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

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3. Configure Buildkite to send webhooks

Buildkite can send webhook requests to your app when events occur in your account. To register for those events:
  • Sign in to Buildkite.
  • On the welcome page, click Settings in the top menu and Notification Services in the left menu.
  • On Notification Services, click Add for the Webhook row.
  • On Add Webhook Notification, enter a description in Description (for example, My LocalHost App) and paste the ngrok URL in Webhook URL (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
  • In Events, select all events.
  • In Pipelines, select All Pipelines and click Add Webhook Notification.

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Run webhooks with Buildkite and ngrok

Buildkite sends different request body contents depending on the event. To trigger new calls from Buildkite to your app:
  • Click Pipelines in the top menu and open one of your pipelines.
If you don’t have a pipeline, click Create your first pipeline and follow the instructions.
  • On the pipeline page, click New Build, enter a message in Message, and click Create Build.
Confirm your localhost app receives the event and logs both headers and body in the terminal. You can also check the webhook request in Buildkite: go to Settings, Notification Services, open your webhook, and look at the Request Log section.

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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 Buildkite 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 Buildkite, go to Settings and Notification Services.
  • On Notification Services, click your webhook tile, copy the value of Token, select Send an HMAC signature, and click Save Webhook Settings.
  • Create a Traffic Policy file named buildkite_policy.yml. Replace {your token} with the value you copied: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: buildkite
          secret: "{your token}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file buildkite_policy.yml
  • Create a new build on one of your pipelines to trigger the webhook.
Your app should receive the request and log it in the terminal.