CSV Input
JSON Output
freecsv2json.app converts CSV to JSON and JSON to CSV entirely in your browser. Paste data into the left pane and the converted result appears live on the right. The parser follows RFC 4180, so quoted fields with embedded commas, escaped quotes, and multi-line values inside quotes all parse correctly — edge cases that break most free converters. Nothing is uploaded: your CSV files containing customer data, exports, or credentials never leave your device.
The tool supports four preset delimiters (comma, semicolon, tab, pipe) plus a custom single-character option for unusual formats. You can output JSON as an array of objects (keyed by header row) or as an array of arrays (no keys). For the reverse direction, freecsv2json.app serialises JSON arrays of flat objects into clean CSV with your chosen quoting strategy and line endings.
Paste your CSV into the input pane on the left. freecsv2json.app auto-detects the delimiter if you've picked "comma", parses the data using the RFC 4180 grammar, and writes valid JSON to the output pane on the right. Toggle the "Header row" checkbox to treat the first row as column names (array of objects) or as just another data row (array of arrays). Click Copy to put the JSON on your clipboard or Download to save it as a .json file.
Yes — switch the mode toggle to "JSON → CSV", or paste JSON that starts with [ or { and the direction auto-detects. Arrays of flat objects (for example, [{"name":"Ada","age":37}, {"name":"Bob","age":29}]) convert to a header-plus-rows CSV cleanly. Nested objects and arrays inside cells are JSON-stringified so nothing is lost, though flat data gives the cleanest output.
freecsv2json.app is completely free with no sign-up, no ads, no tracking, and no account. The app works offline once loaded (it's a progressive web app) and runs everything as local JavaScript in your browser. There are no usage limits for normal use; very large files (over ~10 MB) may simply slow the tab down since all parsing is in-memory.
Most free CSV-to-JSON websites break on three common inputs: quoted fields with commas inside, escaped quotes (""), and multi-line values inside quotes. freecsv2json.app handles all three correctly because the parser follows RFC 4180 character-by-character rather than splitting on delimiters. It also runs entirely client-side, so spreadsheet exports containing private data never touch an external server.
Yes. The interface adapts to small screens: input and output stack vertically on mobile and controls wrap cleanly. You can paste from your clipboard, open a CSV from your Files app, and copy the converted JSON back to your clipboard for use in another app. Dark mode follows your system setting automatically.
Yes. Every line of CSV and JSON you paste stays on your device. freecsv2json.app never sends your content to a server, never stores it in a database, and never uses third-party analytics. The only persistent storage is a small crash-recovery copy of your last input in your browser's local storage, which you can clear at any time.
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.
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.
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.
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.
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.
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.