ICO is an image format that was originally used to store icons for folders, files, and programs in the Windows operating system. Along with the development of the Internet, ICO has also become widespread as an icon format for websites. A large number of websites have a file called favicon.ico that displays a small image in the browser address bar or search results next to the page title. ICO files typically contain square images with transparent backgrounds ranging in size from 16 by 16 to 256 by 256 pixels. The simultaneous presence of images of several sizes in the ICO file provides the ability to scale the icon, if necessary, without degrading the quality. The format also supports various color depths of -16 colors, 32, 64, 128, 256, 16-bit, and so on. Icons can be either black and white or color. Often, an ICO file is created using a PNG conversion.