Your files stay on your device

HMAC generator and verifier

Keyed MACs over any text: SHA-1, SHA-256, SHA-384, SHA-512 through WebCrypto, keys as text, hex, or base64. RFC 4231-exact, computed in your tab.

Inputs

or generate a random 256-bit key in hex

Verify an expected MAC (optional)
Hex, base64, or base64url; uppercase hex and colon grouping tolerated
What this tool does not do
  • No encryption, only authentication: an HMAC proves the message and key match. It hides nothing.
  • The shared secret lives in this tab’s memory while you work, nothing is sent or stored, a browser tab cannot guarantee the memory is zeroized after, and browser extensions can read page content.
  • The comparison here is for pasted digests, not live secrets. Production verifiers compare in constant time.
  • SHA-1 HMAC still resists collision attacks in this role, but new systems pick SHA-256 or better.
Paste, drop, or type to begin. Everything stays on this device.

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