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HMAC Generator

Hash-based Message Authentication Code

🔐 About HMAC

HMAC (Hash-based Message Authentication Code) là một loại mã xác thực thông điệp sử dụng hàm hash mật mã kết hợp với khóa bí mật. HMAC được sử dụng để xác minh tính toàn vẹn và xác thực của thông điệp, thường dùng trong API authentication, JWT, và các giao thức bảo mật.

Free HMAC Generator Online

The HMAC generator online lets you compute a Hash-based Message Authentication Code directly in your browser using popular algorithms such as SHA-256, SHA-512, and MD5. It is built for developers who need to verify API signatures, debug webhook authentication, or validate that a secret key and message produce the expected digest — all without installing any library or writing a single line of code.

Benefits of the HMAC Generator

  • Instant in-browser computation — no terminal, no dependencies, no setup required.
  • Supports HMAC-SHA256, HMAC-SHA512, HMAC-SHA1, and HMAC-MD5 to match any API spec.
  • Completely free with unlimited use; your secret key never leaves your browser.
  • Output is a standard lowercase hex string ready to paste into headers or source code.
  • Cuts debugging time when integrating third-party APIs that require request signing.

Use cases for the HMAC Generator

  • Verify webhook signatures from Stripe, GitHub, or Shopify before deploying your handler.
  • Cross-check an HMAC value received from a partner API against your own calculation to diagnose 401 errors.
  • Generate reliable test vectors to unit-test your own HMAC implementation in any programming language.
  • Prototype request-signing logic for REST APIs that require an Authorization header with an HMAC digest.
  • Learn how message authentication codes work as part of studying application security fundamentals.

How to use the HMAC Generator

  1. Enter the message (the data you want to authenticate) in the first input field.
  2. Enter your secret key — the shared string known only to you and the intended recipient.
  3. Select the hashing algorithm that matches your API or use case (SHA-256 is recommended for new projects).
  4. Click Generate to produce the HMAC digest as a hex string instantly.
  5. Copy the result and paste it into your HTTP header, query parameter, or test assertion.

Frequently asked questions

How is HMAC different from a plain hash like SHA-256? A plain hash summarises data but anyone can recompute it. HMAC folds in a secret key, so only parties who possess that key can produce or validate the correct digest — making it resistant to tampering and forgery.

Is my secret key sent to VSM servers? No. All computation runs entirely client-side in your browser. Neither your message nor your secret key is transmitted to any server.

Which algorithm should I choose? HMAC-SHA256 is the current industry standard and the right choice for most integrations. Avoid HMAC-MD5 and HMAC-SHA1 for new systems since their underlying hash functions are considered cryptographically weak.

Can I use the HMAC output directly as an authentication token? HMAC digests are typically included in an HTTP header such as X-Hub-Signature-256 or combined with a timestamp to create a time-limited signature that prevents replay attacks, rather than used as standalone tokens.