# Virtualization

The DropDownList supports UI virtualization which provides options for significantly improving the performance when working with large datasets.

Regardless of the dataset size, the virtualization technique uses a fixed amount of DOM elements in the popup list of the component. When the list is scrolled, the component displays the relevant data by reusing the existing elements instead of creating new ones.

> Setting the `width` property of the [`popupSettings`](https://www.telerik.com/kendo-angular-ui-develop/components/dropdowns/api/dropdownlistcomponent#popupsettings) to `auto` is not supported when virtual scrolling is enabled.

## Enabling Virtualization

To enable the virtual scrolling, pass a [`VirtualizationSettings`](https://www.telerik.com/kendo-angular-ui-develop/components/dropdowns/api/virtualizationsettings) object to the [`virtual`](https://www.telerik.com/kendo-angular-ui-develop/components/dropdowns/api/dropdownlistcomponent#virtual) input property and specify the desired [`itemHeight`](https://www.telerik.com/kendo-angular-ui-develop/components/dropdowns/api/virtualizationsettings#itemheight).

Although rarely needed, you can control the number of DOM elements that the list will render through the [`pageSize`](https://www.telerik.com/kendo-angular-ui-develop/components/dropdowns/api/virtualizationsettings#pagesize) property.

[Demo Source](https://demos.telerik.com/kendo-angular-ui/demos/dropdowns/dropdownlist/virtualization/source.txt)

## Using with Grouping and Filtering

The following example demonstrates how to use the virtualization functionality of the DropDownList with grouping and filtering.

> The popup list always begins with a grouping `ul` element to ensure accessibility compatibility.

[Demo Source](https://demos.telerik.com/kendo-angular-ui/demos/dropdowns/dropdownlist/virtualization/grouping_and_filtering/source.txt)

## Suggested Links

* [API Reference of the AutoComplete](https://www.telerik.com/kendo-angular-ui-develop/components/dropdowns/api/autocompletecomponent)
* [API Reference of the Data Query](https://www.telerik.com/kendo-angular-ui-develop/components/data-query/api)