Image MIME Reference
JNG
JPEG Network Graphics
image/x-jng
VS
Truevision TGA (Legacy MIME Alias)
image/x-tga
TGA
A complete technical comparison of JPEG Network Graphics and Truevision TGA (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | JNG | TGA |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| 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
Truevision TGA (Legacy MIME Alias)
image/x-tga
Extension
.tga.icb.vda.vst
Container
Truevision TGA Footer/Header
Compression
Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneRLE
Color Depth
8-bit (Grayscale or Indexed), 16-bit (High Color), 24-bit (True Color), 32-bit (True Color with Alpha Channel)
Developed by
Truevision Inc.
Released
1984
Magic Bytes
54 52 55 45 56 49 53 49 4F 4E 2D 58 46 49 4C 45 2E 00 (At the end of the file)
Browser Support Comparison
| Browser | JNG | TGA |
|---|---|---|
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- Completely obsolete today, having been superseded by natively supported, superior formats like WebP, AVIF, and HEIC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
TGA
TGA Strengths
- Incredibly simple byte layout allows developers to write custom loaders and exporters in a few dozen lines of code, bypassing the need for heavy external libraries
- Native support for 8-bit alpha channels ensures flawless transparency masking for real-time 3D rendering
- Fast, predictable RLE decoding requires almost no CPU overhead compared to DEFLATE (PNG) or DCT (JPEG)
Limitations
- RLE compression is relatively weak by modern standards, resulting in large file sizes
- Lacks a standard magic byte header at the beginning of the file, making file-sniffing unreliable for older v1.0 files
- Zero support in web browsers; must be converted to PNG or WebP for web delivery
When to choose which format
JNG
Use JNG when…
- Embedded frames in MNG animations
- Historical web graphics requiring lossy compression with transparency
TGA
Use TGA when…
- Video Game 3D Textures and Materials
- 3D Rendering and Animation Sequences
- Legacy Video Production Workflows