How to choose the best image file type?

All web images must be JPEG (.jpg), GIF (.gif) or PNG (.png) file formats, and must be RGB color mode (not CMYK like print images). TIF, EPS, PSD, BMP and other file types will not display in a web browser. The standard resolution for web images has always been 72 dpi but now some hi-resolution “retina” monitors display images at 144 dpi.

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