@otplib/totp

@otplib/totp

RFC 6238 TOTP implementation for otplib.

Installation

npm install @otplib/totp
pnpm install @otplib/totp
yarn add @otplib/totp

Usage

generate

Generate a TOTP code:

import { generate } from "@otplib/totp";
import { crypto } from "@otplib/plugin-crypto-node";

const secret = new Uint8Array([
  0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36,
  0x37, 0x38, 0x39, 0x30,
]); // 20-byte HMAC key

const token = await generate({
  secret, // Required: Uint8Array or Base32 string
  crypto, // Required: crypto plugin
  algorithm: "sha1", // Optional: 'sha1' | 'sha256' | 'sha512'
  digits: 6, // Optional: 6 | 7 | 8
  period: 30, // Optional: time step in seconds
  epoch: Date.now() / 1000, // Optional: Unix timestamp in seconds (defaults to now)
});

With Base32 secrets

If your secret is a Base32 string (e.g., from Google Authenticator), provide a base32 plugin to decode it:

import { generate } from "@otplib/totp";
import { crypto } from "@otplib/plugin-crypto-node";
import { base32 } from "@otplib/plugin-base32-scure";

const token = await generate({
  secret: "GEZDGNBVGY3TQOJQGEZDGNBVGY",
  crypto,
  base32, // Required when secret is a string
});

With raw string secrets

If your secret is a plain string (e.g. a passphrase), convert it to Uint8Array first using stringToBytes from @otplib/core:

import { generate } from "@otplib/totp";
import { crypto } from "@otplib/plugin-crypto-node";
import { stringToBytes } from "@otplib/core";

const token = await generate({
  secret: stringToBytes("mysecretpassphrase"),
  crypto,
});

Alternatively, @otplib/plugin-base32-alt provides bypass plugins for secrets in other encodings:

import { generate } from "@otplib/totp";
import { crypto } from "@otplib/plugin-crypto-node";
import { bypassAsHex } from "@otplib/plugin-base32-alt";

const token = await generate({
  secret: "48656c6c6f", // hex-encoded secret
  base32: bypassAsHex,
  crypto,
});

Name	Input format
bypassAsString	Raw UTF-8 string
bypassAsHex	Hex string
bypassAsBase64	Base64 string

Raw string and bypass secrets are not compatible with authenticator apps or otpauth:// URIs, which always expect Base32-encoded secrets.

verify

Verify a TOTP code:

import { verify } from "@otplib/totp";
import { crypto } from "@otplib/plugin-crypto-node";

const result = await verify({
  secret, // Required: Uint8Array or Base32 string
  token: "123456", // Required: token to verify
  crypto, // Required: crypto plugin
  algorithm: "sha1", // Optional: hash algorithm
  digits: 6, // Optional: expected digits
  period: 30, // Optional: time step in seconds
  epoch: Date.now() / 1000, // Optional: Unix timestamp in seconds (defaults to now)
  epochTolerance: 30, // Optional: number or [past, future] tuple
  afterTimeStep: lastTimeStep, // Optional: reject time steps <= this value (replay protection)
});

// Returns: { valid: true, delta: number, epoch: number, timeStep: number } | { valid: false }

epochTolerance accepts a number (symmetric window ±n seconds) or a [past, future] tuple for asymmetric control (e.g., [30, 0] accepts only past tokens, as recommended by RFC 6238 for transmission-delay handling).

afterTimeStep is an exclusive lower bound on the matched time step: any match at timeStep <= afterTimeStep is rejected. Pass the timeStep from the previous successful verification to prevent token reuse.

getRemainingTime

Get remaining seconds until the next TOTP period. All parameters are optional and default to the current time with a 30-second period:

import { getRemainingTime } from "@otplib/totp";

const seconds = getRemainingTime(); // uses current time, period=30, t0=0
const seconds2 = getRemainingTime(epoch, 30); // explicit time and period

getTimeStepUsed

Get the current TOTP counter (time step) value. All parameters are optional:

import { getTimeStepUsed } from "@otplib/totp";

const counter = getTimeStepUsed(); // uses current time, period=30, t0=0
const counter2 = getTimeStepUsed(epoch, 30); // explicit time and period

Sync Variants

generateSync and verifySync are synchronous alternatives with the same signatures. They require a crypto plugin that supports sync HMAC operations, such as @otplib/plugin-crypto-node or @otplib/plugin-crypto-noble. Using them with @otplib/plugin-crypto-web will throw.

import { generateSync, verifySync } from "@otplib/totp";
import { crypto } from "@otplib/plugin-crypto-node";

const secret = new Uint8Array([
  0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36,
  0x37, 0x38, 0x39, 0x30,
]);

const token = generateSync({ secret, crypto });
const result = verifySync({ secret, token, crypto });

Compatibility with Authenticator Apps

RFC 4226 (HOTP) and RFC 6238 (TOTP) define flexible algorithms that allow different hash functions, digit lengths, and time steps. However, most authenticator apps (Google Authenticator, Authy, Microsoft Authenticator, 1Password, etc.) and services offering 2 factor authentication use the following defaults:

Parameter	Value
algorithm	sha1
digits	6
period	30
secret	Base32 string

If you are deviating from these values, do validate that it is supported by the target application.

If you need to provision an authenticator app via QR code, use @otplib/uri to generate an otpauth://totp/ URI.

Documentation

Full documentation available at otplib.yeojz.dev:

• Getting Started Guide
• API Reference

License

MIT