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HMAC-SHA512 hash generator
Calculate an HMAC-SHA512 of a message with your own secret key, online and free. The keyed hash appears next to the plain hashes of the same text, in 128 hex characters. Useful for checking webhook signatures and API requests. Nothing is uploaded.
How to calculate an HMAC-SHA512 online
- 1Type the message, or drop a text file
- 2Enter your secret key in the "HMAC key (optional)" box
- 3Copy the HMAC-SHA512 line from the list
- A 128-character HMAC-SHA512, in hex.
What you get
- Your key stays with you.Key and message are used in your browser and are never sent anywhere.
- Keyed and plain together.The HMAC lines come with the plain hashes of the same text.
- Hex output, lower or upper.Switch to capitals with "Uppercase" to match a service's format.
What you can do
- Enter a key and a message and get HMAC-SHA512 at once, updated as you type.
- See HMAC-SHA-1, HMAC-SHA-256, HMAC-SHA-384 and HMAC-SHA-512 of the same message in one list.
- Drop a text file to use its content as the message.
- Compare the result with the signature a webhook or API sends, such as a GitHub or Stripe style header.
- Get the longer 512-bit keyed hash when a service or protocol asks for HS512 or HMAC-SHA512.
Good to know
- HMAC lines only appear once the key box is filled. With an empty key you see plain hashes.
- Key and message are read as UTF-8 text. A binary or hex key is not decoded, so a hex key is used as its characters.
- The message must match byte for byte, including spaces and the final newline, or the HMAC will differ.
- HMAC-SHA512 output is 128 hex characters, or 64 bytes, twice as long as HMAC-SHA256.
Questions
What is HMAC-SHA512?
A hash of a message mixed with a secret key, using SHA512. Only someone with the key can produce the same value, so it proves the message is genuine and unchanged.
Is my secret key sent to a server?
No. The calculation runs in your browser, and neither the key nor the message leaves your device.
Why does my HMAC not match the service's?
Usually the message differs by a space, a line break or the encoding, or the service signs the raw request body. Check those first.
When should I pick HMAC-SHA512 over HMAC-SHA256?
When the other side requires it. Both are secure, and SHA512 only gives a longer value.