What is HDR on a television and do I actually need it?

HDR expands the range between the darkest and brightest parts of an image, and widens the range of colours available. It is a more meaningful improvement than resolution for most content, because the eye responds more to contrast and colour than to pixel count at normal viewing distances.

The important caveat is that HDR is only as good as the display implementing it. Supporting the format and being capable of showing it are different things. A television that accepts an HDR signal but cannot get bright enough, or lacks the contrast control to render dark detail, produces an image that is often worse than the standard version, because the content was mastered assuming capabilities the screen does not have. Inexpensive sets advertising HDR support frequently fall into this category.

What to look for is peak brightness and contrast capability rather than the badge. Displays with per-pixel light control or many local dimming zones deliver it convincingly; edge-lit panels with few zones generally do not.

There are several competing formats. One is the baseline that everything supports. Others add scene-by-scene adjustment, which helps more on displays that cannot reach the brightness the content assumes. Content availability varies by format and service, and this is worth checking against what you actually watch rather than treating more formats as automatically better.

You also need the whole chain to support it: the source, any receiver or switch in between, the cable, and the display. A single link that does not pass it through silently downgrades the result, and this is a common reason people conclude HDR looks no different.

For most viewers a good standard picture beats a poor HDR one.