Invalid HMAC signature fix for webhooks
Invalid HMAC almost always means the message bytes you hash differ from what the provider signed—often raw body vs parsed JSON, wrong secret, or wrong encoding. Fix the message and secret first; only then tune timing headers.
Common causes
- Secret from wrong environment or rotated.
- Middleware mutates body before verify.
- Hex vs base64 signature encoding mismatch.
How to fix
- Verify against raw bytes with HMAC Checker.
- Compare with Signature Validator using sample payloads.
- Confirm provider algorithm (SHA-256) and prefix rules.
Use our tool
Open HMAC CheckerRelated