tl;dr:This post describes this file in more detail and tries to explain how PNGs work along the way. The smallest PNG file has four sections: (1) The PNG signature, the same for every PNG: 8 bytes. (2) The image’s metadata, which includes its dimensions: 25 bytes. (3) The image’s pixel data: 22 bytes. (4) An “end of image” marker: 12 bytes.