Image MIME Reference
HSJ2
JPEG 2000 Image Sequence (Obsolete)
image/hsj2
VS
X Window Dump (Legacy MIME Alias)
image/x-xwindowdump
XWD
A complete technical comparison of JPEG 2000 Image Sequence (Obsolete) and X Window Dump (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | HSJ2 | XWD |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | Yes | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
JPEG 2000 Image Sequence (Obsolete)
image/hsj2
Extension
.hsj2
Container
HEIF / ISOBMFF (ISO/IEC 15444-16 Obsolete)
Compression
Lossy / Lossless
Algorithm
Motion JPEG 2000 (ISO/IEC 15444-3)
Color Depth
8-bit, 10-bit, 12-bit, 16-bit
Developed by
ISO/IEC JTC 1 / ITU-T
Released
2019
Magic Bytes
XX XX XX XX 66 74 79 70 68 73 6A 32
X Window Dump (Legacy MIME Alias)
image/x-xwindowdump
Extension
.xwd.wd
Container
XWDHeader / XWDFileHeader Structure
Compression
Uncompressed
Algorithm
None
Color Depth
8-bit (Indexed), 16-bit (High Color), 24-bit (True Color), 32-bit (True Color with Alpha/Padding)
Developed by
MIT / X Consortium (X Window System)
Released
1987
Magic Bytes
00 00 00 64 (Typically indicates a 100-byte header size followed by version)
Browser Support Comparison
| Browser | HSJ2 | XWD |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
HSJ2
HSJ2 Strengths
- Historically attempted to combine Motion JPEG 2000 sequences with the flexible metadata capabilities of the HEIF container
- Supported mathematically lossless compression and scalable wavelet decoding
Limitations
- Officially deprecated by the standardization body (ISO/IEC JTC 1)
- Completely superseded by image/hej2k, rendering hsj2 files obsolete for any new development or archiving
- Zero web browser compatibility and negligible modern software support
XWD
XWD Strengths
- Provides an exact, raw pixel dump directly from the X11 display server memory without compression overhead
- Extremely fast for Unix environments to generate during low-level graphical debugging
Limitations
- Completely uncompressed, resulting in large, bloated file sizes
- Zero support in web browsers or modern desktop environments without specialized graphics translation tools
- Verbose legacy MIME strings like 'image/x-xwindowdump' require backend normalization in modern applications
When to choose which format
HSJ2
Use HSJ2 when…
- Legacy Archival
- Deprecated Workflows
XWD
Use XWD when…
- X Window System (X11) Display Debugging and Screenshots
- Legacy Unix/Linux System Administration