HMAC Generator

About HMAC Generator Tool

This free online HMAC generator computes Hash-based Message Authentication Codes using SHA-256, SHA-384, SHA-512, and SHA-1 algorithms. HMAC combines a secret key with a message to produce a signature that verifies both data integrity and authenticity. Output is provided in both hexadecimal and Base64 formats. All computation uses the browser's Web Crypto API — your secrets never leave your device.

Why Use HMAC?

HMAC is the standard mechanism for API authentication (AWS Signature V4, Stripe webhooks, GitHub webhooks), message integrity verification, and secure token generation. Unlike plain hashes, HMAC requires a secret key, making it resistant to length extension attacks. Developers need HMAC generators for testing webhook signature verification, debugging API authentication, generating test fixtures, and verifying third-party implementations.

Key Benefits

• Four algorithms: SHA-256, SHA-384, SHA-512, and SHA-1 computed simultaneously
• Dual output: Both hex and Base64 encoding for each algorithm
• Web Crypto API: Cryptographically correct implementation using browser standards
• One-click copy: Copy any individual hash value instantly
• Completely private: Your secrets and messages never leave your browser
• No installation: Works in any modern browser without plugins

Privacy and Security

All HMAC computation happens locally in your browser using the Web Crypto API. Your secret keys, messages, API credentials, and webhook secrets never leave your computer. No cookies, no tracking, no server uploads. Safe for production secrets, API keys, and confidential authentication data.