HMAC generator

Compute an HMAC-SHA signature from a secret key and message, and compare it with an expected value.

Computed in this browser with WebCrypto. The key and message are never sent anywhere.

UTF-8 text inputs, up to 500,000 characters each. Whitespace in the message changes the signature — paste webhook payloads byte-for-byte.

How to use

  1. Paste the message and the secret key.
  2. Choose the hash algorithm.
  3. Read the hex and Base64 signature, or paste an expected value to compare.

What it supports

WebCrypto HMAC over UTF-8 text — SHA-1, SHA-256, SHA-384, or SHA-512, up to 500,000 characters per field. Whitespace changes the signature, so paste payloads exactly. For testing and verification, not for minting production secrets.

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