Free CSV to JSON Converter — Online, Bidirectional

Convert CSV to JSON and JSON to CSV instantly in your browser. Bidirectional, RFC 4180 compliant (handles quoted fields, escaped quotes, multi-line values), supports custom delimiters, and runs 100% client-side — nothing uploaded.

Launch the tool
freecsv2json.app
Open CSV to JSON →

Features

How it works

  1. Open freecsv2json.app in any browser
  2. Paste CSV or JSON into the left pane (or drop a file)
  3. Pick delimiter, header row, and output format options
  4. See converted result live in the right pane
  5. Click Copy or Download, or use ⇄ Swap to round-trip

Common use cases

How it compares

Most free CSV-to-JSON converters break on quoted fields with commas, escaped quotes, and multi-line values. freecsv2json.app follows RFC 4180 strictly so those edge cases parse correctly. It also runs 100% client-side (unlike ConvertCSV.com's server-side upload model), offers a first-class bidirectional workflow, and works offline as a progressive web app.

Privacy

Every line of CSV and JSON you paste stays on your device. freecsv2json.app makes zero network calls after page load, stores no data server-side, and uses no third-party analytics. Safe for CSV exports containing customer data, credentials, or PII.

Frequently asked questions

How do I convert CSV to JSON?

Paste your CSV into the left pane on freecsv2json.app. The tool detects the delimiter, treats the first row as headers, and outputs valid JSON in the right pane in real time. Copy the result or download it as a .json file.

Can it also convert JSON back to CSV?

Yes. Switch the mode toggle to JSON to CSV, or paste JSON that starts with [ or { and freecsv2json.app auto-detects the direction. Arrays of flat objects convert cleanly; nested values are stringified.

Does it handle quoted fields with commas?

Yes. The parser follows RFC 4180, so quoted fields with embedded commas, escaped quotes as double quotes, and multi-line values inside quotes all parse correctly. Most free converters break on these — freecsv2json.app does not.

What delimiters are supported?

Comma, semicolon, tab, pipe, or any single custom character you type. European CSV files usually use semicolons, tab-separated values use tabs. freecsv2json.app supports them all via the delimiter picker.

Is my data uploaded anywhere?

No. All parsing and conversion happens locally in your browser using JavaScript. Nothing is uploaded, logged, or sent to a server. freecsv2json.app is safe for CSV files containing customer data, credentials, or other private content.

How large a file can I convert?

Up to about 10 MB of CSV runs smoothly in most browsers. Beyond that, the tab may slow down since everything processes in memory. For server-side batch or API conversion, the Pro tier is planned.