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Image MIME Reference
HEIC-Sequence

HEVC Image Sequence (HEIF Container)

image/heic-sequence
VS

Network FlashPix

image/vnd.net-fpx
Net-FPX

A complete technical comparison of HEVC Image Sequence (HEIF Container) and Network FlashPix — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

HEIC-Sequence wins on browser support

Feature Support

Feature HEIC-Sequence Net-FPX
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading ✕ No Yes
HDR Support Yes ✕ No
EXIF Metadata Yes Yes
ICC Color Profile Yes Yes
HEVC Image Sequence (HEIF Container)
image/heic-sequence
Extension
.heics.heic
Container HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression Lossy / Lossless
Algorithm
HEVC (H.265)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit
Developed by Moving Picture Experts Group (MPEG) / Apple
Released 2017
Magic Bytes
XX XX XX XX 66 74 79 70 68 65 76 63
Full HEIC-Sequence reference →
Network FlashPix
image/vnd.net-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 Digital Imaging Group (Kodak, HP, Live Picture, Microsoft)
Released 1996
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1
Full Net-FPX reference →

Browser Support Comparison

Browser HEIC-Sequence Net-FPX
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✓ 11+
 ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
HEIC-Sequence

HEIC-Sequence Strengths

  • Incredibly efficient storage for bursts and short animations compared to GIF or motion JPEG
  • Supports 16-bit color, HDR, and alpha channel transparency across all frames
  • Shares frame data blocks, meaning the base image and animation data are heavily optimized for space
Limitations
  • Zero support in web browsers outside the Apple ecosystem (Chrome, Firefox, Edge do not support it)
  • Heavily encumbered by HEVC patent pools, hindering open-source adoption
  • Complex container structure makes parsing and decoding difficult without specialized libraries
Net-FPX

Net-FPX Strengths

  • Revolutionized web imaging in the late 1990s by proving that massive gigapixel images could be navigated seamlessly over 56k dial-up modems
  • Pioneered the tile-based, multi-resolution pyramid concepts that eventually evolved into modern standards like IIIF (International Image Interoperability Framework)
Limitations
  • Completely obsolete, having been replaced by standard JPEG servers and modern tiling formats like Deep Zoom or JPEG 2000/XR
  • Relied on proprietary Java applets or ActiveX controls to render the tiles dynamically in a web browser
  • Extremely complex to parse server-side due to the heavy OLE filesystem container

When to choose which format

HEIC-Sequence
Use HEIC-Sequence when…
  • Apple Live Photos
  • Burst Photography
  • High-Quality Animations
  • Cinemagraphs
Net-FPX
Use Net-FPX when…
  • Historical Internet Imaging Protocol (IIP) Streaming
  • Early E-Commerce Deep Zoom Implementations
  • Legacy High-Resolution Image Servers

More comparisons

HEIC-Sequence vs ACES → Net-FPX vs ACES → HEIC-Sequence vs APNG → Net-FPX vs APNG → HEIC-Sequence vs AVCI → Net-FPX vs AVCI → HEIC-Sequence vs AVCS → Net-FPX vs AVCS → HEIC-Sequence vs AVIF → Net-FPX vs AVIF → All comparisons →
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