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Image MIME Reference
HEJ2K

JPEG 2000 Image (HEIF Container)

image/hej2k
VS

Scalable Vector Graphics

image/svg+xml
SVG

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

SVG wins on browser support

Feature Support

Feature HEJ2K SVG
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
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 →
Scalable Vector Graphics
image/svg+xml
Extension
.svg.svgz
Container XML Document
Compression Uncompressed (Plain Text XML) / Lossless (GZIP via .svgz)
Algorithm
None (for .svg)GZIP (for .svgz)
Color Depth Vector (Independent of bit-depth), CSS Colors (HEX, RGB, HSL, Display-P3)
Developed by World Wide Web Consortium (W3C)
Released 2001
Magic Bytes
3C 73 76 67 (for <svg) / 3C 3F 78 6D 6C (for <?xml)
Full SVG reference →

Browser Support Comparison

Browser HEJ2K SVG
Chrome Chrome
✕
✓ All
Firefox Firefox
✕
✓ All
Safari Safari
✕
✓ All
Edge Edge
✕
✓ All
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
SVG

SVG Strengths

  • Provides infinite resolution scalability, looking perfectly crisp on high-DPI (Retina) displays without increasing file size
  • Extremely lightweight compared to raster formats for flat graphics, logos, and UI elements
  • Can be manipulated dynamically via the browser's CSS and JavaScript engines (DOM integration)
Limitations
  • Unsuitable for complex photographic images or photorealistic textures
  • Poses critical security vulnerabilities (XSS and XML External Entity attacks) if user-uploaded SVGs are not heavily sanitized
  • Rendering performance degrades significantly if the SVG contains tens of thousands of complex nodes or deeply nested paths

When to choose which format

HEJ2K
Use HEJ2K when…
  • Medical Imaging
  • Geospatial Data
  • Scientific Archiving
SVG
Use SVG when…
  • Web Logos & UI Icons
  • Responsive Web Design Elements
  • Interactive Data Visualizations (D3.js)
  • CSS and SMIL Web Animations

More comparisons

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