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

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3. Configure Dropbox to send webhooks

Dropbox can send webhook requests to your app when events occur in your account. To register for those events:
  • Sign in to the Dropbox site and open the Dropbox developer site.
  • On the My apps page, click Create app.
  • On the Create a new app page, click Scoped access, click App folder under Choose the type of access you need, enter a name in App name, check the terms and conditions, and click Create app.
  • On your app page, enter your ngrok URL in the Webhook URIs field (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app) and click Add in the Webhooks section.
  • Confirm your localhost app receives a one-time call from Dropbox and logs the challenge parameter in the terminal.
  • Confirm your webhook appears in the Webhooks section with Enabled status.

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Run webhooks with Dropbox and ngrok

With App folder access, Dropbox creates a folder with your app’s name under Apps. To trigger new calls from Dropbox to your app:
  • In Dropbox, go to Apps under All files in the left menu.
  • Click your app’s folder and upload a file by dragging it from your desktop into the folder.
Dropbox sends a POST request to your app when the upload completes.
The payload does not include file or folder changes; it only indicates which users have changes. Your app must call the Dropbox API to get the latest changes for each user.
You can create an app with Scoped access and Full Dropbox to receive notifications for any folder.

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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 Dropbox 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:
  • On the Dropbox developer site, click your app, open the Settings tab, click Show for App secret, and copy the value.
  • Create a Traffic Policy file named dropbox_policy.yml. Replace {your app secret} with the value you copied: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: dropbox
          secret: "{your app secret}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file dropbox_policy.yml
  • Upload a new file to your app folder in Dropbox to trigger the webhook.
Your app should receive the request and log it in the terminal.