Webhook Failure Diagnostic Checklist for n8n and AI Automation
Webhook failures can come from DNS, SSL, reverse proxy, wrong URL, method mismatch, missing token, payload validation, firewall rules, n8n workflow errors or upstream API failures. This checklist helps you isolate the failing point.
Core principle
A webhook has two sides: the sender and the receiver. Debug both. The sender may fail to deliver, or the receiver may reject, timeout or process the request incorrectly.
Checklist
- Confirm the webhook URL is correct.
- Confirm HTTPS works.
- Check whether the sender receives 200, 400, 401, 403, 404 or 500.
- Check Nginx access log for the incoming request.
- Check Nginx error log for proxy issues.
- Check n8n or app logs.
- Verify HTTP method and payload format.
- Verify token or secret validation.
- Test with curl or a webhook testing tool.
- Check downstream API errors inside the workflow.
Reusable lesson
Webhook debugging is request lifecycle debugging. You need to prove whether the request reached the server, reached the app and completed the workflow.
When to Use This Checklist
Use this checklist when webhooks fail in n8n, AI agents, API workers or automation workflows.
Required Tools
Webhook URL, sender logs, Nginx logs, n8n logs, Docker logs, curl, API credentials
Before You Start
Collect the failing webhook URL, expected method, expected payload and sender error response before changing the workflow.
Structured Checklist Steps
- Confirm webhook URL.
- Check HTTPS.
- Check sender status code.
- Read Nginx access log.
- Read Nginx error log.
- Read app or n8n logs.
- Verify method.
- Verify payload.
- Verify token.
- Check downstream API errors.
Verification Steps
- Webhook request reaches the server.
- Request reaches the app.
- Authentication passes.
- Payload is accepted.
- Workflow completes or fails with a known reason.
Rollback Plan
If a workflow change breaks the webhook, restore the previous workflow version or disable the latest node and retest with a controlled payload.
Common Mistakes
- Debugging workflow logic before checking access logs.
- Using the test URL in production.
- Missing HTTPS.
- Ignoring sender status code.
- Not checking downstream API failure.
Related Commands
curl -I https://automation.example.com/webhook/test
curl -X POST https://automation.example.com/webhook/test -H "Content-Type: application/json" -d '{}'
sudo tail -n 100 /var/log/nginx/access.log
sudo tail -n 100 /var/log/nginx/error.log
docker logs n8n --tail 100