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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

GIMP Image Format

image/x-xcf
XCF

A complete technical comparison of Flexible Image Transport System and GIMP Image Format — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature FITS XCF
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No Yes
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 →
GIMP Image Format
image/x-xcf
Extension
.xcf
Container GIMP Hierarchical Chunk Container
Compression None / RLE (Run-Length Encoding) / Zlib / Deflate (In newer GIMP versions)
Algorithm
NoneRLEZlib
Color Depth 8-bit per channel, 16-bit per channel, 32-bit floating point
Developed by Spencer Kimball, Peter Mattis, and the GIMP Development Team
Released 1995
Magic Bytes
67 69 6D 70 20 78 63 66
Full XCF reference →

Browser Support Comparison

Browser FITS XCF
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
XCF

XCF Strengths

  • Preserves all non-destructive editing elements, layer hierarchies, masks, and alpha channels across GIMP sessions
  • Open and thoroughly documented specification within the open-source community, allowing third-party tools like Krita and ImageMagick to read project files
  • Reliable magic byte header prevents misidentification
Limitations
  • Massive file sizes because raw, unflattened layer bitmaps and masks are stored directly within the project archive
  • Completely proprietary to the GIMP ecosystem for deep editing; cannot be natively rendered or parsed by web browsers
  • Third-party software supporting XCF may occasionally struggle to render complex text layer adjustments or advanced layer blend modes identically to GIMP

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
XCF
Use XCF when…
  • GIMP Native Project Archival
  • Layered Photo Editing and Graphic Design
  • Intermediary Asset Preparation for Export

More comparisons

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