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General dev

HMAC Generator

Runs locally

Use HMAC Generator

What it does

Compute an HMAC-SHA-256 or HMAC-SHA-512 of a message with a secret key, in hex or Base64, for example to check a webhook or API request signature.

It runs entirely in your browser: nothing you enter is uploaded.

Example

Published test vector

Input
The quick brown fox jumps over the lazy dog
Output (captured 2026-10-20)
f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8

With the key "key", HMAC-SHA-256 of this sentence is f7bc83f4…2d1a3cd8 (64 hex characters), the published test value from the HMAC Wikipedia article and many test suites.

FAQ

What exactly does it compute?

An HMAC (RFC 2104) with SHA-256 or SHA-512 over the UTF-8 bytes of the message, with the key taken as UTF-8 text, shown as hex or Base64. A hex or Base64 secret is not decoded first, so it will not match services that expect the raw key bytes.

Why do I get no result, or a different one?

Generate does nothing while the key or the message is empty. An extra space or line break in the message, or a differently encoded key, changes the result completely.

Is my key sent anywhere?

No. The HMAC is computed in your browser with the Web Crypto API; the key and the message are not uploaded or stored.

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