The answer
Because they let React track which cards changed and update only those. Without stable keys, React cannot match old cards to new ones efficiently, causing many unnecessary re-renders.
Optimizing a Long Video List Render in React
Why are stable keys important for a video list?
More FAQs in Optimizing a Long Video List Render in React
Likely because of missing stable keys, loading all thumbnails at once, re-rendering all cards on every update, or rendering the entire list without windowing. Profile with the React DevTools Profiler to find the real bottleneck.
Use stable unique keys, lazy-load thumbnails, memoize cards with React.memo, paginate or window for very long lists, avoid inline objects as props so memoized cards do not re-render unnecessarily, and profile first to fix the real bottleneck.
Because loading hundreds of thumbnails at once on initial render is slow. Lazy-loading means thumbnails load as they enter the viewport, keeping the initial render fast and saving bandwidth for off-screen images.
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