4K (2160p)

What is 4K?

4K is video roughly four thousand pixels wide. In consumer and web video that means 3840×2160 — also written 2160p, and marketed as Ultra HD or UHD. It is exactly double 1080p in each direction, which is why it holds four times the pixels rather than two.

Cinema 4K is a slightly different frame: 4096×2160, the DCI standard used in production and projection. The two are used interchangeably in marketing copy, but a 4096-wide master will be letterboxed or cropped to fit a 3840-wide delivery ladder.

4K dimensions and pixel count

Four times the pixels of 1080p1080p (Full HD)Full HD at 1920×1080 — just over two million pixels. The default target for course, sales and web video.Open definition → and twenty times those of 480p480pStandard-definition video, 480 pixels tall — 854×480 in 16:9. The fallback rung of the adaptive ladder for slow or metered connections.Open definition → — which is also roughly the ratio of what it costs to store and deliver.

Bandwidth and data

With H.264, 4K typically needs 20–35 Mbps — roughly 9–16 GB per hour of viewing. That is where the arithmetic stops being academic: an hour of 4K costs about as much delivery as four hours of 1080p1080p (Full HD)Full HD at 1920×1080 — just over two million pixels. The default target for course, sales and web video.Open definition →.

This is the resolution at which codecCodecThe algorithm that compresses and decompresses video — H.264, H.265 (HEVC) and AV1 are the most common in modern streaming.Open definition → choice pays for itself. H.265 or AV1 hold the same quality at roughly half the bitrateBitrateThe amount of data used per second of video. Higher bitrate means more detail and a larger file; the core lever behind streaming quality.Open definition →, and most devices capable of playing 4K also support them — so the compatibility argument that keeps H.264 alive at lower resolutions carries much less weight up here.

When 4K is worth it

The honest answer for most web video is: less often than people expect. Whether anyone sees the difference depends on screen size and viewing distance, not on the number in the settings menu.

One case is unambiguous though: shoot in 4K even when you deliver 1080p. A downscaled 4K master is cleaner than native 1080p, and it leaves room to crop or reframe without losing detail.

Why protected 4K sometimes refuses to play

4K is the one rung where the viewer\'s cable can veto delivery. HDCPHDCPLink-level encryption between a video source and the display over HDMI or DisplayPort — the layer that blocks a capture card placed in between.Open definition → encrypts the link between a device and its display, and protected 4K generally requires HDCP 2.2 or later. HDCP 1.4 is enough for 1080p but not for this.

That is why the same source can feed 1080p to an older television and go black at 4K, and why an inexpensive HDMI splitter or a docking station in the chain produces the same failure. The player is not at fault, and neither is the encode.

Paired with the WidevineMulti-DRMServing one encrypted library through Widevine, FairPlay and PlayReady at once — no single DRM system covers every browser and device.Open definition → L1 requirement on the device side, protected 4K needs both halves to hold: hardware decryption in the device and an HDCP-clean output. On a general audience, plenty of viewers have neither.

The economics of the top rung

At 20–35 Mbps an hour of 4K moves roughly 9–16 GB. At €0.03 per GB that is 27–48 cents per viewing hour — around ten times 720p720pHigh definition at 1280×720 — 921,600 pixels per frame. The entry point to HD and the fallback rung below Full HD.Open definition → for a difference most viewers on a laptop or phone cannot resolve.

4K also costs at the other end. TranscodingTranscodingRe-encoding a source video into multiple resolutions and bitrates so a player can switch between quality levels on the fly.Open definition → is billed per minute of source, and a 4K master takes longer to process than the same footage at 1080p, so the top rung shows up on the invoice before a single viewer has watched it.

Where it pays is content with genuine fine detail on a large screen: product photography, medical and technical footage, anything intended for a television. For a webinar it is a rung almost nobody will be served and everybody will be billed for.

Further reading

• 4K resolution — Wikipedia — a vendor-neutral overview.
• Resolution — the full ladder, from 360p to 4K.
• 1080p — the rung below, and the right default for most video.

Written by

Denis Konnov Verified

CMO at Kinescope

Denis leads marketing and content at Kinescope, working closely with the platform's engineers. This glossary is reviewed and kept up to date by the team building Kinescope's streaming, encoding and CDN delivery infrastructure.