Finding and fixing performance issues requires proper measurement. Here's how to profile React applications effectively.
React DevTools Profiler
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Chrome Performance Tab
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Finding Re-render Causes
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Measuring Component Performance
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React.memo Optimization
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useMemo and useCallback
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Virtualization for Large Lists
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Code Splitting and Lazy Loading
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Web Vitals
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Best Practices
Profiling:
✓ Profile in production mode
✓ Test with realistic data
✓ Measure before optimizing
✓ Focus on user-perceived performance
Optimization:
✓ Start with architecture (code splitting)
✓ Then component memoization
✓ Then virtualization if needed
✓ Avoid premature optimization
Common Issues:
✓ Unnecessary re-renders
✓ Large bundle sizes
✓ Expensive calculations in render
✓ Memory leaks from subscriptions
Conclusion
Performance profiling starts with measurement. Use React DevTools Profiler for component-level analysis, Chrome Performance tab for overall app performance, and Web Vitals for user-perceived metrics. Optimize based on data, not assumptions. Focus on the biggest bottlenecks first and always verify improvements with profiling.