Not all image file formats are made equal. In fact, many of them were created to address a problem that an already-existing format could not resolve. The JPEG, for instance, came about because image file sizes were eating up way too much storage space.
Believe it or not, the JIF, JPEG, and JPG file extensions more or less refer to the same thing. To understand why the file format has so many names, we need to unravel a little bit of convoluted history.
What Is a JPEG?
The JPEG acronym stands for Joint Photographic Experts Group—the file type was named after the sub-committee that helped create the JPEG Interchange Format (JIF) standard. It was first issued in 1992 by the International Organization for Standardization (ISO).
JPEGs are 24-bit still raster images, with eight bits in each channel of the RGB color model. This leaves no room for an alpha channel, which means that while JPEGs can support over 16 million colors, they cannot support transparency.
When an image is saved as a JPEG, some of its data gets discarded in a process referred to as lossy file compression. In turn, the image takes up 50-75 percent less storage space (in comparison to older formats like BMP) with little to no perceptible loss in image quality.
JPEG compression is based on a lossy image compression technique called the discrete cosine transform (DCT), which was first proposed by electrical engineer Nasir Ahmed in 1972.
What Is a JIF?
You can think of a JIF file is as a JPEG in its "purest" form. However, the format isn't used much anymore because it presented some frustrating limitations. For instance, the color and pixel aspect definitions of a JIF caused compatibility problems between encoders and decoders (viewers).
Thankfully, these problems were later addressed by other "supplementary" standards that built upon the JIF. The first of these was the JPEG File Interchange Format (JFIF), and later, the Exchangeable image file format (Exif) and ICC color profiles.
JPEG/JFIF is the currently most popular format for storing and transmitting photographic images on the internet, while JPEG/Exif is that for digital cameras and other image capture devices. Most folks don't distinguish the difference between these variations and simply refer to them both as just JPEG.
What Is a JPG2 or JPF?
In 2000, the JPEG group released another image file format called the JPEG 2000 (its file extensions are JPG2 and JPF). It was meant to be a successor to the JPEG, but was nowhere near as popular. Even when its advanced encoding method often led to better quality images.
The JPEG 2000 file format flopped for a small handful of reasons. For one, it was based on an entirely new code and thus wasn't backward compatible with the JPEG. On top of that, handling JPEG 2000 files required more memory to process, which was a bit of a deal-breaker back then. After all, the average computer at the time only had 64 MB of memory.
The JPEG 2000 has seen a bit of a resurgence now that computer hardware, in general, has vastly improved over the last 20 years, but the file format is still very much underused. The only internet browser that has support for JPEG 2000 files at the time of writing is Safari.
JPEG vs. JPG
Early versions of Windows (specifically the MS-DOS 8.3 and FAT-16 file systems) had a maximum 3-letter limit when it came to the length of file extensions. JPEG had to be shortened to JPG as to not exceed the limit. Mac and Linux computers never had such a thing, and so users would continue to save images as JPEG.
Popular image editing programs that worked across different operating systems—such as Photoshop and Gimp—would eventually set their default JPEG file extension to JPG in an attempt to minimize confusion.
And that's how we ended up with two file extensions for the same format: JPEG and JPG. When choosing what to save your image as, there is no difference between them.
JPEG vs. PNG: Which Is Better?
The JPEG and the PNG were released within the same decade, with each file format resolving a different digital image problem that the technology world faced back then. You could say that it's only natural that they are constantly compared... and they are, even to this day. Between JPEG and PNG, which image file format reigns supreme?
Quite honestly, the answer depends on what kind of image you're saving.
JPEGs are better suited for photographs because they utilize lossy compression to keep to reasonable file sizes. Photographs are such big, detailed images that compression artifacts (subtle image distortions caused by the compression) aren't very noticeable on them.
On the other hand, images with sharp points, crisp edges, and with large areas of one color (e.g. vector logos, pixel art, etc.) don't look quite right when saved as a JPEG.
This is where the Portable Network Graphics (PNG) file might come in. Developed by the PNG Development Group four years after the release of the JPEG, the PNG supports lossless data compression and transparency. PNGs are thus often used if image quality must be retained and file size is not an issue.
A good rule of thumb is keeping JPEG to photographs, and saving PNG for images with transparency and non-photographic images. For more insight on the many different types of files (not only images), check out our guide to knowing when to use which file format.
JPEG and JPG Are the Same File Format
Despite the confusion the JPEG has caused with its many updates and variations, the eventual flood of digital images on the internet in the mid-90s was undoubtedly primarily caused by its release.
The next time you're ready to export a photo from an image editor and are presented with the long list of available formats, just remember: JPEG and JPG are one and the same.
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