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CSV ↔ JSON Converter

Paste CSV or JSON and get the other format instantly. CSV mode supports custom delimiters and optional header detection (the first row becomes the keys); JSON mode expects an array of objects and writes the union of keys as the header. Quoted fields with commas and embedded quotes are handled correctly. Pretty-print the output in the JSON Formatter and Validator, isolate a single field with the Delimited Column Extractor, or clean up rows with Remove Duplicate Lines.

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How it works

CSV to JSON: split lines, parse each with a small state machine that handles quoted fields and escaped quotes, build an object per row using the headers (or col1/col2/... if no header). JSON to CSV: parse, gather the union of keys, escape any value containing the delimiter or quotes, write header row + data rows.

How to use it

  1. Paste your data

    Drop in a CSV export from a spreadsheet, or a JSON array from an API response. The tool auto-detects which direction to convert.

  2. Pick the delimiter

    Comma is the default. Switch to semicolon for European exports, tab for TSV, or pipe for log files. Quoted fields are handled.

  3. Toggle header detection

    Header on uses the first row as JSON keys; header off emits arrays of arrays. Pick based on whether the first row has labels.

  4. Copy or download

    Take the converted output into a JSON config, a database import, or a CSV pipeline. Round-tripping through the tool is loss-free.

Use cases

Convert a spreadsheet export into a JSON file for an API.

Turn a JSON array into a CSV ready for Excel or Google Sheets.

Inspect what a CSV row will look like as JSON before writing code.

Build mock data for a project from a CSV template.

When NOT to use it

  • On CSVs that contain newlines inside quoted fields and span multiple lines per record. This parser is line-based; use a proper CSV library (csv-parse) for that.
  • For nested JSON-to-CSV. CSV is flat, so nested objects and arrays get JSON.stringified into the cell. If you need true relational flattening, do it before.
  • On gigabyte files. The tool runs entirely in memory; the browser will choke past 50 MB.

Your data never leaves your browser

Every utility runs entirely on your device. Nothing is uploaded, nothing is stored on a server. You can disconnect from the internet and they keep working.

Frequently asked questions

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