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Image MIME Reference
HEIF-Sequence

High Efficiency Image File Format Sequence

image/heif-sequence
VS

Microsoft Image Extension

image/vnd.mix
MIX

A complete technical comparison of High Efficiency Image File Format Sequence and Microsoft Image Extension — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature HEIF-Sequence MIX
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes Yes
High Efficiency Image File Format Sequence
image/heif-sequence
Extension
.heifs.heif.hif
Container HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression Lossy / Lossless
Algorithm
Codec Agnostic (HEVC, AVC, JPEG, AV1)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit
Developed by Moving Picture Experts Group (MPEG)
Released 2015
Magic Bytes
XX XX XX XX 66 74 79 70 6D 73 66 31
Full HEIF-Sequence reference →
Microsoft Image Extension
image/vnd.mix
Extension
.mix
Container Microsoft OLE Structured Storage (COM)
Compression Proprietary (Internal JPEG/RLE)
Algorithm
JPEGDeflateProprietary
Color Depth 8-bit, 24-bit, 32-bit (RGBA)
Developed by Microsoft Corporation
Released 1996
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1
Full MIX reference →

Browser Support Comparison

Browser HEIF-Sequence MIX
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
HEIF-Sequence

HEIF-Sequence Strengths

  • Codec-agnostic container allows for extreme flexibility when storing multi-frame photographic data
  • Maintains the space-saving benefits of ISOBMFF shared frame data blocks
  • Excellent for archiving computational photography workloads like exposure brackets or focal stacks
Limitations
  • Codec ambiguity means a decoder might be able to parse the container but fail to decode the underlying pixels
  • Zero native web browser support
  • Complex container structure requires specialized parsing libraries to extract individual frames
MIX

MIX Strengths

  • Allowed early consumer software to non-destructively edit complex compositions involving photos, text, and vector clipart
  • Shared an architecture with other Microsoft Office products, enabling deep integration (OLE embedding) into Word and PowerPoint at the time
Limitations
  • Completely proprietary and undocumented, leading to a massive loss of historical data for users who archived their family photos in this project format
  • Requires traversing a complex OLE filesystem just to extract the flattened raster image
  • No support in modern image editors like Photoshop, GIMP, or web browsers

When to choose which format

HEIF-Sequence
Use HEIF-Sequence when…
  • Burst Photography
  • Focal Stacking
  • Exposure Bracketing
  • Time-Lapse Data
MIX
Use MIX when…
  • Historical Microsoft Picture It! Projects
  • Microsoft PhotoDraw 2000 Graphics
  • Early 2000s Consumer Digital Scrapbooking

More comparisons

HEIF-Sequence vs ACES → MIX vs ACES → HEIF-Sequence vs APNG → MIX vs APNG → HEIF-Sequence vs AVCI → MIX vs AVCI → HEIF-Sequence vs AVCS → MIX vs AVCS → HEIF-Sequence vs AVIF → MIX vs AVIF → All comparisons →
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