When should I use React.memo?
For components that re-render often with the same props as their parent re-renders. Combine with stable references from useCallback and useMemo so the memoized child only re-renders when props truly change.
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More FAQs in A Roadmap to Understanding React Re-renders and Optimization
In order: understand what causes re-renders, use the Profiler, find unnecessary re-renders, stabilize references with useCallback and useMemo, wrap with React.memo, optimize lists, code split, and measure again after each fix.
A component re-renders when its state changes, when its parent re-renders, or when its props change. Understanding this flow is the first step to optimizing, because you cannot fix what you do not understand.
It records a render and shows which components re-rendered and why, including a 'why did this render' feature. This tells you the real bottleneck and the cause, so you optimize the actual problem, not a guess.
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