Image MIME Reference
AZV
AirZip Accelerator Image
image/vnd.airzip.accelerator.azv
VS
JPEG XR (HD Photo)
image/vnd.ms-photo
JPEG-XR
A complete technical comparison of AirZip Accelerator 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 | AZV | JPEG-XR |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | Yes |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
AirZip Accelerator Image
image/vnd.airzip.accelerator.azv
Extension
.azv
Container
Proprietary AirZip Container
Compression
Lossy (Proprietary) / Lossless (Proprietary)
Algorithm
AirZip Proprietary Compression
Color Depth
8-bit (Indexed), 24-bit (RGB)
Developed by
AirZip, Inc.
Released
1999
Magic Bytes
Unknown (Proprietary)
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 | AZV | JPEG-XR |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ |
✓
|
AZV
AZV Strengths
- Historically allowed internet users to browse the web up to 5x faster over 56k dial-up modems by drastically reducing image payload sizes
- Officially registered in the IANA vendor tree, preventing MIME type conflicts on early web proxy servers
Limitations
- Completely obsolete in the modern broadband era
- Closed-source and proprietary, meaning no modern image manipulation libraries (like ImageMagick or libvips) can decode it
- Zero support in standard web browsers
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
AZV
Use AZV when…
- Dial-up Web Acceleration
- Bandwidth Optimization (Historical)
- Legacy Proxy Servers
JPEG-XR
Use JPEG-XR when…
- Legacy Windows Desktop Backgrounds
- XPS (XML Paper Specification) Documents
- Early High Dynamic Range (HDR) Photography
- DirectX Textures