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Image MIME Reference
HEIC-Sequence

HEVC Image Sequence (HEIF Container)

image/heic-sequence
VS

Khronos Texture 2.0

image/ktx2
KTX2

A complete technical comparison of HEVC Image Sequence (HEIF Container) and Khronos Texture 2.0 — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

HEIC-Sequence wins on browser support

Feature Support

Feature HEIC-Sequence KTX2
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes Yes
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
HEVC Image Sequence (HEIF Container)
image/heic-sequence
Extension
.heics.heic
Container HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression Lossy / Lossless
Algorithm
HEVC (H.265)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit
Developed by Moving Picture Experts Group (MPEG) / Apple
Released 2017
Magic Bytes
XX XX XX XX 66 74 79 70 68 65 76 63
Full HEIC-Sequence reference →
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
Full KTX2 reference →

Browser Support Comparison

Browser HEIC-Sequence KTX2
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✓ 11+
 ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
HEIC-Sequence

HEIC-Sequence Strengths

  • Incredibly efficient storage for bursts and short animations compared to GIF or motion JPEG
  • Supports 16-bit color, HDR, and alpha channel transparency across all frames
  • Shares frame data blocks, meaning the base image and animation data are heavily optimized for space
Limitations
  • Zero support in web browsers outside the Apple ecosystem (Chrome, Firefox, Edge do not support it)
  • Heavily encumbered by HEVC patent pools, hindering open-source adoption
  • Complex container structure makes parsing and decoding difficult without specialized libraries
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

HEIC-Sequence
Use HEIC-Sequence when…
  • Apple Live Photos
  • Burst Photography
  • High-Quality Animations
  • Cinemagraphs
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)

More comparisons

HEIC-Sequence vs ACES → KTX2 vs ACES → HEIC-Sequence vs APNG → KTX2 vs APNG → HEIC-Sequence vs AVCI → KTX2 vs AVCI → HEIC-Sequence vs AVCS → KTX2 vs AVCS → HEIC-Sequence vs AVIF → KTX2 vs AVIF → All comparisons →
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