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

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3. Configure Brex to send webhooks

Brex can send webhook requests to your app when events occur in your account. To register for those events:
  • Sign in to the Brex Dashboard.
  • In the left menu, go to Settings and click Create Token.
  • On Create an API token, enter a name in Token Name, select Write for Referrals and Users, and click Create Token.
  • On the next page, click Allow access to allow the API to access your Brex account.
  • Copy the token value shown, then click Done.
  • In a terminal, create the webhook: 
    curl -i -X POST https://platform.brexapis.com/v1/webhooks \
  -H 'Authorization: Bearer YOUR_TOKEN_HERE' \
  -H 'Content-Type: application/json' \
  -H 'Idempotency-Key: string' \
  -d '{"url": "YOUR_NGROK_URL", "event_types": ["USER_UPDATED"]}'
    Replace YOUR_TOKEN_HERE with the token you copied and YOUR_NGROK_URL with your ngrok URL (for example, https://1a2b-3c4d-5e6f-7g8h-9i0j.ngrok.app).
The Brex API responds with HTTP 200 and JSON containing "status": "ACTIVE".

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Run webhooks with Brex and ngrok

To trigger webhook calls from Brex to your app:
  • In the Brex Dashboard, go to Team, User, and click Invite user.
  • On New user, enter the requested information, set the role to employee, and click Send invite.
Confirm your localhost app receives the event and logs both headers and body in the terminal.
If Brex doesn’t send the notification, check the invitee’s email, open the Brex invitation, and click Create account to accept the invitation.

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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 Brex 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:
  • Get your webhook secret from the Brex API: 
    curl -i -X GET https://platform.brexapis.com/v1/webhooks/secrets \
  -H 'Authorization: Bearer YOUR_TOKEN_HERE'
    Replace YOUR_TOKEN_HERE with the token you copied when configuring the webhook. The response includes JSON with a "secret" value; copy it.
  • Create a Traffic Policy file named brex_policy.yml. Replace {your webhook secret} with the secret value you copied: 
    on_http_request:
  - actions:
      - type: verify-webhook
        config:
          provider: brex
          secret: "{your webhook secret}"
  • Restart ngrok with the policy file: 
    ngrok http 3000 --traffic-policy-file brex_policy.yml
  • Create a new user in the Brex Dashboard (and have the invite accepted) to trigger a webhook.
Your app should receive the request and log it in the terminal.