An image output system includes an obtaining unit, a duplication unit, a generation unit, and an execution unit. The obtaining unit obtains image data. The duplication unit stores duplicate data of the image data in a memory. The generation unit generates a log image based on the duplicate data, and generates log data including the log image, the log data indicating a log of an image output process corresponding to the image data. The execution unit executes, in a case where the duplicate data has been stored, an image output process based on the image data before completion of generation of the log data.