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Image MIME Reference
Apple-ICNS

Apple Icon Image

image/x-icns
VS

AV1 Image File Format

image/avif
AVIF

A complete technical comparison of Apple Icon Image and AV1 Image File Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

AVIF wins on browser support

Feature Support

Feature Apple-ICNS AVIF
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No ✕ No
HDR Support ✕ No Yes
EXIF Metadata ✕ No Yes
ICC Color Profile Yes Yes
Apple Icon Image
image/x-icns
Extension
.icns
Container Chunk-based (OSType Header)
Compression Uncompressed (Legacy) / PNG (Modern) / JPEG 2000 (Modern)
Algorithm
NoneDeflate (via embedded PNG)Wavelet (via embedded JP2)
Color Depth 1-bit (Monochrome), 4-bit, 8-bit, 24-bit (RGB), 32-bit (RGBA)
Developed by Apple Inc.
Released 2001
Magic Bytes
69 63 6E 73
Full Apple-ICNS reference →
AV1 Image File Format
image/avif
Extension
.avif
Container HEIF / ISOBMFF
Compression AV1 Lossy / AV1 Lossless
Algorithm
AV1
Color Depth 8-bit, 10-bit, 12-bit
Developed by Alliance for Open Media (AOMedia)
Released 2019
Magic Bytes
XX XX XX XX 66 74 79 70 61 76 69 66
Full AVIF reference →

Browser Support Comparison

Browser Apple-ICNS AVIF
Chrome Chrome
✕
✓ 85+
Firefox Firefox
✕
✓ 93+
Safari Safari
✕
✓ 16+
Edge Edge
✕
✓ 121+
IE IE (Legacy)
✕ ✕
Apple-ICNS

Apple-ICNS Strengths

  • Seamlessly handles multi-resolution scaling on macOS, perfectly serving both standard and high-DPI (Retina) displays from a single asset
  • Modern versions efficiently embed standard PNG files, making it much easier to parse the high-resolution layers than the legacy raw pixel formats
Limitations
  • Strictly bound to the Apple ecosystem; completely useless natively on Windows, Linux, or the Web
  • The internal chunking structure is notoriously messy, utilizing dozens of different undocumented, legacy OSType tags spanning 20+ years of Apple history
AVIF

AVIF Strengths

  • Best-in-class compression — typically 20–50% smaller than WebP at equivalent quality
  • Native HDR and wide color gamut (BT.2020) support
  • Supports 8, 10, and 12-bit color depth
Limitations
  • Encoding is highly CPU-intensive — significantly slower than JPEG or WebP
  • Requires Edge 121+ (not supported in earlier Edge versions)
  • Limited support in native desktop image viewers

When to choose which format

Apple-ICNS
Use Apple-ICNS when…
  • macOS Application Bundles (.app)
  • macOS Folder Customization
  • Apple Disk Image (.dmg) Styling
AVIF
Use AVIF when…
  • Next-Gen Websites
  • HDR Photography
  • High-Quality Web Images

More comparisons

Apple-ICNS vs ACES → AVIF vs ACES → Apple-ICNS vs APNG → AVIF vs APNG → Apple-ICNS vs AVCI → AVIF vs AVCI → Apple-ICNS vs AVCS → AVIF vs AVCS → All comparisons →
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