HMAC Generator — Free Online HMAC Hash Generator

HMAC (Hash-based Message Authentication Code) solves a fundamental security problem: proving that a message came from someone who knows a shared secret. Unlike regular hashes which are public and deterministic, HMAC output depends on a secret key — without the key, an attacker cannot forge a valid HMAC for any message.

HMAC is foundational to API authentication. AWS Signature Version 4 uses HMAC-SHA256 to sign requests. JWT HS256 tokens use HMAC-SHA256 to sign the header and payload. GitHub, Stripe, and Shopify use HMAC-SHA256 to sign webhook payloads, allowing receiver verification. When you see a signature header like X-Hub-Signature-256: sha256=abc123..., that's HMAC-SHA256.

This tool uses the Web Crypto API (crypto.subtle.importKey +crypto.subtle.sign) for native HMAC computation. Select the algorithm, enter your message and secret key, then click Generate.