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Web Style Guide

Summary: File formats

Uses for GIF and JPEG Files

Netscape Navigator, Microsoft Internet Explorer, and most other browsers support both GIF and JPEG graphics (as of this writing, PNG graphics are not adequately supported). In theory, you could use either graphic format for the visual elements of your Web pages. In practice, however, most Web developers will continue to favor the GIF format for most page design elements, diagrams, and images that must not dither on 8-bit display screens. Designers choose the JPEG format mostly for photographs, complex "photographic" illustrations, medical images, and other types of images in which the compression artifacts of the JPEG process do not severely compromise image quality.

Illustration: Examples of best uses for the GIF format

Advantages of GIF files

  • GIF is the most widely supported graphics format on the Web
  • GIFs of diagrammatic images look better than JPEGs
  • GIF supports transparency and interlacing
Illustration: Examples of best uses for the JPEG format

Advantages of JPEG images

  • Huge compression ratios mean faster download speeds
  • JPEG produces excellent results for most photographs and complex images
  • JPEG supports full-color (24-bit, "true color") images