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Free online HMAC signature generator supporting SHA-256, SHA-512, and more algorithms. Create hash-based message authentication codes for APIs.
About HMAC
HMAC (Hash-based Message Authentication Code) provides both data integrity and authentication using a secret key. It is widely used for API request signing, webhook verification, and token generation.
Generates HMAC (Hash-based Message Authentication Code) signatures using Web Crypto API. Supports SHA-1, SHA-256, SHA-384, and SHA-512 algorithms, producing hex-encoded output for any message and secret key combination.
HMAC is essential for API authentication, webhook verification, and message integrity checks. This tool provides a quick browser-based way to compute HMAC signatures without writing code or using command-line tools.
API developers implementing request signing, backend engineers verifying webhook payloads, and security professionals auditing authentication systems.
Enter the message (data) to be authenticated in the message field
Enter the secret key used for signing
Select the hashing algorithm (SHA-256 is recommended for most use cases)
The hex-encoded HMAC signature appears automatically
Click 'Copy' to copy the signature to your clipboard
Message: 'Hello, World!', Key: 'secret', Algorithm: SHA-256 → Output: hex-encoded 64-character HMACMessage: 'POST /api/webhook', Key: 'whsec_abc123', Algorithm: SHA-512 → Output: hex-encoded 128-character HMACa construction that combines a cryptographic hash with a secret key to authenticate messages.
HMAC uses a symmetric key (shared secret), while digital signatures use asymmetric keys (public/private).
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