HMAC Generator Online

What Is an HMAC Generator?

An HMAC generator creates keyed signatures by combining a message with a secret key and a hash algorithm. Unlike plain hash values, HMAC signatures prove both data integrity and shared-secret ownership, which is why they are common in payment APIs, webhooks, and signed URLs.

Common Use Cases

• Sign API requests with canonical strings and timestamps.
• Verify webhook payload signatures from third-party services.
• Debug signature mismatch between frontend and backend implementations.
• Test secret rotation behavior in staging environments.

HMAC Reference

Common Mistakes

• Using different message canonicalization between signer and verifier.
• Encoding mismatch (UTF-8 vs other charsets) when building signed payload.
• Comparing Base64 signature with Hex output without conversion.
• Including extra newline or whitespace in the signed message.

Recommended Debug Flow

1. Paste exact message bytes and secret used by backend.
2. Select the same HMAC algorithm as production service.
3. Switch output format (Hex/Base64) to match API docs.
4. If message is JSON, normalize with JSON Formatter.
5. If signature payload is encoded, inspect with Base64 Encode Decode.

Related Tools

• Hash Generator
• Base64 Encode Decode
• JSON Formatter
• JWT Decoder
• URL Encode Decode