A few days ago, my former coworker Evan Hahn posted “The world’s smallest PNG”, an article walking through the minimum required elements of the PNG image format. He gave away the answer in the very first line:
The smallest PNG file is 67 bytes. It’s a single black pixel.
However (spoilers!) he later points out that there are several valid 67-byte PNGs, such as a 1x1 all-white image, or an 8x1 all-black image, or a 1x1 gray image. All of these exploit the fact that you can’t have less than one byte of pixel data, so you might as well use all eight bits of it. Clever!
However again…are we really limited to one byte of pixel data?
(At this point you should go read Evan’s article before continuing with mine.)