Util Module in Node.js
From the Node.js Core Modules cheat sheet · Utilities & Advanced · verified Jul 2026
Util Module
Utility functions for debugging and promisification
javascript
const util = require('util')
const fs = require('fs')
// Promisify callback-based functions
const readFile = util.promisify(fs.readFile)
const data = await readFile('file.txt', 'utf8')
// Format strings (like printf)
const msg = util.format('%s:%d', 'Server', 8080)
// 'Server:8080'
// Deep inspect objects
const obj = { a: 1, b: { c: 2, d: [3, 4] } }
console.log(util.inspect(obj, {
showHidden: true,
depth: null,
colors: true
}))💡 promisify() converts callbacks to promises
📌 util.inspect() is great for debugging
⚡ TextEncoder/Decoder for UTF-8 conversion
🟢 Essential for modernizing callback code
🔗 Related: console.dir() for simple inspection
utilitiesdebugging