Image MIME Reference
AOL-ART
AOL ART Image
image/x-jg
VS
MicroStation Design File
image/x-vnd.dgn
DGN
A complete technical comparison of AOL ART Image and MicroStation Design File — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | AOL-ART | DGN |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | Yes | ✕ No |
| HDR Support | ✕ No | ✕ No |
| 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
MicroStation Design File
image/x-vnd.dgn
Extension
.dgn
Container
Microsoft OLE Compound File (V8) / IGDS (V7)
Compression
Uncompressed / OLE Structured Storage
Algorithm
None
Color Depth
Indexed Color (V7), 24-bit True Color (V8)
Developed by
Intergraph (Originally) / Bentley Systems (Currently)
Released
1980
Magic Bytes
D0 CF 11 E0 A1 B1 1A E1 (For V8 DGN)
Browser Support Comparison
| Browser | AOL-ART | DGN |
|---|---|---|
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
DGN
DGN Strengths
- Exceptionally robust at handling massive, coordinate-heavy infrastructure models that would frequently crash older versions of competing CAD software
- Deeply entrenched as the absolute standard format for many global departments of transportation and civil engineering firms
- V8 architecture supports boundless design plane coordinates, eliminating the physical scaling limitations of V7
Limitations
- Deeply proprietary format requiring complex third-party libraries (like the ODA SDK) to parse or write programmatically outside of the Bentley ecosystem
- V8's reliance on the archaic Microsoft OLE Compound File container makes file introspection cumbersome
- Cannot be rendered natively in web browsers without converting to WebGL/Canvas formats or SVG
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
DGN
Use DGN when…
- Civil Engineering and Plant Design
- Large-scale Architecture and Construction (AEC)
- 2D/3D Infrastructure Modeling