD (we'll just say "4K" for simplicity's sake), which offers quad HD resolution with a maximum resolution of 4,096 x 2,160 = about 8 million pixels. In order to be able to process all this information, the corresponding hardware is required.

Not only the TV must be able to deliver this number of pixels (which can essentially be realized via the size), but also the installed hardware (graphics cards) and software (drivers) must first be able to handle this amount of information. Especially the HDMI cables, which have a special responsibility at the interface between the 4K source and the high-end TV. Are they even the bottleneck in the whole thing?

Can all HDMI cables handle 4K (Ultra HD)?
To cut a long story short: No, not all HDMI cables support 4k. If you want to be sure, it's better to go for an HDMI high-speed cable with a premium label. But more on that in a moment. First a short look back:

After the abolition of version numbers, HDMI cables were divided into so-called standard HDMI cables and high-speed HDMI cables. Both types differ mainly in their maximum transfer rates (read more about the HDMI cable differences here).

Standard HDMI cable: 1.782 GBit/s (74.25 MHz × 8 bit × 3, type A)
Highspeed HDMI cable: 8.16 GBit/s (340 MHz × 8 bit × 3, type A + C)
As you can easily see, high-speed HDMI cables are significantly more powerful than standard HDMI cables. The majority of HDMI cables sold today in the home theater sector already comply with the high-speed standard.

HDMI Cable Standards
Logos of the individual standards for HDMI cables. Below in blue: HDMI Highspeed
HDMI Highspeed was already developed with 4K Ultra HD in mind. All HDMI cables that carry the HDMI Highspeed logo are basically suitable for HDMI 2.0 and can therefore fully transmit the high resolutions of 4096×2160p. This is also officially confirmed by the HDMI Licensing Organization:

All High Speed HDMI cables will support 4K functionality when connected to 4K devices. hdmi.org

Conversely, this also means that HDMI cables that are not explicitly labeled "High Speed HDMI" may not be able to transmit the high data rates of 4K.

Do all HDMI high-speed cables really provide enough bandwidth for HDMI 2.0?
And here comes exactly the problem: Up to now, a bandwidth of only 10.2 Gbit/s was required for HDMI Highspeed certification. HDMI 2.0, however, requires 18 Gbit/s. According to HDMI Org. all this is no problem, because:

HDMI 2.0 specification defined a new, more efficient signaling method, for speeds above 1.4b limits (10.2Gbps), to allow higher bandwidths (up to 18Gbps) over existing High Speed HDMI Wire Cables. - hdmi.org

In reality, however, not all HDMI high-speed cables support the HDMI 2.0 (2.0a / 2.0b) version 100%.

In terms of 4K and highspeed HDMI, this means that there are those cables that fully support HDMI 2.0 (i.e. 18 Gbit/s, 4K at 60Hz, HDR) and those cables that only deliver "narrow-gauge" HDMI 2.0 (i.e. 10.2 Gbit/s, 4K at 24Hz, no HDR). At frame rates of 60Hz, the latter cables drop out and do not transmit any image.

So how do I recognize a suitable high-speed HDMI cable for 4K Ultra HD?
To be found in stores from 2016: "Premium Highspeed HDMI Cable" for 4K systems.
Premium Highspeed HDMI Cable for 4K
After this reality check, the HDMI Org. has rowed back and announced a so-called Premium Highspeed HDMI label, which distinguishes such HDMI cables that support higher HDMI 2.0 requirements.

Premium-labeled HDMI cables guarantee performance rates of up to 18 Gbps and all HDMI 2.0b features, such as HDMI HDR.

Premium cables are tested in so-called ATC (authorized test centers) for these features before they receive the label. They are a bit expensive compared to "normal" HDMI highspeed cables, but guarantee unadulterated HDMI 2.0(a/b) pleasure.

What can I do now? If you want to be on the safe side when it comes to HDMI 4K or if you want to use future-proof hardware, you should choose an HDMI cable 4K with a premium label.

If you want to save some money, reach for a slightly cheaper high-speed cable without Premium Label - this can also, but does not have to, work with all HDMI 2.0(b) features.

What about HDMI cables of version 1.3, 1.4, etc.?
Those version designations were done away with a few years ago. The problem then (and now) was that these version numbers actually have no relevance to end users. They merely indicate the range of possibilities that cable manufacturers can equip their HDMI cables with, but do not represent any kind of obligation.

4K support came with HDMI standard 1.4, so for all owners of HDMI cables labeled 1.3, that means a new cable will most likely need to be purchased. For HDMI cables labeled 1.4, you can assume that 4k Ultra HD resolutions are supported at least at 24 Hz. If in doubt, the rule here is: Try it out!

HDMI versions vs. HDMI cable 4K
If your cable has no classification according to standard / highspeed, but only version number, then the 4K support behaves as a rule of thumb as follows:

HDMI cable 1.0 - 1.2 - No 4K Ultra HD support
HDMI cable 1.3 - 4K Ultra HD support rather unlikely
HDMI cable 1.4 - 4K Ultra HD support very likely
HDMI Highspeed Cable - Assured 4K Ultra HD support at frame rates of 24 Hz.
HDMI Highspeed Cable with Premium Label - Secure 4K Ultra HD support at 60Hz and extended color gamut HDR.
Conclusion: Not everything that costs a lot is Premium
4K (= 4k2k, UltraHD, 4K Ultra HD) transmits four times the HD resolution and places special demands on HDMI cables. If you use an HDMI cable with premium label, you are on the safe side. Highspeed cables without premium label can also work - but do not have to.