JPEG Definition | The Interactive Glossary

JPEG is an acronym for Joint Photographic Experts Group, an industry committee that developed a compression standard for still images. JPEG refers to the graphics file format that uses this compression standard. The JPEG format allows image creators to vary the level of compression, depending on size and quality needs. In general, JPEG can compress an image file to one-tenth of its original size without noticeable differences in image quality; however, JPEG is not a lossless file format, so compressing the file too much will result in obvious quality loss.

JPEG is commonly used in digital photography and for a variety of other digital purposes, because it offers a versatile form of compression that allows photographers to store considerably more images on a memory card, computer, or website than would be possible in an uncompressed file format, such as a bitmap file.

JPEG images can be saved with the following extensions:

• .jpg
• .jpeg
• .jpe
• .jif
• .jfif
• .jfi.

Also See: Bitmapped Image, GIF, PNG

Frequently Asked Questions

How does JPEG compare to other image compression formats for the web?

The three primary formats for the web are JPEG, PNG, and GIF. Both PNG and GIF provide lossless compression, meaning they reduce the size of a file without losing any of the original image information or quality. While this seems preferable to JPEG, which does allow loss, it also places strict limits on how effectively PNG and GIF can compress an image. For that reason, both of these formats are preferable for line drawing or images with limited color variation. GIF images, in particularly, should only be used for simplistic images, because the format only supports 256 colors. For realistic artwork or photographs, JPEG is the preferred compression method, because it can reduce even very large files into a size appropriate for distribution over the World Wide Web. While this may result in some quality loss, it is often slight and may not even be visible to the human eye.

If I save a file to JPEG, can I restore it to its original format?

Because JPEG is what’s known as a lossy compression format, when an image is saved, some of the original image information may be lost. This means you can never restore that file to its original state. What’s more, each time you resave a JPEG file its quality degrades a little bit further, so making continuous edits to a single file can result in a permanent loss of image quality, which is why you should always save the original file! It is possible to make some types of edits to and save JPEG images without any loss, and in fact the JPEG format supports lossless compression; however, this feature is not commonly utilized, as there are plenty of other lossless formats available.