Authenticate a message with HMAC

Developers and security teams use HMAC Generator when preparing a check, a local test or integration data.

Generate a message HMAC with a secret key and keep the result ready for testing or integration. Use it for free in your browser, with no account required.

How to use

Choose the algorithm from SHA-256, SHA-384 or SHA-512 according to your integration or test requirements.
Enter the secret key or passphrase in the key field, avoiding production keys on a shared or untrusted device.
Type the exact message to sign, without adding spaces or line breaks that your protocol does not expect.
Generate the result, read it, and compare it with the value expected by your application or documentation.

Example

Use a short test message and a test key to check whether a service accepts the same signature. Because the result depends on the algorithm, key and message, any difference in one of them changes the final value.

Limits and formats

The tool does not reveal your secret key, but you should still avoid handling a production key on an uncontrolled machine.
It does not decrypt anything: HMAC authenticates a message with a shared key, it does not hide the message content.
To validate a signature, the algorithm, key and message must match exactly what the other party used.

Where processing happens

The calculation runs in your browser. The key and message remain on your device and are not sent to any outside service during generation.

Frequently asked questions

How is HMAC different from a simple hash?

A simple hash transforms a message without a key. HMAC adds a secret key to the calculation, which helps verify that a message came from a party that knows the key.

Can I use the result as a password?

No, the result is a signature computed for a specific message and key. It is not meant to be stored as a password and changes whenever the message or key changes.

Why does my signature not match?

Check the selected algorithm, the exact key and the complete message, including spaces and line breaks. A single difference is enough to produce a different result.