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Image MIME Reference
FITS

Flexible Image Transport System

image/fits
VS

JPEG-LS

image/jls
JPEG-LS

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

Equal browser support

Feature Support

Feature FITS JPEG-LS
Transparency (Alpha) ✕ No ✕ No
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes Yes
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 →
JPEG-LS
image/jls
Extension
.jls.jl
Container JPEG Bitstream
Compression Lossless / Near-Lossless (Predictive Coding)
Algorithm
LOCO-I (Low Complexity Lossless Compression for Images)Golomb-Rice Coding
Color Depth 8-bit, 12-bit, 16-bit (Per Channel)
Developed by Joint Photographic Experts Group (ISO/ITU-T) & HP Labs
Released 1999
Magic Bytes
FF D8 FF F7
Full JPEG-LS reference →

Browser Support Comparison

Browser FITS JPEG-LS
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
JPEG-LS

JPEG-LS Strengths

  • Provides state-of-the-art lossless compression ratios for continuous-tone images, often outperforming Lossless JPEG and JPEG 2000
  • Extremely fast and computationally inexpensive to encode/decode, requiring no complex floating-point math or DCTs
  • Highly resilient in constrained hardware environments, making it ideal for medical equipment and deep-space probes (e.g., Mars rovers)
Limitations
  • Zero native support in web browsers or standard consumer operating systems
  • Lacks the advanced resolution scalability and progressive decoding features found in JPEG 2000
  • Primarily relegated to niche enterprise sectors (healthcare/DICOM and aerospace) rather than consumer adoption

When to choose which format

FITS
Use FITS when…
  • Astronomy & Astrophysics
  • Space Telescope Data (Hubble, JWST)
  • Scientific Data Archiving
  • Spectroscopy
JPEG-LS
Use JPEG-LS when…
  • Medical Imaging (DICOM Encapsulation)
  • Space and Planetary Imaging (NASA/ESA)
  • Industrial Machine Vision
  • Scientific Archival Storage

More comparisons

FITS vs ACES → JPEG-LS vs ACES → FITS vs APNG → JPEG-LS vs APNG → FITS vs AVCI → JPEG-LS vs AVCI → FITS vs AVCS → JPEG-LS vs AVCS → FITS vs AVIF → JPEG-LS vs AVIF → All comparisons →
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