JPEG versus JPG


Today’s Question: This may be a silly bit of trivia, but is there a difference between JPEG (4 letters) and JPG (3 letters)? I see it both ways quite often, and I’ve never understood whether there was a difference and if there isn’t why there are two ways to describe the same type of image.

Tim’s Quick Answer: JPEG and JPG both refer to the exact same thing: an image in a standard file format created by the Joint Photographic Experts Group.

More Detail: The JPEG image format gets its name from the committee that shares its name, so technically the initialism for the file format should be JPEG, including the “E”, because that represents the full name of the committee.

The reason JPG (without the “E”) has become a common way to refer to the file format is that when the format was originally created in 1992, computer operating systems typically limited you to a filename in the “8.3” format, with an eight character base filename and a three character filename extension. Thus, the JPEG file format has long been referred to based on the original filename extension of JPG.

With newer operating systems supporting long filenames, including long filename extensions, we can now save files with a complete JPEG filename extension, without having to exclude the “E”. However, in many cases the format is still referred to as JPG, and many software applications still default to using a three-letter filename extension of JPG rather than using the four-character extension of JPEG.

Oh, and I don’t think it’s a silly question at all.