A JPEG image that comes into focus while it is being displayed. Instead of rendering the image a line at a time from top to bottom, the whole image is displayed as very low-quality and fuzzy, which becomes sharper as the lines fill in. It gives the illusion that the page has downloaded faster even though it takes the same time to achieve the final sharpness. The progressive JPEG is created in multiple passes (scans) of the image. See
interlaced GIF and
JPEG.