ICO (Windows Icon Format)

ICO is a container format used for icons on Microsoft Windows and website favicons. A single ICO file can contain multiple images at different sizes and color depths. It remains the standard format for browser tab icons (favicons) alongside PNG.

MIME Type

image/vnd.microsoft.icon

Type

Binary

Compression

Lossless

Advantages

+ Multiple sizes in a single file
+ Universal favicon support across browsers
+ Transparent background support

Disadvantages

− Limited to icon use cases
− Maximum practical size of 256x256 pixels
− Windows-centric format

When to Use .ICO

Use ICO for Windows application icons and website favicons. Include multiple sizes (16x16, 32x32, 48x48) in a single file for best display.

Technical Details

ICO files contain a directory of BMP or PNG images at various sizes (16x16, 32x32, 48x48, 256x256). Modern ICO files typically embed PNG-compressed images for sizes above 48x48.

History

ICO was introduced with Windows 1.0 in 1985 for desktop application icons. It became the web favicon standard when Internet Explorer 5 supported favicon.ico in 1999.

Convert from .ICO

.ico → .avif .ico → .bmp .ico → .gif .ico → .heic .ico → .jpg .ico → .jxl .ico → .png .ico → .psd .ico → .raw .ico → .tiff .ico → .webp

Convert to .ICO

.avif → .ico .bmp → .ico .gif → .ico .heic → .ico .jpg → .ico .jxl → .ico .png → .ico .psd → .ico .raw → .ico .tiff → .ico .webp → .ico

Related Formats

.ai .apng .arw .avif .bmp .cr2 .dng .eps .gif .heic

Related Terms

ICO

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Use Cases

C Batch Exporting Design Assets for Developer Handoff T Generating Favicon Sets from a Single Logo File