Add your FITS file
Drop one or more .fits files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
FITS to JSON
Converting a .fits font to .json repackages the same glyphs and metrics for a different delivery target. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop FITS files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting Flexible Image Transport System to JSON data
Converting a .fits font to .json repackages the same glyphs and metrics for a different delivery target. A .fits file is the standard data format of astronomy: one or more header-data units, each a block of human-readable 80-character keyword cards followed by an N-dimensional array or a table. Essentially every professional telescope and space observatory writes it, and the format has been backwards-compatible since 1981.
A .json file holds JavaScript Object Notation: nested objects, arrays, strings, numbers, booleans, and null written in a strict text syntax. It is the default data language of the web — most APIs speak nothing else. For this route the practical draw is parsers ship in the standard library of essentially every language and readable by humans and machines alike — balanced against no comments — a perpetual annoyance for configuration files, which is worth knowing before you commit a large batch.
Why convert FITS to JSON?
The practical trigger for this conversion is usually a mismatch: with .fits, the 2880-byte block padding wastes space and reflects hardware nobody has used in decades. Switching to .json buys you parsers ship in the standard library of essentially every language, which is why it is the better fit for rEST and HTTP API request and response payloads. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
FITS vs JSON at a glance
| Aspect | Flexible Image Transport System (.fits) | JSON data (.json) |
|---|---|---|
| Format type | Lossless — every pixel or sample is preserved exactly | Text-based — characters and structure, so there is no visual quality loss |
| How it stores data | headers are ASCII cards of exactly 80 characters, in the form KEYWORD = value / comment, padded into 2880-byte blocks — a size inherited from magnetic tape | exactly six value types; no dates, no comments, no trailing commas — the strictness is deliberate |
| Strongest at | telescope and space-observatory imagery and spectra | rEST and HTTP API request and response payloads |
| Weak spot | the 2880-byte block padding wastes space and reflects hardware nobody has used in decades | no comments — a perpetual annoyance for configuration files |
Pick JSON as the output
Select .json in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if JSON is selectable, the route is real and validated.
Convert on your device
Press Convert. The font tables are parsed and rewritten locally with fonteditor-core; glyph outlines, hinting, and kerning survive the trip.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid JSON file. Outputs keep the original filename with the .json extension.
FITS to JSON questions, answered
Will converting FITS to JSON lose quality?
There is no visual quality to lose — fits is lossless-oriented and json is text-oriented, so the question is structural fidelity. Text, ordering, and basic structure are preserved; complex layout, embedded objects, and styling beyond the target's model are simplified.
Is it private to convert FITS files here?
Yes — the .fits file is processed inside your browser tab and never uploaded. The font tables are parsed and rewritten locally with fonteditor-core; glyph outlines, hinting, and kerning survive the trip. Close the tab and the file is gone from memory.
Where will the JSON file work?
Browsers parse it natively through JSON.parse, every mainstream language bundles support, and most editors validate and highlight it out of the box. Viewing a raw .json file is possible in any text editor or browser tab.
Will the JSON file be bigger or smaller than my FITS?
It depends on the content: exactly six value types; no dates, no comments, no trailing commas — the strictness is deliberate. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my FITS file?
In .fits, header cards, including WCS and instrument keywords, are read and exported into the JSON output; PNG carries no channel for them, which is why the loss is stated rather than assumed obvious. Re-encoding through the browser pipeline does not carry embedded metadata into the output, which doubles as a privacy scrub — check the exported file if you specifically need tags preserved.