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HMAC (Hash-based Message Authentication Code) is a specific type of message authentication code that involves a cryptographic hash function and a secret cryptographic key. This tool allows you to generate HMAC hashes online using various algorithms including MD5, SHA1, SHA224, SHA256, SHA384, and SHA512. HMAC provides both data integrity and authentication, making it widely used in security protocols. Simply enter your text, provide a secret key (optional), select your preferred hash algorithm, and click the calculate button to generate your HMAC hash. All calculations are performed locally in your browser, ensuring your data remains private.