How to use it
- Choose how many colours to keep. 256 is nearly always invisible.
- Drop in your PNGs.
- Check the savings and download.
How a PNG gets smaller
A normal PNG can use any of about 16.7 million colours for each pixel, plus a transparency value. Most graphics use nowhere near that many distinct colours, but the file still has to allow for them. This compressor finds the best palette of, say, 256 colours for your image, maps every pixel to its nearest palette colour, and writes an indexed PNG. Each pixel then needs one byte instead of four, and the repeated patterns compress far better.
The technique is called colour quantisation. It is technically lossy, but for flat artwork the lost differences are invisible. Transparency is quantised along with colour, so soft edges and shadows survive.
What it is good at, and what it is not
Excellent for screenshots, UI mock-ups, charts, logos, icons, flat illustrations and pixel art. Less good for photographs and smooth gradients, where 256 colours can cause visible banding; there, use 256 rather than fewer, or consider converting to WebP or JPG instead.
The All (lossless re-pack) option re-writes the PNG without reducing colours. It sometimes saves a little over PNGs exported by software with weak compression, but do not expect miracles.
Questions people ask
Is PNG compression lossless?
Standard PNG is. This tool offers lossy colour reduction for bigger savings, plus a lossless re-pack option.
Will my transparent background be kept?
Yes. Transparency is preserved, including semi-transparent edges.
How much smaller will my PNG get?
Screenshots and graphics often shrink by 50 to 80 percent at 256 colours. Photos saved as PNG shrink too, but may show banding.