What is the difference between 1080p and 4K?

What the numbers count

A resolution is the size of the grid of pixels the video is drawn on. That is all it is. 1080p means the picture is 1080 pixels tall, on a grid 1920 across; 4K means roughly four thousand pixels across, on a grid 2160 tall. Everything else people attach to those labels is inference.

The trailing letter is not a unit. The p stands for progressive — every frame drawn complete, in order — as opposed to the interlaced broadcast formats it replaced. It has nothing to do with pixels, and there is no such thing as more p.

Here are the tiers you will actually be offered, with what each one is:

• 360p — 640 x 360. Small, soft, and mostly a fallback for a weak connection
• 480p — 854 x 480. Standard definition. Perfectly watchable on a phone, and the free tier in Savvy
• 720p — 1280 x 720. HD. The point at which on-screen text and fine detail become comfortable
• 1080p — 1920 x 1080. Full HD, and the practical ceiling for most social video
• 2K — usually 2560 x 1440 in apps like this, though the term is borrowed loosely from cinema, where 2K means something slightly different
• 4K — 3840 x 2160 for consumer video. Four times the pixels of 1080p, not twice, because both dimensions double

Bitrate is the number nobody shows you, and it matters more

If resolution is the size of the canvas, bitrate is how much paint is allowed per second. It is measured in bits per second, and it determines how much of the original detail survived compression.

Video compression works by throwing away information that is expensive to store and hard to notice: fine texture, subtle gradients, the differences between one frame and the next. How aggressively it throws that away is set by the bitrate. Give an encoder plenty and the result is close to the source. Starve it and it starts making visible compromises — blocky squares in dark areas, banding across smooth skies, faces turning to mush the moment somebody moves, detail dissolving in anything with rain, smoke, confetti or foliage in it.

This is why a well-encoded 1080p file routinely looks better than a badly encoded 4K one. The 4K version has four times as many pixels to fill; if it was not given proportionally more data to fill them with, each pixel is a worse guess than its 1080p counterpart. You get a larger, softer, blockier picture and a much larger file for it.

Two practical consequences follow. Resolution sets a ceiling on detail but does not deliver it, so a resolution label is a promise about the grid and not about the picture. And a video's difficulty matters: a static talking head survives a low bitrate almost unscathed, while a handheld shot of a crowd at night falls apart at the same setting. Same numbers, very different results.

• Blocking — visible squares, worst in dark and fast-moving areas. Classic symptom of too little bitrate
• Banding — smooth gradients breaking into stripes, most obvious in skies and studio backdrops
• Smearing — detail dissolving during movement and snapping back when the shot settles
• Softness at high resolution — the tell-tale sign of a big grid with not enough data behind it

Why the 4K option is often simply not there

A quality picker can only offer what exists. It is not a set of processing options; it is a list of the renditions the platform actually holds for that video. If the highest entry is 720p, that is the ceiling for that clip, and no setting anywhere will raise it.

There are three reasons a high tier goes missing, and they stack.

The creator never shot it that way. Plenty of well-made social video is filmed and exported at 1080p, deliberately, because that is what the format is watched at. There is no 4K master to serve.

The platform re-encoded the upload. This is the big one. Social platforms do not store what you give them; they transcode it into their own ladder of renditions, and they compress hard because they are serving billions of streams. Uploading a pristine 4K file does not guarantee a 4K rendition comes out the other end, and the encode is usually more aggressive for large files, poor upload connections and smaller accounts.

The video is old. Renditions get pruned, formats change, and something posted years ago may exist now only in whatever the platform kept.

Which leads to the rule that saves the most coins: downloading cannot add detail that was never uploaded. If the picker lists 720p as its top option, choosing a higher tier elsewhere is not an option you have. And where a higher tier is listed but the source was compressed on the way in, you get a bigger file of the same picture rather than a better one. Look at what the list contains before assuming what it should contain.

What any of this is worth on a phone screen

The uncomfortable answer for anyone selling resolution: on a phone held at normal distance, far less than the numbers suggest.

What your eye can actually resolve depends on how much of your field of view the screen occupies — a function of its size and how far away it is. A six-inch phone at arm's length occupies very little of it. Past a certain density, additional pixels land closer together than the eye can separate, and the picture stops improving no matter what the label says.

In practice, on a phone: the step from 480p to 720p or 1080p is genuinely visible, particularly in on-screen text, faces at a distance, and anything with fine detail. The step from 1080p to 4K, on that same screen, is close to invisible. You are paying for pixels you cannot see and storage you can.

Higher tiers do earn their place, but for specific reasons rather than general ones:

• A big screen — casting to a television, or watching on a laptop or monitor, where the extra detail is resolvable
• Editing — if you intend to crop into the frame, reframe a landscape clip for portrait, or stabilise it, you are effectively zooming, and the spare pixels become real
• Archiving something that matters — a copy of your own work you want to keep at the best available quality
• Text-heavy or detailed footage — screen recordings, presentations, anything where small type has to stay legible

File size, and where it actually comes from

File size follows bitrate multiplied by duration, not resolution directly. Resolution influences it only because higher resolutions are normally given higher bitrates — which is exactly why a badly encoded 4K file can be smaller than a good 1080p one, and look worse.

The consequences are the ones you feel later rather than at the moment of downloading. A phone fills up quietly. A large file over mobile data costs you allowance. Backups and gallery syncing take longer. And thirty saved clips at a high tier will do considerably more damage than the same thirty at SD, for a difference you probably could not pick out in a blind test on that phone.

Savvy's Storage screen exists for exactly this: it shows what each download is taking up and lets you clear several at once, which is a much better habit than discovering the problem when the camera refuses to open. Library is the companion — everything saved, with search and filters, so finding one clip from three weeks ago does not mean scrolling a gallery.

The sensible working rule is to match the tier to the purpose. Something you will watch once on the train and delete does not need 4K. Something going onto a television, or into an edit, or into an archive, might.

What each tier costs in Savvy

Here is the whole of it, with no asterisks.

Standard definition, up to 480p, is free. It comes out of a daily allowance rather than out of any balance, so on an ordinary day you can save clips at SD and spend nothing at all. That is not a trial tier or a teaser — it is the tier most phone viewing genuinely needs, which is why it is the one that is free.

Above 480p the cost is in coins, Savvy's in-app currency:

• SD video, up to 480p — free, from your daily allowance
• HD and Full HD video — 10 coins, or one HD credit if you have one
• 2K video — 15 coins
• 4K video — 20 coins
• Images and audio — 5 coins

Choosing a tier without thinking about it every time

Most people want a default rather than a decision, and the default that costs the least and disappoints the least is SD.

Leave the picker at SD unless something about the specific clip argues otherwise. It is free, it is a small file, and on the screen you will almost certainly watch it on, it is fine. Then step up deliberately, for a reason you can name — a television, an edit, an archive, small text you need to read.

The one check worth doing before spending is looking at what the picker actually lists. If the top option offered is 720p, the money question resolves itself. And if a clip was clearly published from a heavily compressed export — soft, blocky, smeary at the free tier already — a higher tier will hand you the same faults at a larger size. Compression damage is baked into the file, in exactly the way a watermark is.

• Watching on your phone, once — SD. Free, and you will not notice the difference
• Keeping something you will rewatch, or casting it to a TV — HD or Full HD
• Going into an edit where you will crop, reframe or stabilise — 2K or 4K, if the source genuinely offers them
• A clip that already looks soft at SD — no tier will fix it. Save the free version