List Virtualization: Rendering the Viewport, Not the Dataset

List virtualization renders only the visible slice of a huge dataset, keeping your app fast by maintaining a tiny DOM. It's like a sliding window over your data, calculating what to show and where to place it. This is essential for massive scroll surfaces like data grids or infinite feeds where rendering thousands of DOM nodes would kill performance. The main footgun is inaccurate item size estimation; if estimates are wrong, the scrollbar will jump and flicker as the user scrolls and the library measures the actual content.