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HMAC calculator
Calculate HMAC-SHA-256, SHA-384 or SHA-512 using a text or hexadecimal key, useful for checking API signature inputs.
Advanced options
Updates as you type or change an option
About this tool
Calculate HMAC-SHA-256, SHA-384 or SHA-512 using a text or hexadecimal key, useful for checking API signature inputs.
How to use
Select an algorithm and key format, then enter the message and secret key. Text keys use UTF-8; hexadecimal keys decode each pair of digits into one byte. Changing any input recalculates the result.
The output is lowercase hexadecimal. The tool does not sort parameters, join fields or append newlines, so prepare the exact message required by your API. Message limit: 2 MiB; key limit: 64 KiB. Plain HTTP supports SHA-256.
A blank message does not generate an initial result. Enter a key to calculate a signature. To test empty values deliberately, enable the empty-key option in Advanced or use the explicit empty-message action; these are separate choices.
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