Format comparison
ICO vs AVIF
How do ICO and AVIFcompare? Here's everything you need to know to choose the right format — and how to convert between them.
.ico
Full guide →Icon File Format
ICO is the icon file format used by Windows for application icons and website favicons. It can contain multiple image sizes and color depths in a single file.
.avif
Full guide →AV1 Image File Format
AVIF is a next-generation image format based on the AV1 video codec. It offers the best compression ratios available today — significantly better than WebP and JPG — while being royalty-free and open source.
| Specification | ICO | AVIF |
|---|---|---|
| Full name | Icon File Format | AV1 Image File Format |
| Extension | .ico | .avif |
| MIME type | image/x-icon | image/avif |
| Category | Image | Image |
| Developer | Microsoft | Alliance for Open Media |
| Year introduced | 1985 | 2019 |
| Compression | Lossless | Lossy |
ICO advantages
- Multiple sizes in one file
- Standard for Windows icons and favicons
- Widely supported by all browsers
- Small file sizes
ICO limitations
- Limited to small image dimensions
- Primarily Windows-focused format
- Being replaced by PNG favicons in modern web
- Complex internal structure for a simple purpose
AVIF advantages
- Best-in-class compression efficiency
- Royalty-free and open source
- Supports HDR, wide color gamut, and transparency
- Both lossy and lossless modes
AVIF limitations
- Slow encoding speed
- Growing but incomplete browser support
- Limited editing software support
- Relatively new format
Which should you use?
Both ICO and AVIF have their strengths. ICO excels at website favicons, while AVIF is better for cutting-edge web performance optimization.
Best uses for ICO
Website favicons
Windows application icons
Desktop shortcuts
Taskbar and system tray icons
Best uses for AVIF
Cutting-edge web performance optimization
HDR image delivery
Next-gen progressive web apps
Replacing WebP for maximum compression
Convert between ICO and AVIF
Need to switch formats? Convert for free with SquishConvert.