Image MIME Reference
GIF
Graphics Interchange Format
image/gif
VS
Windows Icon (Legacy MIME)
image/x-icon
ICO
A complete technical comparison of Graphics Interchange Format and Windows Icon (Legacy MIME) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | GIF | ICO |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | Yes | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | Yes | ✕ No |
Graphics Interchange Format
image/gif
Extension
.gif
Container
GIF
Compression
Lossless (LZW)
Algorithm
LZW (Lempel-Ziv-Welch)
Color Depth
1-bit, 4-bit, 8-bit (Indexed)
Developed by
CompuServe
Released
1987
Magic Bytes
47 49 46 38 39 61
Windows Icon (Legacy MIME)
image/x-icon
Extension
.ico
Container
ICO Directory Structure
Compression
Uncompressed (DIB/BMP) / Deflate (Embedded PNG)
Algorithm
NoneDeflate (via PNG)
Color Depth
1-bit, 4-bit, 8-bit, 24-bit (True Color), 32-bit (RGBA)
Developed by
Microsoft Corporation
Released
1985
Magic Bytes
00 00 01 00
Browser Support Comparison
| Browser | GIF | ICO |
|---|---|---|
Chrome
|
✓ All
|
✓ 1
|
Firefox
|
✓ All
|
✓ 1
|
Safari
|
✓ All
|
✓ 1
|
Edge
|
✓ All
|
✓ 12
|
IE (Legacy)
|
✓
|
✓
|
GIF
GIF Strengths
- Universal support across all web browsers, operating systems, and messaging apps
- Supports basic frame-by-frame animation out of the box
- Lossless compression is highly effective for simple, flat-color graphics like logos or pixel art
Limitations
- Limited to 256 colors per frame, resulting in poor quality for complex gradients and photographs
- Animations produce massive file sizes compared to modern formats like MP4, WebP, or AVIF
- 1-bit transparency limits edge blending on non-uniform backgrounds
ICO
ICO Strengths
- Universally supported by every web browser in existence for website favicons
- Packs multiple resolutions into a single file, eliminating the need to serve different files for the taskbar vs. the desktop
- Modern support for embedded PNGs (since Windows Vista) allows for excellent 32-bit transparency (alpha channels) and drastically reduced file sizes
Limitations
- Internal file structure is convoluted due to decades of legacy cruft, such as the requirement for BMP data to lack a standard file header but double the height property for an archaic XOR/AND mask
- Larger file size compared to a single optimized PNG or SVG, as it literally stores the same image multiple times at different scales
- The MIME type landscape is highly fragmented (x-icon vs. vnd.microsoft.icon), causing occasional caching or strict-MIME validation errors on restrictive servers
When to choose which format
GIF
Use GIF when…
- Web Animations
- Memes
- Simple Graphics
- Logos with flat colors
ICO
Use ICO when…
- Website Favicons (favicon.ico)
- Windows Application Executable Icons (.exe)
- Desktop Shortcut Icons