A JPG file is an image saved in a compressed image format standardized by the Joint Photographic Experts Group (JPEG). JPEG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. Convert your files from over 120 formats to a JPG image with this free online JPEG converter. JPG is a widely used compressed image format for containing digital images. JPEG compression is used in a number of image file formats.