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This guide shows you how to use ngrok to receive Heroku webhooks on your localhost app. By integrating ngrok with Heroku, you can:
  • Develop and test Heroku webhooks locally without deploying to a public environment or setting up HTTPS.
  • Inspect and troubleshoot requests from Heroku in real time via the inspection UI and API.
  • Modify and replay Heroku webhook requests with a single click instead of reproducing events manually in your Heroku account.
  • Secure your app with Heroku webhook validation provided by ngrok. Invalid requests are blocked by ngrok before reaching your app.

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What you’ll need

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1. Start your app

For this tutorial, you can use the sample Node.js app on GitHub. To install the sample, run the following in a terminal: 
git clone https://github.com/ngrok/ngrok-webhook-nodejs-sample.git
cd ngrok-webhook-nodejs-sample
npm install
Then start the app: 
npm start
The app runs on port 3000 by default. You can confirm it’s running by visiting http://localhost:3000. The app logs request headers and body in the terminal and shows a message in the browser.

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2. Expose your app with ngrok

Once your app is running locally, you’re ready to put it online securely using ngrok.
The ngrok agent uses your authtoken to authenticate when you start a tunnel.
  • Start ngrok: 
    ngrok http 3000
  • Copy the URL ngrok displays. Your app is now exposed at that URL for use with Heroku.

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3. Configure Heroku to send webhooks

Heroku can send webhook requests to your app when events occur in your account. To register for those events:
  • Sign in to Heroku.
  • On the Dashboard, click an app from the Personal app list.
If you don’t have an app, click New and then Create new app.
  • On the app page, click More, View Webhooks, and then Create Webhook.
  • On the New Webhook popup, enter a name in Webhook Name, enter your ngrok URL in Payload URL (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
  • Enter a value in the Secret field (for example, 12345), check api:app and api:build under Event Types, and click Add Webhook.

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Run webhooks with Heroku and ngrok

Heroku sends different request body contents depending on the event. To trigger a call from Heroku to your app:
  • On the Dashboard, click your app, open the Deploy tab, scroll to Manual deploy, select a branch, and click Deploy Branch.
  • After the deployment finishes, confirm your localhost app receives the notification and logs both headers and body in the terminal.
You can verify the webhook in Heroku: click your app, More, View Webhooks, and then click your webhook in the list.

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Inspecting requests

ngrok’s Traffic Inspector captures all requests made through your ngrok endpoint to your localhost app. Select any request to view detailed information about both the request and response.
To avoid exposing secrets, accounts only collect traffic metadata by default. You must enable full capture in the Observability section of your account settings to capture complete request and response data.
Use the traffic inspector to:
  • Validate webhook payloads and response data
  • Debug request headers, methods, and status codes
  • Troubleshoot integration issues without adding logging to your app

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Replaying requests

Test your webhook handling code without triggering new events from your service using the Traffic Inspector’s replay feature:
  1. Send a test webhook from your service to generate traffic in your Traffic Inspector.
  2. Select the request you want to replay in the traffic inspector.
  3. Choose your replay option:
    • Click Replay to send the exact same request again
    • Select Replay with modifications to edit the request before sending
  4. (Optional) Modify the request: Edit any part of the original request, such as changing field values in the request body.
  5. Send the request by clicking Replay.
Your local application will receive the replayed request and log the data to the terminal.

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Secure webhook requests

ngrok can verify that incoming requests are from your Heroku webhook so only that traffic reaches your app.
Webhook verification is limited to 500 validations per month on free accounts. If you need more, you can upgrade to Hobbyist or Pay-as-you-go. See TPU Pricing for details.
To add verification:
  • Create a Traffic Policy file named heroku_policy.yml. Replace {your webhook secret} with the value you entered in the Secret field when you registered the webhook: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: heroku
          secret: "{your webhook secret}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file heroku_policy.yml
  • Run a new build for your app in Heroku to trigger the webhook.
Your app should receive the request and log it in the terminal.