Let’s face it — React is fast... until it’s not. You’ve probably been there: you build a sleek UI, everything works great in dev, but once your app grows or hits production, it starts to lag. Clicks feel sluggish, page loads are slow, and animations stutter. The worst part is that You’re not even sure where it’s going wrong.
**Problem #1: Unnecessary Re-renders Are Sneaky
**One of the most common reasons React apps become sluggish is because components re-render more often than they need to. React re-renders a component whenever its props or state change — but not all changes are meaningful.
Let’s say you’re passing props like this:
<MyComponent someProp={Math.random()} />
Every time the parent re-renders, someProp changes (because Math.random() returns a new value), and that causes MyComponent to re-render — even if nothing user-facing changed.
Fix it:
Use React.memo to memoize your components. This tells React, “only re-render this component if the props actually change.”
const MyComponent = React.memo(({ someProp }) => {
return <div>{someProp}</div>;
});
This simple change can dramatically reduce unnecessary work in large component trees.
Problem #2: Poor List Rendering
Rendering long lists using .map() is fine for small datasets — but once you start dealing with hundreds or thousands of items, it becomes a performance bottleneck.
{items.map(item => <Item key={item.id} data={item} />)}
This approach forces React to render every item, even those that aren’t visible on the screen. That’s a lot of wasted effort.
Fix it:
Use windowing libraries like react-window or react-virtualized to render only the items that are currently in view. Here's an example:
`import { FixedSizeList as List } from 'react-window';
{({ index, style }) => (
)}
`
Your UI stays buttery smooth, no matter how large your list gets.
**Problem #3: You're Loading Too Much JavaScript Upfront
This one’s easy to overlook: if your app loads everything at once — every component, every image, every dependency — the initial load time can become painfully slow.
_**Fix it:
Split your code using React.lazy() and Suspense. You only load what you need, when you need it.
const HeavyComponent = React.lazy(() => import('./HeavyComponent'));
<Suspense fallback={<div>Loading...</div>}>
<HeavyComponent />
</Suspense>
/
Problem #4: Misusing useEffect
Ever faced infinite re-renders or unnecessary network calls? That’s usually a sign that your useEffect dependencies aren’t correctly set.
Fix It:
Understand how dependency arrays work. Avoid writing effects that depend on values being updated inside the effect itself. Use useRef when you need a value that persists but doesn’t trigger re-renders.
** Problem #5 : You're Not Profiling
You can’t fix what you don’t measure. If you’re not using React’s built-in Profiler, you’re flying blind.
**_Fix it:
Install React Developer Tools and use the Profiler tab. You’ll see exactly which components are re-rendering and how long they take.
Even better: combine this with console logs or performance.mark() calls to really dig into bottlenecks.
Some PRO tips :
- Wrap callback functions in useCallback to avoid unnecessary prop changes.
- Avoid anonymous functions inside JSX where possible.
- Keep your component hierarchy flat and logical.
- Use StrictMode in development to catch unexpected behavior early.
A truly great React developer doesn’t just build apps that work. They build apps that feel fast, even under pressure.
Top comments (1)
Thanks, I've been struggling with slow performance of my react app. This was very helpful.