HMAC Generator
Generate HMAC signatures for authentication
This free online hmac generator runs in your browser and is part of our Cryptography collection.
🔑 HMAC Generator
Generate HMAC (Hash-based Message Authentication Code) signatures for secure authentication
About HMAC:
- Authentication: HMAC ensures message authenticity and integrity
- Secret Key: Both sender and receiver must share the same secret key
- Algorithm: SHA-256 is recommended for most use cases
- Use Cases: API authentication, webhook signatures, JWT tokens, message verification
- Security: Keep your secret key confidential and use strong keys (32+ bytes)
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Instant In-Browser Execution
Runs locally in JavaScript without wait times or server delays.
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100% Privacy & Security
Your inputs and files are never stored or logged on remote servers.
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Cross-Device Responsive
Fully optimized for mobile smartphones, tablets, and desktop displays.
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100% Free Forever
No subscription fees, no signups, and no software installations.
How to Use the Online HMAC Generator
1
Enter Secret Key
Provide the shared secret key or API secret used to sign the message.
2
Input Message or Payload
Paste the webhook payload, query string, or message text to be authenticated.
3
Select Hash Algorithm
Choose your desired cryptographic digest: SHA-256 (standard for AWS/GitHub/Stripe), SHA-512, or SHA-1.
4
Compute HMAC Signature
Click "Generate HMAC" to compute the message authentication code in Hex and Base64 formats.
Frequently Asked Questions
Common questions about using this free online hmac generator.
What is an HMAC and how is it used? ▾
A Hash-based Message Authentication Code (HMAC) verifies both data integrity and authentication. A receiver with the shared secret recalculates the HMAC: if it matches, they are certain the message was not modified in transit and originated from an authentic sender.
Why is HMAC safer than simply hashing `hash(key + message)`? ▾
Naively concatenating keys with data in standard MD5 or SHA-1/SHA-256 makes systems vulnerable to Length Extension Attacks, where an attacker can append data without knowing the secret key. HMAC uses a nested two-pass design (IPAD/OPAD) to eliminate this vulnerability.
Which algorithms are most common for webhooks? ▾
HMAC-SHA256 is the modern industry standard used by Stripe, Shopify, GitHub, and Amazon Web Services (AWS Signature Version 4).
Can this tool verify an incoming webhook signature? ▾
Yes. Enter your secret key and the raw payload body to generate the expected signature, then verify if it matches your webhook HTTP header.
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