HMAC Generator Online — Create SHA-256, SHA-384 or SHA-512
Generate an HMAC online from UTF-8 text and a secret key with the browser Web Crypto API.
About this tool
This HMAC generator signs UTF-8 input using a UTF-8 secret key and the selected SHA-256, SHA-384 or SHA-512 algorithm, then returns a hexadecimal authentication code.
How to use
- Enter the message in the first field.
- Enter the secret key and select the required SHA algorithm.
- Generate and compare or copy the hexadecimal HMAC.
Features
- Supports HMAC-SHA-256, SHA-384 and SHA-512.
- Uses native Web Crypto signing.
- Keeps the message and secret key local.
Common use cases
- Reproduce webhook signatures.
- Test request-authentication code.
- Compare HMAC output across implementations.
Common issues and tips
- HMAC depends on the exact message bytes, key encoding and algorithm.
- Do not paste production secrets into shared devices or screenshots.
Privacy
HMAC generation runs locally in your browser. The message and key are not uploaded to Tools12345.
Frequently asked questions
Is HMAC the same as a plain hash?
No. HMAC combines a secret key with a cryptographic hash to authenticate a message.
What encoding is used?
Both the message and secret key are encoded as UTF-8 and the result is hexadecimal.
Which algorithm should I choose?
Use the algorithm required by the protocol; SHA-256 is a common modern default.