React Virtualization Explained — Render Large Lists Efficiently

In this tutorial, you will learn about React Virtualization Explained. We cover key concepts, practical examples, and best practices to help you master this topic.

React virtualization renders only the visible portion of a large list, dramatically reducing DOM nodes and improving performance for lists with thousands of items.

What You'll Learn

• What virtualization is and why it matters
• How to use react-window for fixed-height lists
• How to use react-virtuoso for variable-height lists
• How to implement infinite scrolling
• Performance measurement

Why It Matters

Rendering 10,000 DOM nodes causes jank and high memory usage. Virtualization renders only 10-20 nodes that fit on screen, scrolling the container and replacing items seamlessly.

import { FixedSizeList } from "react-window";

function VirtualList({ items }) {
  const Row = ({ index, style }) => (
    <div style={style} className="list-item">
      {items[index].name}
    </div>
  );

  return (
    <FixedSizeList
      height={400}
      width="100%"
      itemCount={items.length}
      itemSize={50}
    >
      {Row}
    </FixedSizeList>
  );
}

Expected output: A list of 10,000+ items renders smoothly. Only ~8 items are in the DOM at any time, the rest are virtualized.