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MongoDB Webhooks

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

By integrating ngrok with MongoDB, you can:

  • Develop and test MongoDB 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 MongoDB in real-time via the inspection UI and API.
  • Modify and Replay MongoDB Webhook requests with a single click and without spending time reproducing events manually in your MongoDB account.
  • Secure your app with MongoDB 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 MongoDB). ngrok agent running

Step 3: Integrate MongoDB

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

  1. Access the MongoDB console and sign in using your MongoDB account.

  2. On your project home page, click the bell icon below your name at the top-right corner to view the project alerts. Note: If you don't have a project, create one before continuing.

  3. On the Project Alerts page, click Add New Alert and then click Webhooks.

  4. On the Create a New Alert popup, under Alert if, click User as the target, and then click User joined the project as the condition.

  5. Click Add, click Webhook, and enter the URL provided by the ngrok agent to expose your application to the internet in the Webhook URL field (i.e. Frameio URL to Publish

  6. Enter the value 12345 in the Webhook Secret field. This value is used to provide more security to your webhook call. (See Secure webhook requests).

  7. Click Save.

Run Webhooks with MongoDB and ngrok

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

  1. On your project home page, click the person icon to invite to the project.

  2. In the invite new users via email address field, enter an email to invite to your project.

  3. The new user receives an email and is required to register to MongoDB Atlas. After registration, 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 MongoDB's webhooks call, launch the ngrok web interface (i.e., and then click one of the requests sent by MongoDB.

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 MongoDB. To replay a request:

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

  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 humanReadable 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 MongoDB 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. Restart your ngrok agent by running the command, replacing {your webhook secret} with the value of the Webhook Secret field you copied during the webhook registration (See Integrate ngrok and MongoDB.):

    ngrok http 3000 --verify-webhook mongodb --verify-webhook-secret {your webhook secret}
  2. Access your project home page and invite a new person to your project.

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