> ## Documentation Index
> Fetch the complete documentation index at: https://ngrok.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# CircleCI Webhooks

> Develop and test CircleCI webhooks from localhost.

This guide explains how to use ngrok to receive CircleCI webhooks on your localhost app.

By integrating ngrok with CircleCI, you can:

* Develop and test CircleCI webhooks locally without deploying to a public environment or setting up HTTPS.
* Inspect and troubleshoot requests from CircleCI in real time via the inspection UI and API.
* Modify and replay CircleCI webhook requests with a single click instead of reproducing events manually in your CircleCI account.
* Secure your app with CircleCI webhook validation provided by ngrok.
  Invalid requests are blocked by ngrok before reaching your app.

## What you'll need

* An [ngrok account](https://ngrok.com/signup) and your [authtoken](https://dashboard.ngrok.com/get-started/your-authtoken).
* The [ngrok agent](https://ngrok.com/download) installed.
* [Node.js](https://nodejs.org/) installed (for the sample app, or use your own app).
* A CircleCI account.

## 1. Start your app

For this tutorial, you can use the [sample Node.js app on GitHub](https://github.com/ngrok/ngrok-webhook-nodejs-sample).

To install the sample, run the following in a terminal:

```bash theme={null}
git clone https://github.com/ngrok/ngrok-webhook-nodejs-sample.git
cd ngrok-webhook-nodejs-sample
npm install
```

Then start the app:

```bash theme={null}
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.

* Copy [your ngrok authtoken](https://dashboard.ngrok.com/get-started/your-authtoken) from the dashboard.

<Tip>
  The ngrok agent uses your authtoken to authenticate when you start a tunnel.
</Tip>

* Start ngrok:

  ```bash theme={null}
  ngrok http 3000
  ```

* Copy the URL ngrok displays.
  Your app is now exposed at that URL for use with CircleCI.

## 3. Configure CircleCI to send webhooks

CircleCI can send webhook requests to your app when events occur in your account.
To register for those events:

* Sign in to [CircleCI](https://www.circleci.com/).
* On the **All Pipelines** page, click the name of your pipeline.

<Note>
  If you don't have a pipeline, create a new one.
</Note>

* On your pipeline page, click **Project Settings** and then **Webhooks** in the left menu.
* On the **Webhooks** page, click **Add Webhook**.
* On the **Add Webhook** page, enter a name in **Webhook name**, enter your ngrok URL in **Receiver URL** (for example, `https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app`), enter a value in **Secret token** (for example, `MySecretToken`), check **Workflow Completed** and **Job Completed** under **Events**, and click **Add Webhook**.
* On the **Webhooks** page, click your webhook and then click **Test Ping Event**.

Confirm your localhost app receives the test-ping event and logs both headers and body in the terminal.

### Run webhooks with CircleCI and ngrok

CircleCI sends different request body contents depending on the event.
To trigger new calls from CircleCI to your app:

* On the **Pipeline** page, click **Rerun workflow from start** under the **Action** column for your pipeline.

<Note>
  If you're on **Project Settings**, click **\<** at the top left to return to your pipeline page.
</Note>

Confirm your localhost app receives event notifications for the workflow and logs both headers and body in the terminal.

### Inspecting requests

ngrok's [Traffic Inspector](https://dashboard.ngrok.com/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.

<Info>
  To avoid exposing secrets, accounts only collect traffic metadata by default.
  You must enable full capture in the **Traffic Inspector** section of [your account settings](https://dashboard.ngrok.com/settings) to capture complete request and response data.
</Info>

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 CircleCI webhook so only that traffic reaches your app.

<Note>
  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](/pricing-limits/traffic-policy-unit-pricing/) for details.
</Note>

To add verification:

* Create a Traffic Policy file named `circleci_policy.yml`.
  Replace `{your secret token}` with the value you entered in **Secret token** when you registered the webhook:

  ```yaml theme={null}
  on_http_request:
    - actions:
        - type: verify-webhook
          config:
            provider: circleci
            secret: "{your secret token}"
  ```

* Restart ngrok with the policy file:

  ```bash theme={null}
  ngrok http 3000 --traffic-policy-file circleci_policy.yml
  ```

* Rerun your workflow from start in CircleCI to trigger the webhook.

Your app should receive the request and log it in the terminal.