This is the simplest option. In the admin panel, you create a unique URL that contains an access key. There are two types of webhooks: Incoming: allow an external system to call any REST API method. For example, a warehouse system can use the URL to create a new deal or update a deal with the provided ID. Outgoing (reverse): the CRM sends data when an event occurs. For example, when a lead is created, the system makes an HTTP request to a specified address and passes parameters. The advantage is simplicity.
The downside is that permissions are harder to control: the key gives access to everything defined in the webhook rules, and webhooks do not scale well for complex scenarios.
A full-featured REST API
Bitrix24 provides a broad set of methods. With the REST API, you can work with deals, contacts, leads, tasks, documents, calendar, drive, payroll, CRM forms, "smart processes," and more. To access the REST API, you register an app in the Bitrix24 developer panel. You receive a client_id and client_secret. You set up OAuth. The app redirects the user to the authorization page, receives a code, and then an access_token and refresh_token.
Send requests to https://{portal_name}.bitrix24.ru/rest/{method}?auth={access_token}, passing JSON parameters. The REST API supports batch requests and reduces the number of network calls, which matters under heavy load.
Events and WebSockets
For reactive scenarios in Bitrix24, you can subscribe to events: deal updates, contact updates, and invoice creation. Events are sent to the specified address (for example, a message broker) or through a WebSocket connection (Push & Pull). This makes it possible to react to changes immediately without polling.
Automation (robots and business processes)
This is not an API, but it is still an integration mechanism. In a CRM funnel or in Smart Processes, you can configure robots: when moving to the next stage, they call a webhook, send a request to 1C, generate a document in EDI, or send data to a chatbot.