Next.js Lazy Loading and Code Splitting: Load Only What You Need
Code splitting reduces initial page load by 40 to 70 percent. Use next/dynamic for component splitting, route-based splitting, and React.lazy for client components.
Every kilobyte of JavaScript delays interactivity. Code splitting loads only what is needed.
Route-Based Splitting (Automatic)
Next.js App Router automatically code-splits per route. Each page only loads its own JavaScript.
Component-Level Splitting with next/dynamic
import dynamic from 'next/dynamic';const HeavyEditor = dynamic(() => import('./RichTextEditor'), { loading: () =>
, ssr: false }); ```When to Use Dynamic Imports
- ●Modals and Dialogs: Do not load until user clicks
- ●Charts and Graphs: Heavy libraries — load on visibility
- ●Rich Text Editors: Load when needed
- ●Maps: Load when scrolled into view
Intersection Observer Pattern
Use IntersectionObserver to detect when a placeholder enters the viewport, then dynamically import the heavy component.
Measuring Impact
Check First Load JS in next build output. Each route should be under 100KB.
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Written by M Daniyal Amjad Ali
Full Stack Software Engineer with 5+ years of experience. Expert in Next.js, React, Node.js, and Prisma. 100+ projects delivered worldwide.