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ngrok includes a built-in Traffic Inspector that lets you see every HTTP request and response flowing through your tunnel in real time, and replay any captured HTTP request with a single click. This is useful for debugging webhooks, API integrations, and frontend-backend communication. You can enable Traffic Inspector for your endpoints in the ngrok dashboard.

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Inspecting request bodies

The Traffic Inspector automatically formats and syntax-highlights common content types including JSON, XML, HTML, and form data. This makes it easy to verify that webhook payloads, API requests, and form submissions contain the expected data.

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Filtering traffic

Use the search bar in the Traffic Inspector to filter requests by path, method, status code, or any other attribute. This helps you focus on the specific requests you’re debugging.

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Traffic inspection via the API

You can also access captured traffic programmatically through the Agent API. This is useful for building automated tests or integrating traffic inspection into your development workflow.

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How replays work

  1. Start your tunnel with ngrok http <port>
  2. Open Traffic Inspector in ngrok dashboard
  3. Trigger a request (or wait for a webhook delivery)
  4. Click on the request in Traffic Inspector
  5. Click Replay on any captured request to resend it to your local server
The replayed request is sent with the same method, headers, and body as the original, giving you a consistent way to test your handler without external dependencies.

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Use cases for request replays

  • Webhook development: Replay webhook deliveries instead of waiting for the provider to retry.
  • Bug reproduction: Capture a request that triggers a bug, fix your code, and replay to verify the fix.
  • Load testing: Replay requests multiple times to observe how your application handles repeated traffic.

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Modifying replayed requests

You can edit a request before replaying it. Change headers, query parameters, or the request body to test different scenarios without needing external tools like cURL or Postman.

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Next steps

  • Webhooks: use inspection to debug webhook integrations
  • Agent API: access traffic data programmatically