Cra To Next Migration

CRA to Next.js Migration Guide

Comprehensive migration guide for converting Create React App projects to Next.js, covering routing, data fetching, components, styling, and deployment. Contains 148 rules across 17 categories, prioritized by migration impact. After a successful migration the application should work the same as it did before the migration.

When to Apply

Reference these guidelines when:

• Migrating an existing CRA application to Next.js
• Converting React Router routes to file-based routing
• Adopting Server Components in a client-heavy app
• Moving from client-side rendering to SSR/SSG
• Updating environment variables for Next.js
• Optimizing images and fonts with Next.js built-ins

Version Policy

Use Next.js 16.x or later. Do NOT use Next.js 14.x or 15.x.

Before starting migration, check the current latest version:

npm info next version

Use the latest version in your package.json with a caret for minor/patch updates. The minimum supported version for this migration guide is ^16.0.0.

Rule Categories by Priority

Quick Reference

1. Project Setup (CRITICAL)

• setup-initial-structure - Convert CRA folder structure to Next.js App Router
• setup-package-json - Update dependencies and scripts
• setup-next-config - Create and configure next.config.js
• setup-typescript - Migrate TypeScript configuration
• setup-eslint - Update ESLint for Next.js
• setup-gitignore - Update .gitignore for Next.js

2. Dependencies (CRITICAL)

• deps-react19-compatibility - Upgrade dependencies for React 19 compatibility

3. Routing (CRITICAL)

• routing-basic-pages - Convert components to file-based routes
• routing-dynamic-routes - Use [param] syntax for dynamic segments
• routing-catch-all-routes - Use [...slug] for catch-all routes
• routing-optional-catch-all - Use [[...slug]] for optional catch-all
• routing-route-groups - Use (group) folders for organization
• routing-parallel-routes - Use @slot for parallel routes
• routing-intercepting-routes - Use (..) for intercepting routes
• routing-link-component - Replace react-router Link with next/link
• routing-programmatic-navigation - Replace useNavigate with useRouter
• routing-use-params - Replace useParams with Next.js params
• routing-use-search-params - Replace useSearchParams properly
• routing-nested-layouts - Convert nested routes to layouts
• routing-loading-states - Add loading.tsx for suspense
• routing-error-boundaries - Add error.tsx for error handling
• routing-not-found - Add not-found.tsx for 404 pages
• routing-hash-based - Handle hash-based routing for client-only apps
• routing-protected-routes - Implement protected route patterns

4. Data Fetching (CRITICAL)

• data-useeffect-to-rsc - Convert useEffect fetches to Server Components
• data-useeffect-to-ssr - Convert useEffect to getServerSideProps
• data-useeffect-to-ssg - Convert useEffect to getStaticProps
• data-client-fetch - Keep client fetches with proper patterns
• data-server-actions - Use Server Actions for mutations
• data-revalidation - Configure data revalidation strategies
• data-streaming - Use Suspense for streaming data
• data-parallel-fetching - Fetch data in parallel on server
• data-sequential-fetching - Handle sequential data dependencies
• data-caching - Configure fetch caching behavior
• data-client-library-init - Initialize client-only libraries in useEffect

5. Components (HIGH)

• components-use-client - Add 'use client' directive for client components
• components-server-default - Understand server components are default
• components-boundary-placement - Place client boundaries strategically
• components-composition - Use composition to minimize client JS
• components-interleaving - Interleave server and client components
• components-props-serialization - Ensure props are serializable
• components-children-pattern - Pass server components as children
• components-context-providers - Handle Context providers properly
• components-third-party - Wrap third-party client components

6. Environment Variables (HIGH)

• env-prefix-change - Change REACTAPP to NEXTPUBLIC
• env-server-only - Use non-prefixed vars for server-only
• env-runtime-config - Use runtime configuration when needed
• env-local-files - Understand .env file loading order
• env-build-time - Understand build-time vs runtime env vars
• env-validation - Validate required environment variables

7. Styling (HIGH)

• styling-global-css - Move global CSS to app/layout.tsx
• styling-css-modules - CSS Modules work with minor changes
• styling-sass - Configure Sass support
• styling-tailwind - Configure Tailwind CSS
• styling-css-in-js - Handle CSS-in-JS libraries
• styling-styled-components - Configure styled-components for SSR
• styling-emotion - Configure Emotion for SSR
• styling-component-styles - Import component styles properly
• styling-postcss - Configure PostCSS
• styling-scss-global-syntax - Use :global only in CSS Modules
• styling-css-import-order - Control CSS import order in layouts
• styling-dark-mode-hydration - Handle dark mode without hydration mismatch

8. Public Assets (MEDIUM)

• assets-public-folder - Public folder works the same way
• assets-static-imports - Use static imports for assets
• assets-absolute-urls - Reference assets without public prefix
• assets-favicon - Place favicon in app directory
• assets-manifest - Configure web app manifest

9. Images (MEDIUM)

• images-next-image - Replace img with next/image
• images-required-dimensions - Provide width and height
• images-fill-prop - Use fill for responsive images
• images-priority - Use priority for LCP images
• images-placeholder - Configure blur placeholders
• images-remote-patterns - Configure remote image domains
• images-loader - Configure custom image loaders
• images-optimization - Understand automatic optimization

10. Fonts (MEDIUM)

• fonts-next-font - Use next/font for optimization
• fonts-google-fonts - Load Google Fonts properly
• fonts-local-fonts - Load local font files
• fonts-variable-fonts - Configure variable fonts
• fonts-font-display - Configure font-display strategy
• fonts-preload - Understand automatic font preloading

11. SEO & Metadata (MEDIUM)

• seo-metadata-api - Use Metadata API instead of react-helmet
• seo-dynamic-metadata - Generate dynamic metadata
• seo-opengraph - Configure Open Graph metadata