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Image MIME Reference
APNG

Animated Portable Network Graphics

image/vnd.mozilla.apng
VS

Image Exchange Format

image/ief
IEF

A complete technical comparison of Animated Portable Network Graphics and Image Exchange Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

APNG wins on browser support

Feature Support

Feature APNG IEF
Transparency (Alpha) Yes ✕ No
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
Animated Portable Network Graphics
image/vnd.mozilla.apng
Extension
.apng.png
Container PNG Chunk Stream
Compression Deflate (Lossless)
Algorithm
Deflate (zlib)
Color Depth 8-bit (Indexed), 24-bit (TrueColor), 32-bit (RGBA)
Developed by Mozilla Corporation (Stuart Parmenter & Vladimir Vukićević)
Released 2004
Magic Bytes
89 50 4E 47 0D 0A 1A 0A
Full APNG reference →
Image Exchange Format
image/ief
Extension
.ief
Container TIFF Class B (TIFF-B)
Compression Lossless (MH, MR, MMR) / Uncompressed
Algorithm
MHMRMMRUncompressed
Color Depth 1-bit (Monochrome)
Developed by IETF Network Fax Working Group
Released 1992
Magic Bytes
49 49 2A 00 (Little-endian) / 4D 4D 00 2A (Big-endian)
Full IEF reference →

Browser Support Comparison

Browser APNG IEF
Chrome Chrome
✓ 59
 ✕
Firefox Firefox
✓ 3
 ✕
Safari Safari
✓ 8
 ✕
Edge Edge
✓ 79
 ✕
IE IE (Legacy)
✕ ✕
APNG

APNG Strengths

  • Supports 8-bit alpha transparency, completely solving the ugly 'white halo' problem inherent to GIFs
  • Gracefully degrades; viewers that do not support APNG will render a perfectly valid, static PNG of the first frame
  • Provides lossless compression that retains absolute pixel-perfect quality for UI elements and line art
Limitations
  • Because it relies on lossless Deflate compression, file sizes for complex, video-like animations can be massive compared to lossy formats like WebP or AVIF
  • Was initially rejected by the official PNG group, delaying its adoption for nearly a decade
  • Lacks native hardware decoding acceleration, unlike video-based animated formats (like MP4 or WebM)
IEF

IEF Strengths

  • Provided a standard method for exchanging bi-level fax images during the early days of the Internet
  • Supported multi-page documents
  • Leveraged the highly resilient and well-documented TIFF container
Limitations
  • Completely obsolete and unsupported in modern computing environments
  • Strictly limited to 1-bit monochrome data, lacking color or grayscale capabilities
  • Magic bytes overlap completely with standard TIFF, making specific filetype detection difficult without parsing internal tags

When to choose which format

APNG
Use APNG when…
  • High-Quality Web Animations
  • Stickers (Apple iMessage, LINE, Discord)
  • UI Loaders with Alpha Transparency
  • GIF Replacement
IEF
Use IEF when…
  • Legacy Fax Transmissions
  • Early Internet Gateways
  • Archival

More comparisons

APNG vs ACES → IEF vs ACES → APNG vs AVCI → IEF vs AVCI → APNG vs AVCS → IEF vs AVCS → APNG vs AVIF → IEF vs AVIF → All comparisons →
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