Image MIME Reference
Apple-ICNS
Apple Icon Image
image/x-icns
VS
Windows Enhanced Metafile
image/x-emf
EMF
A complete technical comparison of Apple Icon Image and Windows Enhanced Metafile — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Apple-ICNS | EMF |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | Yes | Yes |
Apple Icon Image
image/x-icns
Extension
.icns
Container
Chunk-based (OSType Header)
Compression
Uncompressed (Legacy) / PNG (Modern) / JPEG 2000 (Modern)
Algorithm
NoneDeflate (via embedded PNG)Wavelet (via embedded JP2)
Color Depth
1-bit (Monochrome), 4-bit, 8-bit, 24-bit (RGB), 32-bit (RGBA)
Developed by
Apple Inc.
Released
2001
Magic Bytes
69 63 6E 73
Windows Enhanced Metafile
image/x-emf
Extension
.emf
Container
Windows GDI/GDI+ Record Sequence
Compression
Uncompressed (Binary Drawing Records)
Algorithm
None
Color Depth
Vector (32-bit GDI/GDI+ Colors), Supports embedded 24-bit/32-bit bitmaps
Developed by
Microsoft Corporation
Released
1993
Magic Bytes
01 00 00 00 (Header Type) ... 20 45 4D 46 (Signature at offset 40)
Browser Support Comparison
| Browser | Apple-ICNS | EMF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ |
✓
|
Apple-ICNS
Apple-ICNS Strengths
- Seamlessly handles multi-resolution scaling on macOS, perfectly serving both standard and high-DPI (Retina) displays from a single asset
- Modern versions efficiently embed standard PNG files, making it much easier to parse the high-resolution layers than the legacy raw pixel formats
Limitations
- Strictly bound to the Apple ecosystem; completely useless natively on Windows, Linux, or the Web
- The internal chunking structure is notoriously messy, utilizing dozens of different undocumented, legacy OSType tags spanning 20+ years of Apple history
EMF
EMF Strengths
- Device independent, meaning it renders consistently across different monitors and printers regardless of resolution
- Fully supports 32-bit precision and advanced GDI+ drawing commands, including alpha transparency and anti-aliasing (EMF+)
- Native rendering within the Windows OS ensures fast performance and flawless fidelity in Microsoft Office applications
Limitations
- Heavily tied to the Windows Graphics Device Interface API, making it notoriously difficult to parse perfectly on macOS or Linux
- Completely unsupported by modern web standards; cannot be embedded in HTML without conversion to SVG
- Security history: Like WMF, malicious drawing records can theoretically exploit vulnerabilities in older GDI parsers
When to choose which format
Apple-ICNS
Use Apple-ICNS when…
- macOS Application Bundles (.app)
- macOS Folder Customization
- Apple Disk Image (.dmg) Styling
EMF
Use EMF when…
- Microsoft Office Vector Graphics and Clip Art
- Windows Print Spooling (EMF Spool Files)
- High-fidelity Vector Interchange on Windows