Specialized FormatSince 1985

ICO

Icon File Format

Extension
.ico
Developer
Microsoft
Compression
Lossless
Year
1985

What is ICO?

ICO is an image file format used for icons in Microsoft Windows. A single ICO file can contain multiple images at different sizes and color depths, allowing the operating system to select the most appropriate version for the display context. ICO files are also used as favicons for websites, making them essential for web branding.

Key Features

Lossless Compression
Perfect quality preservation
Transparency
Supports alpha channel
No Animation
Static images only

Common Use Cases

Website favicons
Windows application icons
Desktop shortcuts
Taskbar and system tray icons
File type association icons
Browser tab icons

Advantages

  • Supports multiple sizes in a single file
  • Transparency support
  • Universal favicon format
  • Native Windows integration
  • Supports various color depths

Limitations

  • Limited to small image sizes (typically up to 256x256)
  • Primarily Windows-specific format
  • Not efficient for general-purpose images
  • Outdated compression methods
  • Being replaced by PNG and SVG for favicons in modern browsers

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