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This guide explains how to use ngrok to receive Square webhooks on your localhost app. By integrating ngrok with Square, you can:
  • Develop and test Square webhooks locally without deploying to a public environment or setting up HTTPS.
  • Inspect and troubleshoot requests from Square in real time via the inspection UI and API.
  • Modify and replay Square webhook requests with a single click instead of reproducing events manually in your Square account.
  • Secure your app with Square webhook validation provided by ngrok. Invalid requests are blocked by ngrok before reaching your app.

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What you’ll need

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1. Start your app

For this tutorial, you can use the sample Node.js app on GitHub. To install the sample, run the following in a terminal: 
git clone https://github.com/ngrok/ngrok-webhook-nodejs-sample.git
cd ngrok-webhook-nodejs-sample
npm install
Then start the app: 
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.

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2. Expose your app with ngrok

Once your app is running locally, you’re ready to put it online securely using ngrok.
The ngrok agent uses your authtoken to authenticate when you start a tunnel.
  • Start ngrok: 
    ngrok http 3000
  • Copy the URL ngrok displays. Your app is now exposed at that URL for use with Square.

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3. Configure Square to send webhooks

Square can send webhook requests to your app when events occur in your account. To register for those events:
  • Sign in to Square Developer.
  • Click the plus sign to add an application, enter Application name (for example, myLocalhostApp), accept the terms, and click Save.
  • On Applications, click Open for the app.
  • In the left menu under Webhooks, click Subscriptions.
  • On Webhook subscriptions, select Production and click Add subscription.
  • In the popup, enter a Webhook name (for example, Create Items Webhook), enter your ngrok URL in URL (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
  • Under Events, select catalog.version.updated and click Save.

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Run webhooks with Square and ngrok

Because you selected catalog.version.updated, creating or updating catalog items triggers webhooks:
  • In the Square Dashboard, go to Items & orders and Items (or Items under Quick access).
  • Click Create an item, fill in Name, Category, SKU, Price, and click Save.
Confirm your localhost app receives the notification and logs both headers and body in the terminal.
Square sends different request body contents depending on the event you selected.
You can also check Logs under Webhooks in the Square Developer app page to see the request Square sent.

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Inspecting requests

ngrok’s 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.
To avoid exposing secrets, accounts only collect traffic metadata by default. 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

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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.

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Secure webhook requests

ngrok can verify that incoming requests are from your Square webhook so only that traffic reaches your app.
Webhook verification is limited to 500 validations per month on free accounts. If you need more, you can upgrade to Hobbyist or Pay-as-you-go. See TPU Pricing for details.
To add verification:
  • In Square Developer, open your application.
  • Scroll to Access token, click Show, and copy the value (Sandbox Access token or Production Access token depending on your environment).
  • Create a Traffic Policy file named square_policy.yml. Replace {your access token} with the value you copied: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: square
          secret: "{your access token}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file square_policy.yml
  • Create a new item in the Square Dashboard to trigger the webhook.
Your app should receive the request and log it in the terminal.