4K Ultra HD

4K Ultra HD is a video resolution standard that delivers a significantly sharper, more detailed picture than standard Full HD. Here is what it means in plain terms.

What it is

4K Ultra HD — also written as UHD or 4K — refers to a screen resolution of 3,840 x 2,160 pixels. That works out at roughly 8 million pixels on your screen, which is four times the number you get with Full HD (1,920 x 1,080). The name "4K" comes from the width of the image being close to 4,000 pixels across.

What difference does it make?

More pixels means more detail. Edges look sharper, textures look richer, and fast-moving scenes stay clear rather than blurring. The improvement is most obvious on larger screens: on a big TV, a Full HD image can start to look soft because the gaps between pixels become visible, whereas 4K packs in enough detail to keep the picture crisp at any size.

Many 4K streams also come with HDR (High Dynamic Range), which works alongside the higher resolution to improve contrast — deeper blacks, brighter highlights, and more vivid colour.

What do you need to watch it?

Three things need to line up: a 4K-compatible display, a fast enough broadband connection, and a source of 4K content. Most modern smart TVs from brands such as Samsung, LG, and Sony support 4K. If your TV does not, a streaming stick such as the Amazon Fire TV Stick 4K or Apple TV 4K plugged into an HDMI port will do the job. Games consoles including the PlayStation 5 and Xbox Series X also support 4K streaming.

For broadband, the BBC recommends at least 24 Mbit/s for a full 4K stream via iPlayer, while Netflix suggests around 25 Mbit/s.

Where can you watch 4K content in the UK?

Netflix offers 4K on its Premium plan. BBC iPlayer carries a growing selection of programmes in 4K, including some live events, though the catalogue is still limited compared with subscription services. YouTube also hosts a range of 4K clips for free.

Do you need 4K content to use a 4K TV?

No. A 4K TV will still play HD programmes perfectly well, and many sets will upscale lower-resolution content to make it look better on the larger screen. 4K content simply lets you get the most out of a compatible display.