React Re-render Myths Developers Still Believe

React Re-render Myths Developers Still Believe

Most developers who start learning React quickly encounter this sentence:
"Re-render is bad. You should avoid it."

Over time, this becomes a reflex. When state changes, when a parent component renders, or when props change, developers immediately start worrying about performance. After a while, even the word "re-render" starts to feel like an alarm.

But the reality is this: In React, re-rendering is often not a problem.
The real problem is unnecessary optimizations and incorrect assumptions.

Let's look at the React re-render myths that are still very common today.

Myth 1: Every Re-render Is a Performance Problem

One of the most common misconceptions is that every re-render is a performance issue. When a component renders, developers often assume that the entire DOM is recreated. This leads developers to try avoiding re-renders at all costs.

However, React has a highly optimized rendering mechanism. Thanks to Virtual DOM, React updates only what actually changes. Rendering a component does not mean the entire DOM is rebuilt.

For example:

function Counter() {
  const [count, setCount] = useState(0)

  return (
    <div>
      <h1>{count}</h1>
      <button onClick={() => setCount(count + 1)}>
        Increment
      </button>
    </div>
  )
}

This component re-renders whenever count changes.
This is completely normal and not a performance issue.

Because React only updates what changes.
Rendering and DOM updates are not the same thing.

Understanding this distinction is fundamental to understanding React performance.

Myth 2: Parent Re-render Causes Performance Issues

Another common belief is that when a parent component renders, all child components re-render and create performance issues.

Yes, child components do re-render. But this is usually not expensive. Rendering small components has a very low cost.

For example:

function Parent() {
  const [count, setCount] = useState(0)

  return (
    <>
      <Counter count={count} />
      <StaticComponent />
    </>
  )
}

When the parent renders, StaticComponent also renders.
But unless it contains heavy logic, this usually does not cause problems.

The biggest mistake here is premature optimization. Developers immediately start using React.memo.

const StaticComponent = React.memo(() => {
  return <div>Static content</div>
})

However, this optimization is often unnecessary.
Because React.memo also introduces comparison cost.

Unnecessary memoization can sometimes hurt performance instead of improving it.

Myth 3: useMemo and useCallback Always Improve Performance

This is another very common misconception. Many developers see useMemo and useCallback as performance tools and start using them everywhere.

For example:

const handleClick = useCallback(() => {
  setCount(count + 1)
}, [count])

This usage is often unnecessary.

Because useCallback also introduces overhead:

• Dependency checks

• Reference storage

• Increased memory usage

If the function is not passed down to child components, using useCallback often provides no benefit.

In some cases, it may even reduce performance.

React team also frequently emphasizes this:
Measure first, then optimize.

Myth 4: Re-renders Must Be Prevented Completely

Some developers try to prevent re-renders completely. However, React is designed around rendering.

Rendering is not bad.
Heavy rendering is bad.

Optimization makes sense in situations like:

• Large lists

• Expensive calculations

• Complex component trees

• Frequent state updates

But avoiding re-renders in small components creates unnecessary complexity. This reduces readability and increases maintenance cost.

Where Real Performance Problems Occur

Real performance issues in React usually occur in:

• Large lists (virtualization may be needed)

• Expensive calculations

• Unnecessary state management

• Incorrect context usage

• Large component trees

Instead of optimizing every render, it's better to find real bottlenecks.

Conclusion

React re-renders are usually not something to fear.
The real problem is unnecessary optimization.

Not every React.memo, useMemo, or useCallback improves performance.
Sometimes they can even have the opposite effect.

Good React developers don’t try to avoid every render.
They find real performance bottlenecks and optimize where it matters.

Because performance optimization is not about fewer renders — it's about smarter renders.