What is a webhook?

A webhook is an automatic notification from one app to another. When a particular event happens, such as a payment going through or a form being submitted, the first app sends a short message containing the details to a specific web address, called the webhook URL, that the second app is listening on. The second app can then act on that information straight away.

For example, an online store can be set up to send a webhook to an automation tool whenever an order is placed. The message includes the order number, the customer's details, and what they bought. The automation then adds a row to a fulfillment spreadsheet and notifies the warehouse team, without anyone checking the store dashboard for new orders.

Webhooks are often described as the opposite of polling. With polling, one app keeps asking another whether anything new has happened. With a webhook, the app that has the news sends it once, as soon as it happens. That makes webhooks faster and less wasteful, which is why many instant triggers in automation tools rely on them behind the scenes.

A webhook URL should be kept private, because anyone who has it may be able to send it fake data. Webhooks can also fail quietly if the receiving side is down or the message format changes, so it helps to confirm that a webhook-based automation is still receiving events, especially after either app is updated.

An example

A payment app sends a webhook each time a payment succeeds, and an automation marks the matching invoice as paid.