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Mailchimp Webhooks

TL;DR

To integrate Mailchimp webhooks with ngrok:

  1. Launch your local webhook. npm start
  2. Launch ngrok. ngrok http 3000
  3. Configure Mailchimp webhooks with your ngrok URL.

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

By integrating ngrok with Mailchimp, you can:

  • Develop and test Mailchimp 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 Mailchimp in real-time via the inspection UI and API.
  • Modify and Replay Mailchimp Webhook requests with a single click and without spending time reproducing events manually in your Mailchimp account.

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:

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This will get the project installed locally.

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

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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:

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

Step 3: Integrate Mailchimp​

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

  1. Access Mailchimp and sign in using your Mailchimp account.

  2. On the Mailchimp Home page, click Audience on the left menu and then click Audience dashboard.

  3. On the Audience page, click Manage Audience and then click Settings.

  4. On the Settings page, click Webhooks and then click Create New Webhook.

  5. On the Create new webhook page, enter the URL provided by the ngrok agent to expose your application to the internet in the Callback URL field (i.e. https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app) and then click Save. URL to Publish

    Confirm your localhost app receives a GET request and logs both headers and body in the terminal.

Run Webhooks with Mailchimp and ngrok​

Mailchimp sends different request body contents depending on the audience you register your webhook, as well as depending on the event taking place. You can trigger new calls from Mailchimp to your application by following the instructions below.

  1. On the Mailchimp Home page, click Audience on the left menu and then click All Contacts.

  2. On the Audience page, click Add contacts and then click Add a subscriber.

  3. On the Add subscriber page, enter a valid email address in the Email Address field, click the This person gave me permission to email them checkbox, and then click Subscribe. Note: If you don't have the email address on your contact list, you need to import this contact.

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

Inspecting requests​

ngrok's Traffic Inspector captures all requests made through your ngrok endpoint to your localhost app. Click on any request to view detailed information about both the request and response.

info

By default, accounts only collect traffic metadata to avoid exposing secrets. 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

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. Modify the request (optional): 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.