otplibOne-Time Password Library
TypeScript-first library for HOTP and TOTP authentication with multi-runtime support and pluggable architecture
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RFC Compliant /
Key Features
Built with modern practices
TypeScript Native
Written in TypeScript with complete type definitions. Async-first API design with synchronous alternatives.
Pluggable Architecture
Swap crypto and Base32 implementations via plugins. Use Web Crypto, Node crypto, or bring your own.
RFC Compliant /
Authenticator Compatible
Full implementation of RFC 4226 (HOTP) and RFC 6238 (TOTP) specifications.
Compatible with common authenticator apps like Google, Microsoft, Authy and many more.
Interactive Demo
See it in action
TOTP
Time-based tokens that refresh every 30 seconds. The standard for authenticator apps.
Setup
Client (Generate)
Server (Verify)
HOTP
Counter-based tokens that increment with each use. Ideal for hardware tokens.
Setup
Client (Generate)
Counter: 0
Click to increment the counter and generate the next OTP.
Server (Verify)
Expected Counter: 0
The server accepts any token from the current counter up to a window ahead (resync).