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Image MIME Reference
APNG

Animated Portable Network Graphics

image/vnd.mozilla.apng
VS

Microsoft Document Imaging

image/vnd.ms-modi
MODI

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

APNG wins on browser support

Feature Support

Feature APNG MODI
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 →
Microsoft Document Imaging
image/vnd.ms-modi
Extension
.mdi
Container TIFF Variant
Compression LZW / Proprietary MS Compression
Algorithm
LZW (Modified)
Color Depth 1-bit (Monochrome), 8-bit (Grayscale), 24-bit (RGB)
Developed by Microsoft Corporation
Released 2001
Magic Bytes
49 49 2A 00
Full MODI reference →

Browser Support Comparison

Browser APNG MODI
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)
MODI

MODI Strengths

  • Historically provided an excellent all-in-one scanned document format with built-in OCR and annotations before PDF editing became universally accessible
  • Tightly integrated with Microsoft Office and SharePoint workflows in the early 2000s
Limitations
  • Completely proprietary and obsolete; Microsoft abandoned it in favor of standard TIFF and PDF
  • Causes widespread identification conflicts since its file signature is identical to a standard TIFF
  • Extremely difficult to open on modern operating systems without relying on third-party conversion utilities

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
MODI
Use MODI when…
  • Legacy Scanned Document Archival
  • Microsoft Office XP/2003/2007 Workflows
  • Embedded OCR Text Storage

More comparisons

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