JPG

JPEG, short for Joint Photographic Experts Group, is a widely used method of lossy compression for digital images, particularly photographs. The format was developed by the Joint Photographic Experts Group and published as a standard in 1992 (ISO/IEC 10918-1). The term JPEG refers both to the group and to the compression algorithm it created.

Image files are commonly named with the .jpg or .jpeg extension. Windows historically used three-character extensions, which led to .jpg; the two extensions refer to the same format and are generally interchangeable.

Technically, JPEG uses a discrete cosine transform to convert image data into frequency components, followed by quantization and entropy coding. It typically handles 24-bit color (8 bits per RGB channel) and often employs chroma subsampling to reduce color detail, which humans perceive less accurately than brightness detail. The compression ratio is adjustable, trading off image quality against file size. Baseline JPEG is widely supported for web use, while progressive JPEG provides a version that loads in successive passes, improving perceived speed.

JPEG is ideal for complex photographic images but is less suitable for images with sharp edges, text, or line art, where artifacts such as blurring or blockiness can occur after high compression or repeated editing. For this reason, lossless formats like PNG or TIFF are preferred when editing is frequent. JPEG files commonly include metadata such as Exif, IPTC, and XMP, storing camera settings, location data, and author information.

See also: JPEG 2000, WebP, HEIC, PNG.