Following are the most commonly used graphics file formats for putting
graphics on the World Wide Web and how each differs from the others.
Short for Joint Photographic Experts Group,
the original name of the committee that wrote the standard. JPG is one
of the image file formats supported on the Web. JPG is a lossy compression
technique that is designed to compress color and grayscale
continuous-tone images. The information that is discarded in the
compression is information that the human eye cannot detect. JPG images
support 16 million colors and are best suited for photographs and
complex graphics. The user typically has to compromise on either the
quality of the image or the size of the file. JPG does not work well on
line drawings, lettering or simple graphics because there is not a lot
of the image that can be thrown out in the lossy process, so the image
loses clarity and sharpness.
Short for Graphics Interchange Format, another of the graphics formats supported by the Web. Unlike JPG, the GIF format is a lossless compression
technique and it supports only 256 colors. GIF is better than JPG for
images with only a few distinct colors, such as line drawings, black
and white images and small text that is only a few pixels high. With an animation editor, GIF images can be put together for animated images. GIF also supports transparency,
where the background color can be set to transparent in order to let
the color on the underlying Web page to show through. The compression
algorithm used in the GIF format is owned by Unisys, and companies that
use the algorithm are supposed to license the use from Unisys.*
Short for Portable Network Graphics, the third graphics standard supported by the Web (though not supported by all browsers).
PNG was developed as a patent-free answer to the GIF format but is also
an improvement on the GIF technique. An image in a lossless PNG file
can be 5%-25% more compressed than a GIF file of the same image. PNG
builds on the idea of transparency in GIF images and allows the control
of the degree of transparency, known as opacity. Saving, restoring and re-saving a PNG image will not degrade its quality. PNG does not support animation like GIF does.
*Unisys announced in 1995 that it
would require people to pay licensing fees in order to use GIF. This
does not mean that anyone who creates or uses a GIF image has to pay
for it. Authors writing programs that output GIF images are subject to
For further information on these graphics formats, see:
GIF vs. JPG -- Which Is Best?
GIF, JPG and PNG -- What's the difference?
Myths and Facts about JPG
RFC 2083: PNG Specification