HD (High Definition)

What is high definition?

HD, high definition, is video at 720p (1280×720) or higher. 720p720pHigh definition at 1280×720 — 921,600 pixels per frame. The entry point to HD and the fallback rung below Full HD.Open definition → is the entry point — the reason older TVs were sold as "HD ready" — and 1080p1080p (Full HD)Full HD at 1920×1080 — just over two million pixels. The default target for course, sales and web video.Open definition → (1920×1080) is Full HD, the resolution most web video actually targets.

The label separates modern video from the standard-definitionSD (Standard Definition)Standard definition — video below the HD line, in practice 480p (854×480) or smaller. The fallback tier of the resolution ladder.Open definition → broadcast and DVD era below it. Above HD sits 4K4K (2160p)Ultra HD at 3840×2160 — four times the pixels of Full HD, and the point where codec choice starts paying for itself.Open definition → (2160p), which some marketing calls Ultra HD.

HD in the resolution ladder

HD is a band, not a single number — it covers the two rungs most people watch on:

720p and 1080p are both HD; 1080p is specifically "Full HD". Below is SDSD (Standard Definition)Standard definition — video below the HD line, in practice 480p (854×480) or smaller. The fallback tier of the resolution ladder.Open definition →, above is 4K4K (2160p)Ultra HD at 3840×2160 — four times the pixels of Full HD, and the point where codec choice starts paying for itself.Open definition →.

HD against SD and 4K

HD is the sweet spot: a clear step up from SD, without the bandwidth cost of 4K that most screens cannot show off anyway.

The SD→HD jump is the one viewers notice; the HD→4K jump is visible only on large screens viewed close. For most course, webinar and sales video, Full HD is the right target.

What HD costs to deliver

With H.264, 720p needs roughly 2.5–4 Mbps and 1080p 5–8 Mbps — about 1.1–1.8 GB and 2.25–3.6 GB per hour respectively. A modern codecCodecThe algorithm that compresses and decompresses video — H.264, H.265 (HEVC) and AV1 are the most common in modern streaming.Open definition → (H.265 or AV1) holds the same look 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 →.

You do not pick a single figure, though: adaptive bitrateAdaptive Bitrate (ABR)Automatically adjusts video quality in real time to match each viewer’s connection speed — smooth playback from 480p to 4K with no buffering.Open definition → encodes several HD renditions and the player switches between them as the connection changes.

Why "HD" is a poor thing to promise

HD covers two rungs with a two-fold gap in what they cost to deliver. 720p720pHigh definition at 1280×720 — 921,600 pixels per frame. The entry point to HD and the fallback rung below Full HD.Open definition → runs about 1.1–1.8 GB per hour, 1080p1080p (Full HD)Full HD at 1920×1080 — just over two million pixels. The default target for course, sales and web video.Open definition → about 2.25–3.6 GB — roughly 3–5 cents against 7–11 cents per viewing hour at €0.03 per GB.

So "we deliver in HD" is not a specification. In a contract or an RFP it can mean either rung, and the difference across a large catalogue is the difference between one delivery bill and two. Name the number instead: 720p or 1080p.

The same ambiguity runs the other way when protection is involved. A DRM policy that requires WidevineMulti-DRMServing one encrypted library through Widevine, FairPlay and PlayReady at once — no single DRM system covers every browser and device.Open definition → L1 for 1080p will still serve 720p to software-decrypting devices — both are honestly "HD", and the viewer receives the lower one.

Further reading

• High-definition video — Wikipedia — a vendor-neutral overview.
• SD (standard definition) — the tier below.
• 720p, 1080p and 4K — the numbers behind the labels.

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.