> ## Documentation Index
> Fetch the complete documentation index at: https://ngrok.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Mailchimp Webhooks

> Develop and test Mailchimp webhooks from localhost.

This guide shows you how to use ngrok to receive Mailchimp webhooks on your localhost app.

By integrating ngrok with Mailchimp, you can:

* Develop and test Mailchimp webhooks locally without deploying to a public environment or setting up 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 instead of reproducing events manually in your Mailchimp account.
* Secure your app with Mailchimp webhook validation provided by ngrok.
  Invalid requests are blocked by ngrok before reaching your app.

## What you'll need

* An [ngrok account](https://ngrok.com/signup) and your [authtoken](https://dashboard.ngrok.com/get-started/your-authtoken).
* The [ngrok agent](https://ngrok.com/download) installed.
* [Node.js](https://nodejs.org/) installed (for the sample app, or use your own app).
* A Mailchimp account.

## 1. Start your app

For this tutorial, you can use the [sample Node.js app on GitHub](https://github.com/ngrok/ngrok-webhook-nodejs-sample).

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

```bash theme={null}
git clone https://github.com/ngrok/ngrok-webhook-nodejs-sample.git
cd ngrok-webhook-nodejs-sample
npm install
```

Then start the app:

```bash theme={null}
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.

## 2. Expose your app with ngrok

Once your app is running locally, you're ready to put it online securely using ngrok.

* Copy [your ngrok authtoken](https://dashboard.ngrok.com/get-started/your-authtoken) from the dashboard.

<Tip>
  The ngrok agent uses your authtoken to authenticate when you start a tunnel.
</Tip>

* Start ngrok:

  ```bash theme={null}
  ngrok http 3000
  ```

* Copy the URL ngrok displays.
  Your app is now exposed at that URL for use with Mailchimp.

## 3. Configure Mailchimp to send webhooks

Mailchimp can send webhook requests to your app when events occur in your audience.
To register for those events:

* Sign in to [Mailchimp](https://mailchimp.com/).
* Click **Audience** and then **Audience dashboard**.
* Click **Manage Audience** and **Settings**.
* On the **Settings** page, click **Webhooks** and then **Create New Webhook**.
* On **Create new webhook**, enter your ngrok URL in **Callback URL** (for example, `https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app`) and click **Save**.

Confirm your localhost app receives the 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 and event.
To trigger new calls from Mailchimp to your app:

* Click **Audience** and **All Contacts**.
* Click **Add contacts** and **Add a subscriber**.
* On **Add subscriber**, enter a valid email in **Email Address**, check **This person gave me permission to email them**, and click **Subscribe**.

<Note>
  If the email is not on your contact list, you may need to import the contact first.
</Note>

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

### Inspecting requests

ngrok's [Traffic Inspector](https://dashboard.ngrok.com/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.

<Info>
  To avoid exposing secrets, accounts only collect traffic metadata by default.
  You must enable full capture in the **Traffic Inspector** section of [your account settings](https://dashboard.ngrok.com/settings) to capture complete request and response data.
</Info>

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. (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.