HMAC Generator
Free HMAC generator — compute keyed HMAC-SHA256/384/512 digests in hex and Base64 using your browser’s WebCrypto. Runs locally.
Runs entirely in your browser — nothing you enter is uploaded or stored.
Generate an HMAC signature
Compute an HMAC over any message using a secret key and SHA-256, SHA-384 or SHA-512. HMACs are widely used to sign API requests, webhooks and tokens so the receiver can confirm the payload was created by someone who knows the shared secret and hasn't been altered in transit.
The message and key are encoded as UTF-8 bytes; the result is shown as lowercase hex and as standard Base64. Everything is computed in-browser with the WebCrypto API.
Frequently asked questions
What is an HMAC?
HMAC (Hash-based Message Authentication Code) combines a secret key with your message and a hash function to produce a tag that proves both integrity and authenticity — anyone with the same key can recompute and compare it.
Which algorithm should I use?
SHA-256 is the modern default. SHA-384 and SHA-512 give longer outputs and are also fine. Avoid HMAC-MD5/SHA-1 for new systems.
Does encoding of the key matter?
Here both the message and the key are treated as UTF-8 text. If your system expects a hex or base64 key, decode it to bytes first — the resulting HMAC will differ.
Is my input uploaded?
No — everything runs locally via your browser (WebCrypto). Nothing leaves the page.