FITS Preview is a lightweight and fast viewer for images in FITS format (Flexible Image Transport System) introduced by NASA and HEASARC.

The viewer is based on CFITSIO library and supports all standard monochromatic and color FITS image formats. It shows both an image (zoomed and stretched automatically, but manual correction of black and white point is available), an image metadata and histogram. The viewer can flip, rotate, debayer image (automatically if offsets fields in header are set correctly) and export images to JPEG format.

What’s New

Version 2.4

FITS Preview now supports file names containing UTF-8 characters (with exception of "(", ")", "["and "]" with special meaning for FITSIO).

Ratings and Reviews

4.3 out of 5
3 Ratings

3 Ratings

Grimstod ,

Fast and makes Astrophotorgraphy sorting easier

It now allows you to zoom in quite far. 400% and I can now see indavidual pixels. Makes sorting and viewwing images out of my ZWO much faster. All the data that it gives you in the info pain is also especially helpful. I really love having the ability to change bayer patterns too.

Vrenios ,

FITS Preview Review

I am an amateur astronomer who is also a retired computer scientist. So I thought I’d heard about every possible file format by now - that is, until FITS.

The NSO, National Solar Observatories, had some online files that I wanted to see. I went through all the hoops and filally downloaded the ones I wanted. They came in as tar files, which arw easily unwraped, giving me a couple of tgz files, which I also undid. Now I’ve got my files, but they are all .fits - say what?

I looked around online and found a ton of Win solutions but had to go directly to the App store to find anything for my Apple iMac. I downloaded FITS Preview, aimed it at one of my files and voila - a beautiful image of the Sun. Very nice, and easy enough to use, once you finally get the fits files out of their cocoons.

spratdog ,

Views FITS files, nothing more.

It does in fact display my FITS images. It does not zoom past 100% to see individual pixels clearly. It does have black & white point sliders, small sliders, with no histogram for reference or numeric values. It does not have any value pickers or magnifying glass allowing me to get the original value from any particular pixel.


CloudMakers, s. r. o.
2.9 MB

OS X 10.8 or later, 64-bit processor



Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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