JSON ↔ CSV Converter

How to convert JSON to CSV online

jsonsql.dev converts JSON arrays to CSV instantly in your browser. No data is sent to any server — your JSON stays on your machine.

How to convert CSV to JSON online

jsonsql.dev converts CSV to JSON instantly in your browser. No data is sent to any server — your data stays on your machine.

How nested JSON is flattened to CSV

Nested JSON objects are flattened to CSV columns using dot notation — for example, {"address": {"city": "NYC"}} becomes a column named address.city. This approach preserves the hierarchy in a flat, spreadsheet-friendly format.

When you enable the Flatten nested option, each nested key path becomes its own column header. Arrays within values are joined with semicolons.

Input (nested JSON):

[
  {
    "id": 1,
    "name": "Acme Corp",
    "address": {
      "street": "123 Main St",
      "city": "New York",
      "state": "NY"
    },
    "contact": {
      "email": "[email protected]",
      "phone": {
        "office": "555-0100",
        "mobile": "555-0101"
      }
    }
  },
  {
    "id": 2,
    "name": "Globex Inc",
    "address": {
      "street": "456 Oak Ave",
      "city": "Chicago",
      "state": "IL"
    },
    "contact": {
      "email": "[email protected]",
      "phone": {
        "office": "555-0200",
        "mobile": "555-0201"
      }
    }
  }
]

Output (flattened CSV):

id,name,address.street,address.city,address.state,contact.email,contact.phone.office,contact.phone.mobile
1,Acme Corp,123 Main St,New York,NY,[email protected],555-0100,555-0101
2,Globex Inc,456 Oak Ave,Chicago,IL,[email protected],555-0200,555-0201

CSV parsing rules (RFC 4180)

RFC 4180 defines the CSV format: fields containing commas, newlines, or double quotes must be enclosed in double quotes, and literal double quotes are escaped by doubling them. This standard ensures interoperability between different tools and platforms.

• Field separator: Fields are separated by a delimiter character. The default is a comma (,), but other delimiters like tab, semicolon, or pipe are common in practice.
• Quoted fields: Any field that contains the delimiter character, a newline, or a double quote must be enclosed in double quotes. For example: "San Francisco, CA" is a single field.
• Escaping double quotes: A double quote inside a quoted field is escaped by writing two double quotes. For example: "She said ""hello""" represents the value She said "hello".
• Trailing newline: A trailing newline at the end of the file is optional. Most parsers handle both cases correctly.
• Line endings: Both \r\n (Windows) and \n (Unix) line endings are accepted. Our converter handles both automatically.

JSON to CSV type mapping

When converting JSON values to CSV, each JSON type is mapped to a CSV string representation:

Code examples

Python

import csv, json, io

# JSON to CSV
data = json.loads(json_string)
output = io.StringIO()
writer = csv.DictWriter(output, fieldnames=data[0].keys())
writer.writeheader()
writer.writerows(data)
csv_string = output.getvalue()

# CSV to JSON
reader = csv.DictReader(io.StringIO(csv_string))
json_data = [row for row in reader]
json_string = json.dumps(json_data, indent=2)

Node.js

// JSON to CSV (using json2csv)
import { Parser } from 'json2csv';
const parser = new Parser({ flatten: true });
const csv = parser.parse(jsonArray);

// CSV to JSON (using Papa Parse)
import Papa from 'papaparse';
const result = Papa.parse(csvString, {
  header: true,
  dynamicTyping: true,
  skipEmptyLines: true
});
const json = result.data;

CLI (jq + csvkit)

# JSON to CSV
cat data.json | jq -r '(.[0] | keys_unsorted) as $keys | $keys, (.[] | [.[$keys[]]] ) | @csv' > out.csv

# CSV to JSON
csvjson data.csv > out.json

JSON ↔ CSV vs other tools

Related tools

Frequently asked questions