TL;DRTo integrate Alchemy webhooks with ngrok:
  1. Launch your local webhook. npm start
  2. Launch ngrok. ngrok http 3000
  3. Configure Alchemy webhooks with your ngrok URL.
  4. Secure your webhook requests with verification.
This guide covers how to use ngrok to integrate your localhost app with Alchemy by using Webhooks. Alchemy webhooks can be used to notify an external application whenever specific events occur in your Alchemy account. By integrating ngrok with Alchemy, you can:
  • Develop and test Alchemy webhooks locally, eliminating the time in deploying your development code to a public environment and setting it up in HTTPS.
  • Inspect and troubleshoot requests from Alchemy in real time via the inspection UI and API.
  • Modify and Replay Alchemy Webhook requests with a single click and without spending time reproducing events manually in your Alchemy account.
  • Secure your app with Alchemy validation provided by ngrok. Invalid requests are blocked by ngrok before reaching your app.

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Step 1: Start your app

For this tutorial, we’ll use the sample NodeJS app available on GitHub. To install this sample, run the following commands in a terminal: 
git clone https://github.com/ngrok/ngrok-webhook-nodejs-sample.git
cd ngrok-webhook-nodejs-sample
npm install
This will get the project installed locally. Now you can launch the app by running the following command: 
npm start
The app runs by default on port 3000. You can validate that the app is up and running by visiting http://localhost:3000. The application logs request headers and body in the terminal and responds with a message in the browser.

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Step 2: Launch ngrok

Once your app is running successfully on localhost, let’s get it on the internet securely using ngrok!
  1. If you’re not an ngrok user yet, just sign up for ngrok for free.
  2. Download the ngrok agent.
  3. Go to the ngrok dashboard and copy your Authtoken.
    Tip: The ngrok agent uses the auth token to log into your account when you start a tunnel.
  4. Start ngrok by running the following command: 
    ngrok http 3000
  5. ngrok will display a URL where your localhost application is exposed to the internet (copy this URL for use with Alchemy). ngrok agent running

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Step 3: Integrate Alchemy

To register a webhook on your Alchemy account follow the instructions below:
  1. Access the Alchemy dashboard and sign in using your Alchemy account.
  2. On the left menu, click the Data icon and then click Webhooks.
  3. On the Webhooks page, click Create Webhook for one of the types presented on the screen. In this tutorial, click Create Webhook for the Address Activity type.
  4. Select the Chain and the Network you want to monitor activities and then enter the URL provided by the ngrok agent to expose your application to the internet in the WEBHOOK URL field (i.e. https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app). Alchemy ENDPOINT URL
  5. Click Test Webhook and verify your localhost application receives a notification event.
  6. Enter your wallet address in the Ethereum Address field and then click Create Webhook.

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Run Webhooks with Alchemy and ngrok

Alchemy sends different request body contents depending on the type of webhook. In this example, because you chose the Address Activity webhook, you need to receive or send tokens to your address. To test your webhook, follow the steps below:
  1. Access the Alchemy dashboard and sign in using your Alchemy account.
  2. On the left menu, click the Data icon and then click Webhooks.
  3. On the Webhooks page, scroll down to the Address Activity section, click the 3 dots for the webhook you registered, and then click Send Test Notification. Confirm your localhost app receives the test event notification and logs both headers and body in the terminal.

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Inspecting requests

ngrok’s Traffic Inspector captures all requests made through your ngrok endpoint to your localhost app. Click on any request to view detailed information about both the request and response.
By default, accounts only collect traffic metadata to avoid exposing secrets. 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. Modify the request (optional): 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

The ngrok signature webhook verification feature allows ngrok to assert that requests from your Alchemy webhook are the only traffic allowed to make calls to your localhost app. Note: This ngrok feature is limited to 500 validations per month on free ngrok accounts. For unlimited, upgrade to Pro or Enterprise. This is a quick step to add extra protection to your application.
  1. Access the Alchemy dashboard and sign in using your Alchemy account.
  2. On the left menu, click the Data icon and then click Webhooks.
  3. On the Webhooks page, scroll down to the Address Activity section, click the 3 dots for the webhook you registered, and then click Signing Key.
  4. On the pop-up, copy the value of the Signing key field and click Close.
  5. Create a traffic policy file named alchemy_policy.yml, replacing {your signing key} with the value you have copied before: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: alchemy
          secret: "{your signing key}"
  6. Restart your ngrok agent by running the command: 
    ngrok http 3000 --traffic-policy-file alchemy_policy.yml
Note: After restarting the ngrok agent, the address of the agent will be modified. Because Alchemy doesn’t allow you to edit your webhook registration, it’s recommended that you create a domain on your ngrok account, and run the agent using the following parameter --url https://myexample.ngrok.app
  1. Access the Alchemy dashboard and test the webhook endpoint or create an event by using the Alchemy SDK.
Verify that your local application receives the request and logs information to the terminal.