JPEG (JPG)

JPEG is a family of image coding methods defined by the Joint Photographic Experts Group. In everyday use, a JPEG is a raster image saved with a .jpg or .jpeg extension. Those extensions are alternate names for the same format family, not two separate design file types.

The familiar photographic JPEG is usually lossy: encoding can discard image information to reduce file size. JPEG images contain a fixed grid of pixels; changing the resolution label or enlarging the file does not restore lost detail. A filename alone does not reveal its encoding, color profile, dimensions, or fitness for production.

JPEG is the name of the standards group and, in common speech, the image format people use for photographs. JPEG 1 includes more than one coding mode. The familiar .jpg image is commonly a DCT-based lossy image, but the extension by itself is not evidence of a particular encoding. JFIF, Exif, and ICC information may accompany the image data; these describe interchange, metadata, and color interpretation rather than creating a separate JPG format.

Think of JPEG as a delivery image, not a design project. A camera or editor can produce a compact finished picture that many applications can display. The saved image does not normally preserve the editor's live typography, adjustment layers, masks, linked assets, or original raw capture. Keep those upstream materials when future revisions or product adaptations are expected.