How lossless PNG compression works
PNG stores images losslessly. The pixels you get back are always identical to the ones you put in. The file size depends on how efficiently that data is packed. This compressor re-saves the image with maximum-effort compression settings, which is often smaller than the PNG an app or screenshot tool produced.
If the image uses 256 colors or fewer, the tool also tries a palette-based PNG and keeps it only if the colors match exactly and the file is smaller. Logos, icons and simple diagrams often shrink most this way.
When PNG compression helps, and when it doesn't
Savings vary a lot. Screenshots, charts and graphics with flat color often get noticeably smaller. A PNG that was already optimized may only lose a few percent. Photos saved as PNG stay large, because a photo has millions of slightly different colors that lossless compression can't pack tightly.
There are no method, quality or target size controls here, because lossless compression has nothing to trade away. The result is simply the smallest PNG the tool can make.
Need a much smaller file? Try WebP or JPG
If the PNG is a photo, or you need to hit a size limit, a lossy format will get you much further. WebP keeps transparency and supports target sizes, so it is the natural next step for web images. JPG is the most compatible choice when transparency doesn't matter. Both are available in the Image Compressor.
How to compress a PNG
Upload a PNG and the optimized version is ready within moments. The panel shows the original and new size and the percentage saved. If the result is barely smaller, the original was already efficient and you can keep it. Large images take a little longer, because maximum-effort compression works harder to pack the data. The dimensions never change.