Image MIME Reference
Generic-RAW
Digital Camera Raw (Generic Linux MIME)
image/x-dcraw
VS
JPEG XS Image (HEIF Container)
image/jxsi
JPEG-XS-(HEIF)
A complete technical comparison of Digital Camera Raw (Generic Linux MIME) and JPEG XS Image (HEIF Container) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | Generic-RAW | JPEG-XS-(HEIF) |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | Yes |
| EXIF Metadata | Yes | Yes |
| ICC Color Profile | Yes | Yes |
Digital Camera Raw (Generic Linux MIME)
image/x-dcraw
Extension
.raw
Container
Varies (Predominantly TIFF/EP)
Compression
Lossless / Uncompressed
Algorithm
Varies (Often Lossless JPEG ITU-T81 or uncompressed)
Color Depth
12-bit, 14-bit, 16-bit
Developed by
freedesktop.org (MIME mapping) / Dave Coffin (dcraw tool)
Released
1997
Magic Bytes
Varies by vendor format
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
Browser Support Comparison
| Browser | Generic-RAW | JPEG-XS-(HEIF) |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
Generic-RAW
Generic-RAW Strengths
- Provides a unified, highly useful catch-all MIME type for application developers who just need to know if a file is a raw image, rather than tracking 50+ individual camera extensions
- Deeply integrated into the Linux desktop ecosystem, ensuring file manager thumbnails work seamlessly via tools like ufraw-thumbnailer
Limitations
- Not an official IANA standard
- Can cause conflicts where standard TIFF files are misidentified as raw camera data by over-aggressive MIME sniffers
- The underlying 'dcraw' tool was abandoned by its creator in 2018 (though its successor, LibRaw, continues to maintain the ecosystem)
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
When to choose which format
Generic-RAW
Use Generic-RAW when…
- Linux Desktop File Associations (GNOME/KDE)
- Thumbnail Generation for Raw Images (UFRaw/LibRaw)
- Server-side Image Processing Fallbacks
JPEG-XS-(HEIF)
Use JPEG-XS-(HEIF) when…
- Live Broadcast Infrastructure
- Medical Imaging & Archival
- Video over IP Networks
- Automotive & Drone Systems