jpeg vs gif for web images

The two most popular image formats for the web are JPEG and GIF. These formats represent very different approaches to the problem of delivering an image with minimum file size anddownload time. This page describes the difference between these approaches and offers tips on when to use JPEG and when to use GIF.

While GIF is great for computer generated images with limited palettes, JPEG is far better for photographs. It gives better quality images for the same file size.

Below is a comparison. The image on the top is a blowup of a very small region of a large image compressed with JPEG. The image on the bottom is the same region compressed using GIF. The GIF file is 2.4 times bigger than the JPEG, but is clearly of lower quality.

Note the use of pixel dithering to try to match the color gradations in the photo. (You may want to back up from your monitor for a more realistic comparison of the appearance of the images.)

The JPEG (28,238 bytes):

The GIF (9,042 bytes):

When to use GIF?