Image MIME Reference
FITS
Flexible Image Transport System
image/fits
VS
Microsoft Document Imaging
image/vnd.ms-modi
MODI
A complete technical comparison of Flexible Image Transport System and Microsoft Document Imaging — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | FITS | MODI |
|---|---|---|
| Transparency (Alpha) | ✕ No | ✕ No |
| Animation Support | ✕ No | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
Flexible Image Transport System
image/fits
Extension
.fits.fit.fts
Container
FITS
Compression
Uncompressed / Tile Compressed (Rice, GZIP)
Algorithm
UncompressedRiceGZIPHcompress
Color Depth
8-bit, 16-bit, 32-bit, 64-bit (Float/Double)
Developed by
IAU FITS Working Group / NASA
Released
1981
Magic Bytes
53 49 4D 50 4C 45 20 20 3D 20
Microsoft Document Imaging
image/vnd.ms-modi
Extension
.mdi
Container
TIFF Variant
Compression
LZW / Proprietary MS Compression
Algorithm
LZW (Modified)
Color Depth
1-bit (Monochrome), 8-bit (Grayscale), 24-bit (RGB)
Developed by
Microsoft Corporation
Released
2001
Magic Bytes
49 49 2A 00
Browser Support Comparison
| Browser | FITS | MODI |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
FITS
FITS Strengths
- The undisputed global standard for archiving and sharing astronomical data
- Self-documenting: Headers are written in plain ASCII, ensuring data is readable decades later regardless of software
- Supports incredibly high dynamic range, N-dimensional arrays, and complex binary tables
Limitations
- No support in standard consumer software or web browsers
- Uncompressed raw FITS files from modern telescopes can be excessively large
- Does not use standard metadata models like EXIF or XMP, requiring specialized parsers
MODI
MODI Strengths
- Historically provided an excellent all-in-one scanned document format with built-in OCR and annotations before PDF editing became universally accessible
- Tightly integrated with Microsoft Office and SharePoint workflows in the early 2000s
Limitations
- Completely proprietary and obsolete; Microsoft abandoned it in favor of standard TIFF and PDF
- Causes widespread identification conflicts since its file signature is identical to a standard TIFF
- Extremely difficult to open on modern operating systems without relying on third-party conversion utilities
When to choose which format
FITS
Use FITS when…
- Astronomy & Astrophysics
- Space Telescope Data (Hubble, JWST)
- Scientific Data Archiving
- Spectroscopy
MODI
Use MODI when…
- Legacy Scanned Document Archival
- Microsoft Office XP/2003/2007 Workflows
- Embedded OCR Text Storage