TOTP and HOTP utilities.

Usage no npm install needed!

<script type="module">
  import faUtils from 'https://cdn.skypack.dev/2fa-utils';


Two-Factor Authentication

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Using the algorithm provided in RFC 4226, can generate and verify HMAC-based one-time password (HOTP) and time-based one-time password (TOTP).


  • Generate base-32 encoded secrets.
  • Generate HMAC-based one-time passwords (HOTP) at a specific length.
  • Generate time-based HOTPs at a specific amount of windows.
  • Verify generated tokens.


Generating Secret

For each account, a secret must be generated and shared between the server and the client. This secret will be used to create and verify HOTPs.

const secret = twoFA.generateSecret();

Generating HOTP

HOTP requires a base32-encoded secret and a counter with time-step.

// Generate base32 secret
const secret = twoFA.generateSecret();
// Create counter with 30 seconds interval 
const counter = Math.floor(Date.now() / 30000);

const hotp = twoFA.generateHOTP(secret, counter, 6)

Generating TOTP

Generating TOTP allows you to get a HOTP in a specific time window.

const secret = twoFA.generateSecret();

// Get the current time window's token
const currentTotp = twoFA.generateTOTP(secret, 0);

// Get the future time window's token (1 window ahead)
const futureTotp = twoFA.generateTOTP(secret, 1);

// Get the past time window's token (1 window behind)
const pastTotp = twoFA.generateTOTP(secret, -1);

Verifying HOTP

Verify tokens supplied via user input.

function verifyHOTP(inputToken) {
  const secret = twoFA.generateSecret();
  const counter = Math.floor(Date.now() / 30000);

  // Actual token generated by the server
  const actualToken = twoFA.generateHOTP(secret, counter)

  if (inputToken === actualToken) return true;
  return false

Verifying TOTP

Verify tokens supploed via user input with a time tolerance.

const secret = twoFA.generateSecret();

const inputToken = '111111';

/* This will return true if the input token 
  - is currently valid,
  - was previously valid in the last window,
  - will be valid in the next window.
const isTokenValid = twoFA.verifyTOTP(inputToken, secret, 1);



  • Boran Seckin


This project is licensed under the MIT License - see the LICENSE.md file for details.