Compress an Image to 20 KB

• Searches the quality of a JPEG or WebP downward first and halts at 50, measuring the real length of every encode it writes.
• Scales the picture to 80% of its width and height when that floor is still over the line, then searches the new size again.
• Prints the finished width, height, byte count and quality under the result, and says in a sentence when the picture was made smaller.

• Resizes nothing under Keep the dimensions: the pixel box you started with is held, and the quality search does all of the work.
• Never re-encodes a PNG lossily, because there is no quality dial for one here — under this policy it steps down in size instead.
• Hands back no file that quietly misses the ceiling; a target it cannot reach is reported with the smallest size the picture managed.

1. Decide whether the pixels may move. The ceiling is already 20 KB and the page is already allowed to make the picture smaller if it has to. Where a field states a pixel box as firmly as it states the bytes, switch to keep dimensions before you start.
2. Add the picture. Drag a JPEG, PNG or WebP into the panel above, or pick one from your files. It is read where it already sits, so there is no transfer to wait through.
3. Let it search. Quality is tried first and goes no lower than 50. If the ceiling is still out of reach, the picture is scaled to 80% of its width and height and the search begins again, up to 8 times.
4. Read the three figures under the result. You get the width and height you finished on, the real byte count and the quality that produced it, with a sentence saying so whenever the picture was made smaller. Download it once those figures suit the field you are filling in.

Twenty kilobytes is 20,480 bytes, or 163,840 bits. That is the entire budget for describing every pixel in the picture, and whether it is generous or absurd depends on nothing except how many pixels there are to describe.

Those figures are before the file’s own headers take their cut, which on a JPEG is most of a kilobyte before a single pixel is stored. Read the bottom two rows as the reason this page behaves the way it does: past roughly half a bit for each pixel a photograph stops looking like one, so anything much beyond a few hundred pixels a side has to give up pixels rather than fidelity.

A signature is two tones doing all the work: dark ink, pale paper. PNG stores that kind of picture by describing runs of identical colour, so a clean scan of a name frequently lands in a couple of kilobytes with every stroke exactly as it was drawn.

JPEG works the other way round. It approximates, and approximation shows worst against a hard edge — the grey halo that creeps around each stroke at low quality is the encoder guessing at an edge it cannot afford to store. At the pixel boxes signature fields use, PNG is regularly both smaller and cleaner, so try it that way first and change only if it will not fit.

Either way, take the paper off before you compress. A photographed page is mostly margin, and margin costs pixels this budget cannot spare — trimming to the ink alone is often the whole fix. The signature resizer is the page built for that job; come here when the crop is already right and only the number is wrong.

Quality goes first. The encoder runs, the real length is measured, and the setting is narrowed towards the best-looking version that still fits underneath the ceiling — but it halts at quality 50. Lower than that a JPEG shows blocking and ringing that nobody wants on a document, so the floor is treated as a floor instead of grinding on towards single digits.

When quality 50 at full size is still over the line, the picture is scaled to 80% of its width and height and searched again. That repeats at most 8 times and never takes the short side under 32 pixels. All 8 steps land at roughly 17% of the width you started with, which is enough to bring most photographs beneath a very small number.

None of that is silent. Permission to shrink is granted on this page before anything runs, and the finished picture is labelled with the width and height it ended on next to the bytes and the quality, in a sentence as well as in figures.

Switch to keep dimensions and only the quality is allowed to change: same width, same height, and where 20 KB is genuinely beyond that picture you are told the smallest it could be made rather than handed something over the line.

That answer is worth having on its own. Learning that a scan bottoms out at 34 KB tells you the crop is too generous or the scan was made at too high a resolution, both of which you can fix, whereas a file that quietly missed the requirement gets discovered by the form instead of by you.

PNG needs a note of its own here. The PNG encoder in this build is lossless and carries no quality control at all, so under keep dimensions there is nothing for a search to turn down and WebP is offered instead, which reaches far smaller numbers at the same pixel size. With shrinking permitted a PNG steps down in dimensions instead, and the encoding stays lossless at every step even though there are fewer pixels left to encode.

The last row of the table is the honest bad news: a twelve-megapixel picture has about a hundredth of a bit for each of its pixels at this ceiling. No encoder turns that back into a photograph, and a page that promised otherwise would simply be handing you a grey mess with the right file size.

What works instead is being clear about what the field is for. If it wants a face, cut down to the face and let the result be a couple of hundred pixels wide, where 20 KB is comfortable. If it wants a document, a flat scan is far kinder to the encoder than a hand-held photograph of the same page, where shadow, paper texture and a slight blur all eat the budget before the writing does.

Trim the frame first when the subject is buried in a wider shot. Halving each side removes three quarters of the pixels, and every one of those is budget handed back to the part of the picture anybody is going to look at.

The figure above can be edited, so anything from 10 KB to 20 MB can be reached from this page. 100 KB and 200 KB have pages of their own because they behave differently: at those ceilings quality on its own usually arrives, and the picture keeps the dimensions it came with. Where a slider suits you better than a number, use the main compressor.

• Shrinking is a one-way trade — the pixels a step removes are gone from the file you download, though the original on your device is left alone.
• The short side is never taken below 32 pixels, so a picture that still misses the ceiling at that size is reported rather than reduced any further.
• A PNG cannot be made smaller by quality, because the encoder here has none; under keep dimensions the alternative offered is WebP.