What Is HMAC and Why Use It?
HMAC (Hash-based Message Authentication Code) combines a cryptographic hash function with a secret key to prove both that a message has not been tampered with and that it came from someone who knows the key, something a plain hash alone cannot do since anyone can compute a plain hash of any message. An hmac signature generator lets you compute that signature instantly for a given message and secret, which is exactly what you need when testing an API that signs requests, debugging a webhook that is rejecting your payload, or verifying a signature your backend produced.
How to Generate an HMAC With This Tool
Enter the message you want to sign and the shared secret key, and this hmac generator online computes HMAC-SHA1, HMAC-SHA256, and HMAC-SHA512 for it simultaneously, so you do not need to pick an algorithm before seeing a result, whether you need an hmac sha256 generator or the SHA1/SHA512 variants. Toggle hmac hex to base64 output depending on what format your API or webhook provider expects, copy the signature you need, and everything updates live as you type since the computation happens entirely client-side.
How to Verify an HMAC Signature
Paste an HMAC value you received or generated elsewhere into the verify field, and the tool checks it against all three computed signatures at once, reporting which algorithm it matches or that it does not match any of them. This is the fastest way to verify hmac online without knowing in advance whether a signature was produced with hmac sha1 sha512 online or hmac sha256 online.
Choosing an Algorithm: SHA1 vs. SHA256 vs. SHA512
HMAC-SHA256 is the practical default and what most modern APIs and webhook providers expect. HMAC-SHA1 still shows up in older systems and legacy integrations but should be avoided in new designs since SHA-1 itself is considered weak, though HMAC construction makes the attack surface different from using SHA-1 alone. HMAC-SHA512 offers a larger output and is used where a longer signature is explicitly required, without being meaningfully more secure than SHA256 for most practical purposes.
Common Use Cases
Handling webhook signature verification for providers like GitHub, Stripe, and Shopify, which all sign their webhook payloads with HMAC-SHA256, debugging an API integration that signs requests with a shared secret, needing to generate hmac signature values to confirm your backend verification logic works correctly, and understanding how JWT HS256 algorithm derives its name are all common reasons to reach for an hmac generator. Because the computation runs entirely in your browser, your secret key never leaves your machine.