They're just for different jobs. JPEG is lossy, in ways that were initially optimized for photographs. The details it loses are often not details photographs a

They're just for different jobs. JPEG is lossy, in ways that were initially optimized for photographs. The details it loses are often not details photographs are good at providing in the first place. As the upside for losing some data, it gets to pick the data it gets to compress, and it chooses it in such a way as to minimize the size of the compressed data. PNG is a lossless format. It's practically mandatory when you need 100% fidelity, as with icons or other graphics that are intended to have high contrast in small areas. It's able to optimize large areas of the same color very well, but suffers when colors change rapidly. It's especially unsuitable for photographs, as sensor noise (or film grain, if the source was film) create subtle color variations that are very difficult for it to encode efficiently. You basically never have a situation where either one is appropriate. They are for different things, and should be used as such.