PNG optimisation

Exporting an identical image from different design tools results in different file sizes. Why? What can be done to optimise them to reduce downloading time and disk space? To test, we can use an image that is a single pixel. A 1×1 white pixel PNG shows the efficiency of how various tools package their exports, and if metadata or additonal data chunks are included. Here’s how the various tools and common export methods rank. Sizes are in bytes and smaller is better.