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

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3. Configure Terraform Cloud to send webhooks

Terraform Cloud can send webhook requests to your app when workspace events occur. To register for those events:
  • Sign in to Terraform Cloud and open your workspace.
  • Click Settings and Notifications in the left menu.
  • On Notifications, click Create Notification.
  • On Create a Notification, click the Webhook tile, enter a Name (for example, ngrok), and enter your ngrok URL in Webhook URL (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
  • Under Triggers, click All events.
Confirm your localhost app receives the verification request and logs both headers and body in the terminal. You can also click Send a test on the notification details page to trigger a test notification.

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Run webhooks with Terraform Cloud and ngrok

Terraform Cloud sends different request body contents depending on the event. To trigger a run:
  • At the top of the workspace, click Actions and Start new run.
  • Enter a reason (for example, My New Run), select Plan and apply for Choose run type, and click Start run.
Confirm your localhost app receives event notifications and logs both headers and body in the terminal.

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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 Terraform Cloud 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:
  • In Terraform Cloud, open your workspace, then Settings, Notifications, and the notification you created (for example, ngrok).
  • Click Edit Notification, enter a value in the Token field (for example, 12345), and click Update notification.
  • Create a Traffic Policy file named terraform_policy.yml. Replace {your webhook token} with that token value: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: terraform
          secret: "{your webhook token}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file terraform_policy.yml
  • Start a new run (e.g. Actions > Start new run with Plan and apply) to trigger the webhook.
Your app should receive the request and log it in the terminal.