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Microsoft Windows Icon (.ico)

The ICO file format is a raster image format designed by Microsoft for desktop computer icons in Microsoft Windows systems. An ICO file can contain multiple icons, either in BMP or PNG image format.

ICO Specifications

Name Microsoft Windows Icon
File Extension(s) .ico
Category Raster Images
Use For Desktop icons of Windows systems and web favicons.
Developer Microsoft
MIME Type(s) image/x-icon image/vnd.microsoft.icon
License N/A
File Sample(s) N/A
Compression BMP-format icons nearly always use lossless compression, but lossy methods are available. PNG icons are always compressed losslessly.
Max Dimensions 256×256 pixels
Color Modes
Mode Bits Description
Greyscale (BMP) 1 Each bit represents a single pixel, which can be either black or white.
True color (BMP) 8 and 16 Each pixel is represented by three values representing the red, green, and blue color components; each is D bits.
Indexed color (BMP) 2, 4, and 8 Each pixel is represented by a value which is one 2, 4, or 8 bits, serving as an index into the color table.
Greyscale with alpha (BMP) N/A BMP has no distinct grayscale format.
True color with alpha (BMP) 8 and 16 Each pixel is represented by four values representing the red, green, blue, and alpha color components; each is D bits.
Greyscale (PNG) 1, 2, 4, 8, and 16 Each pixel consists of a single D-bit value indicating the brightness of the greyscale pixel.
True color (PNG) 8 and 16 Each pixel is represented by three D-bit values indicating the level of the red, green, and blue color components.
Indexed color (PNG) 1, 2, 4, and 8 Each pixel is a D-bit value indicating an index into a color palette which is contained within a PLTE chunk in the APNG file; the colors in the palette all use an 8-bit depth.
Greyscale with alpha (PNG) 8 and 16 Each pixel is represented by two D-bit values: the intensity of the greyscale pixel and an alpha sample, indicating how opaque the pixel is.
True color with alpha (PNG) 8 and 16 Each pixel is comprised of four D-pixel color components: red, green, blue, and the alpha sample indicating how opaque the pixel is.
Animation No
Transparency Yes
Interlacing Yes
Metadata No
Layers No
Multipage Yes