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Facebook Webhooks

TL;DR

To integrate Facebook webhooks with ngrok:

  1. Launch your local webhook. npm run startFacebook
  2. Launch ngrok. ngrok http 3000 --domain myexample.ngrok.dev
  3. Configure Facebook 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 Facebook by using Webhooks. Facebook webhooks can be used to notify an external application whenever page or account events occur in your Facebook account.

By integrating ngrok with Facebook, you can:

  • Develop and test Facebook 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 Facebook in real-time via the inspection UI and API.
  • Modify and Replay Facebook Webhook requests with a single click and without spending time reproducing events manually in your Facebook account.
  • Secure your app with Facebook validation provided by ngrok. Invalid requests are blocked by ngrok before reaching your app.

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 run startFacebook

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.

Step 2: Launch ngrok​

Once your app is running successfully on localhost, let's get it on the internet securely using ngrok!

Note: This integration requires an ngrok Pro or Enterprise license because Facebook validates your ngrok domain and certificate.

  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, click Your Authtoken, and copy your Authtoken.
    Tip: The ngrok agent uses the auth token to log into your account when you start a tunnel.

  4. On the left menu, expand Cloud Edge and then click Domains. Tip: If you don't have an ngrok Pro or Enterprise license, sign up for one by clicking Update Subscription and follow the subscribe procedure.

  5. On the Domains page, click + Create Domain or + New Domain.

  6. In the Domain pane, provide a value for the Domain field (i.e. myexample.ngrok.dev), and then click Continue. ngrok New Domain Tip: Make sure your domain is available.

  7. Close the Start a Tunnel pane and then close the Domain pane.

  8. Start ngrok by running the following command in a terminal on your local desktop:

    ngrok http 3000 --domain myexample.ngrok.dev

  9. ngrok will display a URL where your localhost application is exposed to the internet (copy this URL for use with Facebook). ngrok agent running

Step 3: Integrate Facebook​

To register a webhook on your Facebook account follow the instructions below:

Requirements: You'll need a Facebook page and a Facebook app associated with your Facebook page. Create one before following the rest of these steps.

  1. Access the Meta for Developers page, and Log in using your Facebook account.

  2. On the Developers page, click My Apps and then click your app.

  3. On the app dashboard, click Add Product on the left menu, and then click Set up inside the Webhooks tile.

  4. On the Webhooks page, select Page from the combo box and then click Subscribe to this object.

  5. In the Edit User subscription popup, enter the URL provided by the ngrok agent to expose your application to the internet in the Callback URL field, with /webhooks at the end (i.e. https://myexample.ngrok.dev/webhooks). Callback URL

  6. Enter 12345 in the Verify token field, click No on the Include values slider to turn it to Yes, and then click Verify and save.

  7. After you add a webhook to Facebook, Facebook will submit a validation post request to your application through ngrok. Confirm your localhost app receives the validation get request and logs WEBHOOK_VERIFIED in the terminal.

  8. Back to the Webhooks page, click Subscribe for the feed field. Tip: You can subscribe to multiple fields within the Page object, as well as select other objects to subscribe to. For each of them, you provide the same URL.

  9. Click Test for the feed field, click Send to My Server, and confirm your localhost app receives the test post request.

  10. On the top of your app's page, make sure App Mode is Live.

Run Webhooks with Facebook and ngrok​

Depending on the object and the field you subscribe to, Facebook sends different request body contents.

Because you selected the feed action, you can test the integration by creating a post on your page or by clicking "like" on a post of your page:

  1. Access your Facebook account and then under Your Pages and profiles click your page.

  2. On the Manage Page for your page, click Create post, write something and then click Post.

Confirm your localhost app receives the feed message and logs both headers and body in the terminal.

Inspecting requests​

When you launch the ngrok agent on your local machine, you can see two links:

  • The URL to your app (it ends with ngrok-free.app for free accounts or ngrok.app for paid accounts when not using custom domains)
  • A local URL for the Web Interface (a.k.a Request Inspector).

The Request Inspector shows all the requests made through your ngrok tunnel to your localhost app. When you click on a request, you can see details of both the request and the response.

Seeing requests is an excellent way of validating the data sent to and retrieved by your app via the ngrok tunnel. That alone can save you some time dissecting and logging HTTP request and response headers, methods, bodies, and response codes within your app just to confirm you are getting what you expect.

To inspect Facebook's webhooks call, launch the ngrok web interface (i.e. http://127.0.0.1:4040) and then click one of the requests sent by Facebook.

From the results, review the response body, header, and other details:

ngrok Request Inspector

Replaying requests​

The ngrok Request Inspector provides a replay function that you can use to test your code without the need to trigger new events from Facebook. To replay a request:

  1. In the ngrok inspection interface (i.e. http://localhost:4040), select a request from Facebook.

  2. Click Replay to execute the same request to your application or select Replay with modifications to modify the content of the original request before sending the request.

  3. If you choose to Replay with modifications, you can modify any content from the original request. For example, you can modify the email field inside the body of the request.

  4. Click Replay.

Verify that your local application receives the request and logs the corresponding information to the terminal.

Secure webhook requests​

The ngrok signature webhook verification feature allows ngrok to assert that requests from your Facebook 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 Meta for Developers page, log in using your Facebook account, and then click My Apps in the top right corner.

  2. On the Developers page, expand Settings on the left menu and then click Basic.

  3. In the Basic Settings page, click Show to reveal the App secret value and copy this value.

  4. Restart your ngrok agent by running the command, replacing {your app secret} with the value you have copied before:

    ngrok http 3000 --domain myexample.ngrok.dev --verify-webhook facebook_graph_api --verify-webhook-secret {your app secret}

  5. Access the Facebook page you have assigned to your webhook and send a message to another Facebook user.

    Verify that your local application receives the request and logs information to the terminal.