JFIF

JFIF stands for JPEG File Interchange Format. It is a minimal, widely supported container for storing and transferring JPEG-compressed images. JFIF defines a simple file structure that wraps a JPEG bitstream with a small header to promote interoperability across software and platforms.

In a typical JFIF file, the JPEG compressed data stream forms the primary image data. This stream is usually preceded by an APP0 marker segment that identifies the file as JFIF and carries basic metadata, such as the JFIF version, color space information, and image density. The APP0 segment may also include an optional thumbnail image. The density units field indicates how the X and Y density values should be interpreted (for example, dots per inch or dots per centimeter).

JFIF specifies the use of the YCbCr color space for JPEG images and supports the common chroma subsampling schemes used in JPEG encoding. While the core image data remains the JPEG bitstream, the header provides enough information for decoders to render the image correctly on a wide range of devices and software.

Historically, JFIF is often encountered alongside other metadata formats in JPEG files, most notably Exif. Exif data is typically stored in an APP1 segment and can coexist with the JFIF header in the same file. This coexistence has contributed to the broad compatibility of JPEG images across cameras, image editors, and viewing software.

Overall, JFIF serves as a simple, practical standard that facilitated reliable interchange of JPEG images across diverse environments and remains a foundational format in the JPEG ecosystem.