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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

Digital Camera Raw (Generic Linux MIME)

image/x-dcraw
Generic-RAW

A complete technical comparison of Flexible Image Transport System and Digital Camera Raw (Generic Linux MIME) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature FITS Generic-RAW
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes Yes
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 →
Digital Camera Raw (Generic Linux MIME)
image/x-dcraw
Extension
.raw
Container Varies (Predominantly TIFF/EP)
Compression Lossless / Uncompressed
Algorithm
Varies (Often Lossless JPEG ITU-T81 or uncompressed)
Color Depth 12-bit, 14-bit, 16-bit
Developed by freedesktop.org (MIME mapping) / Dave Coffin (dcraw tool)
Released 1997
Magic Bytes
Varies by vendor format
Full Generic-RAW reference →

Browser Support Comparison

Browser FITS Generic-RAW
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
Generic-RAW

Generic-RAW Strengths

  • Provides a unified, highly useful catch-all MIME type for application developers who just need to know if a file is a raw image, rather than tracking 50+ individual camera extensions
  • Deeply integrated into the Linux desktop ecosystem, ensuring file manager thumbnails work seamlessly via tools like ufraw-thumbnailer
Limitations
  • Not an official IANA standard
  • Can cause conflicts where standard TIFF files are misidentified as raw camera data by over-aggressive MIME sniffers
  • The underlying 'dcraw' tool was abandoned by its creator in 2018 (though its successor, LibRaw, continues to maintain the ecosystem)

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
Generic-RAW
Use Generic-RAW when…
  • Linux Desktop File Associations (GNOME/KDE)
  • Thumbnail Generation for Raw Images (UFRaw/LibRaw)
  • Server-side Image Processing Fallbacks

More comparisons

FITS vs ACES → Generic-RAW vs ACES → FITS vs APNG → Generic-RAW vs APNG → FITS vs AVCI → Generic-RAW vs AVCI → FITS vs AVCS → Generic-RAW vs AVCS → FITS vs AVIF → Generic-RAW vs AVIF → All comparisons →
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