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Image MIME Reference
AZV

AirZip Accelerator Image

image/vnd.airzip.accelerator.azv
VS

JPEG Network Graphics

image/x-jng
JNG

A complete technical comparison of AirZip Accelerator Image and JPEG Network Graphics — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature AZV JNG
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading Yes Yes
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No Yes
ICC Color Profile ✕ No Yes
AirZip Accelerator Image
image/vnd.airzip.accelerator.azv
Extension
.azv
Container Proprietary AirZip Container
Compression Lossy (Proprietary) / Lossless (Proprietary)
Algorithm
AirZip Proprietary Compression
Color Depth 8-bit (Indexed), 24-bit (RGB)
Developed by AirZip, Inc.
Released 1999
Magic Bytes
Unknown (Proprietary)
Full AZV reference →
JPEG Network Graphics
image/x-jng
Extension
.jng
Container PNG-style Chunk Structure (JHDR, JDAT, IDAT, IEND)
Compression Lossy (JPEG/DCT for color) / Lossless (Deflate for alpha mask)
Algorithm
JPEG (Discrete Cosine Transform)Deflate (LZ77)
Color Depth 8-bit, 12-bit, 24-bit (RGB), 32-bit (RGBA)
Developed by MNG Development Group (Glenn Randers-Pehrson et al.)
Released 2001
Magic Bytes
8B 4A 4E 47 0D 0A 1A 0A
Full JNG reference →

Browser Support Comparison

Browser AZV JNG
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
AZV

AZV Strengths

  • Historically allowed internet users to browse the web up to 5x faster over 56k dial-up modems by drastically reducing image payload sizes
  • Officially registered in the IANA vendor tree, preventing MIME type conflicts on early web proxy servers
Limitations
  • Completely obsolete in the modern broadband era
  • Closed-source and proprietary, meaning no modern image manipulation libraries (like ImageMagick or libvips) can decode it
  • Zero support in standard web browsers
JNG

JNG Strengths

  • Solved a massive technical hurdle in the early 2000s by combining high-compression lossy photographic data with crisp, 8-bit alpha transparency
  • Utilized the highly robust, extensible chunk-based architecture of the PNG format
  • Provided an excellent, bandwidth-saving alternative to massive 32-bit transparent PNGs for web design
Limitations
  • Failed to achieve critical mass; browser vendors largely abandoned the MNG/JNG standard due to implementation complexity
  • Completely obsolete today, having been superseded by natively supported, superior formats like WebP, AVIF, and HEIC
  • Decoding requires a hybrid engine that can parse PNG chunks while simultaneously decoding a JPEG stream and a Deflate stream, complicating software support

When to choose which format

AZV
Use AZV when…
  • Dial-up Web Acceleration
  • Bandwidth Optimization (Historical)
  • Legacy Proxy Servers
JNG
Use JNG when…
  • Embedded frames in MNG animations
  • Historical web graphics requiring lossy compression with transparency

More comparisons

AZV vs ACES → JNG vs ACES → AZV vs APNG → JNG vs APNG → AZV vs AVCI → JNG vs AVCI → AZV vs AVCS → JNG vs AVCS → AZV vs AVIF → JNG vs AVIF → All comparisons →
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