Favicon.ICO Format

Favicon.ico (or simply. ico) is a multi-resolution image with .ico extension that is actually a storage of several tiny images. ICO is abbreviation for icon, a well known image that has been used for years for desktop icons.

Favicon.ico size, dimensions

Each .ico file contains favicon in two different sizes (16x16 and 32x32 pixels) and in two color formats (16 and 256 colors). When a website is loaded, computer automatically scans favicon.ico file, and chooses the most appropriate one.

Favicon.ico vs .bmp

A lot of people think that favicon.ico is just a renamed BMP. This is not correct. Favicon contains several images, while BMP is a single image.