HMAC Hash Generator
Generate HMAC-SHA256, SHA-384 or SHA-512 signatures online. Verify message authenticity with a secret key. Free, runs in your browser.
Uses the Web Crypto API. Your message and key never leave this page.
Frequently asked questions
- What is an HMAC?
- A keyed hash that proves a message came from someone holding the secret key and was not tampered with. Common in API request signing.
- Which algorithms are available?
- HMAC-SHA256, HMAC-SHA384 and HMAC-SHA512, the three used most often by REST APIs and webhooks.
- Is my secret key safe?
- Yes. The Web Crypto API computes the signature locally in your browser; nothing is transmitted.
- How do I verify a signature?
- Recompute the HMAC of the received message with the shared key and compare it with the signature sent, using a constant-time comparison.
This tool runs entirely in your browser. No data is uploaded anywhere.