HMAC Generator — Free Online Tool
Generate HMAC (Hash-based Message Authentication Code) digests for any message and secret key. HMAC combines a cryptographic hash (SHA-256 or SHA-512) with a secret key to produce a unique signature that verifies both message integrity and the sender's identity. Used in API authentication, webhook verification, and data integrity checks.
100% client-side. No uploads. Your data never leaves your browser.
How to use HMAC Generator
- Enter your message in the message area.
- Enter your secret key in the key field.
- HMAC-SHA256 and HMAC-SHA512 digests appear instantly.
- Copy either digest with its Copy button.
Frequently Asked Questions
What is HMAC used for?
HMAC is used to authenticate API requests (e.g., AWS Signature v4, GitHub webhooks) and verify message integrity. It ensures a message was sent by someone who knows the shared secret key.
Is HMAC the same as a password hash?
No. HMAC uses a secret key and is designed for message authentication, not password storage. For passwords, use bcrypt, scrypt, or Argon2.
Which algorithm should I use, SHA-256 or SHA-512?
Both are secure. SHA-256 produces a 64-character hex digest; SHA-512 produces 128 characters. SHA-256 is more common in API authentication. Use SHA-512 if your system requires a longer digest.
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