tanstack-virtual

Overview

TanStack Virtual provides virtualization logic for rendering only visible items in large lists, grids, and tables. It calculates which items are in the viewport and positions them with absolute positioning, keeping DOM node count minimal regardless of dataset size.

Package:

@tanstack/react-virtual

Core:

@tanstack/virtual-core

(framework-agnostic)

Installation

bash

npm install @tanstack/react-virtual

Core Pattern

tsx

import { useVirtualizer } from '@tanstack/react-virtual'

function VirtualList() {
  const parentRef = useRef<HTMLDivElement>(null)

  const virtualizer = useVirtualizer({
    count: 10000,
    getScrollElement: () => parentRef.current,
    estimateSize: () => 35, // estimated row height in px
    overscan: 5,
  })

  return (
    <div ref={parentRef} style={{ height: '400px', overflow: 'auto' }}>
      <div
        style={{
          height: `${virtualizer.getTotalSize()}px`,
          width: '100%',
          position: 'relative',
        }}
      >
        {virtualizer.getVirtualItems().map((virtualItem) => (
          <div
            key={virtualItem.key}
            style={{
              position: 'absolute',
              top: 0,
              left: 0,
              width: '100%',
              height: `${virtualItem.size}px`,
              transform: `translateY(${virtualItem.start}px)`,
            }}
          >
            Row {virtualItem.index}
          </div>
        ))}
      </div>
    </div>
  )
}

Virtualizer Options

Required

Option	Type	Description
`count`	`number`	Total number of items
`getScrollElement`	`() => Element \| null`	Returns scroll container
`estimateSize`	`(index) => number`	Estimated item size (overestimate recommended)

Optional

Option	Type	Default	Description
`overscan`	`number`	`1`	Extra items rendered beyond viewport
`horizontal`	`boolean`	`false`	Horizontal virtualization
`gap`	`number`	`0`	Gap between items (px)
`lanes`	`number`	`1`	Number of lanes (masonry/grid)
`paddingStart`	`number`	`0`	Padding before first item
`paddingEnd`	`number`	`0`	Padding after last item
`scrollPaddingStart`	`number`	`0`	Offset for scrollTo positioning
`scrollPaddingEnd`	`number`	`0`	Offset for scrollTo positioning
`initialOffset`	`number`	`0`	Starting scroll position
`initialRect`	`Rect`	-	Initial dimensions (SSR)
`enabled`	`boolean`	`true`	Enable/disable
`getItemKey`	`(index) => Key`	`(i) => i`	Stable key for items
`rangeExtractor`	`(range) => number[]`	default	Custom visible indices
`scrollToFn`	`(offset, options, instance) => void`	default	Custom scroll behavior
`measureElement`	`(el, entry, instance) => number`	default	Custom measurement
`onChange`	`(instance, sync) => void`	-	State change callback
`isScrollingResetDelay`	`number`	`150`	Delay before scroll complete

Virtualizer API

typescript

// Get visible items
virtualizer.getVirtualItems(): VirtualItem[]

// Get total scrollable size
virtualizer.getTotalSize(): number

// Scroll to specific index
virtualizer.scrollToIndex(index, { align: 'start' | 'center' | 'end' | 'auto', behavior: 'auto' | 'smooth' })

// Scroll to offset
virtualizer.scrollToOffset(offset, options)

// Force recalculation
virtualizer.measure()

VirtualItem Properties

typescript

interface VirtualItem {
  key: Key           // Unique key
  index: number      // Index in source data
  start: number      // Pixel offset (use for transform)
  end: number        // End pixel offset
  size: number       // Item dimension
  lane: number       // Lane index (multi-column)
}

Dynamic/Variable Heights

Use

measureElement

ref for items with unknown heights:

tsx

const virtualizer = useVirtualizer({
  count: items.length,
  getScrollElement: () => parentRef.current,
  estimateSize: () => 50, // overestimate
})

{virtualizer.getVirtualItems().map((virtualItem) => (
  <div
    key={virtualItem.key}
    data-index={virtualItem.index}  // REQUIRED for measurement
    ref={virtualizer.measureElement} // Attach for dynamic measurement
    style={{
      position: 'absolute',
      top: 0,
      left: 0,
      width: '100%',
      transform: `translateY(${virtualItem.start}px)`,
      // Do NOT set fixed height - let content determine it
    }}
  >
    {items[virtualItem.index].content}
  </div>
))}

Horizontal Virtualization

tsx

const virtualizer = useVirtualizer({
  count: columns.length,
  getScrollElement: () => parentRef.current,
  estimateSize: () => 100,
  horizontal: true,
})

// Use width for container, translateX for positioning
<div style={{ width: `${virtualizer.getTotalSize()}px`, position: 'relative' }}>
  {virtualizer.getVirtualItems().map((item) => (
    <div style={{
      position: 'absolute',
      height: '100%',
      width: `${item.size}px`,
      transform: `translateX(${item.start}px)`,
    }}>
      Column {item.index}
    </div>
  ))}
</div>

Grid Virtualization (Two Virtualizers)

tsx

function VirtualGrid() {
  const parentRef = useRef<HTMLDivElement>(null)

  const rowVirtualizer = useVirtualizer({
    count: 10000,
    getScrollElement: () => parentRef.current,
    estimateSize: () => 35,
    overscan: 5,
  })

  const columnVirtualizer = useVirtualizer({
    count: 10000,
    getScrollElement: () => parentRef.current,
    estimateSize: () => 100,
    horizontal: true,
    overscan: 5,
  })

  return (
    <div ref={parentRef} style={{ height: '500px', width: '500px', overflow: 'auto' }}>
      <div style={{
        height: `${rowVirtualizer.getTotalSize()}px`,
        width: `${columnVirtualizer.getTotalSize()}px`,
        position: 'relative',
      }}>
        {rowVirtualizer.getVirtualItems().map((virtualRow) => (
          <Fragment key={virtualRow.key}>
            {columnVirtualizer.getVirtualItems().map((virtualColumn) => (
              <div
                key={virtualColumn.key}
                style={{
                  position: 'absolute',
                  width: `${virtualColumn.size}px`,
                  height: `${virtualRow.size}px`,
                  transform: `translateX(${virtualColumn.start}px) translateY(${virtualRow.start}px)`,
                }}
              >
                Cell {virtualRow.index},{virtualColumn.index}
              </div>
            ))}
          </Fragment>
        ))}
      </div>
    </div>
  )
}

Window Scrolling

tsx

import { useWindowVirtualizer } from '@tanstack/react-virtual'

function WindowList() {
  const listRef = useRef<HTMLDivElement>(null)

  const virtualizer = useWindowVirtualizer({
    count: 10000,
    estimateSize: () => 45,
    overscan: 5,
    scrollMargin: listRef.current?.offsetTop ?? 0,
  })

  return (
    <div ref={listRef}>
      <div style={{
        height: `${virtualizer.getTotalSize()}px`,
        position: 'relative',
      }}>
        {virtualizer.getVirtualItems().map((item) => (
          <div
            key={item.key}
            style={{
              position: 'absolute',
              height: `${item.size}px`,
              transform: `translateY(${item.start - virtualizer.options.scrollMargin}px)`,
            }}
          >
            Row {item.index}
          </div>
        ))}
      </div>
    </div>
  )
}

Infinite Scrolling

tsx

import { useVirtualizer } from '@tanstack/react-virtual'
import { useInfiniteQuery } from '@tanstack/react-query'

function InfiniteList() {
  const { data, fetchNextPage, hasNextPage, isFetchingNextPage } = useInfiniteQuery({
    queryKey: ['items'],
    queryFn: ({ pageParam = 0 }) => fetchItems(pageParam),
    getNextPageParam: (lastPage) => lastPage.nextCursor,
  })

  const allItems = data?.pages.flatMap((page) => page.items) ?? []

  const virtualizer = useVirtualizer({
    count: hasNextPage ? allItems.length + 1 : allItems.length,
    getScrollElement: () => parentRef.current,
    estimateSize: () => 50,
    overscan: 5,
  })

  useEffect(() => {
    const items = virtualizer.getVirtualItems()
    const lastItem = items[items.length - 1]
    if (lastItem && lastItem.index >= allItems.length - 1 && hasNextPage && !isFetchingNextPage) {
      fetchNextPage()
    }
  }, [virtualizer.getVirtualItems(), hasNextPage, isFetchingNextPage, allItems.length])

  // Render virtual items, show loader row for last item if loading
}

Sticky Items

tsx

import { defaultRangeExtractor, Range } from '@tanstack/react-virtual'

const stickyIndexes = [0, 10, 20, 30] // Header indices

const virtualizer = useVirtualizer({
  count: 1000,
  getScrollElement: () => parentRef.current,
  estimateSize: () => 50,
  rangeExtractor: useCallback((range: Range) => {
    const next = new Set([...stickyIndexes, ...defaultRangeExtractor(range)])
    return [...next].sort((a, b) => a - b)
  }, [stickyIndexes]),
})

// Render sticky items with position: sticky; top: 0; zIndex: 1

Smooth Scrolling

tsx

const virtualizer = useVirtualizer({
  scrollToFn: (offset, { behavior }, instance) => {
    if (behavior === 'smooth') {
      // Custom easing animation
      instance.scrollElement?.scrollTo({ top: offset, behavior: 'smooth' })
    } else {
      instance.scrollElement?.scrollTo({ top: offset })
    }
  },
})

// Usage
virtualizer.scrollToIndex(500, { align: 'center', behavior: 'smooth' })

Best Practices

Overestimate
estimateSize
- prevents scroll jumps (items shrinking causes issues)
Increase
overscan
(3-5) to reduce blank flashing during fast scrolling
Use
transform: translateY()
over
```
top
```
for GPU-composited positioning
Add
data-index
attribute when using
```
measureElement
```
for dynamic sizing
Don't set fixed height on dynamically measured items
Use
getItemKey
for stable keys when items can reorder
Use
gap
option instead of margins (margins interfere with measurement)
Use
paddingStart/End
instead of CSS padding on the container
Use
enabled: false
to pause when the list is hidden
Memoize callbacks (
```
estimateSize
```
,
```
getItemKey
```
,
```
rangeExtractor
```
)
Use
will-change: transform
CSS on items for GPU acceleration

Common Pitfalls

Setting fixed height on dynamically measured items
Using CSS margins instead of the
```
gap
```
option
Forgetting
```
data-index
```
with
```
measureElement
```
Not providing
```
position: relative
```
on the inner container
Underestimating
```
estimateSize
```
(causes scroll jumps)
Setting
```
overscan
```
too low for fast scrolling (blank items)
Forgetting to subtract
```
scrollMargin
```
from
```
translateY
```
in window scrolling
Not memoizing the
```
estimateSize
```
function (causes re-renders)