What is a FITS file?
A .FITS file is a Flexible Image Transport System file. It is the most common digital file format in astronomy. Organizations like NASA and the International Astronomical Union (IAU) use this format to store, transmit, and process scientific data. A .FITS file can contain multi-dimensional arrays, such as 2D images, and complex data tables. It also stores structural metadata in a human-readable ASCII header.
How to open FITS files?
Specialized software is usually required to open .FITS files natively. Astronomers often use tools like SAOImage DS9 or Fv FITS Viewer to inspect these images. Software developers can use the Astropy library in Python to read and process the underlying data arrays. Standard image editors like GIMP or ImageJ can also open them if you install the correct plugins.
Best practices and troubleshooting
If you cannot open a .FITS file, it might contain complex data tables or spectra instead of a simple 2D image. Because .FITS has multiple possible meanings and internal structures, we recommend using viewer.online/fits to identify the actual format of your file. If you simply need to view the visual data, we recommend file conversion to sensible target formats on convert.guru. You can easily convert .FITS files to .JPG or .PNG formats for quick sharing.
Summary
The viewer.online/fits platform analyzes .FITS files to identify their exact format and creator software, shows which programs can open the file, and usually previews it. Our tool directly opens and previews .FITS files in the browser, eliminating the need to install software or troubleshoot compatibility issues.