Free webp to jpg
EN
Image MIME Reference
ICO

Windows Icon (Legacy MIME)

image/x-icon
VS

Khronos Texture 2.0

image/ktx2
KTX2

A complete technical comparison of Windows Icon (Legacy MIME) and Khronos Texture 2.0 — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

ICO wins on browser support

Feature Support

Feature ICO KTX2
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No Yes
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
Windows Icon (Legacy MIME)
image/x-icon
Extension
.ico
Container ICO Directory Structure
Compression Uncompressed (DIB/BMP) / Deflate (Embedded PNG)
Algorithm
NoneDeflate (via PNG)
Color Depth 1-bit, 4-bit, 8-bit, 24-bit (True Color), 32-bit (RGBA)
Developed by Microsoft Corporation
Released 1985
Magic Bytes
00 00 01 00
Full ICO 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 ICO KTX2
Chrome Chrome
✓ 1
 ✕
Firefox Firefox
✓ 1
 ✕
Safari Safari
✓ 1
 ✕
Edge Edge
✓ 12
 ✕
IE IE (Legacy)
✓
 ✕
ICO

ICO Strengths

  • Universally supported by every web browser in existence for website favicons
  • Packs multiple resolutions into a single file, eliminating the need to serve different files for the taskbar vs. the desktop
  • Modern support for embedded PNGs (since Windows Vista) allows for excellent 32-bit transparency (alpha channels) and drastically reduced file sizes
Limitations
  • Internal file structure is convoluted due to decades of legacy cruft, such as the requirement for BMP data to lack a standard file header but double the height property for an archaic XOR/AND mask
  • Larger file size compared to a single optimized PNG or SVG, as it literally stores the same image multiple times at different scales
  • The MIME type landscape is highly fragmented (x-icon vs. vnd.microsoft.icon), causing occasional caching or strict-MIME validation errors on restrictive servers
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

ICO
Use ICO when…
  • Website Favicons (favicon.ico)
  • Windows Application Executable Icons (.exe)
  • Desktop Shortcut Icons
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

ICO vs ACES → KTX2 vs ACES → ICO vs APNG → KTX2 vs APNG → ICO vs AVCI → KTX2 vs AVCI → ICO vs AVCS → KTX2 vs AVCS → ICO vs AVIF → KTX2 vs AVIF → All comparisons →
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