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Signal Sciences Webhooks

This guide covers how to use ngrok to integrate your localhost app with Signal Sciences by using Webhooks. Signal Sciences webhooks can be used to notify an external application whenever specific events occur in your Signal Sciences account.

By integrating ngrok with Signal Sciences, you can:

  • Develop and test Signal Sciences webhooks locally, eliminating the time in deploying your development code to a public environment and setting it up in HTTPS.
  • Inspect and troubleshoot requests from Signal Sciences in real-time via the inspection UI and API.
  • Modify and Replay Signal Sciences Webhook requests with a single click and without spending time reproducing events manually in your Signal Sciences account.
  • Secure your app with Signal Sciences validation provided by ngrok. Invalid requests are blocked by ngrok before reaching your app.

Step 1: Start your app

For this tutorial, we'll use the sample NodeJS app available on GitHub.

To install this sample, run the following commands in a terminal:

git clone
cd ngrok-webhook-nodejs-sample
npm install

This will get the project installed locally.

Now you can launch the app by running the following command:

npm start

The app runs by default on port 3000.

You can validate that the app is up and running by visiting http://localhost:3000. The application logs request headers and body in the terminal and responds with a message in the browser.

Step 2: Launch ngrok

Once your app is running successfully on localhost, let's get it on the internet securely using ngrok!

  1. If you're not an ngrok user yet, just sign up for ngrok for free.

  2. Download the ngrok agent.

  3. Go to the ngrok dashboard and copy your Authtoken.
    Tip: The ngrok agent uses the auth token to log into your account when you start a tunnel.

  4. Start ngrok by running the following command:

    ngrok http 3000
  5. ngrok will display a URL where your localhost application is exposed to the internet (copy this URL for use with Signal Sciences). ngrok agent running

Step 3: Integrate Signal Sciences

To register a webhook on your Signal Sciences account follow the instructions below:

  1. Access the Signal Sciences Dashboard and sign in using your Signal Sciences account.

  2. On the Dashboard page, select your site from the Sites drop-down menu on the top of the screen, click Site Manage on the top menu, click Site Integrations, and then click Add site integration.

  3. On the Add site integration page, click Generic Webhook.

  4. On the Generic Webhook page, enter the URL provided by the ngrok agent to expose your application to the internet in the Webhook URL field (i.e. signalsciences URL to Publish

  5. Select All activity and then click Create site integration.

Run Webhooks with Signal Sciences and ngrok

Signal Sciences sends different request body contents depending on the event that is being triggered. You can trigger new calls from Signal Sciences to your application by following the instructions below.

  1. Access the Signal Sciences Dashboard, sign in, and change your site display name.

    Confirm your localhost app receives an event notification and logs both headers and body in the terminal.

Inspecting requests

When you launch the ngrok agent on your local machine, you can see two links:

  • The URL to your app (it ends with for free accounts or for paid accounts when not using custom domains)
  • A local URL for the Web Interface (a.k.a Request Inspector).

The Request Inspector shows all the requests made through your ngrok tunnel to your localhost app. When you click on a request, you can see details of both the request and the response.

Seeing requests is an excellent way of validating the data sent to and retrieved by your app via the ngrok tunnel. That alone can save you some time dissecting and logging HTTP request and response headers, methods, bodies, and response codes within your app just to confirm you are getting what you expect.

To inspect Signal Sciences' webhooks call, launch the ngrok web interface (i.e., and then click one of the requests sent by Signal Sciences.

From the results, review the response body, header, and other details:

ngrok Request Inspector

Replaying requests

The ngrok Request Inspector provides a replay function that you can use to test your code without the need to trigger new events from Signal Sciences. To replay a request:

  1. In the ngrok inspection interface (i.e. http://localhost:4040), select a request from Signal Sciences.

  2. Click Replay to execute the same request to your application or select Replay with modifications to modify the content of the original request before sending the request.

  3. If you choose to Replay with modifications, you can modify any content from the original request. For example, you can modify the id field inside the body of the request.

  4. Click Replay.

Verify that your local application receives the request and logs the corresponding information to the terminal.

Secure webhook requests

The ngrok signature webhook verification feature allows ngrok to assert that requests from your Signal Sciences webhook are the only traffic allowed to make calls to your localhost app.

Note: This ngrok feature is limited to 500 validations per month on free ngrok accounts. For unlimited, upgrade to Pro or Enterprise.

This is a quick step to add extra protection to your application.

  1. Access the Signal Sciences Dashboard, sign in, click Site Integrations in the Manage menu, and then click on your webhook.

  2. On the Webhook page, click the eye icon to reveal the secret key value and then copy this value.

  3. Restart your ngrok agent by running the command, replacing {your webhook secret} with the value you have copied before:

    ngrok http 3000 --verify-webhook signalsciences --verify-webhook-secret {your webhook secret}
  4. Access the Signal Sciences Dashboard, sign in, and change your site display name.

    Confirm your localhost app receives an event notification and logs both headers and body in the terminal.