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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

X Bitmap (Legacy MIME Alias)

image/x-xbm
XBM

A complete technical comparison of Flexible Image Transport System and X Bitmap (Legacy MIME Alias) — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature FITS XBM
Transparency (Alpha) ✕ No Yes
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
Full FITS reference →
X Bitmap (Legacy MIME Alias)
image/x-xbm
Extension
.xbm
Container C Source Code Header (.h)
Compression Uncompressed (Source Code)
Algorithm
None
Color Depth 1-bit (Monochrome)
Developed by MIT / X Consortium (X Window System)
Released 1988
Magic Bytes
23 64 65 66 69 6e 65 (ASCII '#define')
Full XBM reference →

Browser Support Comparison

Browser FITS XBM
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
XBM

XBM Strengths

  • Can be compiled directly into C or C++ source code without needing an external file loader or binary asset manager
  • Human-readable structure allows developers to inspect, edit, or hand-craft tiny icons directly within a text editor
  • Extremely predictable and lightweight for 1-bit hardware displays and embedded systems
Limitations
  • Strictly limited to 1-bit monochrome (black and white) graphics with no gray or color support
  • Text-based C syntax creates massive file bloat compared to binary 1-bit formats like PBM
  • Completely deprecated in modern web browsers and desktop GUI frameworks

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
XBM
Use XBM when…
  • X Window System (X11) Cursors and Icons
  • Embedded C/C++ Firmware UI Assets
  • Early 1990s Unix Web Graphics

More comparisons

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