# Webhooks overview

Webhooks allow your apps to receive information when events matching your Trigger conditions occur, and respond however you define.

Webhooks deliver data to your apps as they happen; you get the data you want immediately instead of having to poll (look) for changes to data. For example, we can send your app a notification when the balance of any of the wallets you're watching changes.

We don't currently support webhook request authentication via headers, but it's on our roadmap. 

You should **always verify** that webhook requests originate from the `api.dispatch.esprezzo.io` domain; any other origin is not a legitimate Dispatch webhook request.

{% hint style="danger" %}
**Important**

You should always verify that webhook requests originate from the <mark style="color:purple;">`api.dispatch.esprezzo`</mark> domain.

Any other origin is **not** a legitimate Dispatch webhook request and could pose a security risk.
{% endhint %}

### Event types

Webhooks can be triggered by several types of events (Triggers) in Dispatch:

* **Address activity**: wallet balance of a specific token changed, or went above or below a threshold
* **Smart contract activity**: anytime selected events are emitted by, or functions are called in smart contracts
  * Lots of possibilities:&#x20;
    * Alerts for unexpected AdminChange, Pause, Unpause events that could indicate security vulnerabilities
    * Mint, transfer, upgrade & gameplay events on ERC721, ERC1155, ERC1967, ERC-4337
    * Swap, trade & new pair/pool events on DEX contracts
    * Any verified contract on Ethereum, Polygon, Base & Avalanche, with more networks coming soon

### Webhook format

Every Dispatch webhook uses the same format, regardless of event type. The webhook request is a standard HTTP POST, and the request body will contain a JSON payload with the following top-level keys:

* <mark style="color:purple;">`patch`</mark>: information about the associated Patch (e.g. <mark style="color:purple;">`patch.id`</mark>, <mark style="color:purple;">`patch.name`</mark>, etc). This object also contains information about the Trigger as well (e.g. <mark style="color:purple;">`trigger.template_id`</mark>, <mark style="color:purple;">`trigger.settings`</mark>, etc).
* <mark style="color:purple;">`details`</mark>: information about the actual event that has occurred (e.g. <mark style="color:purple;">`details.token_symbol`</mark>, <mark style="color:purple;">`details.new_balance`</mark>, etc for "address balance change" Triggers).

The <mark style="color:purple;">`details`</mark> object will contain different data based on the Trigger type. See the [Webhook Reference](https://docs.esprezzo.io/webhooks/webhook-reference) for more details.

### What you'll need

1. **Dispatch account** ([log in](https://dispatch.esprezzo.io/login) or [sign up](https://dispatch.esprezzo.io/signup))
2. **A webhook URL**: an endpoint on your server that receives requests from Dispatch alerting you about events that happen

{% hint style="warning" %}
**Important:** Make sure your endpoint is publicly accessible so we can send unauthenticated POST requests.
{% endhint %}

### Example: Sending smart contract or wallet activity to Google Sheets&#x20;

With webhooks, you can use Dispatch with Zapier to send on-chain data to apps in the Zapier ecosystem, or use on-chain activity to automate tasks in apps you and your team already use.

Check out this guide to see an example: [Automatically log on-chain activity to Google Sheets without code](https://blog.esprezzo.io/automatically-log-on-chain-activity-to-google-sheets-without-any-code)