Flexible Image Transport System

Writable

image · also known as FITS

Flexible Image Transport System (FITS) is an open standard defining a digital file format useful for storage, transmission and processing of data: formatted as multi-dimensional arrays (for example a 2D image), or tables. FITS is the most commonly used digital file format in astronomy. The FITS standard was designed specifically for astronomical data, and includes provisions such as describing photometric and spatial calibration information, together with image origin metadata. The FITS format was first standardized in 1981; it has evolved gradually since then, and the most recent version (4.0) was standardized in 2016. FITS was designed with an eye towards long-term archival storage, and the maxim once FITS, always FITS represents the requirement that developments to the format must be backward compatible.

Identify it

Extensions	`.fits.fts.fit`
MIME types	`image/fitsapplication/fits`
Signatures	`53494d504c4520203d202020202020202020202020202020202020202054` at byte 0 (FITS)
PRONOM	`x-fmt/383`
Wikidata	`Q1428303`
Library of Congress	`fdd000317`

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Open it

GIMPOpen sourcereads and writes · GNU General Public License, version 3.0
ImageMagickOpen sourcereads and writes · ImageMagick License
KStarsOpen sourcereads and writes · GNU General Public License, version 2.0
Aladin Sky AtlasOpen sourcereads · GNU General Public License, version 3.0
ConverseenOpen sourcereads · GNU General Public License, version 3.0
DevILOpen sourcereads · GNU Lesser General Public License, version 2.1
imageioOpen sourcereads · 2-clause BSD License
kstOpen sourcereads · GNU General Public License
LabPlotOpen sourcereads · GNU General Public License, version 2.0
Montage Image Mosaic SoftwareOpen sourcereads · 3-clause BSD License
OpenImageIOOpen sourcereads · BSD licenses
PhotoRecOpen sourcereads · GNU General Public License
SAOImage DS9Open sourcereads · BSD licenses / GNU General Public License / GNU Lesser General Public License
GIMP 2.0.2reads and writes
Mathematicareads and writes · proprietary license
Q650922writes · freeware / proprietary license
Sirilreads and writes
Affinity Photoreads
Graphic Workshopreads
IrfanViewreads · freeware
Konvertorreads
VisADreads

Convert it

To	With	Fidelity	Command and losses
Portable Network Graphics	ImageMagick	Lossless	`convert in.fits out.png` Pixels kept; some metadata, colour profiles or layers may be dropped.
Tagged Image File Format	ImageMagick	Lossless	`convert in.fits out.tif` Pixels kept; some metadata, colour profiles or layers may be dropped.
GIF 89a	ImageMagick	Lossy	`convert in.fits out.gif` Reduced to 256 colours.
JPEG File Interchange Format 1.02	ImageMagick	Lossy	`convert in.fits out.jpg` Lossy compression.
WebP	ImageMagick	Lossy	`convert in.fits out.webp` Lossy compression.

Sources

From Converters (FFmpeg, ImageMagick, Pandoc, LibreOffice), Just Solve the File Format Problem (File Formats Wiki), PRONOM, Wikidata. Updated 2026-10-24.

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