About HMAC generator
Use the HMAC generator online to reproduce a message authentication code for a known input. You can generate HMAC SHA-256 with a UTF-8 key or choose another offered SHA-2 variant. Enter exact message bytes as text and verify the encoding rules required by your protocol.
How to generate an HMAC for a text message
- Enter the message and a nonempty UTF-8 secret key.
- Select the SHA-2 algorithm and select Process.
- Copy the hexadecimal MAC, then reset the tool to clear the message and secret.
A practical example
- Input
The quick brown fox jumps over the lazy dog
- Result
f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8
The literal UTF-8 key is key; it is not hex-decoded or Base64-decoded.
Supported input and limitations
- The message is limited to 5 MB and the nonempty secret to 64 KB. Only UTF-8 text keys and lowercase hexadecimal output are supported.
- This page does not implement request canonicalization, webhook verification, key storage, or timing-safe server verification. Its drafts and results are excluded from workspace recovery; copies and downloads remain your responsibility.
Processing happens on your device. Read about local processing and optional workspace recovery.
Frequently asked questions
Is the HMAC secret saved in workspace recovery?
No. The complete HMAC tool draft is excluded from workspace recovery, including its input, options, and result. The page can still hold the entered key in memory until reset or a full page unload.
Can I paste a hex or Base64 key directly?
Only if the protocol means those literal characters as the key. This tool treats the key as UTF-8 text and does not decode another key representation.