🧠 Why My React App Lagged on Scroll And What I Learned Fixing It

While building a blog application in React, I ran into a frustrating issue:

Everything looked perfect… until we tested it on mobile.

The scroll was laggy, blog cards took time to appear, and the whole experience felt sluggish especially on low-end Android devices.

🔍 Step 1: Identifying the Root Cause

Here’s what I found after a quick audit using Chrome DevTools:

• ❌ Too many DOM elements rendered at once

• ❌ Non-memoized components re-rendering unnecessarily

• ❌ Heavy cover images loading immediately

• ❌ Unoptimized fonts causing layout shifts

This combination was killing the scroll performance.

⚙️ Step 2: Fixing the Scroll Lag (One by One)

✅ a) Virtualization with react-window

Instead of rendering 100 blog cards at once, I switched to virtualized rendering using:

🎯 Result: DOM size reduced drastically = smoother scroll ✅

✅ b) Memoizing Components & Callbacks

Many child components were re-rendering unnecessarily, especially .

I wrapped them in and passed stable props using :

🎯 Result: Reduced re-render frequency ✅

✅ c) Lazy Load Blog Images

Instead of loading all images at once, I added:

🎯 Result: Faster initial load and better scroll performance ✅

✅ d) Optimize Fonts and Covers

• Switched to system fonts for faster FCP (first contentful paint)

• Compressed cover images using TinyPNG before uploading

🎯 Result: Cleaner UI + faster load ✅

🧪 Step 3: Test on Real Devices

Don’t just test on your high-end laptop.

Always test on mid-range Android and iPhones to catch real-world issues.

💡 Key Takeaways

• UI performance issues often come from death by a thousand cuts

• Start thinking about performance from day one

• Use DevTools + Lighthouse + throttle mode regularly

🤝 Let’s Talk

Have you ever faced scroll jank or mobile lag in your React apps?

Drop a comment, or DM me if you’re stuck I love solving real-world React problems.

🔗 Resources

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