Free PNG Compressor Online

How PNG compression works — and why it can cut so much without looking different

PNG is technically lossless, but that doesn’t mean it can’t be made much smaller. A 500KB logo can often come down to 90KB and look identical in a browser. Here’s the process behind that:

1. Colour palette reduction — a typical PNG uses 24-bit colour, which means 16 million possible values. But your logo probably uses fewer than 100 distinct colours. The compressor figures out the 256 that best represent the image and throws out the rest. For logos, icons, and screenshots, you can’t tell the difference.
2. Transparency remapping — each of those 256 palette colours gets its own alpha value, so transparent and semi-transparent areas still look right. Soft shadows and anti-aliased text edges are preserved.
3. Better re-compression — indexed colour data (256 colours) is much more repetitive than 24-bit data, so the compression algorithm at the end of the process gets a much higher ratio. That’s where most of the size reduction actually comes from.
4. Metadata cleanup — creation timestamps, colour profile chunks, software comments — these are written by editors but never displayed. Removing them saves another 5–15KB per file.

When this approach doesn’t work as well

This technique shines on graphics, logos, icons, and screenshots. It doesn’t work as well on photographs saved as PNG, because photos have millions of gradually-changing colour values that can’t collapse to a 256-colour palette without looking banded. If you have a photo in PNG format, converting it to WebP at quality 80 will get you a smaller file with better results than palette compression will.