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Image MIME Reference
APNG

Animated Portable Network Graphics

image/vnd.mozilla.apng
VS

FlashPix

image/vnd.fpx
FPX

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

APNG wins on browser support

Feature Support

Feature APNG FPX
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading Yes ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
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 →
FlashPix
image/vnd.fpx
Extension
.fpx
Container Microsoft OLE Structured Storage (COM)
Compression JPEG (Lossy) / Uncompressed / Single-color (Solid)
Algorithm
JPEGNone
Color Depth 8-bit (Grayscale/Indexed), 24-bit (RGB), 32-bit (CMYK/RGBA)
Developed by Eastman Kodak, Microsoft, Hewlett-Packard, Live Picture
Released 1996
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1
Full FPX reference →

Browser Support Comparison

Browser APNG FPX
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)
FPX

FPX Strengths

  • Allowed early, low-RAM computers to view and edit massive, high-resolution digital photos instantly by only loading the needed tiles and resolutions
  • Pioneered the multi-resolution pyramid and tiling concepts heavily used today in modern deep-zoom and web mapping applications (like Google Maps)
Limitations
  • Completely obsolete and unsupported by modern web browsers or operating systems
  • Uses the complex, proprietary Microsoft OLE container format, making it incredibly difficult to parse or extract data from without dedicated legacy libraries
  • Prone to being misidentified by MIME sniffers as an old Microsoft Office document

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
FPX
Use FPX when…
  • Legacy Digital Photography
  • Kodak Picture CDs (Historical)
  • Early High-Resolution Image Viewers

More comparisons

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