Image MIME Reference
DGN
MicroStation Design File
image/x-vnd.dgn
VS
HEVC Image Sequence (HEIF Container)
image/heic-sequence
HEIC-Sequence
A complete technical comparison of MicroStation Design File and HEVC Image Sequence (HEIF Container) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
HEIC-Sequence wins on browser support
Feature Support
| Feature | DGN | HEIC-Sequence |
|---|---|---|
| Transparency (Alpha) | Yes | Yes |
| Animation Support | ✕ No | Yes |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | ✕ No | Yes |
| EXIF Metadata | ✕ No | Yes |
| ICC Color Profile | ✕ No | Yes |
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)
HEVC Image Sequence (HEIF Container)
image/heic-sequence
Extension
.heics.heic
Container
HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression
Lossy / Lossless
Algorithm
HEVC (H.265)
Color Depth
8-bit, 10-bit, 12-bit, 16-bit
Developed by
Moving Picture Experts Group (MPEG) / Apple
Released
2017
Magic Bytes
XX XX XX XX 66 74 79 70 68 65 76 63
Browser Support Comparison
| Browser | DGN | HEIC-Sequence |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ |
✓ 11+
|
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
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
HEIC-Sequence
HEIC-Sequence Strengths
- Incredibly efficient storage for bursts and short animations compared to GIF or motion JPEG
- Supports 16-bit color, HDR, and alpha channel transparency across all frames
- Shares frame data blocks, meaning the base image and animation data are heavily optimized for space
Limitations
- Zero support in web browsers outside the Apple ecosystem (Chrome, Firefox, Edge do not support it)
- Heavily encumbered by HEVC patent pools, hindering open-source adoption
- Complex container structure makes parsing and decoding difficult without specialized libraries
When to choose which format
DGN
Use DGN when…
- Civil Engineering and Plant Design
- Large-scale Architecture and Construction (AEC)
- 2D/3D Infrastructure Modeling
HEIC-Sequence
Use HEIC-Sequence when…
- Apple Live Photos
- Burst Photography
- High-Quality Animations
- Cinemagraphs