Security

HMAC Generator

Generate an HMAC signature from a message, secret, and algorithm in the browser.

Last reviewed: April 30, 2026Free toolMethodology

HMAC Generator

These fields start with sample inputs. Keep them or replace them, then run the tool to show a fresh result.

Output

Calculating the sample result.

Why it matters

HMAC signing is common in webhook validation, API authentication, and request-signing workflows.

When to use

  • Testing signed payloads
  • Debugging webhook signature mismatches
  • Verifying that two systems agree on the same message and secret

Inputs & Outputs

Inputs

  • Message is the exact string to sign.
  • Secret is the shared signing key.
  • Algorithm selects the HMAC hash algorithm.

Outputs

  • Hex signature shows the HMAC digest in a common readable format.
  • Length output helps confirm which algorithm was used.

HMAC signing method

The tool imports the provided secret into Web Crypto, signs the UTF-8 message with the selected SHA algorithm, and renders the HMAC as hexadecimal.

HMAC combines a shared secret with a hash function to create a keyed digest

Worked example

1

Webhook troubleshooting

A developer wants to confirm the expected signature for a payload before comparing it with a webhook header.

Inputs

  • Message: order=8472&status=paid
  • Secret: demo-secret
  • Algorithm: SHA-256

Steps

  • Import the secret as an HMAC key
  • Sign the message
  • Render the result as hex

Result

  • The resulting signature can be compared with another system's output.

Edge cases & caveats

  • Whitespace and line ending changes will alter the signature.
  • Treat secrets carefully even when using a local browser-based tool.

Frequently Asked Questions

Is HMAC the same as hashing?

No. HMAC uses a secret key in addition to the message, which makes the output suitable for integrity checks between trusted parties.

Can I compare this output with server-side HMACs?

Yes, as long as the message bytes, secret, and algorithm all match exactly.

Keep going

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