Why 20KB usually needs a resize, not just lower quality
Quality settings throw away detail within each block of pixels, but they cannot change how many blocks there are. A 4000 pixel wide photograph has around forty times the pixel count of a 640 pixel wide one, and below a certain quality the encoder starts producing visible squares rather than a smaller file. That is the point where reducing dimensions stops being optional.
A practical order of operations: set a maximum width first, then let the quality search find its level. Six hundred pixels wide is a sensible starting point for a 20KB budget and is still perfectly readable on a phone. If the result lands well under target, raise the width until it stops fitting.
What survives at this budget and what does not
Flat artwork does well. Logos, signatures, screenshots of text and simple diagrams have large areas of a single colour, which encoders handle cheaply, so they reach 20KB with room to spare and often look untouched.
Detailed photographs do not. Foliage, crowds, textured fabric and fine hair are the expensive parts of any picture, and at this budget they turn mushy. If the image is a portrait for a form, crop tightly to the face before compressing — a smaller subject area spends the budget where it matters.
When the target genuinely cannot be met
DropKB tells you when even the lowest quality setting leaves the file above your target, instead of quietly handing back something too large. That message is a prompt to reduce the maximum width, not a failure. Halving the width cuts the pixel count to a quarter and usually settles the matter in one step.
Questions
- Why does my photo refuse to go below 20KB?
- Because it has too many pixels for that budget. Compression removes detail but not resolution, and past a point the encoder cannot discard anything more without producing obvious blocks. Set a maximum width — 600 pixels is a good first try — and the target becomes reachable immediately.
- Should I use JPEG or WebP for a 20KB target?
- WebP reaches a given size with noticeably better detail, so prefer it when whatever receives the file accepts it. Government and bank upload forms frequently do not, and reject anything that is not JPEG. This page defaults to JPEG for that reason; switch to WebP if you know the destination is a website or a messaging app.
- Will a 20KB image still be readable if it contains text?
- Usually yes, provided you keep the pixel width generous and use PNG or a high quality setting. Text is made of hard edges, which lossy formats blur first. For a screenshot with small text, a 20KB PNG at modest dimensions often beats a 20KB JPEG at large dimensions.