| name | bundle-barrel-imports |
| description | Import directly from source files instead of barrel files. Apply when using libraries like lucide-react, @mui/material, or @radix-ui/react-* to reduce bundle size and improve dev boot time. |
Avoid Barrel File Imports
Import directly from source files instead of barrel files to avoid loading thousands of unused modules. Barrel files are entry points that re-export multiple modules (e.g., index.js that does export * from './module').
Popular icon and component libraries can have up to 10,000 re-exports in their entry file. For many React packages, it takes 200-800ms just to import them, affecting both development speed and production cold starts.
Why tree-shaking doesn't help: When a library is marked as external (not bundled), the bundler can't optimize it. If you bundle it to enable tree-shaking, builds become substantially slower analyzing the entire module graph.
Incorrect (imports entire library):
import { Check, X, Menu } from 'lucide-react'
import { Button, TextField } from '@mui/material'
Correct (imports only what you need):
import Check from 'lucide-react/dist/esm/icons/check'
import X from 'lucide-react/dist/esm/icons/x'
import Menu from 'lucide-react/dist/esm/icons/menu'
import Button from '@mui/material/Button'
import TextField from '@mui/material/TextField'
Alternative (Next.js 13.5+):
module.exports = {
experimental: {
optimizePackageImports: ['lucide-react', '@mui/material']
}
}
import { Check, X, Menu } from 'lucide-react'
Direct imports provide 15-70% faster dev boot, 28% faster builds, 40% faster cold starts, and significantly faster HMR.
Libraries commonly affected: lucide-react, @mui/material, @mui/icons-material, @tabler/icons-react, react-icons, @headlessui/react, @radix-ui/react-*, lodash, ramda, date-fns, rxjs, react-use.
Reference: How we optimized package imports in Next.js