Free · no signup · browser-local
HMAC SHA-256, SHA-384 and SHA-512 Generator
Sign text locally with a UTF-8 or hexadecimal key, export a hex or Base64 HMAC and optionally compare an expected signature using the selected algorithm.
Result
Choose inputs and run the tool to see the result.
Getting started
Enter the message and key, choose the algorithm and output encoding, then generate. Optionally compare an expected signature.
Before you use the result
The message and key remain in this page memory until cleared. A matching HMAC alone does not establish who supplied a key. JavaScript timing is not guaranteed constant.
Try an example
With message “Hi There”, hex key 0b repeated 20 times and SHA-256, the HMAC starts b0344c61d8db3853 (RFC 4231 case 1).
How it works
WebCrypto imports a nonextractable HMAC key and signs exact UTF-8 message bytes. Hex/base64 expected signatures are decoded and compared across every byte without an early content exit.
Frequently asked questions
Generate SHA-256, SHA-384 or SHA-512 HMAC locally from UTF-8 or hex keys.
How do I use HMAC Generator & Checker?
Enter the message and key, choose the algorithm and output encoding, then generate. Optionally compare an expected signature.
Does this tool upload my data?
Inputs and files are processed in your browser. Page-view analytics do not contain your tool input.
What should I check before using the result?
The message and key remain in this page memory until cleared. A matching HMAC alone does not establish who supplied a key. JavaScript timing is not guaranteed constant.