Motion JPEG (MJPEG) is a video codec in which each individual image is compressed separately as a JPEG image.

Unlike the video formats specified in international standards such as MPEG-2 and the format specified in the JPEG still-picture coding standard, there is no document that defines a single exact format that is universally recognized as a complete specification of “Motion JPEG” for use in all contexts. This raises compatibility concerns about file outputs from different manufacturers. However, each particular file format usually has some standard on how M-JPEG is encoded. For example, Microsoft documents their standard format to store M-JPEG in AVI files, Apple documents how M-JPEG is stored in QuickTime files, RFC 2435 describes how M-JPEG is implemented in an RTP stream, and an M-JPEG CodecID is planned for the Matroska file format.