Free tool 03 // Converter
CSV ↔ JSON Converter
Drop a file or paste raw data. The converter detects the format from the content — not the extension — and hands back the other one. All of it happens in your browser.
100% client-sideNo signupMax 5 MB5 uses / hour
Download links expire after 1 hour
Same data, new shape — it never leaves your browser.
How it works
Three steps · No queueDrop in a CSV or JSON file, or paste data straight into the input panel. The converter reads the first bytes of content to detect the format — the file extension is ignored.
Conversion runs locally in your browser: CSV streams through the parser in 1 MB chunks, JSON is read and converted in a single pass. Nothing touches a server.
The converted file is ready the moment the progress bar fills — download it or copy it to your clipboard. Download links expire after one hour, and no data is stored on our servers.
File size guidelines
5 MB cap · 5 uses per hourThe tool accepts files up to 5 MB in either direction. What changes is the output: JSON is a more verbose container than CSV, so expect the size to move when you convert.
| Direction | Input limit | Typical output size | Example |
|---|---|---|---|
| CSV → JSON | 5 MB | 1.5–2× the input | 4 MB CSV → ~6–8 MB JSON |
| JSON → CSV | 5 MB | 0.5–0.7× the input | 4 MB JSON → ~2–3 MB CSV |
Example output
Same rows, new shapename,age,city John Doe,30,New York Jane Smith,25,London Bob Johnson,45,Paris
[{
"name": "John Doe",
"age": "30",
"city": "New York"
}, {
"name": "Jane Smith",
"age": "25",
"city": "London"
}, {
"name": "Bob Johnson",
"age": "45",
"city": "Paris"
}]
Every value comes through as a string — the converter doesn't guess at types, so nothing gets mangled on the way through.
Common questions
Straight answersIs my data uploaded anywhere?
No. Parsing and conversion run entirely in your browser — the file never leaves your machine, and nothing is stored on our servers. The only network requests this page makes are for the page itself.
How does format detection work?
The converter reads the first few kilobytes of your file. If the content starts with { or [, it's treated as JSON and converted to CSV; anything else is parsed as CSV and converted to JSON. The file extension plays no part.
Why the 5 MB limit?
Conversion happens in browser memory, and JSON output can be up to twice the size of the CSV input. The cap keeps conversions fast and your tab responsive. The tool also allows 5 conversions per hour.
How long does the download link last?
One hour. After that the link expires and you'll need to re-run the conversion. Nothing persists — the output only ever exists in your browser session.
More than a format swap
Converting is the easy part.
If the data inside the file is the real problem — duplicates, decay, formats that don't agree — start with a free audit and we'll show you exactly what's wrong.