Short for Joint Photographic Experts Group, and pronounced jay-peg. JPEG is a lossy compression technique for color images. Although it can reduce files sizes to about 5% of their normal size, some detail is lost in the compression. There is a JPEG committee which supervises the activities in the sector.

A JPEG file is created by choosing from a range of compression qualities (actually, from one of a suite of compression algorithms). When you create a JPEG or convert an image from another format to a JPEG, you are asked to specify the quality of image you want. Since the highest quality results in the largest file, you can make a trade-off between image quality and file size. Formally, the JPEG file format is specified in ISO standard 10918. The JPEG scheme includes 29 distinct coding processes although a JPEG implementor may not use them all.

Together with the Graphic Interchange Format (GIF) and Portable Network Graphics (PNG) file formats, the JPEG is one of the image file formats supported on the World Wide Web, usually with the file suffix of ".jpg". You can create a progressive JPEG that is similar to an interlaced GIF.

The JPEG committee has created many standards since it was created in 1986. ISO had actually started to work on this 3 years earlier, in April 1983, in an attempt to find methods to add photo quality graphics to the text terminals of the time, but the 'Joint' that the 'J' in JPEG stands for refers to the merger of several groupings in an attempt to share and develop their experience.

The formal name of the standard that most people refer to as 'JPEG' is ISO/IEC IS 10918-1 | ITU-T Recommendation T.81, as the document was published by both ISO through its national standards bodies, and CCITT, now called ITU-T. IS 10918 has actually 4 parts -

Part 1 - The basic JPEG standard, which defines many options and alternatives for the coding of still images of photographic quality
Part 2 - which sets rules and checks for making sure software conforms to Part 1
Part 3 - set up to add a set of extensions to improve the standard, including the SPIFF file format
Part 4 - defines methods for registering some of the parameters used to extend JPEG As well as the standard we created, nearly all of its real world applications require a file format, and example reference software to help implementers. These functions were added to our work by others - the file format was created originally by Eric Hamilton, the then convenor of JPEG as part of his work at C-Cube Microsystems, and was placed by them into the public domain under the name JFIF

Probably the largest and most important contribution however was the work of the Independent JPEG Group (IJG), and Tom Lane in particular. Their Open Source software implementation, as well as being one of the major Open Source packages was key to the success of the JPEG standard and was incorporated by many companies into a variety of products such as image editors and Internet browsers.

After creating the JPEG standard described above, the committee started to look at some of the criticisms of the existing standard. High amongst these was the poor quality (and lack of integration) of lossless coding in the standard. With this in mind, the committee developed the JPEG-LS standard - ISO/IEC IS 14495-1 | ITU-T Recommendation T.87.