Image MIME Reference
AOL-ART
AOL ART Image
image/x-jg
VS
Portable Pixmap
image/x-portable-pixmap
PPM
A complete technical comparison of AOL ART Image and Portable Pixmap — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | AOL-ART | PPM |
|---|---|---|
| Transparency (Alpha) | ✕ No | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
AOL ART Image
image/x-jg
Extension
.art
Container
Johnson-Grace Proprietary
Compression
Proprietary Wavelet (Photos) / Proprietary Palette-based (Graphics)
Algorithm
Wavelet (similar to early JPEG 2000 concepts)Lossy DCT
Color Depth
8-bit (Indexed), 24-bit (RGB)
Developed by
Johnson-Grace Company (Acquired by AOL)
Released
1994
Magic Bytes
4A 47 03 00 or 4A 47 04 00
Portable Pixmap
image/x-portable-pixmap
Extension
.ppm
Container
Netpbm
Compression
Uncompressed
Algorithm
None
Color Depth
24-bit (RGB), 48-bit (RGB High Color)
Developed by
Jef Poskanzer (Netpbm Project)
Released
1988
Magic Bytes
50 33 (ASCII) or 50 36 (Binary)
Browser Support Comparison
| Browser | AOL-ART | PPM |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
AOL-ART
AOL-ART Strengths
- Historically provided massive file size reductions (up to 3x smaller than JPEGs of the era) and highly optimized progressive rendering for 14.4k modems
- Enabled faster web browsing on the AOL network during the early days of the commercial internet
Limitations
- Completely proprietary, heavily patent-encumbered, and never officially reverse-engineered for the open-source community
- On-the-fly proxy compression ruined the visual fidelity of many 1990s websites for AOL users
- Virtually impossible to open on modern operating systems without installing niche, legacy image viewers
PPM
PPM Strengths
- Absolute structural simplicity allows parsers and renderers (such as custom raytracers) to write directly to the format with virtually no overhead or external libraries
- Supports 16-bit per channel (48-bit total) precision, preserving deep color accuracy before converting to final delivery formats
- ASCII encoding ('P3') allows manual editing and visual inspection of RGB values directly within a text editor
Limitations
- Zero compression results in astronomical file sizes, making it entirely impractical for web delivery or consumer storage
- Does not natively support an alpha channel for transparency (this is handled by the newer PAM extension format within the Netpbm suite)
- Lacks support for modern metadata standards like EXIF, XMP, or embedded ICC color profiles
When to choose which format
AOL-ART
Use AOL-ART when…
- Historical AOL Dial-up Web Browsing
- Legacy America Online Client Assets
- 1990s Internet Archival
PPM
Use PPM when…
- Intermediary Format for Image Format Conversion
- Academic Computer Graphics and Raytracing Output
- Unix/Linux Command-Line Image Pipelines