Image MIME Reference
JNG
JPEG Network Graphics
image/x-jng
VS
PTI Image (Personal/Vanity Tree)
image/prs.pti
PTI
A complete technical comparison of JPEG Network Graphics and PTI Image (Personal/Vanity Tree) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | JNG | PTI |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
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
PTI Image (Personal/Vanity Tree)
image/prs.pti
Extension
.pti
Container
Proprietary
Compression
Unknown / Proprietary
Algorithm
Unknown
Color Depth
Unknown
Developed by
Jürn Laun
Released
1999
Magic Bytes
Unknown
Browser Support Comparison
| Browser | JNG | PTI |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
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- Completely obsolete today, having been superseded by natively supported, superior formats like WebP, AVIF, and HEIC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
PTI
PTI Strengths
- Provided a registered MIME type namespace for a specific application's proprietary image format without conflicting with standard web types
Limitations
- Completely undocumented and unsupported in modern ecosystems
- Zero web browser compatibility
- Falls into the 'vanity' tree, making it irrelevant for standard cross-platform data exchange
When to choose which format
JNG
Use JNG when…
- Embedded frames in MNG animations
- Historical web graphics requiring lossy compression with transparency
PTI
Use PTI when…
- Legacy Application Specific Workflows
- Proprietary Image Storage