HOTP GeneratorGenerate HMAC-based one-time passwords (HOTP) with counter tracking.
HOTP Generator
Generate HMAC-based one-time passwords (HOTP) with counter tracking.
Enter Secret
Base32 secret.
Set Counter
Counter value.
Generate
Generate code.
What Is HOTP Generator?
HOTP uses a shared secret and incrementing counter per RFC 4226. Unlike TOTP (time-based), HOTP is event-based. Suitable for hardware tokens and offline scenarios. Computes HMAC-SHA1 with dynamic truncation. This tool tracks history and auto-increments. All processing uses Web Crypto API client-side.
Why Use Our HOTP Generator?
- RFC 4226 compliant
- Counter auto-increment
- Generation history
- 100% client-side
Common Use Cases
Hardware Tokens
Test HOTP.
Development
Counter-based codes.
Offline Auth
No time sync.
Education
Counter vs time OTP.
Technical Guide
HOTP: (1) Decode Base32. (2) 8-byte big-endian counter. (3) HMAC-SHA1. (4) Dynamic truncation: last nibble offset, 4 bytes, mask, mod 10^digits. Counter must sync client/server.
Tips & Best Practices
- 1Sync counter
- 2Codes don't expire
- 3Keep history
- 4Use TOTP if time available
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Encoding & CryptoFrequently Asked Questions
QFree?
QHOTP vs TOTP?
QSecret safe?
QExpire?
QAuto-increment?
About HOTP Generator
HOTP Generator is a free online tool from FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration required. No ads. Just fast, reliable tools.