FITS Viewer
FITS Viewer is a free, browser-based tool for opening and analyzing astronomical FITS images. Unlike desktop software like DS9 or Aladin, FITS Viewer runs entirely in your browser — no installation, no account, no data uploaded to any server.
Whether you're a professional astronomer inspecting raw telescope data, an amateur astrophotographer reviewing stacked images, or a student learning about FITS format for the first time, FITS Viewer gives you the tools you need, instantly.
What makes FITS Viewer different?
100% browser-based
Your FITS files never leave your device. All processing happens locally using JavaScript and WebAssembly.
15+ colormaps
Grayscale, Heat, Viridis, Magma, Inferno, Plasma, and more. Adjust stretch with Linear, Log, Sqrt, or Asinh.
WCS coordinates
Live RA and Dec readout as you move your cursor. Supports both degrees and sexagesimal format.
Region analysis
Draw rectangular regions to compute mean, sigma, min, and max pixel statistics.
FITS header viewer
Browse, search, and inspect every keyword in your FITS header metadata.
Export anywhere
Export displayed images as PNG and region statistics as CSV. Share results with colleagues.
Supported FITS formats
FITS Viewer supports all common FITS file extensions: .fits, .fit, and .fts. Both single-HDU and multi-extension FITS files are supported, including image extensions and binary tables.
Who uses FITS Viewer?
- Astronomers checking raw telescope data before detailed analysis
- Astrophotographers reviewing stacked and calibrated images
- University lecturers demonstrating FITS data in the classroom
- Students learning astronomical data formats
- Anyone who needs to quickly open a FITS file without installing software
How does FITS Viewer compare to DS9 and Aladin?
SAOImage DS9 and Aladin are powerful desktop tools used by professional astronomers. FITS Viewer is not meant to replace them for advanced analysis. Instead, it fills the gap for quick viewing, inspection, and sharing of FITS images. Think of it as the “quick look” tool you always wished you had in your browser.