Test Box Webhooks Locally (Receive Box Webhooks on localhost)

You are building a Box integration and you need to watch your handler react to a real event. The problem hits immediately: Box will only POST to a public URL, and your handler is running on localhost:8080. Box has no way to reach it.

The usual workarounds are slow. Deploying to a staging environment for every code change kills your iteration speed. Copying a sample payload out of the docs into curl gives you a guess at the real request, not the exact headers and body Box actually sends. What you really want is to test Box webhooks locally — real events, hitting your local handler, on a URL that does not change every time you restart.

This guide shows how to do exactly that.

Why testing Box webhooks locally is tricky

A webhook is just an HTTP request that Box sends to a URL when something changes. Box lives on the public internet; your dev machine usually does not. It sits behind a router, a corporate firewall, or both, with no public IP and no inbound ports open.

So you need something in the middle: a public endpoint Box can hit that relays each request down to your laptop without you opening a single firewall port. That is what Webhook Relay does — and unlike a random tunnel URL, the endpoint is stable, so you configure Box once and never touch it again.

Step 1: Inspect the real payload with Webhook Bin

Before you write any handler code, find out what Box actually sends. Open the free Webhook Bin — no signup — and you get an instant public URL.

1. Copy the Webhook Bin URL.
2. In the Box Developer Console, create a Webhook (V2) on a file or folder, set the URL, choose the triggers, and copy the primary and secondary signature keys.
3. Trigger a real event and inspect the captured request.

You will see the full body and every header. The body is JSON describing the trigger and the source item. Each request carries Box-Signature-Primary, Box-Signature-Secondary and Box-Delivery-Timestamp headers.

Now you know the exact shape of the data before writing a line of code. For more on this approach, see How to test webhooks and What is a webhook.

Step 2: Forward the events to localhost with the relay agent

Once you know the payload, route those same events into your local handler. Sign up for Webhook Relay, install the relay agent (CLI or Docker), and create a bucket — say box. The bucket gives you a stable public input endpoint.

Start forwarding to your local server:

relay forward --bucket box http://localhost:8080/webhook

The agent opens an outbound connection to Webhook Relay and streams every incoming request down to http://localhost:8080/webhook. Because the connection is outbound, there are no firewall ports to open and no public IP needed — this works from your laptop, behind a corporate proxy, or inside a Kubernetes cluster. Running in Docker? The same command works in the official webhookrelay/webhookrelayd image. Full details are in the localhost forwarding docs.

Now point the Box webhook at your Webhook Relay endpoint (or create it there from the start), trigger an event, and watch it arrive on localhost.

Box-specific configuration and quirks

A few Box details worth knowing:

• Where to add it: the Box Developer Console → your app → Webhooks (V2) on a file/folder.
• Two keys: primary + secondary let you rotate without downtime — accept either.
• Timestamp: the signature covers body + Box-Delivery-Timestamp; reject stale ones.

Step 3: Verify the Box webhook signature

Box signs each request with HMAC-SHA256 (base64) over the raw body concatenated with the Box-Delivery-Timestamp, using your primary signature key, and sends it in Box-Signature-Primary (with Box-Signature-Secondary for key rotation). Validate against either key, and reject deliveries whose Box-Delivery-Timestamp is older than ~10 minutes.

To sanity-check an HMAC implementation, paste a captured body, your secret, and the received signature into the free HMAC signature verifier. For language-specific code and the common pitfalls (reading the body after a JSON parser has already consumed it, timing-safe comparison), read Verify a webhook signature.

Replay and iterate

This is where local development gets fast:

• Replay from Webhook Relay — past requests are stored on your bucket, so you can resend a captured event against your handler without touching Box at all.
• Iterate on your handler by editing code and replaying the same delivery until it behaves correctly. No commits, no pushes, no deploys just to test a single code path.
• Keep relay forward running while you work — events stream straight to localhost as you trigger them in Box.

Because the Webhook Relay endpoint is stable, you can stop and restart the agent, reboot your machine, or come back next week — the Box configuration never needs to change.

Get started

1. Inspect the real payload in the free Webhook Bin — no signup needed.
2. Create a Webhook Relay account, install the agent, and run relay forward --bucket box http://localhost:8080/webhook.
3. Point your Box webhook at the stable endpoint, trigger an event, and watch it hit localhost.

You will be testing real Box events against your local handler in a few minutes — no deploys, no open firewall ports, and a URL you configure exactly once.