Image MIME Reference
JPEG-XS-(HEIF)
JPEG XS Image (HEIF Container)
image/jxsi
VS
Windows Metafile
image/x-wmf
WMF
A complete technical comparison of JPEG XS Image (HEIF Container) and Windows Metafile — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | JPEG-XS-(HEIF) | WMF |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
JPEG XS Image (HEIF Container)
image/jxsi
Extension
.jxsi.jxs.hif
Container
HEIF / ISOBMFF (ISO/IEC 23008-12)
Compression
Lossy (Visually Lossless) / Mathematically Lossless
Algorithm
JPEG XS (ISO/IEC 21122-1)
Color Depth
8-bit, 10-bit, 12-bit, 14-bit, 16-bit
Developed by
Joint Photographic Experts Group (JPEG)
Released
2019
Magic Bytes
XX XX XX XX 66 74 79 70 6A 78 73 69
Windows Metafile
image/x-wmf
Extension
.wmf.emf
Container
Windows GDI Metafile Command Stream
Compression
Uncompressed (Command Stream)
Algorithm
None
Color Depth
Varies based on GDI rendering engine
Developed by
Microsoft Corporation
Released
1990
Magic Bytes
D7 CD C6 9A (Aldus Placeable Metafile Header) or 01 00 09 00 (Standard WMF Header)
Browser Support Comparison
| Browser | JPEG-XS-(HEIF) | WMF |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ |
✓
|
JPEG-XS-(HEIF)
JPEG-XS-(HEIF) Strengths
- Provides sub-millisecond encoding and decoding latency while retaining visually lossless quality
- Brings the extensive metadata, EXIF, XMP, and color-profiling capabilities of the HEIF container to JPEG XS
- Allows grouping of multiple high-quality JPEG XS frames into a single collection file
Limitations
- Zero web browser compatibility, limiting it entirely to professional and industrial hardware workflows
- Extremely niche adoption compared to standard HEVC-based HEIC or raw JPEG XS codestreams
- Requires custom parsing logic to extract the JPEG XS codestream from the HEIF boxes
WMF
WMF Strengths
- Infinitely scalable vector format that remains remarkably compact for simple geometric illustrations and charts
- Historically served as a seamless conduit for copying and pasting vector graphics between disparate Windows applications via the system clipboard
Limitations
- Notoriously plagued by historic security vulnerabilities, making raw WMF parsing a vector for exploits in legacy software
- Completely obsolete and unsupported in modern web environments (browsers cannot render them)
- Strictly tied to the Windows GDI architecture, making cross-platform rendering inconsistent across Linux and macOS
When to choose which format
JPEG-XS-(HEIF)
Use JPEG-XS-(HEIF) when…
- Live Broadcast Infrastructure
- Medical Imaging & Archival
- Video over IP Networks
- Automotive & Drone Systems
WMF
Use WMF when…
- Legacy Microsoft Office Clip Art and Icons
- Windows GDI Graphics Export
- Early Windows Desktop Publishing