Image MIME Reference
Apple-ICNS
Apple Icon Image
image/x-icns
VS
JPEG XR (HD Photo)
image/vnd.ms-photo
JPEG-XR
A complete technical comparison of Apple Icon Image and JPEG XR (HD Photo) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Apple-ICNS | JPEG-XR |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | Yes |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | Yes |
| 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
JPEG XR (HD Photo)
image/vnd.ms-photo
Extension
.jxr.wdp.hdp
Container
TIFF-like Image File Directory (IFD)
Compression
Lossy (Lapped Bi-orthogonal Transform) / Lossless
Algorithm
Lapped Bi-orthogonal Transform (LBT)
Color Depth
8-bit (Grayscale, RGB, CMYK), 16-bit, 32-bit Floating Point (HDR)
Developed by
Microsoft Corporation (later Joint Photographic Experts Group)
Released
2006
Magic Bytes
49 49 BC 01
Browser Support Comparison
| Browser | Apple-ICNS | JPEG-XR |
|---|---|---|
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
JPEG-XR
JPEG-XR Strengths
- Excellent support for 16-bit and 32-bit floating-point HDR images without massive file size bloat
- Native support for alpha transparency, which standard JPEG fundamentally lacks
- Computational complexity for decoding/encoding is relatively low, making it hardware-friendly
Limitations
- Suffered a complete failure of adoption in the web browser market outside of Microsoft's ecosystem
- Fully superseded by modern, open formats like WebP, AVIF, and JPEG XL which offer better compression and universal browser support
- Multiple file extensions (.wdp, .hdp, .jxr) and MIME types cause confusion and parsing fragmentation
When to choose which format
Apple-ICNS
Use Apple-ICNS when…
- macOS Application Bundles (.app)
- macOS Folder Customization
- Apple Disk Image (.dmg) Styling
JPEG-XR
Use JPEG-XR when…
- Legacy Windows Desktop Backgrounds
- XPS (XML Paper Specification) Documents
- Early High Dynamic Range (HDR) Photography
- DirectX Textures