PNG to JPG

PNG to JPG is the conversion most people actually need, most of the time. Photos stored as PNG waste enormous amounts of disk space and bandwidth — a 5 MB PNG photo of a child's birthday becomes a 500 KB JPG with no visible quality loss. The conversion is the right move whenever the source PNG contains photo-like content (continuous tones, gradients, many colors) rather than flat-color graphics (logos, icons, screenshots with text).

The transparent-areas-to-background-color question is worth thinking about. PNGs can have transparent regions; JPGs can't. When you convert, those transparent regions need to be filled with something. White is the right default for most documents (white paper background). For images that will be placed on a colored background, pick the matching color — a logo on a transparent background, converted to JPG with a white background, looks terrible on a navy website; the same logo converted with a navy background blends seamlessly.

Quality matters more than people realize. Quality 95 looks identical to quality 100 to the human eye but is much smaller. Quality 85 is the sweet spot for sharing — barely distinguishable from the original at typical viewing sizes, dramatically smaller. Quality 70 is the floor for any image you care about; below that, artifacts become visible.