Open FITS files online.
The free FITS viewer for your browser — no sign-up, no install, no cost. Explore pixel data, WCS coordinates, image statistics, and full header metadata instantly.
Explore every detail
From planetary imaging to deep-sky objects — FITS Viewer lets you inspect every pixel with precision. Switch color maps, adjust stretch, and measure regions with a clean, distraction-free interface.
- •Real-time histogram with draggable cut controls
- •WCS coordinate readout for RA and Dec
- •Region statistics: mean, sigma, min, max
- •15+ color maps including Viridis, Magma, and more
Loved by astronomers
What people are saying about FITS Viewer.
“Finally a FITS viewer I can use without installing anything. Perfect for quick checks on the go.”
“The histogram stretch and region stats are incredibly useful for my imaging pipeline. Open source and fast.”
“I use this to show FITS data to students during lectures. Works on every browser. Clean interface.”
Frequently Asked Questions
Everything you need to know about FITS Viewer.
What is a FITS file?
FITS (Flexible Image Transport System) is a standard data format used in astronomy for storing, transmitting, and processing scientific images.
Is this FITS viewer free?
Yes, completely free. No account, no paywall, no limits.
Do my files leave my browser?
No. All processing happens locally. Your files are never uploaded.
How do I open a FITS file?
Click “Open FITS file” or drag and drop a .fits, .fit, or .fts file. You can also try the included sample.
What color maps are supported?
15+ including Grayscale, Heat, Rainbow, Viridis, Magma, Inferno, Plasma, Cool, and more.
Can I analyze pixel values?
Yes. Probe mode shows individual pixel values, WCS coordinates, and local 3×3 statistics.
What stretch types are available?
Linear, Log, Square Root, and Arcsinh. Presets include 99%, ZScale, Full, and custom cuts.
Is there a file size limit?
No hard limit. Performance depends on your device. Very large files (>200 MP) may be slower.