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Image MIME Reference
AVIF

AV1 Image File Format

image/avif
VS

FAST Search & Transfer Image

image/vnd.fst
FST-Image

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

AVIF wins on browser support

Feature Support

Feature AVIF FST-Image
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 →
FAST Search & Transfer Image
image/vnd.fst
Extension
.fst
Container Proprietary FAST Container
Compression Proprietary
Algorithm
Unknown (Proprietary FAST encoding)
Color Depth Unknown
Developed by FAST Search & Transfer ASA (Arild Fuldseth)
Released 2000
Magic Bytes
Unknown (Proprietary)
Full FST-Image reference →

Browser Support Comparison

Browser AVIF FST-Image
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
FST-Image

FST-Image Strengths

  • Historically served as an optimized, compressed format for FAST's early multimedia and live streaming engines over constrained late-1990s bandwidth
Limitations
  • Completely obsolete and non-functional in modern software ecosystems
  • Undocumented, closed-source binary structure with zero support in modern image processing libraries
  • Shares its file extension with several other distinct file types (such as FL Studio state files or FAST Search dictionaries), leading to easy misidentification

When to choose which format

AVIF
Use AVIF when…
  • Next-Gen Websites
  • HDR Photography
  • High-Quality Web Images
FST-Image
Use FST-Image when…
  • Historical FAST Enterprise Search Indexing
  • Legacy Proprietary Multimedia Streaming (late 1990s)
  • Internal Media Transmission

More comparisons

AVIF vs ACES → FST-Image vs ACES → AVIF vs APNG → FST-Image vs APNG → AVIF vs AVCI → FST-Image vs AVCI → AVIF vs AVCS → FST-Image vs AVCS → All comparisons →
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