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api: 'Merchant API'
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# Webhooks

A `webhook` (also called a web callback) allows your system to receive an event from a different app immediately after it happens.

For example, you can subscribe to a webhook when an order changes from `pending` to `completed` status. When the payment is cleared and the order is completed, Revolut servers send a notification to the URL of your choice. This is a more efficient way to know when an order is paid as opposed to trying to get the status of the order every few seconds.

Many events that happen to a Revolut Merchant account are synchronous, which means they arrive instantly and have immediate results. For example, a successful request to create a customer immediately returns a `Customer` object. Such requests don't require webhooks.

The Revolut Merchant API supports webhooks for events including `ORDER_COMPLETED` and `ORDER_AUTHORISED`.

:::note
Because we cannot guarantee the delivery order of the status (`events`), you might receive the status not in the expected order. Make sure that your implementation does not rely on the order that the events are being received in.
:::

For example, for a completed order, you should receive the `ORDER_AUTHORISED` status first and then `ORDER_COMPLETED`. However, if the `ORDER_AUTHORISED` status isn't sent successfully at first, it's moved to the queue to be resent in the next few minutes. Before then, if the `ORDER_COMPLETED` status is sent successfully, you get `ORDER_COMPLETED` first and then `ORDER_AUTHORISED`.

Check out our tutorial for [Using webhooks to keep track of the payment lifecycle](/docs/guides/merchant/monitor-and-observe/webhooks/using-webhooks).

:::info
For more information about the order and payment lifecycle, see: [Order and payment lifecycle](/docs/guides/merchant/reference/order-lifecycle).
:::