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Image MIME Reference
AVIF

AV1 Image File Format

image/avif
VS

Group 3 Fax Image

image/g3fax
G3-Fax

A complete technical comparison of AV1 Image File Format and Group 3 Fax Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

AVIF wins on browser support

Feature Support

Feature AVIF G3-Fax
Transparency (Alpha) Yes ✕ No
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 →
Group 3 Fax Image
image/g3fax
Extension
.g3
Container Raw Bitstream
Compression Lossless (CCITT Group 3)
Algorithm
CCITT Group 3 (Modified Huffman / READ)
Color Depth 1-bit (Monochrome)
Developed by CCITT (now ITU-T) / IETF
Released 1980
Magic Bytes
None (Raw Bitstream)
Full G3-Fax reference →

Browser Support Comparison

Browser AVIF G3-Fax
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
G3-Fax

G3-Fax Strengths

  • Extremely efficient compression for 1-bit black-and-white text and line art
  • Standardized via RFC 1494 for email and internet fax transmission
  • Low bandwidth requirements
Limitations
  • Raw format lacks metadata (such as image width and resolution), requiring out-of-band information to decode accurately
  • Strictly limited to 1-bit monochrome imagery
  • Zero native web browser support

When to choose which format

AVIF
Use AVIF when…
  • Next-Gen Websites
  • HDR Photography
  • High-Quality Web Images
G3-Fax
Use G3-Fax when…
  • Telefacsimile (Fax) Transmission
  • Internet Fax (T.37)
  • Document Archiving
  • Telephony Systems

More comparisons

AVIF vs ACES → G3-Fax vs ACES → AVIF vs APNG → G3-Fax vs APNG → AVIF vs AVCI → G3-Fax vs AVCI → AVIF vs AVCS → G3-Fax vs AVCS → All comparisons →
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