> Markdown version of [Integration](https://vaadin.com/docs/next/building-apps/integration). Section index: [llms.txt](https://vaadin.com/docs/next/building-apps/llms.txt)

# Integration

A Vaadin application doesn’t need a REST API for its own user interface. Flow views call application services directly on the server, and [React views](https://vaadin.com/docs/next/building-apps/react.md) call them through browser-callable services. You need a REST API when other systems have to access the data of your application.

[REST API Alongside Vaadin](https://vaadin.com/docs/next/building-apps/integration/rest-api.md) shows how to expose REST endpoints, either from a separate artifact or from the same module as your views. It also shows how to configure security so that the endpoints and the views can coexist.

When your application calls other systems, make the calls from [application services](https://vaadin.com/docs/next/building-apps/business-logic/add-service.md). This keeps the integration out of your views, like the rest of the application layer.

## <a id="topics"></a>Topics

- [REST API](https://vaadin.com/docs/next/building-apps/integration/rest-api.md): Integration of REST API within the Vaadin application.