QOI to FITS Converter
Processing entirely on your device — large files may take a moment.
Quite OK Image and Flexible Image Transport System exist for different jobs: QOI (Quite OK Image) is a 2022 lossless format with a ~200-line spec — PNG-class simplicity that compresses similarly fast. Convert FITS frames to PNG or JPG to preview telescope data, or pack them into a ZIP for sharing.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How QOI compares to FITS
| QOI | FITS | |
|---|---|---|
| Compression | Lossless (RLE/delta) | None (optionally Rice/GZIP) |
| Transparency | Supported | Not supported |
| Animation | Not supported | Not supported |
| Metadata | None | Rich text header (WCS) |
| Best for | Hobby engines, lossless simplicity | Telescope frames, science data |
How to convert QOI to FITS
- 1
Select your files
Drag & drop your QOI 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 QOI format
QOI (Quite OK Image, 2021) is a lossless format defined in one short specification document: a stream of simple run-length and delta ops over linear pixels. An encoder fits in 300 lines, decodes faster than PNG, and compresses comparably for photographic content.
It has found a home in emulators, demoscene projects and hobby engines — anywhere people want images without a codec dependency. Viewers rarely support it, so converting QOI to PNG is the way to bring these files into normal tools.
+Strengths
- ✓Radically simple spec (~200 lines)
- ✓Lossless with fast decode
- ✓No patent or licensing questions
!Limitations
- −Almost no viewer support
- −Larger than modern codecs for many images
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 QOI to FITS?
Converting makes sense where the strengths of FITS meet what QOI cannot give you. Self-documenting science headers Meanwhile Almost no viewer support One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this QOI 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 QOI to FITS?
No — FITS is a lossless format, so every pixel of the converted image matches your original QOI file. You can also adjust the quality/size balance before converting when the target format supports compression.
Can I convert several QOI files at once?
Yes — drop as many files as you like into the tool and they are converted in one batch. When more than one file comes out, everything is bundled into a ZIP for a single download.
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.