HMAC Generator
Generate an HMAC signature for a message with a secret key.
Computed entirely in your browser. Your secret is never sent anywhere.
- SHA-1, SHA-256, SHA-384 and SHA-512 via the browser's Web Crypto — real, spec-correct output.
- Updates live as you change the key, algorithm or message.
- The key and message never leave your browser.
Why this is private
- Computed entirely in your browser. Your secret is never sent anywhere.
- Open your browser's DevTools → Network tab while using this tool — you won't see a request carrying your input, because it never leaves your device.
- Nothing you enter is uploaded to a server or shared with us — the processing happens entirely on your device.
Overview
Computes an HMAC (Hash-based Message Authentication Code) — used to verify both the integrity and authenticity of a message, since producing a valid HMAC requires knowing the secret key.
How to use it
- 1Enter the secret key.
- 2Choose a hash algorithm.
- 3Enter the message.
- 4The HMAC updates automatically.
Tips
- Only use this for testing and debugging — never paste a real production signing secret into any web-based tool.
Frequently asked questions
What people use it for
Verify a webhook signatureRecompute the HMAC over a payload and compare it to the `X-Signature` header a provider sent.
Build a signed API request in developmentGenerate the signature string an API expects while you wire up the client.
Check your signing code matches the specCompare your implementation's output against this tool's for the same inputs.
Learn how HMAC worksChange one character of the message and watch the whole digest change.
Related tools
All developer toolsHash GeneratorGenerate MD5, SHA-1, SHA-256 and SHA-512 hashes, in hex or Base64, with a compare mode.JWT GeneratorCreate and sign a JWT with an HMAC secret — HS256, HS384 or HS512.JWT DecoderDecode JWT headers and payloads, and verify HMAC signatures with a secret.Password Strength CheckerCheck a password's strength and estimated crack time.
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HMAC Generator