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In this question Erik needs to generate a secure random token in Node.js. There's the method crypto.randomBytes that generates a random Buffer. However, the base64 encoding in node is not url-safe, it includes / and + instead of - and _. Therefore, the easiest way to generate such token I've found is

require('crypto').randomBytes(48, function(ex, buf) {
    token = buf.toString('base64').replace(/\//g,'_').replace(/\+/g,'-');
});

Is there a more elegant way?

In this question Erik needs to generate a secure random token in Node.js. There's the method crypto.randomBytes that generates a random Buffer. However, the base64 encoding in node is not url-safe, it includes / and + instead of - and _. Therefore, the easiest way to generate such token I've found is

require('crypto').randomBytes(48, function(ex, buf) {
    token = buf.toString('base64').replace(/\//g,'_').replace(/\+/g,'-');
});

Is there a more elegant way?

• javascript
• node.js
• base64
• securestring

• What is the rest of the code? – Lion789 Commented Aug 3, 2013 at 5:01
• 7 There's nothing more needed. What rest would you like to see? – Hubert OG Commented Aug 12, 2013 at 13:46
• Nevermind, I got it to work, was just unsure of how you threw it in, but got a better grasp of the concept – Lion789 Commented Aug 12, 2013 at 19:22
• 1 Shameless self-plug, I created yet another npm package: tokgen. You can specify allowed characters using a range syntax similar to character classes in regular expressions ('a-zA-Z0-9_-'). – Max Truxa Commented Aug 9, 2016 at 19:18
• 1 This may be convenient for anyone who'd like a specific string length. The 3/4th's is to handle the base conversion. /*returns a base64 encoded string of length*/ function randomString(length){ return crypto.randomBytes(length*3/4).toString('base64'); } Works nice for those databases with those character limits. – TheUnknownGeek Commented Oct 19, 2017 at 21:51

16 Answers 16

Try crypto.randomBytes():

require('crypto').randomBytes(48, function(err, buffer) {
  var token = buffer.toString('hex');
});

The 'hex' encoding works in node v0.6.x or newer.

Synchronous option in-case if you are not a JS expert like me. Had to spend some time on how to access the inline function variable

var token = crypto.randomBytes(64).toString('hex');

1. Using nanoid third party library [NEW!]

A tiny, secure, URL-friendly, unique string ID generator for JavaScript

https://github.com/ai/nanoid

import { nanoid } from "nanoid";
const id = nanoid(48);

2. Base 64 Encoding with URL and Filename Safe Alphabet

Page 7 of RCF 4648 describes how to encode in base 64 with URL safety.

This is natively supported by Node.js >=v14.18.0:

const crypto = require("crypto");

/** Sync */
function randomStringAsBase64Url(size) {
  return crypto.randomBytes(size).toString("base64url");
}

Usage example:

randomStringAsBase64Url(20);
// Returns "AXSGpLVjne_f7w5Xg-fWdoBwbfs" which is 27 characters length.

Note that the returned string length will not match with the size argument (size != final length).

If you are using Node.js <v14.18.0 you can use an existing library like base64url to do the job. The function will be:

const crypto = require("crypto");
const base64url = require("base64url");
    
/** Sync */
function randomStringAsBase64Url(size) {
  return base64url(crypto.randomBytes(size));
}

3. Crypto random values from limited set of characters

Beware that with this solution the generated random string is not uniformly distributed.

You can also build a strong random string from a limited set of characters like that:

const crypto = require("crypto");

/** Sync */
function randomString(length, chars) {
  if (!chars) {
    throw new Error("Argument 'chars' is undefined");
  }

  const charsLength = chars.length;
  if (charsLength > 256) {
    throw new Error("Argument 'chars' should not have more than 256 characters"
      + ", otherwise unpredictability will be broken");
  }

  const randomBytes = crypto.randomBytes(length);
  let result = new Array(length);

  let cursor = 0;
  for (let i = 0; i < length; i++) {
    cursor += randomBytes[i];
    result[i] = chars[cursor % charsLength];
  }

  return result.join("");
}

/** Sync */
function randomAsciiString(length) {
  return randomString(length,
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789");
}

Usage example:

randomAsciiString(20);
// Returns "rmRptK5niTSey7NlDk5y" which is 20 characters length.

randomString(20, "ABCDEFG");
// Returns "CCBAAGDGBBEGBDBECDCE" which is 20 characters length.

As of Node.js 14.18 and 15.7, url-safe base64 encoding support is built-in:

const token = crypto.randomBytes(48).toString('base64url');

If you want to use the async version (because the function may have to wait for entropy), it can be promisified to align better with modern patterns:

const randomBytesAsync = util.promisify(crypto.randomBytes);

const token = (await randomBytesAsync(48)).toString('base64url');

The up-to-date right way to do this asynchronously using ES 2016 standards of async and await (as of Node 7) would be the following:

const crypto = require('crypto');

function generateToken({ stringBase = 'base64', byteLength = 48 } = {}) {
  return new Promise((resolve, reject) => {
    crypto.randomBytes(byteLength, (err, buffer) => {
      if (err) {
        reject(err);
      } else {
        resolve(buffer.toString(stringBase));
      }
    });
  });
}

async function handler(req, res) {
   // default token length
   const newToken = await generateToken();
   console.log('newToken', newToken);

   // pass in parameters - adjust byte length
   const shortToken = await generateToken({byteLength: 20});
   console.log('newToken', shortToken);
}

This works out of the box in Node 7 without any Babel transformations

Random URL and filename string safe (1 liner)

Crypto.randomBytes(48).toString('base64').replace(/\+/g, '-').replace(/\//g, '_').replace(/\=/g, '');

With async/await and promisification.

const crypto = require('crypto')
const randomBytes = Util.promisify(crypto.randomBytes)
const plain = (await randomBytes(24)).toString('base64').replace(/\W/g, '')

Generates something similar to VjocVHdFiz5vGHnlnwqJKN0NdeHcz8eM

Check out:

var crypto = require('crypto');
crypto.randomBytes(Math.ceil(length/2)).toString('hex').slice(0,length);

crypto-random-string is a nice module for this.

const cryptoRandomString = require('crypto-random-string');
 
cryptoRandomString({length: 10});                          // => '2cf05d94db'
cryptoRandomString({length: 10, type: 'base64'});          // => 'YMiMbaQl6I'
cryptoRandomString({length: 10, type: 'url-safe'});        // => 'YN-tqc8pOw'
cryptoRandomString({length: 10, type: 'numeric'});         // => '8314659141'
cryptoRandomString({length: 6, type: 'distinguishable'});  // => 'CDEHKM'
cryptoRandomString({length: 10, type: 'ascii-printable'}); // => '`#Rt8$IK>B'
cryptoRandomString({length: 10, type: 'alphanumeric'});    // => 'DMuKL8YtE7'
cryptoRandomString({length: 10, characters: 'abc'});       // => 'abaaccabac'

cryptoRandomString.async(options) add .async if you want to get a promise.

in your terminal just write

node -e "console.log(crypto.randomBytes(48).toString('hex'))"

Or in your code use:

const randomToken = () => {
   crypto.randomBytes(48).toString('hex');
}

Look at real_ates ES2016 way, it's more correct.

import crypto from 'crypto';

function spawnTokenBuf() {
    return function(callback) {
        crypto.randomBytes(48, callback);
    };
}

async function() {
    console.log((await spawnTokenBuf()).toString('base64'));
};

Generator/Yield Way

var crypto = require('crypto');
var co = require('co');

function spawnTokenBuf() {
    return function(callback) {
        crypto.randomBytes(48, callback);
    };
}

co(function* () {
    console.log((yield spawnTokenBuf()).toString('base64'));
});

https://www.npmjs.com/package/crypto-extra has a method for it :)

var value = crypto.random(/* desired length */)

The npm module anyid provides flexible API to generate various kinds of string ID / code.

To generate random string in A-Za-z0-9 using 48 random bytes:

const id = anyid().encode('Aa0').bits(48 * 8).random().id();
// G4NtiI9OYbSgVl3EAkkoxHKyxBAWzcTI7aH13yIUNggIaNqPQoSS7SpcalIqX0qGZ

To generate fixed length alphabet only string filled by random bytes:

const id = anyid().encode('Aa').length(20).random().id();
// qgQBBtDwGMuFHXeoVLpt

Internally it uses crypto.randomBytes() to generate random.

0 dependency free solution... Works in browsers, deno & nodejs (with new global web crypto)

const random = size => btoa(
  String.fromCharCode(
    ...crypto.getRandomValues(
      new Uint8Array(size)
    )
  )
).replaceAll('+', 'x').replaceAll('/', 'I').slice(0, size)

for (let i = 5; i--;) console.log(random(16))

All doe I would just have used one single uint8array \w predefined length and called crypto.getRandomValues whenever I need something uniq (and slice it if i have to) and never deal with strings or base64, base64 is just unnecessary overhead. (allocating lots of buffer to fast can be costly)

const buf256 = new Uint8Array(256)
const random = crypto.getRandomValues.bind(crypto, buf256)

for (let i = 5; i--;) random()//.slice()

Simple function that gets you a token that is URL safe and has base64 encoding! It's a combination of 2 answers from above.

const randomToken = () => {
    crypto.randomBytes(64).toString('base64').replace(/\//g,'_').replace(/\+/g,'-');
}

You can use the random-token lib. it's very easy to use . :)

var randomToken = require('random-token').create('abcdefghijklmnopqrstuvwxzyABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789');
var token = randomToken(16);

And also you can not use different salt

var randomToken = require('random-token');
var token = randomToken(16); // output -> d8d4kd29c40f021 ```

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