ICO file format
Windows Picture and Fax Viewer
ICO – is a special format for displaying icons, shortcuts, icons in Windows OS. It represents two bitmaps. The first is the image mask, and the second is the icon displayed on the front. It is used to connect a picture with an OS file. Users of devices with operating systems from Microsoft can edit the ICO files to create unique icons. It can be converted to files with popular JEPG and PNG extensions. Saving files in ICO is used when developing graphics in indicators, icons, and similar graphical elements. They are used as an icon and site logo. Any application opens them for viewing images and special programs like ACDSee or Axialis IconWorkshop.
The .ico extension is used from the first versions of Windows OS, gradually adding in size and a maximum number of supported hues. For example, the "seven" can help icons up to 256x256 pixels in 32 bits. To ensure the compatibility with earlier versions of Windows, it is better to use eight-bit icon versions.