CONVERT
FITS → AVIF
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Fast, secure FITS to AVIF conversion. No registration required.
Setup: FITS is a raster image format with its own balance of compression, colour depth, and software support. Goal: an interchangeable AVIF. A FITS → AVIF operation is one of the simplest image jobs there is: same pixel grid, different wrapper. What genuinely changes is how lossy the codec is, whether alpha survives, and how large the final file ends up. KaijuConverter picks safe defaults for each of those and lets you override them under Advanced. Context: FITS is a raster image format with its own balance of compression, colour depth, and software support. AVIF is the AV1-based next-gen image codec, extremely efficient with full HDR and alpha support.
FITS Astronomical Image
Source formatFITS (Flexible Image Transport System) is the standard digital file format in astronomy for storing images, tables, and metadata from telescopes and satellites. It supports multi-dimensional arrays and extensive header metadata for scientific observation records.
AVIF Image
Target formatAVIF is a next-generation image format based on the AV1 video codec. It offers significantly better compression than JPEG and WebP while maintaining excellent visual quality, including HDR and wide color gamut support.
Why convert FITS to AVIF
The real reason to move from FITS to AVIF is almost never picture quality — both raster formats store essentially the same pixels. It is about the tools downstream: which editors open the file natively, which CMSes upload it without transcoding, which social platforms accept it. Picking AVIF solves those edge cases at the cost of a short conversion step.
HOW TO CONVERT
FITS → AVIF
Provide the FITS
Click or drag to upload. We accept a single FITS file per job, with an optional queue of additional images for batch mode.
Encode to AVIF
The conversion decodes the FITS, resolves the colour space to sRGB and writes the AVIF container around the pixel data.
Save the AVIF
The download is streamed back over HTTPS. If you uploaded multiple files, a ZIP with all AVIF outputs is produced instead.
Common Use Cases
Share across platforms
Send AVIF files to anyone without worrying about whether they have the right software for FITS.
Embed in documents
Drop AVIF output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
AVIF often produces smaller files than FITS for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
FITS vs AVIF — Strengths and limitations
What each format does best, and where it falls short.
FITS Strengths
- Self-documenting — every file carries complete observational metadata.
- Lossless — bit-exact storage of detector readouts.
- Stable since 1981 with zero breaking changes.
- Mandatory for professional astronomy — every research publication uses it.
- Open standard endorsed by IAU.
Limitations
- Niche — used almost exclusively in astronomy.
- File sizes are large (no default compression).
- Not a display format outside specialized viewers (DS9, AstroBin).
AVIF Strengths
- Best-in-class compression efficiency — 30-50% smaller than JPEG for the same quality.
- Royalty-free and patent-unencumbered (unlike HEIC).
- Supports alpha transparency, HDR, wide gamut (BT.2020), and up to 12-bit color.
- Progressive decoding: a blurry preview appears while the file is still downloading.
- Supported in all major browsers since late 2022 — no polyfills needed.
Limitations
- Encoding is CPU-expensive — an AVIF export can take 10-30× longer than JPEG.
- Older software (pre-2022) cannot open AVIF without plugins.
- Email clients still largely ignore it — stick to JPEG for attachments.
FITS vs AVIF — Technical specifications
Side-by-side comparison of the technical details.
FITS
- MIME type
- image/fits
- Extensions
- .fits, .fit, .fts
- Standard
- IAU-endorsed FITS 4.0 (latest revision)
- Header records
- 80-character ASCII cards
- Encoding
- IEEE big-endian integers and floats
AVIF
- MIME type
- image/avif
- Container
- HEIF (ISOBMFF)
- Codec
- AV1 (intra-only)
- Max dimensions
- 65 536 × 65 536 px
- Color depth
- Up to 12-bit per channel
- Color spaces
- sRGB, Display-P3, BT.2020, arbitrary ICC
| Specification | FITS | AVIF |
|---|---|---|
| MIME type | image/fits | image/avif |
| Extensions | .fits, .fit, .fts | — |
| Standard | IAU-endorsed FITS 4.0 (latest revision) | — |
| Header records | 80-character ASCII cards | — |
| Encoding | IEEE big-endian integers and floats | — |
| Container | — | HEIF (ISOBMFF) |
| Codec | — | AV1 (intra-only) |
| Max dimensions | — | 65 536 × 65 536 px |
| Color depth | — | Up to 12-bit per channel |
| Color spaces | — | sRGB, Display-P3, BT.2020, arbitrary ICC |
FITS vs AVIF — Typical file sizes
Approximate file sizes for common scenarios.
FITS
- Backyard-telescope CCD shot (5 MP) 10-30 MB
- Hubble WFC3 single exposure ~65 MB
- JWST NIRCam full detector ~650 MB
AVIF
- Thumbnail (400px) 10-30 KB
- Web photo (1920px) 80-300 KB
- 4K photo (3840px) 300 KB - 1.2 MB
- Lossless copy of 24MP photo 8-15 MB
Quality & Compatibility
FITS-to-AVIF conversion does not change the visible content. Quality is capped by the FITS decode; re-encoding a lossy source at high quality cannot recover detail that was already discarded. For archival masters, keep the original FITS alongside the AVIF copy.
Tips for Best Results
- Large FITS files may look identical to small AVIF files for photographic content; pick quality based on end use, not headline megapixels.
- For print, export AVIF at 300 DPI minimum and check that the colour profile embedded matches the print shop specification.
- Batch-convert related FITS images in one pass so they share identical encoder settings and look consistent side-by-side.
Frequently Asked Questions
It depends on the codecs involved. If both FITS and AVIF are lossy, the pixels are re-encoded and a small amount of detail is discarded — invisible at default quality settings on photographs. If AVIF is lossless (PNG, TIFF, BMP) the output keeps every pixel of the decoded FITS exactly, but cannot recover detail that FITS had already compressed away.
Often yes, especially when AVIF is lossless. FITS tuned for efficient web delivery will usually produce smaller files than AVIF's default settings. If file size matters, drop the quality in Advanced or pick a more compressed target format instead.
KaijuConverter uploads over HTTPS, processes the image in an isolated container and deletes both the source and the output within two hours. No account is required, file contents are never logged, and we do not use uploads to train any model. For confidential material, the paid plan includes a data-processing agreement.
Related comparisons
See these formats side by side to understand which fits your use case best.
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Read guideSecure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.