JSON to CSV: How to Convert JSON Arrays to Spreadsheet Format

JSON is the lingua franca of APIs; CSV is the lingua franca of spreadsheets. Converting between them is a daily task for data engineers, analysts, and developers pulling data from APIs into Excel, Google Sheets, or a SQL import. This guide covers how the conversion works, the edge cases that trip people up, and code examples in JavaScript and Python.

When you need JSON → CSV

• API data into spreadsheets — export REST API responses to Excel or Google Sheets for non-technical stakeholders
• Database exports — MongoDB and Firestore export JSON; downstream tools often expect CSV
• Data science pipelines — pandas, R, and most ML toolkits read CSV natively and have no built-in JSON array reader
• Bulk imports — CRMs, email platforms, and accounting tools almost universally accept CSV for data import

How JSON arrays map to CSV

The conversion only makes sense for a JSON array of objects with consistent keys. Each object becomes a row; the keys become column headers.

// Input JSON
[
  { "name": "Alice", "age": 30, "city": "Mumbai" },
  { "name": "Bob",   "age": 25, "city": "Delhi"  },
  { "name": "Carol", "age": 35, "city": "Pune"   }
]

// Output CSV
name,age,city
Alice,30,Mumbai
Bob,25,Delhi
Carol,35,Pune

Convert online (DevBench)

1. Open DevBench JSON to CSV
2. Paste your JSON array (or upload a .json file)
3. Click Convert — headers are auto-detected from the first object's keys
4. Copy the CSV output or download as a .csv file

DevBench handles nested objects by flattening them with dot notation (address.city) and arrays by joining values with a semicolon.

Convert in JavaScript

function jsonToCsv(arr) {
  if (!arr.length) return "";
  const headers = Object.keys(arr[0]);
  const escape = (val) => {
    const str = String(val ?? "");
    return str.includes(",") || str.includes('"') || str.includes("\n")
      ? `"${str.replace(/"/g, '""')}"`
      : str;
  };
  const rows = arr.map((obj) =>
    headers.map((h) => escape(obj[h])).join(",")
  );
  return [headers.join(","), ...rows].join("\n");
}

const data = [
  { name: "Alice", age: 30, city: "Mumbai" },
  { name: "Bob",   age: 25, city: "Delhi"  },
];
console.log(jsonToCsv(data));

The escape function handles the RFC 4180 quoting rules: wrap in double-quotes if the value contains a comma, double-quote, or newline; double up any embedded double-quotes.

Convert in Python

import json, csv, io

with open("data.json") as f:
    data = json.load(f)

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

Python's csv.DictWriter handles all quoting automatically. Replace io.StringIO() with open("output.csv", "w", newline="") to write directly to a file. The newline="" argument is required on Windows to prevent double line endings.

Edge cases and how to handle them

Handling nested JSON: flatten vs stringify

Two strategies for nested objects:

• Flatten — recursively expand { "address": { "city": "Mumbai", "pin": "400001" } } into two columns: address.city and address.pin. Good when nested structure is shallow and consistent.
• Stringify — JSON-encode the nested value as a string and put it in a single column. Good for deeply nested or variable-structure objects — preserves data without exploding column count.

// Flatten approach
function flatten(obj, prefix = "") {
  return Object.entries(obj).reduce((acc, [k, v]) => {
    const key = prefix ? `${prefix}.${k}` : k;
    if (v && typeof v === "object" && !Array.isArray(v)) {
      Object.assign(acc, flatten(v, key));
    } else {
      acc[key] = v;
    }
    return acc;
  }, {});
}

const flat = data.map(flatten);
console.log(jsonToCsv(flat));

For quick conversions without writing code, use the DevBench JSON to CSV converter — paste your array and download the result in one click.