Why measure before optimizing React?
Because optimization without measurement is guesswork. The Profiler tells you which components are actually slow and why, so you fix the real bottleneck. Premature optimization adds overhead without benefit.
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More FAQs in How to Measure and Fix Performance in a React App
Use the React DevTools Profiler to record a render and find which components are slow or re-render too much. The Profiler tells you the real bottleneck and can show why a component re-rendered, so you fix the actual cause.
Wrap expensive computations in useMemo so they only recompute when dependencies change. This is often the clearest win after measurement, and it directly addresses the measured bottleneck.
Stabilize prop references. If the parent passes new function or object references on every render, children re-render. Use useCallback and useMemo to stabilize references, and combine with React.memo for heavily re-rendered components.
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