Next.js Compiler Cheat Sheet

A concise cheat sheet on the Next.js compiler, covering optimizations, Rust-based architecture, SWC transformations, and best practices for faster builds.

💡 Key Takeaways

⚙️ SWC Compiler: Next.js uses a Rust-based SWC compiler by default for high speed and low memory use.
🚀 Turbopack: The next-gen bundler (in beta) built on Rust for parallel compilation.
🧠 Optimization: Enable SWC minification, tree-shaking, and dynamic imports for leaner builds.

⚙️ Compiler Basics

SWC replaces Babel for faster builds
Turbopack is the upcoming Rust-based bundler
Configure options in next.config.js

const nextConfig = {
  compiler: {
    removeConsole: process.env.NODE_ENV === 'production',
    reactRemoveProperties: true,
    emotion: true
  },
  experimental: {
    swcMinify: true,
    optimizeCss: true
  }
};
module.exports = nextConfig;

⚡ Why Rust & SWC

Rust offers native performance and concurrency
SWC compiles JS/TS 10–20× faster than Babel
Fully integrated into Next.js builds

# SWC replaces Babel automatically
next build

🔀 Dynamic Imports

Load heavy components lazily with dynamic()
Use loading placeholders for smoother UX
Disable SSR when not needed

import dynamic from 'next/dynamic';
const LazyComp = dynamic(() => import('./HeavyComp'), {
  loading: () => <p>Loading...</p>,
  ssr: false
});

🌲 Tree Shaking

Use named ESM imports for better optimization
Avoid default imports of entire libraries
Enable optimizePackageImports for fine-tuning

// ✅ Good
import { debounce } from 'lodash-es';

// ❌ Avoid
import _ from 'lodash';

📦 Bundle Analyzer

Helps inspect bundle size and module weight
Enables ANALYZE=true next build
Integrates easily with next.config.js

const withBundleAnalyzer = require('@next/bundle-analyzer')({
  enabled: process.env.ANALYZE === 'true'
});
module.exports = withBundleAnalyzer(nextConfig);

🚀 Performance Tips

Use swcMinify: true for faster builds
Clean up console.log in production
Set "target": "es2020" in .swcrc

// .swcrc
{
  "minify": true,
  "jsc": { "target": "es2020" }
}

🧩 TypeScript Setup

Use strict mode for safer code
Avoid emitting files on build
Configure aliases with paths

{
  "compilerOptions": {
    "strict": true,
    "noEmit": true,
    "baseUrl": ".",
    "paths": { "@/*": ["./src/*"] }
  }
}

🎨 Styling Options

Use CSS Modules for scoped styles
Enable Emotion or Styled Components in compiler
Keep styling consistent per component

import styles from './style.module.css';

const Button = styled.button`
  background: ${props => props.primary ? 'blue' : 'white'};
`;

🧠 Turbopack (Optional)

Next-gen Rust bundler for faster dev builds
Still experimental (--turbo flag)
Great for large monorepos

"scripts": {
  "dev:turbo": "next dev --turbo"
}

🧭 Debugging & Telemetry

Add a ProgressPlugin to show build status
Enable Next.js telemetry debugging
Inspect compiler performance locally

webpack: (config, { webpack }) => {
  config.plugins.push(new webpack.ProgressPlugin());
  return config;
};

NEXT_TELEMETRY_DEBUG=1