Is the key sent anywhere?

No — signing is done locally by crypto.subtle; nothing is transmitted.

HMAC Generator

Compute HMAC-SHA-256 or HMAC-SHA-512 signatures in your browser. Your key and message stay on your device.

By AbraCalc Editorial Team · Reviewed by AbraCalc Methodology Review · Last reviewed: 2026-06-25

Message

Secret key

Algorithm Base64 output

Pure browser JavaScript — uses the Web Crypto API (crypto.subtle).

Embed this tool on your site

<iframe src="https://abracalc.com/app/hmac-generator/" width="100%" height="640" style="border:1px solid #e4e7ec;border-radius:12px" loading="lazy"></iframe>

How to use this tool

Enter the message and secret key.
Choose HMAC-SHA-256 or HMAC-SHA-512.
Click Sign — copy the hex or Base64 digest.

Compute HMAC-SHA-256 or HMAC-SHA-512 signatures in your browser. Your key and message stay on your device.

Frequently asked questions

Is the key sent anywhere?: No — signing is done locally by crypto.subtle; nothing is transmitted.

References & sources

HMAC (Wikipedia)

HMAC Generator

How to use this tool

Frequently asked questions

References & sources

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