A PNG stores every pixel exactly, with no detail thrown away, which is what people mean when they call the format lossless. That fidelity is also why the files run large: a full-color PNG-24 reserves 24 bits of color for every pixel whether the artwork needs that range or not, and a PNG-32 adds an 8-bit alpha channel on top for transparency. Screenshots, exported renders, and anything with soft gradients pile on the bytes fastest. The format never discards data on its own, so a heavy PNG stays heavy until you change what it has to describe.
There are two honest ways to make one smaller. The first is a tighter lossless re-encode — the compressor runs a maximum zlib pass and strips embedded metadata, giving back a few kilobytes with zero visible change. The second, and the bigger lever, is reducing the color count: quantizing a PNG-24 down to a limited palette can cut the size dramatically, and the alpha channel is carried through the whole operation, semi-transparent edges included. That step is opt-in and one-way, so you decide when a graphic can spare the colors.
This tool puts that choice in front of you instead of hiding it behind one button. A Colors control sets the target palette, a stats bar reports the new size and percent saved as you adjust, and the compare slider sweeps between the original and the compressed copy on the same graphic. When a PNG is really a photograph in disguise, palette reduction will band the gradients — so the copy points you toward WebP or JPG for those, rather than pretending a flat palette suits every image.