Chapter 4 · Practice 2 of 5

Use useMemo and useCallback only as an escape hatch

Why it matters

With React Compiler on, useMemo and useCallback become an escape hatch, not a habit.

Situation	What to do
New code, compiler on	Write it without manual memoization and let the compiler decide
Need precise control, such as a stable effect dependency	Keep `useMemo` or `useCallback` there
Existing memoization, compiler just enabled	Leave it in place, or test carefully before removing it
No compiler	Memoize only after profiling shows a real cost

Removing existing memoization can change what the compiler outputs, which is why the React team advises caution.

Avoid