JPEG, or in full Joint Photographic Export Group, is an ISO-certified bitmap compression format used for lossy compressions. The advantage that comes with the JPEG image format is the flexibility to decide the balance between a photo’s quality and its storage size. Then we also have JPG. Fundamentally, there is no difference between the two formats, except that one has three characters and the other has four. In fact, you can interchange these two extensions, and your image file should continue to work properly. JPG only exists because earlier versions of Windows used to only accept file extensions with at most three characters. So the format creators decided to shorten “.jpeg” to “.jpg” so Windows users could also use the format.