Compress PNG
Palette-quantise PNGs for big savings on flat graphics.
Fewer colours mean a smaller file. Flat graphics, icons and screenshots usually look identical well below 256 — photos need more colours to avoid visible banding.
How to use Compress PNG
- Drop your PNG files onto the upload area.
- Choose lossless mode, or reduce the palette to 256, 64 or 16 colours for a much smaller file.
- Click Compress.
- Check the new sizes, then download each file or click Download all for a zip.
A browser's own PNG encoder is always lossless and always full 24-bit colour, which is why simply "re-saving" a PNG rarely makes it meaningfully smaller. The real savings come from palette quantisation — reducing the image to a limited set of colours and storing each pixel as a small index into that palette instead of a full colour value. This tool does that directly, the same technique behind TinyPNG and similar compressors.
It works best on images that don't actually use many colours to begin with: icons, logos, screenshots, flat illustrations. A quantised 256-colour version of a typical icon is often visually identical to the original at a fraction of the size. Photographs are the case where it shows its limits — reducing a gradient-heavy photo to a small palette introduces visible banding.
Everything happens in your browser, so drop in a batch and compress them all together, then download as a ZIP.
Questions
What does "palette quantisation" actually mean?
Instead of storing a full colour for every pixel, the image is reduced to a limited palette (say, 64 colours) and each pixel just stores which palette entry it uses. Fewer colours means less data per pixel, which is where the size reduction comes from.
Will this work well on my photo?
Less well than on flat graphics. Photos have continuous gradients that a small palette can't represent smoothly, so you'll see visible colour banding at low colour counts. For photos, JPG or WebP compression is usually the better tool.
What's the difference between Quantised and Lossless mode?
Quantised mode reduces the colour palette for the size savings described above. Lossless mode re-encodes the file without touching a single pixel, which saves less space but guarantees an exact copy.
How many colours should I pick?
256 is a reasonable starting point for most icons and graphics. Icons and simple illustrations often look identical all the way down to 16-64 colours, which saves considerably more — lower it and check.
Can quantising ever make the file bigger?
On its own, yes — a very smooth image (a clean gradient with almost no noise) can end up larger with a big palette than a plain lossless re-encode, because the palette table adds overhead without saving much. This tool checks for that and automatically falls back to the lossless encode whenever it would produce a smaller file, so Compress never hands back something bigger than a straightforward re-save.
Are my images uploaded anywhere?
No. Quantisation and encoding both happen entirely in your browser — the files never leave your device.