What is an HMAC?
An HMAC combines a secret key with a message to produce a signature that verifies both the message’s integrity and its authenticity, commonly used for API request signing and webhook verification.
HMAC Generator
Enter a secret key and a message, choose an algorithm, and generate the HMAC signature instantly.
How it works
- 1
Fill in the form fields the tool shows.
- 2
Change modes or toggles if available.
- 3
Copy the generated output when it looks right (often updates live).
Why use this tool
- Runs entirely in your browser — nothing is uploaded to a server.
- 100% free, no sign-up, no limits.
- Works in any modern browser — no app install, no extension, no account.
How to use HMAC Generator
Complete the fields in HMAC Generator. Output is produced in your browser from those inputs — copy it when ready.
Tips for better results
Empty optional fields if you want a minimal result. Invalid combinations should surface an error message.
Privacy and offline-friendly processing
Whenever possible, HMAC Generator processes your data locally with JavaScript in this page. That means drafts, secrets, and unfinished work stay on your device by default. Prefer this workflow when you do not want to upload sensitive text, tokens, passwords, or files to a third-party service.
Frequently asked questions
How is HMAC different from a plain hash?
A plain hash only verifies data integrity; an HMAC also proves the sender knew the secret key, providing authentication.
Is my secret key sent anywhere?
No, the HMAC is computed entirely in your browser using the Web Crypto API — the key never leaves your device.
Is my data uploaded when I use this tool?
For most FlyUtils tools, no. Processing happens in your browser with JavaScript. If a tool ever needs a server, that will be stated clearly on the page.
Is HMAC Generator free to use?
Yes. HMAC Generator is free, with no sign-up and no artificial usage caps for normal personal and work use.
Does HMAC Generator work on mobile?
Yes. The page is mobile-first, so you can paste input, tweak options, and copy results from a phone or tablet.