How to Convert JSON to CSV — 3 Methods Explained

Converting JSON to CSV is one of the most common data transformation tasks in development. Whether you're exporting data for a non-technical user, importing into Excel, or feeding a machine learning pipeline, here are three reliable methods — no matter your stack.

Why convert JSON to CSV?

• Business users need data in spreadsheets (Excel, Google Sheets)
• CSV is required by many data import tools and databases
• CSV is faster to process for large flat datasets
• Reporting tools often require CSV format

What JSON structure works for CSV?

CSV is a flat format — it doesn't support nested structures. The ideal JSON for CSV conversion is a flat array of objects:

[
  { "name": "Alice", "age": 28, "city": "Paris" },
  { "name": "Bob",   "age": 34, "city": "London" },
  { "name": "Carol", "age": 25, "city": "Berlin" }
]

Each object becomes a row. Each key becomes a column header.

Method 1: Online converter (instant, no code)

If you just need a one-time conversion, an online tool is by far the fastest option.

Method 2: Convert JSON to CSV in JavaScript

function jsonToCSV(jsonArray) {
  if (!jsonArray.length) return '';

  // Get all unique keys as headers
  const headers = [...new Set(jsonArray.flatMap(row => Object.keys(row)))];

  // Build CSV rows
  const escape = (val) => {
    const str = val === null || val === undefined ? ''
               : typeof val === 'object' ? JSON.stringify(val)
               : String(val);
    return str.includes(',') || str.includes('"') || str.includes('\n')
      ? `"${str.replace(/"/g, '""')}"`
      : str;
  };

  const rows = jsonArray.map(row =>
    headers.map(h => escape(row[h])).join(',')
  );

  return [headers.join(','), ...rows].join('\n');
}

// Usage
const data = [
  { name: "Alice", age: 28, city: "Paris" },
  { name: "Bob",   age: 34, city: "London" }
];

const csv = jsonToCSV(data);
console.log(csv);
// name,age,city
// Alice,28,Paris
// Bob,34,London

// Download as file in browser
const blob = new Blob([csv], { type: 'text/csv' });
const url = URL.createObjectURL(blob);
const a = document.createElement('a');
a.href = url; a.download = 'data.csv'; a.click();

Method 3: Convert JSON to CSV in Python

import json
import csv
import io

def json_to_csv(json_data):
    if isinstance(json_data, str):
        data = json.loads(json_data)
    else:
        data = json_data

    if not data:
        return ''

    output = io.StringIO()
    writer = csv.DictWriter(output, fieldnames=data[0].keys())
    writer.writeheader()
    writer.writerows(data)
    return output.getvalue()

# Usage
data = [
    {"name": "Alice", "age": 28, "city": "Paris"},
    {"name": "Bob",   "age": 34, "city": "London"}
]

csv_output = json_to_csv(data)
print(csv_output)

# Save to file
with open('output.csv', 'w', newline='') as f:
    f.write(csv_output)

Using pandas (recommended for large datasets)

import pandas as pd
import json

# From a JSON file
df = pd.read_json('data.json')
df.to_csv('output.csv', index=False)

# From a JSON string
json_str = '[{"name":"Alice","age":28},{"name":"Bob","age":34}]'
df = pd.read_json(json_str)
df.to_csv('output.csv', index=False)

# From an API response
import requests
response = requests.get('https://api.example.com/users')
df = pd.DataFrame(response.json())
df.to_csv('users.csv', index=False)

Handling nested JSON

Nested JSON doesn't map cleanly to CSV. You have two options:

• Flatten it: Convert {"address": {"city": "Paris"}} to {"address.city": "Paris"}
• Stringify it: Store the nested object as a JSON string in the CSV cell

# Python: flatten nested JSON with pandas
df = pd.json_normalize(data)  # automatically flattens nested keys
df.to_csv('flattened.csv', index=False)