JSON to CSV Converter Online — How to Convert JSON to CSV, Excel & Spreadsheets Free

Basic: flat JSON array to CSV

The simplest case — a JSON array of objects with consistent keys and primitive values.

import json
import csv

# Load JSON from a file
with open("data.json", "r") as f:
    data = json.load(f)

# Extract column headers from the first object
fieldnames = list(data[0].keys())

# Write to CSV
with open("output.csv", "w", newline="", encoding="utf-8") as f:
    writer = csv.DictWriter(f, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerows(data)

print(f"Written {len(data)} rows to output.csv")

Flatten nested JSON before converting

Use a recursive flatten function to convert nested keys like address.city into flat column names before writing.

import json
import csv

def flatten(obj, parent_key="", sep="."):
    """Recursively flatten a nested dict."""
    items = {}
    for k, v in obj.items():
        new_key = f"{parent_key}{sep}{k}" if parent_key else k
        if isinstance(v, dict):
            items.update(flatten(v, new_key, sep))
        elif isinstance(v, list):
            # Join list values with a pipe separator
            items[new_key] = "|".join(str(i) for i in v)
        else:
            items[new_key] = v
    return items

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

# Flatten every record
flat_data = [flatten(record) for record in data]

# Collect ALL unique keys across all records
all_keys = []
for record in flat_data:
    for key in record:
        if key not in all_keys:
            all_keys.append(key)

with open("output.csv", "w", newline="", encoding="utf-8") as f:
    writer = csv.DictWriter(
        f, fieldnames=all_keys, extrasaction="ignore"
    )
    writer.writeheader()
    writer.writerows(flat_data)

Convert JSON string (not file) to CSV

When working with an API response or JSON already in memory as a string — use json.loads() instead of json.load().

import json
import csv
import io

json_string = '''[
  {"id": 1, "name": "Alice", "score": 95},
  {"id": 2, "name": "Bob",   "score": 87}
]'''

data = json.loads(json_string)  # Note: loads(), not load()
fieldnames = list(data[0].keys())

# Write to an in-memory string buffer (useful for web apps)
output = io.StringIO()
writer = csv.DictWriter(output, fieldnames=fieldnames)
writer.writeheader()
writer.writerows(data)

csv_string = output.getvalue()
print(csv_string)

Using pandas (recommended for data analysis)

If you're already using pandas, json_normalize() handles nested JSON flattening automatically.

import pandas as pd
import json

# From a file
with open("data.json") as f:
    data = json.load(f)

# json_normalize flattens nested objects automatically
df = pd.json_normalize(data)

# Preview the columns
print(df.columns.tolist())
print(df.head())

# Export to CSV
df.to_csv("output.csv", index=False)

# For deeply nested JSON, use the 'sep' and 'max_level' params:
# df = pd.json_normalize(data, sep="_", max_level=2)

Browser: convert JSON to CSV and download

Paste this function into any browser console or script to convert a JSON array and trigger a file download.

function jsonToCsv(data, delimiter = ",") {
  if (!Array.isArray(data) || data.length === 0) return "";

  // Collect all unique keys across all objects
  const allKeys = [...new Set(data.flatMap(Object.keys))];

  const escape = (val) => {
    const str = val === null || val === undefined ? "" : String(val);
    // Wrap in quotes if value contains delimiter, quotes, or newlines
    return str.includes(delimiter) || str.includes('"') || str.includes("\n")
      ? `"${str.replace(/"/g, '""')}"`
      : str;
  };

  const header = allKeys.join(delimiter);
  const rows = data.map((obj) =>
    allKeys.map((key) => escape(obj[key])).join(delimiter)
  );

  return [header, ...rows].join("\n");
}

function downloadCsv(csvString, filename = "data.csv") {
  const blob = new Blob([csvString], { type: "text/csv;charset=utf-8;" });
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename;
  a.click();
  URL.revokeObjectURL(url);
}

// Usage:
const data = [
  { id: 1, name: "Alice", city: "Paris" },
  { id: 2, name: "Bob",   city: "Tokyo" },
];

downloadCsv(jsonToCsv(data), "users.csv");

Node.js: read JSON file, write CSV file

A complete Node.js script — read a JSON file, convert it, and write the output to a CSV file.

const fs = require("fs");

function flattenObj(obj, prefix = "", sep = ".") {
  return Object.entries(obj).reduce((acc, [key, val]) => {
    const newKey = prefix ? `${prefix}${sep}${key}` : key;
    if (val !== null && typeof val === "object" && !Array.isArray(val)) {
      Object.assign(acc, flattenObj(val, newKey, sep));
    } else {
      acc[newKey] = Array.isArray(val) ? val.join("|") : val;
    }
    return acc;
  }, {});
}

function jsonToCsv(data, delimiter = ",") {
  const flat = data.map((r) => flattenObj(r));
  const keys = [...new Set(flat.flatMap(Object.keys))];

  const escape = (v) => {
    const s = v === null || v === undefined ? "" : String(v);
    return s.includes(delimiter) || s.includes('"') || s.includes("\n")
      ? `"${s.replace(/"/g, '""')}"`
      : s;
  };

  const lines = [
    keys.join(delimiter),
    ...flat.map((row) => keys.map((k) => escape(row[k])).join(delimiter)),
  ];
  return lines.join("\n");
}

// Read → Convert → Write
const input = JSON.parse(fs.readFileSync("data.json", "utf8"));
const csv = jsonToCsv(input);
fs.writeFileSync("output.csv", csv, "utf8");

console.log(`Converted ${input.length} records to output.csv`);

1. Open Excel and go to File → Open.
2. Select "All Files (*.*)" in the file type dropdown.
3. Browse to your downloaded .csv file and click Open.
4. The Text Import Wizard opens. Select "Delimited" and click Next.
5. Check "Comma" (or whichever delimiter you used). Click Finish.
6. Your JSON data now appears in columns. Save as .xlsx to preserve formatting.

1. Open Google Sheets and create a new spreadsheet.
2. Go to File → Import.
3. Click "Upload" and drag your .csv file into the dialog.
4. Under "Separator type", select "Comma" (or Custom for other delimiters).
5. Click "Import data". Your JSON data appears in a new sheet.

1. Open LibreOffice Calc and go to File → Open.
2. Select your .csv file. The Text Import dialog opens automatically.
3. Under "Separator options", check "Comma" or set a custom separator.
4. Check "String delimiter" is set to a double-quote (").
5. Click OK. Your data loads in column layout.