4K HDMI cable: which one to buy, or none at all

For 4K at 60 frames per second with HDR, you need a certified Premium High Speed HDMI cable, which means 18 Gbps. For a console at 4K 120 Hz or a soundbar over eARC, look at Ultra High Speed. And if your TV already shows 4K, change nothing.

Which HDMI cable do you need for 4K?

It depends on the frame rate, not only the resolution. HDMI.org, the body that manages the standard, sorts its cables into four categories, and that category is what counts, not the version number printed on the box.

Source: HDMI.org, cables page, checked 14 October 2026. Bandwidths are those published by the body.

A back-of-envelope calculation sheds light on these figures. A 4K picture at 60 Hz in 8-bit, with the standard's synchronisation margins (4,400 by 2,250 points), needs roughly 17.8 Gbps once encoded. 4K at 30 Hz needs 8.9. The first figure sits right under the 18 Gbps of Premium High Speed, with one point of headroom. Calculated 14 October 2026, an estimate, not a bench test.

Hence the rule. Below the right category, the TV does not always complain: it flickers.

Should you replace the cable that came with the decoder?

Not before looking at the screen.

Proximus's TV Box Android page (Proximus runs its own copper, fibre and mobile networks) advertises 4K Ultra HD and HDR, and says you need a 4K TV, 4K content and at least 23 Mbps. The manual says to connect the box to the TV with an HDMI cable. It does not say whether that cable is in the box, nor which HDMI version the box uses (checked 14 October 2026).

Here is the test, which takes two minutes. Start a programme advertised in 4K, open the TV's info banner and read the resolution and HDR mode. If you read 3,840 x 2,160 and HDR, keep the cable. Replace it only if the picture is capped at HD or flickers.

For a second TV the question changes nature: a second TV Box rents for €9 a month at Proximus, or €216 over 24 months, far more than a cable. Our guide to the second Proximus decoder prices the trade-off, and the one on Android TV boxes gives the other route.

Why does everyone talk about HDMI 2.1 for 4K?

Because manufacturers have blurred port version and cable category, and the result confuses everyone. The 2.1 port on the TV is a capability. The Ultra High Speed cable is what lets you use it.

It only matters in two cases: a console outputting 4K at 120 Hz, or a PC plugged into the TV. For watching a Belgian operator's decoder, neither applies. A Premium High Speed cable covers 4K at 60 Hz with HDR, and that is all television asks.

Same verdict for the "8K cable" sold at a premium: the Proximus TV Box page advertises 4K, not 8K. Paying for the most expensive cable "to be safe" means buying bandwidth your living room will never use.

HDMI ARC, eARC or optical: which cable for a soundbar?

The cable is not the real issue, the port is. ARC sends the TV's sound back to the soundbar over a single HDMI cable, and eARC is its much higher-bandwidth version. HDMI.org states that eARC supports DTS-HD Master Audio, DTS:X, Dolby TrueHD and Dolby Atmos, up to 192 kHz at 24 bits.

The result is surprising. According to Sony France's support page, high-speed HDMI cables with Ethernet are enough for eARC, and Ultra High Speed works too without being mandatory. In other words, you spend less on a soundbar setup than you might think. The optical output does not carry those high-bitrate formats.

Plug into the TV port marked ARC or eARC. The others do not send sound back.

How do you recognise a certified cable?

Look at the packaging, before the price and before the brand.

• The category spelled out: High Speed, Premium High Speed or Ultra High Speed. A "4K cable" with nothing else is not a certification.
• The scannable label on Ultra High Speed cables: HDMI.org says it can be checked with its cable verification app.
• The length: certification applies to the length tested.
• The manufacturer: Belkin, UGREEN and others sell cables in several categories. A known brand does not excuse you from reading the category, and we have tested none of these cables.
• The absence of a numeric promise that HDMI.org does not recognise, such as "4K HDR 8K" with no category.

To buy, the usual Belgian retailers (Coolblue, MediaMarkt, Krëfel) and Amazon all stock every category. No affiliate link here, and no price quoted: I did not check any specific cable listing for this guide.

Which cable for which situation?

The trap to avoid: the "4K" cable with no category

A cable sold as "4K" with no category may be a plain High Speed one, so 4K at 30 frames per second. For a film, that passes. For a football match, the difference shows the first time the ball crosses the screen.

To see TV plans and the prices that go with these screens, the ranking of Belgian bundles remains the reference page.

Sources: Proximus TV Box Android page and TV Box manual (checked 14 October 2026), HDMI.org, HDMI cables, HDMI.org, Ultra High Speed, HDMI.org, eARC, Sony France, ARC and eARC support, LDLC (4K HDMI cable buying guide).