I often use JPEG images, and I have noticed that there are two very similar file extensions: .jpg, which my mobile's camera and the Preview application use, and .jpeg, with which Image Capture saves the images from scanning with my Canon MX455 printer. LaTeX doesn't seem to distinguish, as I gave it a .jpeg with the extension changed to .jpg and the result seems to be the same as if it had been a .jpg right from the start. I have wondered what the difference between the two is. I have come across this question, and will certainly read through it, though at the moment I'm slightly out of time. However, from what I saw giving it a quick look, it seems not to distinguish the two extensions. In fact, it seems the file type's name is JPEG and the file extension is .jpg:
JPEG (or JPG, for the file extension; Joint Photographic Experts Group)
(excerpted from the first answer there). So is there any big difference between the two extensions? And if so, what is it?
JPG and JPEG stand both for an image format proposed and supported by the Joint Photographic Experts Group. The two terms have the same meaning and are interchangeable.
To read on, check out Difference between JPG and JPEG.
The reason for the different file extensions dates back to the early versions of Windows. The original file extension for the Joint Photographic Expert Group File Format was ‘.jpeg’; however in Windows all files required a three letter file extension. So, the file extension was shortened to ‘.jpg’. However, Macintosh was not limited to three letter file extensions, so Mac users used ‘.jpeg’. Eventually, with upgrades Windows also began to accept ‘.jpeg’. However, many users were already used to ‘.jpg’, so both the three letter file extension and the four letter extension began to be commonly used, and still is.
Today, the most commonly accepted and used form is the ‘.jpg’, as many users were Windows users. Imaging applications, such as Adobe Photoshop, save all JPEG files with a ".jpg" extension on both Mac and Windows, in an attempt to avoid confusion. The Joint Photographic Expert Group File Format can also be saved with the upper-case ‘.JPEG’ and ‘.JPG’ file extensions, which are less common, but also accepted.