Overview & Technical Profile
ICO is the standard container format for website favicons and Microsoft Windows desktop application icons.
| Standard / Specification | Microsoft Windows Shell Format |
|---|---|
| MIME Type | image/x-icon |
| Compression Scheme | Uncompressed DIB or embedded PNG stream |
| Transparency Support | Yes (1-bit mask or 32-bit RGBA alpha) |
| Animation Capability | No |
| Color Depth | Up to 32-bit Truecolor with alpha channel |
| Typical File Size | 5 KB – 100 KB |
| Global Browser Support | 100% Universal for browser favicons |
History & Engineering Background
Introduced with Windows 1.0 in 1985 and standardized for the web by Internet Explorer 5 in 1999, favicon.ico remains an essential requirement for every website.
Best Use Cases
Website root favicons (favicon.ico), browser bookmark icons, and Windows desktop application shortcuts.
When NOT to Use ICO
General photo sharing, website body graphics, document illustration, or print layouts.
Popular Conversion Workflows for ICO
Easily transform ICO files into compatible or more optimized formats right in your browser: