Large Bundle Size - App Loads Slowly
Your JavaScript bundle is very large (over 500KB), making the app slow to load. First Contentful Paint takes several seconds even on good connections.
Users on slow networks experience long loading times.
Error Messages You Might See
Common Causes
- Importing entire library when only small part needed
- Large image assets embedded in bundle instead of loaded separately
- Unused code not being tree-shaken by build tool
- Moment.js or similar heavy date libraries (use date-fns, dayjs instead)
- Loading all routes upfront instead of code splitting by route
How to Fix It
Use tree-shakeable imports: import { map } from 'lodash-es' not import lodash
Lazy load heavy components: const Component = dynamic(() => import('@/components/Heavy'))
Replace heavy libraries: moment.js -> date-fns or dayjs, @apollo/client -> urql
Optimize images: use next/image, convert to WebP, serve appropriate sizes
Enable code splitting in Next.js config (automatic for routes)
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Get HelpFrequently Asked Questions
What's a good target bundle size?
JavaScript: <200KB. With gzip: <50KB. For comparison, heavy frameworks are ~200KB
How do I check actual bundle size?
npm run build shows Next.js Size. Use webpack-bundle-analyzer for detailed breakdown
What about image sizes?
Use next/image for automatic optimization. Aim for <100KB total images, <30KB per image