CSV to JSON converter — both directions, fully private

Why quoting is where converters go wrong

Splitting lines on commas works until the first value that contains one — an address, a company name like "Miller, Alex", a note with a line break. The CSV standard wraps such fields in quotes and doubles any quotes inside them, and this converter implements exactly that, in both directions. If a naive script or regex has ever shifted your columns, this is the reason.

Type detection matters just as much for the JSON side: whether 42 arrives as a number or the string "42" changes how every downstream tool treats it. Detection here is conservative on purpose — real numbers convert, but IDs with leading zeros and values too long to hold exactly stay strings, because silently corrupting identifiers is worse than an extra pair of quotes.

Common jobs this handles

Turning an Excel or spreadsheet export into JSON seed data or fixtures for an API. Converting an API response into a CSV a colleague can open in Excel. Inspecting a semicolon-separated export from a European ERP. Reshaping survey results before loading them into a database. For anything sensitive — customer lists, payroll, credentials-adjacent exports — the in-browser approach means there is no server to trust.

Working with LLM pipelines? JSON datasets feed straight into prompts — the AI token cost calculator estimates what processing them will cost. And if the result is documentation, the markdown editor turns it into clean HTML.

Frequently asked questions

How does the CSV to JSON conversion work?

The parser follows the CSV standard (RFC 4180): fields wrapped in quotes may contain commas, line breaks and doubled quotes, and both Windows and Unix line endings are handled. With the header option on, the first row becomes the keys and every following row becomes one JSON object. The delimiter — comma, semicolon, tab or pipe — is detected automatically, or you can pick it yourself.

Does it convert JSON back to CSV too?

Yes — switch the direction to JSON → CSV. An array of objects becomes a table whose columns are the union of all keys in order of first appearance; an array of arrays becomes rows as-is. Values containing the delimiter, quotes or newlines are quoted and escaped correctly.

Is my data uploaded to a server?

No. Parsing and conversion run entirely in your browser — the file never leaves your device, nothing is stored, and there is no sign-up. That makes it safe for exports containing customer, financial or internal data that must not touch third-party servers.

Why do numbers like 007 or long IDs stay as strings?

Type detection deliberately keeps values with leading zeros and numbers longer than 15 digits as strings, because converting them would corrupt the data — 007 would become 7, and very long IDs lose precision in JavaScript. Genuine numbers, true/false and null are converted; anything ambiguous is left alone. You can switch detection off to keep every value a string.

My CSV uses semicolons — will it work?

Yes. Spreadsheets exported from Excel in many European locales separate fields with semicolons; the auto-detector recognises that, along with tab-separated (TSV) and pipe-separated files. If detection ever guesses wrong, set the delimiter explicitly from the dropdown.

What does Toolizto Pro add to the converter?

The free tier converts both directions without size or row limits. Pro ($9.99/month or $79.99/year, covering every Toolizto tool) adds flattening of nested JSON into dot-notation columns (user.address.city), an Excel-ready CSV download with a UTF-8 byte-order mark, and removes ads.