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

​
What you’ll need

​
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.

​
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 SendGrid.

​
3. Configure SendGrid to send webhooks

SendGrid can send webhook requests to your app with information about events as it processes your email. To register for those events:
  • Sign in to the SendGrid Dashboard.
  • Click Settings and Mail Settings.
  • On Mail Settings, click Event Webhook.
  • In the Event Webhook popup, set Authorization Method to None and enter your ngrok URL in HTTP Post URL (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
  • Click Test Your Integration and confirm your localhost app receives the test.
  • Under DELIVERABILITY DATA, select Select All.
  • Under Event Webhook Status, set to ENABLED and click Save.

​
Run webhooks with SendGrid and ngrok

To trigger webhooks, send an email through SendGrid (Web API or SMTP); SendGrid notifies your app on delivery success or failure.
  • In SendGrid, go to Email API and Integration Guide.
  • Choose Web API and cURL, enter a key name (for example, myappkey), and click Create Key.
  • Run the curl command from the guide (use your sender identity and a real recipient email).
Confirm your localhost app receives notifications about the email being processed and delivered.
SendGrid sends different request body contents depending on the events you selected.
You can confirm delivery under Activity and Search in the SendGrid UI.

​
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

​
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.

​
Secure webhook requests

ngrok can verify that incoming requests are from your SendGrid 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 SendGrid Dashboard, go to Settings and Mail Settings.
  • Click Signed Event Webhook Requests.
  • In the popup, click Generate Verification Key, copy the key value, and click Close.
Ensure Signed Event Webhook Request Status is ENABLED.
  • Create a Traffic Policy file named sendgrid_policy.yml. Replace {your verification key} with the value you copied: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: sendgrid
          secret: "{your verification key}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file sendgrid_policy.yml
  • Send an email through SendGrid to trigger the webhook.
Your app should receive the request and log it in the terminal.