How to Format JSON in JavaScript

Using JSON.stringify in JavaScript

The built-in JSON.stringify() method converts a JavaScript object to a JSON string. The third parameter controls indentation.

const data = { name: "DevUtils", version: 2, active: true };

// Unformatted
JSON.stringify(data);
// {"name":"DevUtils","version":2,"active":true}

// Formatted with 2 spaces
JSON.stringify(data, null, 2);
// {
//   "name": "DevUtils",
//   "version": 2,
//   "active": true
// }

Format JSON with 4 spaces

JSON.stringify(data, null, 4);

Change the third argument to any number to control indentation. Most style guides recommend 2 or 4 spaces.

Format JSON using tabs

JSON.stringify(data, null, "	");

Parse and format a JSON string

If you have a JSON string and want to format it, parse it first then stringify it back.

const jsonString = '{"name":"DevUtils","version":2}';
const parsed = JSON.parse(jsonString);
const formatted = JSON.stringify(parsed, null, 2);
console.log(formatted);

Format JSON in Node.js

const fs = require('fs');
const data = JSON.parse(fs.readFileSync('data.json', 'utf8'));
fs.writeFileSync('data-formatted.json', JSON.stringify(data, null, 2));

Common formatting mistakes