What is SharePoint webhooks?

 Ans:-

SharePoint webhooks enable developers to build applications that subscribe to receive notifications on specific events that occur in SharePoint. When an event is triggered, SharePoint sends an HTTP POST payload to the subscriber. Webhooks are easier to develop and consume than Windows Communication Foundation (WCF) services used by SharePoint Add-in remote event receivers because webhooks are regular HTTP services (web API).

Currently webhooks are only enabled for SharePoint list items. SharePoint list item webhooks cover the events corresponding to list item changes for a given SharePoint list or a document library. SharePoint webhooks provide a simple notification pipeline so that your application can be aware of changes to a SharePoint list without polling the service. 

The following information is required for creating a new subscription:

• Resource. The resource endpoint URL you are creating the subscription for. For example, a SharePoint List API URL.
• Server notification URL. Your service endpoint URL. SharePoint sends an HTTP POST to this endpoint when events occur in the specified resource.
• Expiration date. The expiration date for your subscription. The expiration date should not be more than 180 days. By default, subscriptions are set to expire 180 days from when they are created.

You can also include the following information if needed:

• Client State. An opaque string passed back to the client on all notifications. You can use this for validating notifications, tagging different subscriptions, or other reasons.