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

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3. Configure Plivo to send webhooks

Plivo can send webhook requests to your app when SMS and MMS messages are sent to your Plivo numbers. To register for those events:
  • Sign in to the Plivo Console.
  • Click Messaging and PHLO under Applications.
  • On Your PHLOs, click Create New PHLO and Build My Own.
  • On the PHLO page, click the pencil next to the title, name it (for example, Webhook PHLO), and click Save.
  • Drag HTTP Request from the left panel to the center and click it.
  • In the right panel, set HTTP Method to POST and enter your ngrok URL in the URL field (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
  • Click FETCH RESPONSE, confirm the response in Response, and click VALIDATE.
  • Drag a line from Incoming Message on Start to the HTTP Request component and click Save.
  • Click Phone Numbers and select a number (or Buy Number if needed).
  • On the phone number page, set Application Type to PHLO, PHLO Name to your PHLO, and click Update Number.

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Run webhooks with Plivo and ngrok

Plivo sends different request body contents depending on the event. To trigger a call: send an SMS to your Plivo phone number. Confirm your localhost app receives the notification and logs both headers and body in the terminal. You can verify in Plivo: Messaging, SMS/MMS under Logs, then open a log and check Status Callbacks.

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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 Plivo 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 the Plivo Console, click the eye icon next to Auth Token and copy the value.
  • Create a Traffic Policy file named plivo_policy.yml. Replace {your auth token} with the value you copied: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: plivo
          secret: "{your auth token}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file plivo_policy.yml
  • Send an SMS to your Plivo number to trigger the webhook.
Your app should receive the request and log it in the terminal.