Free tool

Webhook signature simulator

Sign a test payload with HMAC-SHA256, then check whether a receiver would accept or reject the signature it gets — and why.

Everything runs in your browser. Your payload and secret are never sent anywhere.

1. The signing rule

What the sender and receiver both agree on.

Payload (the raw request body, byte for byte) Secret key

Signature header

Signature format

2. Simulate the receiver

Paste the signature your sender actually put in the header.

Received signature value

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