This content originally appeared on DEV Community and was authored by hamza4600
If you've been building React apps for a while, you know how painful unnecessary re-renders can be.
Changing one small piece of state and suddenly half your UI re-renders — it’s frustrating and often hard to debug.
For years, our go-to solutions have been React.memo, useMemo, and useCallback.
They work… but they make code messy and easy to misuse. Forget one memoization wrapper, and your app starts lagging again.
That’s why the new React Compiler caught my eye. It claims to automatically handle a lot of these optimizations for you.
So, I decided to test it myself and see if it’s really worth the hype.
⚙️ What Is the React Compiler?
In simple terms, the React Compiler is a build-time optimization tool that integrates with your bundler (like Babel or Next.js).
It analyzes your components, props, and hooks — then automatically memoizes things that don’t need to re-render.
So instead of writing this manually:
const slowFn = useCallback(() => doSomething(), []);
const value = useMemo(() => expensiveComputation(), []);
🧪 Setting It Up
I tested it in a Next.js project using the experimental React 19 build.
Here’s what I did:
npm install next@canary react@canary react-dom@canary
npm install babel-plugin-react-compiler
Then, I enabled it in next.config.js:
@type {import('next').NextConfig} */
const nextConfig = {
experimental: {
reactCompiler: true,
},
};
export default nextConfig;
That’s literally it.
Once you start the dev server and open React DevTools, you’ll notice components marked as memoized automatically.
Pretty cool.
🔍 Quick Tests
Example 1: State Change Re-Renders
I had a parent component that toggled a state while rendering a slow child component.
Normally, both would re-render on every toggle.
With the compiler enabled → only the parent re-rendered. ✅
Example 2: Passing Arrays and Callbacks
Usually, we wrap arrays and functions in useMemo or useCallback to prevent re-renders.
With the compiler, I removed all those wrappers… and the child component still didn’t re-render. ✅
Example 3: Children Elements
Memoizing children has always been a headache.
Surprisingly, the compiler handled this case better than expected — no extra renders. ✅
Testing It in Real Apps
I tested the compiler across three real-world projects (ranging from 10k–150k lines of code).
Here’s a quick snapshot:
| App | Size | Unnecessary re-renders found | Fixed by Compiler |
|---|---|---|---|
| Legacy internal app | ~150k LOC | ~10 | 2 fixed |
| Mid-sized dashboard | ~30k LOC | ~10 | 2 fixed |
| Small weekend project | ~8k LOC | 8 | 1 fixed |
So yes — it did help, but it wasn’t magic. It fixed a few issues automatically but didn’t replace manual optimizations entirely.
⚠️ What It Couldn’t Fix
While testing, I noticed a few limitations worth mentioning:
Hooks like useMutation (from react-query) return non-memoized objects. The compiler doesn’t catch those yet.
Lists using array index as key confuse the compiler. Switching to a unique ID fixes that.
Sometimes, splitting big components into smaller ones improves compiler accuracy.
So, the rule of thumb still applies:
The compiler helps, but understanding React’s rendering model is still crucial.
✅ My Verdict
Pros
Easy to enable — literally one config flag.
Automatically reduces some re-renders.
Makes your codebase cleaner by removing extra memo hooks.
Cons
Still experimental — expect occasional quirks.
Doesn’t solve all performance issues in large apps.
You still need to understand React performance fundamentals.
Should You Use It?
If you’re building something new — absolutely, give it a try.
It’s free optimization with almost zero setup cost.
But for big production apps, I’d say:
Use it alongside manual profiling and optimizations.
Don’t treat it as a silver bullet… yet.
Final Thoughts
The React Compiler feels like a big step forward for React as a framework.
Even though it’s early days, it’s clear where React is heading — toward a world where developers write simpler code, and the compiler takes care of performance behind the scenes.
I’m honestly excited about this direction.
If React continues improving compiler intelligence, we might finally stop worrying about memoization one day.
Until then, keep an eye on it — and experiment early
This content originally appeared on DEV Community and was authored by hamza4600
hamza4600 | Sciencx (2025-10-25T17:59:29+00:00) Hands-On with React Compiler — Can It Replace React.memo, useMemo & useCallback?. Retrieved from https://www.scien.cx/2025/10/25/hands-on-with-react-compiler-can-it-replace-react-memo-usememo-usecallback/
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