compress png to 500 kb for a diagram that stays PNG
Use this page to compress png to 500 kb when a diagram or a chart should stay PNG and remain under 500 KB. A lossless pass often cannot hit 500 KB, so the tool posterises and then scales. A flat graphic fares better than a photo saved as PNG.
Preset: Compress PNG to 500 KB
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Steps to compress png to 500 kb
- Add the PNG, or a picture you are willing to save as PNG. It stays in this tab while you compress png to 500 kb.
- Confirm the target reads 500 KB. Format is PNG, and reduce colours is on.
- Run the compress. The tool posterises first, then scales if the file is still above 500 KB.
- Download the PNG and check both the file size and whether any gradient has started to band.
How this target is applied
PNG stays lossless on a normal pass, and that pass often cannot hit a small cap. This preset posterises, which reduces the number of colours, and then scales down if the file is still above 500 KB.
A flat icon or a screenshot with broad colour fields shrinks more than a photograph saved as PNG. Banding on a gradient is the visible cost of posterise.
Why 500 KB is the PNG cap
Diagrams and charts that would blur as JPEG belong in PNG under 500 KB. Posterise helps flat colour. Fine gradients may band, which is the trade for a smaller file. A lossless pass often cannot hit even this larger cap when the PNG is a photo in disguise. Scaling is the next step when posterise is not enough.
Use 500 KB when the publisher wants PNG and names half a megabyte. A simple chart may fit after posterise alone.
Why posterise comes before scale
A lossless pass keeps every pixel exact, so a noisy photograph in PNG barely shrinks. Posterise throws away close colours so flat areas store more cheaply. That is the right first move for an icon, a UI capture, or a chart.
If posterise is not enough, the scale ladder reduces width and height until the PNG is under 500 KB or the ladder ends. You may still miss the cap. The page leaves you the smallest PNG rather than pretending the target was hit.
Limits, formats and output
| Accepted input | PNG, JPEG, WEBP |
|---|---|
| Files per batch | 1–100 |
| Soft size warning | 50 MB each |
| Hard stop | 500 MB total in memory |
| Output | The chosen image format, or a ZIP for a batch |
| Account | None. The tool runs in this tab. |
Your file never leaves your device
Your PNG is processed only in this browser and is never uploaded. The work runs in a Web Worker in this tab, using WebAssembly for the heavy parts, and the result comes back as a local blob. This site does not upload the file, store it, or log its name.
To verify: load the page, turn on airplane mode, and drop the file again. It still finishes. Or open DevTools, choose Network, and watch the run: there is no upload. The architecture is described on How it works.
Frequently asked questions
Why not a lossless pass for 500 KB?
A lossless pass often cannot hit a small cap, because PNG keeps every sample. 500 KB is small enough that exact pixels usually cost too much. Posterise reduces the colour count first. Scale follows only if the file is still too big. A diagram benefits.
What does posterise change?
Posterise groups similar colours into fewer flat values. Large areas of one colour get smaller in the file. Fine gradients can band into visible steps. Text on a flat background usually survives better than a photograph. You should look at the download before you send it to a form that cares about colour.
When does the tool scale the PNG?
After posterise, if the file is still over 500 KB. The scale ladder steps the width and height down and encodes again. It stops at the first result under the cap. A small icon may never reach that stage. A large screenshot or a photo in PNG often will.
What if 500 KB is missed?
You keep the smallest PNG the search made, and you can see that 500 KB was not reached. Add fewer colours in the source, or crop away empty margin, and run again. A photo that must stay photographic will do better as a JPEG if the form allows that type.
Does this preset stay PNG?
Yes. Format is PNG, and reduce colours is on. The download is a PNG even when posterise and scale have changed the pixels. Transparency can remain, unlike a JPEG. If you needed JPEG bytes under a cap, this is the wrong preset.
Last updated 2026-09-26. By Tam.