Test GitHub webhooks locally

GitHub webhooks are easiest to debug when you can see the JSON payload and delivery headers outside the repository settings page. Use Mercur’s online tester first, then forward to localhost when your app is ready.

1. Get a public HTTPS URL

Open the webhook tester

Copy the temporary endpoint. Guest mode needs no account and expires after idle TTL.

2. Add a repository webhook

In your GitHub repo: Settings → Webhooks → Add webhook.

Payload URL — paste your Mercur URL
Content type — application/json (recommended)
Secret — optional for first inspection; required later for signature checks in your app
Events — start with Just the push event, or choose Send me everything while debugging

Click Add webhook. GitHub sends a ping event immediately.

3. Compare deliveries

Open Recent Deliveries in GitHub and the request history in Mercur side by side:

Confirm the X-GitHub-Event header (ping, push, …)
Inspect the JSON body GitHub posted
Note X-Hub-Signature-256 when a secret is configured

If GitHub shows a failed delivery but Mercur has no log entry, the request never reached the endpoint (URL typo, DNS, or blocked outbound). If Mercur has the entry, the provider side succeeded and you can focus on your handler.

4. Trigger a real event

Push a commit, open a pull request, or redeliver from Recent Deliveries. Each attempt appears in Mercur with the same headers GitHub sent.

5. Forward to localhost

When you need your local server to respond:

Register for a free Mercur account
Start a Local Tunnel to your local port
Update the GitHub Payload URL to the tunnel endpoint
Use Record Session in the console to capture live tunnel traffic

Keep the webhook secret in your app’s environment for X-Hub-Signature-256 verification.

Inspect a GitHub delivery now