ICO Format — What is Icon File Format?
ICO is the standard icon format for Windows and web favicons. It can contain multiple image sizes and color depths within a single file.
Extension
.ico
Compression
Lossless
Transparency
Yes
MIME Type
image/x-icon
Pros & Cons
✅ Pros
- • Multiple sizes in one file
- • Favicon standard
- • Transparency support
- • Windows icon standard
❌ Cons
- • Limited to small sizes
- • Windows-centric
- • Not for general images
- • Complex structure
Best Use Cases
- Website favicons
- Windows application icons
- Desktop shortcuts
- Browser tab icons
Technical Details
ICO files use a directory structure that can contain multiple BMP or PNG images at different sizes (16x16, 32x32, 48x48, 256x256). Modern ICO files often embed PNG data.
History
ICO was introduced by Microsoft with Windows 1.0 in 1985. It remains the standard format for favicons on the web and Windows application icons.
Frequently Asked Questions About ICO
What is ICO (Icon File Format)?
ICO is the standard icon format for Windows and web favicons. It can contain multiple image sizes and color depths within a single file.
Can I open ICO files on Windows and Mac?
Yes, ICO files can be opened on both Windows and Mac using built-in image viewers and most image editing software.
Does ICO support transparency?
Yes, ICO supports transparency (alpha channel), making it suitable for logos, icons, and overlays where you need transparent backgrounds.
Is ICO lossy or lossless?
ICO uses lossless compression, meaning no image data is lost. The image quality is preserved exactly as the original.
How do I convert ICO to JPG or PNG?
You can convert ICO to JPG or PNG instantly using FormatPic's free online converter. Simply upload your ICO file, choose your output format, and download the result. All processing happens in your browser — no files are uploaded to any server.
What is ICO best used for?
ICO is best used for website favicons, windows application icons, desktop shortcuts, browser tab icons. Multiple sizes in one file is one of its key advantages.