This tool reads your PNG image directly in the browser and encodes a JPG copy, so there is no upload, no queue and no waiting for a server. It works on desktop and mobile.
Screenshots and graphics saved as PNG are often several times larger than they need to be for email or web posting. Converting to JPG typically cuts a photo-like PNG to a fraction of its size, with a small, usually invisible loss of detail.
JPG has no transparency. Transparent areas are filled with white, so convert logos on transparent backgrounds with care.