PNG Compressor

PNG keeps every pixel exactly, which makes screenshots, logos and illustrations needlessly large. Most of them need far fewer than the 16 million colours a normal PNG can hold. This compressor reduces each image to a palette of up to 256 well-chosen colours, smooths gradients with dithering, and writes a compact indexed PNG — the same idea TinyPNG and pngquant use — while keeping transparency. It runs in your browser, so nothing is uploaded.

How to use this tool

1. Choose one or more PNG files (screenshots, logos, icons, UI graphics).
2. Keep 256 colours for the best quality, or go lower for even smaller files — 64 or 32 often still looks identical for flat graphics.
3. Leave dithering on for gradients and photos; turn it off for flat artwork, where it only adds noise and bytes.
4. Compare the sizes, then download each file or all of them as a ZIP.

Formula

Bit depth = 1 for ≤ 2 colours, 2 for ≤ 4, 4 for ≤ 16, otherwise 8

The palette is built with pairwise-nearest-neighbour clustering (gifenc’s quantiser, on RGB565, or RGBA4444 when the image has transparency; very colourful pictures with more than 4,000 distinct RGB565 colours use RGB444, which keeps big photos fast). Each pixel is mapped to its nearest palette colour; with dithering the rounding error is spread to the neighbours with Floyd–Steinberg weights 7/16, 3/16, 5/16 and 1/16. The indices are packed at the bit depth above, filtered, deflated and stored with PLTE and tRNS chunks.

Example

A 1920 × 1080 px app screenshot saved by the system as a 1.4 MB truecolour PNG usually drops to about 300–450 KB at 256 colours — 70–80% smaller — and looks the same at normal zoom. A 512 × 512 px flat logo with 16 colours is stored at 4 bits per pixel, so its raw pixel data shrinks from 1 MB (RGBA) to 128 KB before deflate compression.