Image MIME Reference
HSJ2
JPEG 2000 Image Sequence (Obsolete)
image/hsj2
VS
Khronos Texture 2.0
image/ktx2
KTX2
A complete technical comparison of JPEG 2000 Image Sequence (Obsolete) and Khronos Texture 2.0 — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | HSJ2 | KTX2 |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | Yes | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | Yes | Yes |
| 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
Khronos Texture 2.0
image/ktx2
Extension
.ktx2
Container
KTX 2.0
Compression
Basis Universal (ETC1S / UASTC) / Zstandard (zstd) Supercompression / Uncompressed
Algorithm
ETC1SUASTCZstandard (zstd)Raw GPU Formats (ASTC, BCn)
Color Depth
8-bit, 16-bit, 32-bit (Float)
Developed by
Khronos Group
Released
2021
Magic Bytes
AB 4B 54 58 20 32 30 BB 0D 0A 1A 0A
Browser Support Comparison
| Browser | HSJ2 | KTX2 |
|---|---|---|
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- Completely superseded by image/hej2k, rendering hsj2 files obsolete for any new development or archiving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
KTX2
KTX2 Strengths
- Universal hardware compatibility: write once, transcode anywhere to the target GPU's preferred format (ASTC, BC7, PVRTC, etc.)
- Drastically reduces transmission size over networks thanks to Basis Universal and Zstandard supercompression
- Seamless integration with the glTF ecosystem for optimized 3D asset delivery
Limitations
- Requires WebAssembly (Wasm) decoders and JavaScript loaders for web viewing, increasing initial application payload slightly
- Encoding textures into high-quality Basis Universal UASTC can be computationally intensive and slow
- Zero support in traditional 2D image viewers or native OS previews
When to choose which format
HSJ2
Use HSJ2 when…
- Legacy Archival
- Deprecated Workflows
KTX2
Use KTX2 when…
- glTF 3D Models (KHR_texture_basisu)
- WebGPU and WebGL Applications
- Game Engines (Unity, Unreal, Godot)
- Augmented and Virtual Reality (AR/VR)