Virtuoso

Virtuoso

Virtuoso<ItemData, Context>(props): ReactElement

A virtualized list component for efficiently rendering large datasets. Automatically measures and handles variable-sized items without configuration.

Type Parameters

Type Parameter	Default type	Description
ItemData	any	The type of data items in the list
Context	any	The type of additional context passed to callbacks

Parameters

Parameter	Type	Description
props	VirtuosoProps<ItemData, Context> & object	VirtuosoProps

Returns

ReactElement

Example

tsx

See

• VirtuosoProps for available props
• VirtuosoHandle for imperative methods

---

VirtuosoProps

The props for the Virtuoso component.

See

• Virtuoso for the component
• VirtuosoHandle for imperative methods

Extends

• ListRootProps

Type Parameters

Type Parameter	Description
Data	The type of data items in the list
Context	The type of additional context passed to callbacks

Properties

alignToBottom?: boolean

Setting alignToBottom to true aligns the items to the bottom of the list if the list is shorter than the viewport. Use followOutput property to keep the list aligned when new items are appended.

---

atBottomStateChange()?

optional atBottomStateChange: (atBottom) => void

Called with true / false when the list has reached the bottom / gets scrolled up. Can be used to load newer items, like tail -f.

Parameters

Parameter	Type
atBottom	boolean

Returns

void

---

atBottomThreshold?: number

The property accepts pixel values.

By default 4. Redefine to change how much away from the bottom the scroller can be before the list is not considered not at bottom.

---

atTopStateChange()?

optional atTopStateChange: (atTop) => void

Called with true / false when the list has reached the top / gets scrolled down.

Parameters

Parameter	Type
atTop	boolean

Returns

void

---

atTopThreshold?: number

The property accepts pixel values.

By default 0. Redefine to change how much away from the top the scroller can be before the list is not considered not at top.

---

components?: Components<Data, Context>

Use the components property for advanced customization of the elements rendered by the list.

---

computeItemKey?: ComputeItemKey<Data, Context>

If specified, the component will use the function to generate the key property for each list item.

---

context?: Context

Additional context available in the custom components and content callbacks

---

customScrollParent?: HTMLElement

Pass a reference to a scrollable parent element, so that the list won’t wrap in its own.

---

data?: readonly Data[]

The data items to be rendered. If data is set, the total count will be inferred from the length of the array.

---

defaultItemHeight?: number

By default, the component assumes the default item height from the first rendered item (rendering it as a “probe”).

If the first item turns out to be an outlier (very short or tall), the rest of the rendering will be slower, as multiple passes of rendering should happen for the list to fill the viewport.

Setting defaultItemHeight causes the component to skip the “probe” rendering and use the property value as default height instead.

---

endReached()?

optional endReached: (index) => void

Gets called when the user scrolls to the end of the list. Receives the last item index as an argument. Can be used to implement endless scrolling.

Parameters

Parameter	Type
index	number

Returns

void

---

firstItemIndex?: number

Use when implementing inverse infinite scrolling - decrease the value this property in combination with data or totalCount to prepend items to the top of the list.

Warning: the firstItemIndex should be a positive number, based on the total amount of items to be displayed.

---

fixedGroupHeight?: number

Can be used to improve performance if the rendered group header items are of known size. Setting it causes the component to skip measuring group headers. The value is in pixels. This value has no effect if fixedItemHeight is not set.

---

fixedItemHeight?: number

Can be used to improve performance if the rendered items are of known size. Setting it causes the component to skip item measurements.

---

followOutput?: FollowOutput

If set to true, the list automatically scrolls to bottom if the total count is changed. Set to "smooth" for an animated scrolling.

By default, followOutput scrolls down only if the list is already at the bottom. To implement an arbitrary logic behind that, pass a function:

tsx

---

headerFooterTag?: string

Set to customize the wrapper tag for the header and footer components (default is div).

---

heightEstimates?: number[]

Use when you have items with widely varying heights and can estimate each item’s height upfront.

Pass an array of estimated heights for each item (by index). This helps the component calculate a more accurate initial total height for the list, reducing layout shifts during initial scrolling.

The estimates don’t need to be exact - they’re used to build the initial size tree before actual measurements are taken. Once items are rendered and measured, their real heights replace the estimates.

Example

tsx

---

horizontalDirection?: boolean

When set, turns the scroller into a horizontal list. The items are positioned with inline-block.

---

increaseViewportBy?: number | { bottom: number; top: number; }

The property accepts pixel values.

Set the increaseViewportBy property to artificially increase the viewport size, causing items to be rendered before outside of the viewport. The property causes the component to render more items than the necessary, but can help with slow loading content. Using { top?: number, bottom?: number } lets you set the increase for each end separately.

---

initialItemCount?: number

Use for server-side rendering - if set, the list will render the specified amount of items regardless of the container / item size.

---

initialScrollTop?: number

Set this value to offset the initial location of the list. Warning: using this property will still run a render cycle at the scrollTop: 0 list window. If possible, avoid using it and stick to initialTopMostItemIndex instead.

---

initialTopMostItemIndex?: number | IndexLocationWithAlign

Set to a value between 0 and totalCount - 1 to make the list start scrolled to that item. Pass in an object to achieve additional effects similar to scrollToIndex.

---

isScrolling()?

optional isScrolling: (isScrolling) => void

Called when the list starts/stops scrolling.

Parameters

Parameter	Type
isScrolling	boolean

Returns

void

---

itemContent?: ItemContent<Data, Context>

Set the callback to specify the contents of the item.

---

itemSize?: SizeFunction

Allows customizing the height/width calculation of Item elements.

The default implementation reads el.getBoundingClientRect().height and el.getBoundingClientRect().width.

---

itemsRendered()?

optional itemsRendered: (items) => void

Called with the new set of items each time the list items are rendered due to scrolling.

Parameters

Parameter	Type
items	ListItem<Data>[]

Returns

void

---

logLevel?: LogLevel

set to LogLevel.DEBUG to enable various diagnostics in the console, the most useful being the item measurement reports.

Ensure that you have “all levels” enabled in the browser console too see the messages.

---

minOverscanItemCount?: number | { bottom: number; top: number; }

Set the minimum number of items to render before and after the visible viewport boundaries. This is useful when rendering items with dynamic or very tall content, where the pixel-based increaseViewportBy may not be sufficient to prevent empty areas during rapid resizing or scrolling. Using { top?: number, bottom?: number } lets you set the count for each end separately.

---

overscan?: number | { main: number; reverse: number; }

The property accepts pixel values.

Set the overscan property to make the component “chunk” the rendering of new items on scroll. The property causes the component to render more items than the necessary, but reduces the re-renders on scroll. Setting { main: number, reverse: number } lets you extend the list in both the main and the reverse scrollable directions. See the increaseViewportBy property for a similar behavior (equivalent to the overscan in react-window).

---

rangeChanged()?

optional rangeChanged: (range) => void

Called with the new set of items each time the list items are rendered due to scrolling.

Parameters

Parameter	Type
range	ListRange

Returns

void

---

restoreStateFrom?: StateSnapshot

pass a state obtained from the getState() method to restore the list state - this includes the previously measured item sizes and the scroll location. Notice that you should still pass the same data and totalCount properties as before, so that the list can match the data with the stored measurements. This is useful when you want to keep the list state when the component is unmounted and remounted, for example when navigating to a different page.

---

scrollerRef()?

optional scrollerRef: (ref) => any

Provides access to the root DOM element

Parameters

Parameter	Type
ref	HTMLElement | Window | null

Returns

any

---

scrollIntoViewOnChange()?

optional scrollIntoViewOnChange: (params) => false | ScrollIntoViewLocation | null | undefined

Implement this callback if you want to adjust the list position when the list total count changes. Return a ScrollIntoViewLocation object to scroll to a specific item, or falsey value to avoid scrolling. Use the context contents if you need to implement custom logic based on the current state of the list.

Parameters

Parameter	Type
params	{ context: Context; scrollingInProgress: boolean; totalCount: number; }
params.context	Context
params.scrollingInProgress	boolean
params.totalCount	number

Returns

false | ScrollIntoViewLocation | null | undefined

---

scrollSeekConfiguration?: false | ScrollSeekConfiguration

Use to display placeholders if the user scrolls fast through the list.

Set components.ScrollSeekPlaceholder to change the placeholder content.

---

skipAnimationFrameInResizeObserver?: boolean

When set, the resize observer used to measure the items will not use requestAnimationFrame to report the size changes. Setting this to true will improve performance and reduce flickering, but will cause benign errors to be reported in the console if the size of the items changes while they are being measured. See https://github.com/petyosi/react-virtuoso/issues/1049 for more information.

---

startReached()?

optional startReached: (index) => void

Called when the user scrolls to the start of the list.

Parameters

Parameter	Type
index	number

Returns

void

---

topItemCount?: number

Set the amount of items to remain fixed at the top of the list.

For a header that scrolls away when scrolling, check the components.Header property.

---

totalCount?: number

The total amount of items to be rendered.

---

totalListHeightChanged()?

optional totalListHeightChanged: (height) => void

Called when the total list height is changed due to new items or viewport resize.

Parameters

Parameter	Type
height	number

Returns

void

---

useWindowScroll?: boolean

Uses the document scroller rather than wrapping the list in its own.

---

VirtuosoHandle

Exposes the Virtuoso component methods for imperative control. Access via ref on the Virtuoso component.

See

• Virtuoso for the component
• VirtuosoProps for available props

Methods

autoscrollToBottom()

autoscrollToBottom(): void

Use this with combination with follow output if you have images loading in the list. Listen to the image loading and call the method.

Returns

void

---

getState()

getState(stateCb): void

Obtains the internal size state of the component, so that it can be restored later. This does not include the data items.

Parameters

Parameter	Type	Description
stateCb	StateCallback	Callback that receives the state snapshot

Returns

void

---

scrollBy()

scrollBy(location): void

Scrolls the component with the specified amount. See ScrollToOptions (MDN)

Parameters

Parameter	Type	Description
location	ScrollToOptions	The scroll offset options

Returns

void

---

scrollIntoView()

scrollIntoView(location): void

Scrolls the item into view if necessary. See the website example for an implementation.

Parameters

Parameter	Type	Description
location	FlatScrollIntoViewLocation	The scroll into view location options

Returns

void

---

scrollTo()

scrollTo(location): void

Scrolls the component to the specified location. See ScrollToOptions (MDN)

Parameters

Parameter	Type	Description
location	ScrollToOptions	The scroll position options

Returns

void

---

scrollToIndex()

scrollToIndex(location): void

Scrolls the component to the specified item index. See IndexLocationWithAlign for more options.

Parameters

Parameter	Type	Description
location	number | FlatIndexLocationWithAlign	The item index or location with alignment options

Returns

void

---

Components

Customize the Virtuoso rendering by passing a set of custom components.

Example

tsx

See

VirtuosoProps.components for usage in Virtuoso

Type Parameters

Type Parameter	Default type	Description
Data	unknown	The type of data items in the list
Context	unknown	The type of additional context passed to components

Properties

EmptyPlaceholder?: ComponentType<ContextProp<Context>>

Set to render a custom UI when the list is empty.

---

Footer?: ComponentType<ContextProp<Context>>

Set to render a component at the bottom of the list.

---

Group?: ComponentType<Pick<DetailedHTMLProps<HTMLAttributes<HTMLDivElement>, HTMLDivElement>, "style" | "children"> & object & ContextProp<Context>>

Set to customize the group item wrapping element. Use only if you would like to render list from elements different than a div.

---

Header?: ComponentType<ContextProp<Context>>

Set to render a component at the top of the list.

The header remains above the top items and does not remain sticky.

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Item?: ComponentType<Pick<DetailedHTMLProps<HTMLAttributes<HTMLDivElement>, HTMLDivElement>, "style" | "children"> & object & ContextProp<Context>>

Set to customize the item wrapping element. Use only if you would like to render list from elements different than a div.

---

List?: ComponentType<Pick<DetailedHTMLProps<HTMLAttributes<HTMLDivElement>, HTMLDivElement>, "style" | "children"> & RefAttributes<HTMLDivElement> & object & ContextProp<Context>>

Set to customize the items wrapper. Use only if you would like to render list from elements different than a div.

---

Scroller?: ComponentType<Pick<DetailedHTMLProps<HTMLAttributes<HTMLDivElement>, HTMLDivElement>, "style" | "tabIndex" | "children"> & RefAttributes<HTMLDivElement> & object & ContextProp<Context>>

Set to customize the outermost scrollable element. This should not be necessary in general, as the component passes its HTML attribute props to it.

---

ScrollSeekPlaceholder?: ComponentType<ScrollSeekPlaceholderProps & ContextProp<Context>>

Set to render an item placeholder when the user scrolls fast. See the scrollSeek property for more details.

---

TopItemList?: ComponentType<TopItemListProps & ContextProp<Context>>

Set to customize the top list item wrapping element. Use if you would like to render list from elements different than a div or you want to set a custom z-index for the sticky position.

---

ItemContent

ItemContent<Data, Context> = (index, data, context) => React.ReactNode

Callback type for rendering item content in a Virtuoso list.

Type Parameters

Type Parameter	Description
Data	The type of the data item
Context	The type of context passed from the component

Parameters

Parameter	Type
index	number
data	Data
context	Context

Returns

React.ReactNode

Example

tsx

See

• VirtuosoProps.itemContent for usage in Virtuoso
• GroupItemContent for grouped list variant

---

ItemProps

ItemProps<Data> = Pick<React.ComponentProps<"div">, "children" | "style"> & object

Passed to the Components.Item custom component

Type Declaration

data-index

number

data-item-group-index?: number

data-item-index

number

data-known-size

number

item

Data

Type Parameters

Type Parameter
Data

---

ListProps

ListProps = Pick<React.ComponentProps<"div">, "children" | "style"> & React.RefAttributes<HTMLDivElement> & object

Passed to the Components.List custom component

Type Declaration

data-testid

string

---

ListRootProps

ListRootProps = Omit<React.HTMLProps<HTMLDivElement>, "data" | "ref">

---

ScrollSeekPlaceholderProps

Passed to the Components.ScrollSeekPlaceholder custom component

Properties

groupIndex?: number

The group index if this placeholder represents a group header

---

height

number

The height of the placeholder in pixels

---

index

number

The index of the item being replaced by the placeholder

---

type

"group" | "item"

Whether this placeholder represents a group header or a regular item

---

TopItemListProps

TopItemListProps = Pick<React.ComponentProps<"div">, "children" | "style">

---

VirtuosoMockContext

const VirtuosoMockContext: Context<VirtuosoMockContextValue | undefined>

React context for mocking Virtuoso component measurements in tests. Wrap your Virtuoso component with this provider to bypass DOM measurements.

Example

tsx

---

VirtuosoMockContextValue

Mock context value for testing Virtuoso components. Provides fixed dimensions to bypass DOM measurements.

Properties

itemHeight

number

Fixed height for each item in pixels

---

viewportHeight

number

Fixed viewport height in pixels