ICO to FITS Converter
Processing entirely on your device — large files may take a moment.
ICO is the Windows icon format. A single ICO file can bundle several sizes (16×16 up to 256×256) of the same icon, used for shortcuts, application icons and website favicons. Convert FITS frames to PNG or JPG to preview telescope data, or pack them into a ZIP for sharing.
Because the whole conversion happens on your device, it is instant, unlimited and genuinely private — no accounts, no watermarks, no files on anyone's server. Multiple files are converted in one go.
How ICO compares to FITS
| ICO | FITS | |
|---|---|---|
| Compression | BMP members, PNG for large sizes | None (optionally Rice/GZIP) |
| Transparency | Supported (1-bit or alpha) | Not supported |
| Animation | No (that is .cur/.ani) | Not supported |
| Metadata | None | Rich text header (WCS) |
| Best for | Favicons and Windows app icons | Telescope frames, science data |
How to convert ICO to FITS
- 1
Select your files
Drag & drop your ICO files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to FITS". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted FITS file individually, or grab everything at once as a ZIP archive.
About the ICO format
ICO is the Windows icon container, and one of the oldest formats still in daily use. A single ICO file bundles several renderings of the same icon — 16×16, 32×32, 48×48 up to 256×256 — so Windows can pick the right sharpness for shortcuts, Explorer views and taskbars. Each member is stored as classic BMP data or, for large sizes, PNG compression.
On the web, favicon.ico at the site root remains the one icon request every browser makes automatically, which keeps the format alive despite cleaner alternatives like PNG and SVG icons. Keep ICOs small: every visitor downloads one.
+Strengths
- ✓Multiple sizes bundled in one file
- ✓Every browser falls back to /favicon.ico automatically
- ✓Deep Windows integration for app icons
!Limitations
- −Practical size ceiling around 256×256
- −Windows-centric; little use outside icons
- −Quality is frozen at export time
About the FITS format
FITS (Flexible Image Transport System) has carried professional astronomy data since 1981: every file opens with a plain-text header that records telescope, instrument, exposure, filters and world coordinates, followed by raw pixel arrays — often 16-bit or float, sometimes data cubes.
Values can be negative or far above display range, so FITS never looks right in a photo viewer. Converting to PNG applies a simple scaling pass that reveals the nebula or galaxy in the numbers — good for previews, while science pipelines keep the original.
+Strengths
- ✓Self-documenting science headers
- ✓High bit depth (16/32-bit, float)
- ✓The standard of every observatory
!Limitations
- −Not display-ready
- −Files are large and uncompressed
Why convert ICO to FITS?
There is a concrete reason this conversion exists: Practical size ceiling around 256×256 FITS sidesteps that — Self-documenting science headers If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this ICO to FITS converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Will I lose quality converting ICO to FITS?
No — FITS is a lossless format, so every pixel of the converted image matches your original ICO file. You can also adjust the quality/size balance before converting when the target format supports compression.
Will transparent areas survive the conversion to FITS?
Transparency is kept whenever FITS actually supports an alpha channel. If the target format has none (like JPG), transparent areas are flattened onto a white background — that is a property of the format, not of this tool.
What happens to EXIF data and other metadata?
Conversions here re-encode the image, and re-encoding generally does not carry the original metadata over. If the EXIF data of your ICO files matters (camera model, GPS, timestamps), keep the original file as the master and treat the converted copy as the shareable version.