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Image MIME Reference
Apple-ICNS

Apple Icon Image

image/x-icns
VS

AVC Image (HEIF Container)

image/avci
AVCI

A complete technical comparison of Apple Icon Image and AVC Image (HEIF Container) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Apple-ICNS AVCI
Transparency (Alpha) Yes Yes
Animation Support ✕ No ✕ No
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 →
AVC Image (HEIF Container)
image/avci
Extension
.avci.hif
Container HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression Lossy / Lossless
Algorithm
AVC (Advanced Video Coding / H.264)
Color Depth 8-bit, 10-bit, 12-bit
Developed by Moving Picture Experts Group (MPEG) / ISO/IEC JTC 1
Released 2015
Magic Bytes
XX XX XX XX 66 74 79 70 61 76 63 69
Full AVCI reference →

Browser Support Comparison

Browser Apple-ICNS AVCI
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
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
AVCI

AVCI Strengths

  • Shares the robust, flexible HEIF container architecture that allows for rich metadata, HDR, and depth maps.
  • Backed by the highly ubiquitous AVC (H.264) codec, which is widely supported in hardware decoding.
  • Supports rectangular cropping and rotation metadata without needing to re-encode the pixel data.
Limitations
  • No native support within web browsers for HTML rendering.
  • Inferior compression efficiency when compared to newer container formats like HEIC (HEVC) or AVIF (AV1).
  • Easily confused with HEIC and AVIF, which use the same base ISOBMFF container.

When to choose which format

Apple-ICNS
Use Apple-ICNS when…
  • macOS Application Bundles (.app)
  • macOS Folder Customization
  • Apple Disk Image (.dmg) Styling
AVCI
Use AVCI when…
  • Digital Photography
  • Camera Capture
  • Archival Storage

More comparisons

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