HMAC Generator
Generate HMAC signatures with SHA-256/512.
About HMAC Generator
Generate an HMAC signature to authenticate a message with a shared secret key. HMAC combines a hash function such as SHA-256 with a secret key to produce a code that proves a message has not been altered and that it came from someone who knows the key, which is why APIs use it to sign webhooks and requests. Enter your message and secret and choose an algorithm to compute the HMAC instantly. The signing happens locally in your browser using its built-in crypto, so your secret key is never transmitted or stored, keeping it safe. The tool is free with no signup and is a favorite for testing API integrations.
How to use this tool
- 1Enter your message and secret key.
- 2Choose the hash algorithm.
- 3Copy the HMAC signature.
Frequently asked questions
What is HMAC used for?
HMAC verifies both the integrity and authenticity of a message using a shared secret key, common in API request signing and webhooks.
Is my secret key sent anywhere?
No. The HMAC is computed locally with the Web Crypto API; your key and message never leave the browser.
Related guide
6 min readHashing Explained: MD5 vs SHA-256, and Why It Matters
What cryptographic hashing actually does, why MD5 is broken, when SHA-256 is the right choice, and why none of them should store your passwords.