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Image MIME Reference
AVIF

AV1 Image File Format

image/avif
VS

Windows Metafile

image/x-wmf
WMF

A complete technical comparison of AV1 Image File Format and Windows Metafile — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

AVIF wins on browser support

Feature Support

Feature AVIF WMF
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
AV1 Image File Format
image/avif
Extension
.avif
Container HEIF / ISOBMFF
Compression AV1 Lossy / AV1 Lossless
Algorithm
AV1
Color Depth 8-bit, 10-bit, 12-bit
Developed by Alliance for Open Media (AOMedia)
Released 2019
Magic Bytes
XX XX XX XX 66 74 79 70 61 76 69 66
Full AVIF reference →
Windows Metafile
image/x-wmf
Extension
.wmf.emf
Container Windows GDI Metafile Command Stream
Compression Uncompressed (Command Stream)
Algorithm
None
Color Depth Varies based on GDI rendering engine
Developed by Microsoft Corporation
Released 1990
Magic Bytes
D7 CD C6 9A (Aldus Placeable Metafile Header) or 01 00 09 00 (Standard WMF Header)
Full WMF reference →

Browser Support Comparison

Browser AVIF WMF
Chrome Chrome
✓ 85+
 ✕
Firefox Firefox
✓ 93+
 ✕
Safari Safari
✓ 16+
 ✕
Edge Edge
✓ 121+
 ✕
IE IE (Legacy)
✕
✓
AVIF

AVIF Strengths

  • Best-in-class compression — typically 20–50% smaller than WebP at equivalent quality
  • Native HDR and wide color gamut (BT.2020) support
  • Supports 8, 10, and 12-bit color depth
Limitations
  • Encoding is highly CPU-intensive — significantly slower than JPEG or WebP
  • Requires Edge 121+ (not supported in earlier Edge versions)
  • Limited support in native desktop image viewers
WMF

WMF Strengths

  • Infinitely scalable vector format that remains remarkably compact for simple geometric illustrations and charts
  • Historically served as a seamless conduit for copying and pasting vector graphics between disparate Windows applications via the system clipboard
Limitations
  • Notoriously plagued by historic security vulnerabilities, making raw WMF parsing a vector for exploits in legacy software
  • Completely obsolete and unsupported in modern web environments (browsers cannot render them)
  • Strictly tied to the Windows GDI architecture, making cross-platform rendering inconsistent across Linux and macOS

When to choose which format

AVIF
Use AVIF when…
  • Next-Gen Websites
  • HDR Photography
  • High-Quality Web Images
WMF
Use WMF when…
  • Legacy Microsoft Office Clip Art and Icons
  • Windows GDI Graphics Export
  • Early Windows Desktop Publishing

More comparisons

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