When PNG is the right output
PNG is lossless and supports transparency — the two things JPG can't do. Screenshots, UI mockups, logos, icons, diagrams, and anything with sharp edges or text should be PNG. File sizes are larger than JPG for photographic content (usually 2-5×), so PNG is a bad choice for photographs unless you specifically need lossless. Note: PNG has no metadata for camera EXIF, so converting a photo JPG → PNG loses the camera info.