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Image MIME Reference
HEJ2K

JPEG 2000 Image (HEIF Container)

image/hej2k
VS

Khronos Texture

image/ktx
KTX

A complete technical comparison of JPEG 2000 Image (HEIF Container) and Khronos Texture — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature HEJ2K KTX
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading Yes ✕ No
HDR Support Yes Yes
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG 2000 Image (HEIF Container)
image/hej2k
Extension
.hej2
Container HEIF / ISOBMFF (ISO/IEC 15444-16)
Compression Lossy / Lossless
Algorithm
JPEG 2000HTJ2K
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 6A 32 6B 69
Full HEJ2K reference →
Khronos Texture
image/ktx
Extension
.ktx
Container KTX (Khronos Texture 1.1)
Compression Uncompressed / GPU Compressed (ASTC, ETC, BCn, PVRTC)
Algorithm
ASTCETC1 / ETC2BCn (DXT)PVRTCBasis Universal (in KTX2)
Color Depth 8-bit, 16-bit, 32-bit (Integer/Float)
Developed by Khronos Group
Released 2010
Magic Bytes
AB 4B 54 58 20 31 31 BB 0D 0A 1A 0A
Full KTX reference →

Browser Support Comparison

Browser HEJ2K KTX
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
HEJ2K

HEJ2K Strengths

  • Brings the extensive capabilities of the HEIF container (like EXIF/XMP, thumbnails, and depth maps) to JPEG 2000
  • Supports mathematically lossless compression via wavelet transformation
  • High scalability and progressive decoding out of the box
Limitations
  • Extremely limited software support outside of niche industries
  • Zero native compatibility with web browsers
  • High computational complexity compared to simpler formats like JPEG or PNG
KTX

KTX Strengths

  • Enables direct-to-GPU texture uploading, drastically reducing load times and CPU overhead in 3D applications
  • Supports complex texture types natively (mipmaps, cubemaps, 3D volumes, texture arrays)
  • Standardized across major Khronos APIs (OpenGL, Vulkan, WebGL) unlike vendor-specific formats like DDS
Limitations
  • Requires custom JavaScript loaders to parse and display on the web
  • Zero native support in consumer image viewers or 2D photo editing software
  • Format fragmentation: a KTX file containing an ASTC payload will fail to render on hardware that only supports BCn compression (KTX2 and Basis Universal solve this)

When to choose which format

HEJ2K
Use HEJ2K when…
  • Medical Imaging
  • Geospatial Data
  • Scientific Archiving
KTX
Use KTX when…
  • Real-time 3D Graphics
  • WebGL / WebGPU Applications
  • Mobile Games
  • Virtual/Augmented Reality (VR/AR)

More comparisons

HEJ2K vs ACES → KTX vs ACES → HEJ2K vs APNG → KTX vs APNG → HEJ2K vs AVCI → KTX vs AVCI → HEJ2K vs AVCS → KTX vs AVCS → HEJ2K vs AVIF → KTX vs AVIF → All comparisons →
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