Problem Introduction
Webhook requests arrive but are rejected as invalid signatures.
Why It Happens
- •Raw body was mutated by middleware
- •Wrong signing secret
- •Incorrect signature header extraction
- •Unsafe string compare
Step-by-Step Fix
- 1Capture raw body before JSON parsing.
- 2Read exact Clerk signature header.
- 3Verify secret source and environment.
- 4Use timing-safe compare.
- 5Retest with a known-good event.
Common Mistakes
- •Comparing signatures as plain strings
- •Re-serializing parsed JSON
- •Mixing staging and production secrets
Debugging Workflow
Header capture -> raw payload hash -> expected vs received comparison -> replay test.
Preventive Best Practices
- •Centralize provider-specific signature modules
- •Log mismatch reason categories
- •Alert on mismatch spikes
Works with webhooks and other async event systems (including AI callbacks).
Instead of guessing, inspecting the exact payload and headers can help debug faster. Tools like Hookmetry support this workflow.
Try the free webhook testerRelated Documentation