Performance Is a Feature
A slow React app isn't just a technical problem — it's a user experience problem. Studies show that every 100ms of latency costs measurable engagement. Here's how to make your React apps fast.
Profiling First
Never optimize without profiling. React DevTools and Chrome Performance panel will show you where time is actually spent. Common surprises:
- Unnecessary re-renders are the #1 performance killer
- Bundle size matters more than you think on mobile
- Third-party libraries often contribute more weight than your own code
Memoization
React.memo, useMemo, and useCallback are your primary tools for preventing unnecessary re-renders. But use them strategically:
- Memoize expensive calculations, not every value
- useCallback for functions passed to memoized child components
- React.memo for components that render the same output for the same props
Code Splitting and Lazy Loading
Don't ship code your users don't need yet:
- React.lazy for route-level code splitting
- Dynamic imports for heavy components like charts and editors
- Intersection Observer for lazy loading below-the-fold content
Virtualization
For long lists and tables, render only what's visible. Libraries like react-window and TanStack Virtual make this straightforward. The performance improvement is dramatic — from seconds to milliseconds.
State Management
Global state that triggers widespread re-renders is a common bottleneck. Keep state as close to where it's used as possible. Consider:
- Splitting context providers to avoid unnecessary subscribers
- Using state management libraries with fine-grained subscriptions
- Moving server state to React Query or SWR
Conclusion
React performance optimization is about understanding your render cycle and eliminating waste. Profile first, optimize where it matters, and measure the impact. Fast apps don't just feel better — they convert better.