HMAC Generator

Free online HMAC generator to create keyed message authentication codes with HMAC-SHA256 or HMAC-SHA512. Enter a message and secret key to compute a signature and verify webhooks and APIs.

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Last updated: 2026 · Free online tool

What is HMAC Generator?

Free online HMAC generator to create keyed message authentication codes with HMAC-SHA256 or HMAC-SHA512. Enter a message and secret key to compute a signature and verify webhooks and APIs.

How to Use

1
Select Mode— Choose generation or verification mode.
2
Enter Input— Enter the message and secret key.
3
View Result— Copy the generated HMAC or check the verification result (match/mismatch).

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Frequently Asked Questions

HMAC (Hash-based Message Authentication Code) is a method that generates message authentication codes using a secret key and hash function.

HMAC-SHA256 and HMAC-SHA512 are supported, using the Web Crypto API.

Presets for commonly used API signatures like Stripe, GitHub, and Slack webhooks are provided.

Yes, verification mode uses constant-time comparison to prevent timing attacks.

No. All calculations are performed in the browser via Web Crypto API.

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