Which HDMI cable do I actually need?

HDMI carries a digital signal, which behaves quite differently from an old analogue one. There is no gradual softening with a cheaper cable: it works, or it produces sparkles, dropouts and black flashes, or it produces nothing. That is why the entire premium cable market for ordinary lengths is selling a difference that cannot exist, and why the only specification that matters is whether the cable is rated to carry what you are sending down it.

Step by step

1. Work out what you are actually sending.Ordinary high-definition broadcast and streaming need very little. A 4K picture needs more. A 4K picture at a high refresh rate for gaming, or with high dynamic range, needs considerably more again. The cable only has to meet the highest demand you will place on it.
2. Buy by the rating name, not the marketing.The tiers are named — high speed, premium high speed, ultra high speed — and each corresponds to a defined bandwidth. Certified cables carry a label or a scannable mark. Terms like 'gold plated' and version numbers printed on packaging are not the rating.
3. Ignore the version number on the box.Cables are not versioned in a meaningful way; the standard's version numbers describe features of the equipment at each end. A cable is only ever a pipe of a certain capacity, which is what the speed rating states.
4. Keep it as short as the layout allows.Bandwidth is harder to sustain over distance. Under about two metres almost any properly rated cable is reliable. Beyond five metres at high bandwidth, look for an active or optical cable designed for the run.
5. Use the right socket at the television end.A perfect cable in a slower socket still gives the slower result. On many sets only one or two of the HDMI sockets support the highest bandwidth, and only one supports the audio return channel.
6. Enable the enhanced input mode if the picture is missing features.Many televisions ship with the higher-bandwidth mode switched off per input, under a name like enhanced or deep colour, because older equipment can be confused by it. If a console reports it cannot use its best output, this setting is a frequent cause.
7. Test before buying anything.Swap in a cable you know is good and see whether the symptom changes. Sparkling white dots, momentary black frames and audio dropouts are all classic marginal-bandwidth symptoms and are cheap to confirm.

Tips

• Cables bundled with equipment are usually adequate for that equipment's own output, which makes them a reasonable free test.
• If a cable has to go through a wall or under a floor, buy one rated a tier above what you need now. The cost difference is small and replacing an in-wall cable is not.
• Where a cable must run a long way, an active optical HDMI cable is directional — the ends are marked, and fitting it the wrong way round produces no picture at all.

Common mistakes

• Paying a large premium for a short cable — A digital signal either arrives or does not. Once a cable meets the required rating, a more expensive one carries exactly the same picture.
• Assuming a cable fault when the socket is the limit — The socket, the setting on that input, and the equipment at both ends all cap the result independently of the cable. Check those before spending.

If it doesn't work

Questions people ask