How to Handle Zapier Webhooks Locally with Tunnelmole and Express.js

Learn how to receive and debug Zapier webhooks on your local Express.js app using Tunnelmole, the open source tunneling tool. Step-by-step guide for developers and automation pros.

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Introduction

Zapier is the go-to platform for automating workflows between thousands of apps. But when you’re building or testing a Zap that sends webhooks to your own code, you hit a common roadblock: Zapier requires a public HTTPS endpoint, but your Express.js app is running on localhost.

Tunnelmole solves this instantly by giving your local server a secure, public URL. In this guide, you’ll learn how to:

• Set up a local Express.js app to receive Zapier webhooks
• Use Tunnelmole to expose your local server to the internet
• Configure a Zapier webhook action to hit your local endpoint
• Debug and verify webhook delivery end-to-end

Whether you’re building custom integrations, testing automations, or learning about webhooks, this tutorial will get you up and running—no cloud deployment or firewall changes required.

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What are Zapier Webhooks?

Zapier webhooks let you connect any app or service to your own code. With the “Webhooks by Zapier” app, you can:

• Trigger a Zap when your server receives a webhook (Catch Hook)
• Send data from a Zap to your server (POST, GET, PUT, etc.)

This guide focuses on the “POST” action—where Zapier sends a POST request to your endpoint with data from your Zap.

Common use cases:

• Integrate SaaS tools with your custom backend
• Automate notifications, data sync, or business logic
• Prototype new APIs and integrations

When a Zap runs, Zapier sends a POST request (with JSON or form data) to your specified URL.

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Why You Need a Public URL for Zapier Webhooks

Zapier’s servers must be able to reach your webhook endpoint over the public internet. If your Express.js app is running on localhost:3000, Zapier can’t access it directly.

You need a public HTTPS URL that forwards requests to your local server.

Typical workflow:

1. Start your Express.js app on localhost:3000
2. Use Tunnelmole to get a public URL (e.g., https://abc123.tunnelmole.net)
3. Configure your Zap to send webhooks to this URL
4. Zapier sends webhooks to your Tunnelmole URL, which forwards them to your local app

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Why Use Tunnelmole for Zapier Webhooks?

Tunnelmole is a modern, open source tunneling tool that makes local webhook development fast and easy:

• 100% open source (MIT/AGPLv3)
• Free public HTTPS URLs (no login required)
• Self-hostable for privacy and custom domains
• Native Node.js app, easy one-line install
• Works on Mac, Linux, Windows

Step 1: Create a Local Express.js Webhook Receiver

If you already have an endpoint to receive Zapier webhooks, you can skip this section.

Let’s build a simple Express.js app that listens for POST requests from Zapier.

Install dependencies:

npm init -y
npm install express body-parser

Create webhook-server.js:

const express = require('express');
const bodyParser = require('body-parser');

const app = express();
const PORT = 3000;

// Parse JSON and form data
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

// Webhook endpoint (e.g., /webhook/zapier)
app.post('/webhook/zapier', (req, res) => {
  console.log('Received Zapier webhook:', req.body);
  // You can add validation or business logic here
  res.status(200).send('Webhook received');
});

app.listen(PORT, () => {
  console.log(`Express webhook server listening at http://localhost:${PORT}`);
});

Start your server:

node webhook-server.js

You should see:

Express webhook server listening at http://localhost:3000

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Step 2: Install and Run Tunnelmole

Tunnelmole gives your local server a public HTTPS URL in seconds.

Install Tunnelmole (Linux/Mac/WSL):

curl -O https://install.tunnelmole.com/xD345/install && sudo bash install

Or install with npm (requires Node.js 16.10+):

sudo npm install -g tunnelmole

Start a tunnel to your Express app:

tmole 3000

Example output:

Your Tunnelmole Public URLs are below and are accessible internet wide. Always use HTTPs for the best security

https://abc123.tunnelmole.net ⟶ http://localhost:3000
http://abc123.tunnelmole.net ⟶ http://localhost:3000

Copy the HTTPS URL (e.g., https://abc123.tunnelmole.net)—you’ll use this as your Zapier webhook endpoint.

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Step 3: Configure a Zapier Webhook Action

Now, let’s set up a Zap in Zapier to send a webhook to your local server (via Tunnelmole).

1. Create a New Zap

• Go to Zapier and log in.
• Click Create Zap.

2. Set Up a Trigger

• Choose any trigger app (e.g., “Schedule by Zapier” for testing).
• Configure the trigger as needed.

3. Add a Webhooks by Zapier Action

• Click + Add Action.
• Search for Webhooks by Zapier.
• Choose POST.

4. Configure the Webhook

• URL: Paste your Tunnelmole HTTPS URL + endpoint (e.g., https://abc123.tunnelmole.net/webhook/zapier)
• Payload Type: json (recommended)
• Data: Add key-value pairs to send (e.g., name: "Tunnelmole Test")
• Headers: (Optional) Add custom headers if needed

Example configuration:

5. Test the Action

• Click Test & Review or Test & Continue.
• Zapier will send a POST request to your Tunnelmole URL.

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Step 4: Test and Debug Zapier Webhooks Locally

Check your Express app’s terminal:

You should see the webhook payload logged:

Received Zapier webhook: { name: 'Tunnelmole Test' }

Debugging tips:

• If you don’t see the webhook, check that Tunnelmole is running and the URL matches your Express endpoint
• Check Zapier’s task history for errors
• Use console.log or a debugger to inspect the request payload

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Security: Validating Zapier Webhook Requests

Unlike Shopify, Zapier webhooks don’t include a built-in signature or secret by default. If you want to restrict access:

• Add a secret token as a header or query param in your Zapier action
• Check for this token in your Express handler

Example:

In Zapier, add a header:

In your Express handler:

app.post('/webhook/zapier', (req, res) => {
  const key = req.get('X-Webhook-Key');
  if (key !== 'my-secret-key') {
    return res.status(401).send('Unauthorized');
  }
  console.log('Received verified Zapier webhook:', req.body);
  res.status(200).send('Webhook received');
});

Note: Never expose secrets in public repos or logs.

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Troubleshooting Common Issues

1. Zapier says “We had trouble sending your request”

• Double-check your Tunnelmole URL and endpoint path
• Ensure your Express app is running and listening on the correct port
• Make sure Tunnelmole is running and hasn’t timed out

2. Webhook handler not triggered

• Confirm the Zap is actually running (check Zapier task history)
• Check for typos in the endpoint path (e.g., /webhook/zapier)
• Look at Zapier’s error details for more info

3. Security/validation fails

• Ensure your secret token matches between Zapier and your Express handler
• Check for header name typos or case sensitivity

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Summary and Next Steps

With Tunnelmole, you can develop and debug Zapier webhooks on your local machine—no cloud deployment, no firewall headaches, and no closed-source black boxes.

Next steps:

• Add more webhook endpoints for different Zaps or apps
• Integrate webhook handling into your app’s business logic
• Use Tunnelmole’s self-hosting for custom domains or privacy
• Share your public URL with collaborators for live demos

Ready to automate faster?
Get started with Tunnelmole

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FAQ: Zapier Webhooks and Tunnelmole

How do I test Zapier webhooks locally?

Use Tunnelmole to expose your local Express.js server to the internet. Register the Tunnelmole HTTPS URL as your webhook endpoint in Zapier.

Is Tunnelmole secure for handling webhooks?

Tunnelmole uses HTTPS for all public URLs. For production, always validate incoming requests (e.g., with a secret token) and consider self-hosting for maximum control.

Can I use Tunnelmole for other webhook providers?

Yes! Tunnelmole works with any service that needs to reach your local server—Stripe, GitHub, Shopify, IFTTT, and more.

What happens if I restart Tunnelmole?

You’ll get a new public URL unless you use a custom domain (paid/self-hosted). Update your Zapier webhook endpoint if the URL changes.

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References

• Zapier Webhooks Documentation
• Tunnelmole GitHub
• Tunnelmole Website
• Express.js Documentation

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Build, test, and debug Zapier webhooks locally—faster and easier with Tunnelmole.