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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

Multi-resolution Seamless Image Database

image/x-mrsid-image
MrSID

A complete technical comparison of Flexible Image Transport System and Multi-resolution Seamless Image Database — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature FITS MrSID
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No Yes
HDR Support Yes ✕ No
EXIF Metadata ✕ No Yes
ICC Color Profile ✕ No Yes
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
Full FITS reference →
Multi-resolution Seamless Image Database
image/x-mrsid-image
Extension
.sid
Container Proprietary MrSID Container
Compression Proprietary Wavelet (Lossy) / Proprietary Wavelet (Lossless)
Algorithm
Discrete Wavelet Transform (DWT)
Color Depth 8-bit (Grayscale), 24-bit (RGB), Multi-spectral (Multiple bands)
Developed by Los Alamos National Laboratory / LizardTech (Extensis)
Released 1992
Magic Bytes
6D 73 69 64
Full MrSID reference →

Browser Support Comparison

Browser FITS MrSID
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE 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
MrSID

MrSID Strengths

  • Incredible compression ratios enable multi-gigabyte geographical datasets to be stored on standard hard drives or transmitted easily
  • Multi-resolution architecture means panning and zooming across a massive map is completely fluid, as the system decodes only the visible quadrant at the required zoom level
  • Supports multi-spectral bands critical for remote sensing and agricultural GIS analysis
Limitations
  • Deeply proprietary; creating or decoding MrSID files typically requires expensive commercial software or the proprietary Extensis DSDK
  • Open-source geospatial libraries like GDAL require compiling against the proprietary SDK to legally enable MrSID support, causing licensing headaches for Linux server deployments
  • Not natively viewable on the web without specialized geospatial map servers (like GeoServer or MapServer) tiling the image into PNGs or JPEGs on the fly

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
MrSID
Use MrSID when…
  • Geographic Information Systems (GIS)
  • Satellite Imagery Archival
  • Aerial Orthophotography Mosaics

More comparisons

FITS vs ACES → MrSID vs ACES → FITS vs APNG → MrSID vs APNG → FITS vs AVCI → MrSID vs AVCI → FITS vs AVCS → MrSID vs AVCS → FITS vs AVIF → MrSID vs AVIF → All comparisons →
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