When creating graphics for the Web, reducing file size means reducing download time. The fewer colours an image has, the smaller the file can be.

For GIF images, the table below provides guidelines as to how to dither images with rich colour down into images with fewer colours, without sacrificing image quality.

Note that in each case, you should choose to use an “Adaptive” colour palette for the best results. Some programs offer a “Web” palette, which can be used to force the image to use only the 216 safe web colours. This may not provide the best result, depending on your image.

Image	Colours	Dither
Photograph (colourful) Photograph (few colours) Photograph (monochrome) Illustration (with gradients) Illustration (solid colours) Screen Capture	256 or 128 128 or 64 64 or 32 128 to 32 128 to 32 32 to 8	Diffusion Diffusion Diffusion Diffusion None (exact) None (exact)