HMAC Generator Online Free — SHA-256, SHA-512 HMAC Calculator

Generate HMAC signatures with SHA-256 or SHA-1 for API verification and webhooks. Free, no signup required.

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How to Use

Enter or paste the message to sign
Enter the secret key
Select the hash algorithm (SHA-256, SHA-1, or SHA-512)
Copy the generated HMAC signature in hex or Base64

Common Use Cases

Verifying webhook signatures from payment providers
Signing API requests for authentication
Generating message authentication codes for secure communication
Testing HMAC implementations during development

Frequently Asked Questions

What is the difference between HMAC and a regular hash?

A regular hash (like SHA-256) only takes a message as input. HMAC also requires a secret key, so only parties who know the key can generate or verify the signature. This prevents tampering.

Which HMAC algorithm should I use?

HMAC-SHA256 is the most common and recommended choice. It offers strong security and is required by most modern APIs. Use SHA-1 only for legacy compatibility.

How do I verify a webhook signature with HMAC?

Compute the HMAC of the webhook payload using your secret key, then compare it to the signature in the webhook header. If they match, the webhook is authentic and untampered.