Most favicons are created in a single resolution only, which by default is 16x16 pixels. This is often fine, but low resolution 16x16 favicons look pixelated when seen in some browsers and when used for bookmarking and application icons in e.g. IOS. Some browsers expects favicons in different sizes e.g. 16x16, 32x32, 48x48, 64x64, and 128x128. Most browsers can deal with favicons. GIF, JPG, PNG formats, and Microsoft Icon format (.