Nuxt 4 Core Fundamentals

Project setup, configuration, routing, SEO, and error handling for Nuxt 4 applications.

Quick Reference

Version Requirements

Package	Minimum	Recommended
nuxt	4.0.0	4.2.x
vue	3.5.0	3.5.x
nitro	2.10.0	2.12.x
vite	6.0.0	6.2.x
typescript	5.0.0	5.x

Key Commands

# Create new project
bunx nuxi@latest init my-app

# Development
bun run dev

# Build for production
bun run build

# Preview production build
bun run preview

# Type checking
bun run postinstall  # Generates .nuxt directory
bunx nuxi typecheck

# Add a page/component/composable
bunx nuxi add page about
bunx nuxi add component MyButton
bunx nuxi add composable useAuth

Directory Structure (Nuxt v4)

my-nuxt-app/
├── app/                    # Default srcDir in v4
│   ├── assets/             # Build-processed assets (CSS, images)
│   ├── components/         # Auto-imported Vue components
│   ├── composables/        # Auto-imported composables
│   ├── layouts/            # Layout components
│   ├── middleware/         # Route middleware
│   ├── pages/              # File-based routing
│   ├── plugins/            # Nuxt plugins
│   ├── utils/              # Auto-imported utility functions
│   ├── app.vue             # Main app component
│   ├── app.config.ts       # App-level runtime config
│   ├── error.vue           # Error page component
│   └── router.options.ts   # Router configuration
│
├── server/                 # Server-side code (Nitro)
│   ├── api/                # API endpoints
│   ├── middleware/         # Server middleware
│   ├── plugins/            # Nitro plugins
│   ├── routes/             # Server routes
│   └── utils/              # Server utilities
│
├── public/                 # Static assets (served from root)
├── shared/                 # Shared code (app + server)
├── content/                # Nuxt Content files (if using)
├── layers/                 # Nuxt layers
├── modules/                # Local modules
├── .nuxt/                  # Generated files (git ignored)
├── .output/                # Build output (git ignored)
├── nuxt.config.ts          # Nuxt configuration
├── tsconfig.json           # TypeScript configuration
└── package.json            # Dependencies

Key Change in v4: The app/ directory is now the default srcDir. All app code goes in app/, server code stays in server/.

When to Load References

Load references/configuration-deep.md when:

• Configuring advanced nuxt.config.ts options
• Setting up modules and plugins
• Customizing Vite or Nitro configuration
• Configuring experimental features

Load references/routing-advanced.md when:

• Implementing complex routing patterns
• Creating route middleware with authentication
• Using catch-all routes or optional parameters
• Configuring router options

Load references/plugins-architecture.md when:

• Creating Nuxt plugins
• Injecting global utilities or composables
• Integrating third-party libraries
• Understanding plugin execution order

Configuration

Basic nuxt.config.ts

export default defineNuxtConfig({
  // Enable Nuxt 4 features
  future: {
    compatibilityVersion: 4
  },

  // Development tools
  devtools: { enabled: true },

  // Modules
  modules: [
    '@nuxt/ui',
    '@nuxt/content',
    '@nuxt/image'
  ],

  // Runtime config (environment variables)
  runtimeConfig: {
    // Server-only (not exposed to client)
    apiSecret: process.env.API_SECRET,
    databaseUrl: process.env.DATABASE_URL,

    // Public (client + server)
    public: {
      apiBase: process.env.API_BASE || 'https://api.example.com',
      appName: 'My App'
    }
  },

  // App config
  app: {
    head: {
      title: 'My Nuxt App',
      meta: [
        { charset: 'utf-8' },
        { name: 'viewport', content: 'width=device-width, initial-scale=1' }
      ]
    }
  },

  // Nitro config (server)
  nitro: {
    preset: 'cloudflare-pages'
  },

  // TypeScript
  typescript: {
    strict: true,
    typeCheck: true
  }
})

Runtime Config Usage

// In composables or components
const config = useRuntimeConfig()

// Public values (client + server)
const apiBase = config.public.apiBase

// Server-only values (only in server/)
const apiSecret = config.apiSecret  // undefined on client!

Critical Rule: Always use useRuntimeConfig() instead of process.env for environment variables in production.

App Config vs Runtime Config

Feature	App Config	Runtime Config
Location	app.config.ts	nuxt.config.ts
Hot reload	Yes	No
Secrets	No	Yes (server-only)
Use case	UI settings, themes	API keys, URLs

// app/app.config.ts - UI settings (hot-reloadable)
export default defineAppConfig({
  theme: {
    primaryColor: '#3490dc'
  },
  ui: {
    rounded: 'lg'
  }
})

// Usage
const appConfig = useAppConfig()
const color = appConfig.theme.primaryColor

Routing

File-Based Routing

app/pages/
├── index.vue              → /
├── about.vue              → /about
├── users/
│   ├── index.vue          → /users
│   └── [id].vue           → /users/:id
└── blog/
    ├── index.vue          → /blog
    ├── [slug].vue         → /blog/:slug
    └── [...slug].vue      → /blog/* (catch-all)

Dynamic Routes

<!-- app/pages/users/[id].vue -->
<script setup lang="ts">
const route = useRoute()

// Get route params
const userId = route.params.id

// Reactive (updates when route changes)
const userId = computed(() => route.params.id)

// Fetch user data
const { data: user } = await useFetch(`/api/users/${userId.value}`)
</script>

<template>
  <div>
    <h1>{{ user?.name }}</h1>
  </div>
</template>

Navigation

<script setup>
const goToUser = (id: string) => {
  navigateTo(`/users/${id}`)
}

const goBack = () => {
  navigateTo(-1)  // Go back in history
}

// With options
const goToLogin = () => {
  navigateTo('/login', {
    replace: true,  // Replace current history entry
    external: false // Internal navigation
  })
}
</script>

<template>
  <!-- Declarative navigation -->
  <NuxtLink to="/about">About</NuxtLink>
  <NuxtLink :to="`/users/${user.id}`">View User</NuxtLink>

  <!-- Prefetching (default: on hover) -->
  <NuxtLink to="/dashboard" prefetch>Dashboard</NuxtLink>

  <!-- No prefetch -->
  <NuxtLink to="/admin" :prefetch="false">Admin</NuxtLink>
</template>

Route Middleware

// app/middleware/auth.ts
export default defineNuxtRouteMiddleware((to, from) => {
  const { isAuthenticated } = useAuth()

  if (!isAuthenticated.value) {
    return navigateTo('/login')
  }
})

<!-- app/pages/dashboard.vue -->
<script setup lang="ts">
definePageMeta({
  middleware: 'auth'
})
</script>

Global Middleware

// app/middleware/analytics.global.ts
export default defineNuxtRouteMiddleware((to, from) => {
  // Runs on every route change
  if (import.meta.client) {
    window.gtag?.('event', 'page_view', {
      page_path: to.path
    })
  }
})

Page Meta

<script setup lang="ts">
definePageMeta({
  title: 'Dashboard',
  middleware: ['auth'],
  layout: 'admin',
  pageTransition: { name: 'fade' },
  keepalive: true
})
</script>

SEO & Meta Tags

useSeoMeta (Recommended)

<script setup lang="ts">
useSeoMeta({
  title: 'My Page Title',
  description: 'Page description for search engines',
  ogTitle: 'My Page Title',
  ogDescription: 'Page description',
  ogImage: 'https://example.com/og-image.jpg',
  ogUrl: 'https://example.com/my-page',
  twitterCard: 'summary_large_image',
  twitterTitle: 'My Page Title',
  twitterDescription: 'Page description',
  twitterImage: 'https://example.com/og-image.jpg'
})
</script>

useHead (More Control)

<script setup lang="ts">
useHead({
  title: 'My Page Title',
  meta: [
    { name: 'description', content: 'Page description' },
    { property: 'og:title', content: 'My Page Title' }
  ],
  link: [
    { rel: 'canonical', href: 'https://example.com/my-page' }
  ],
  script: [
    { src: 'https://example.com/script.js', defer: true }
  ]
})
</script>

Dynamic Meta Tags

<script setup lang="ts">
const { data: post } = await useFetch(`/api/posts/${route.params.slug}`)

useSeoMeta({
  title: () => post.value?.title,
  description: () => post.value?.excerpt,
  ogImage: () => post.value?.image
})
</script>

Title Template

// nuxt.config.ts
export default defineNuxtConfig({
  app: {
    head: {
      titleTemplate: '%s | My App'  // "Page Title | My App"
    }
  }
})

Error Handling

Error Page

<!-- app/error.vue -->
<script setup lang="ts">
import type { NuxtError } from '#app'

const props = defineProps<{
  error: NuxtError
}>()

const handleError = () => {
  clearError({ redirect: '/' })
}
</script>

<template>
  <div class="error-page">
    <h1>{{ error.statusCode }}</h1>
    <p>{{ error.message }}</p>
    <button @click="handleError">Go Home</button>
  </div>
</template>

Error Boundaries (Component-Level)

<template>
  <NuxtErrorBoundary @error="handleError">
    <template #error="{ error, clearError }">
      <div class="error-container">
        <h2>Something went wrong</h2>
        <p>{{ error.message }}</p>
        <button @click="clearError">Try again</button>
      </div>
    </template>

    <!-- Your component content -->
    <MyComponent />
  </NuxtErrorBoundary>
</template>

<script setup>
const handleError = (error: Error) => {
  console.error('Component error:', error)
  // Send to error tracking service
}
</script>

Throwing Errors

// In pages or components
throw createError({
  statusCode: 404,
  statusMessage: 'Page Not Found',
  fatal: true  // Shows error page, stops rendering
})

// Non-fatal error (shows inline)
throw createError({
  statusCode: 400,
  message: 'Invalid input'
})

API Error Handling

const { data, error } = await useFetch('/api/users')

if (error.value) {
  // Handle error gracefully
  showError({
    statusCode: error.value.statusCode,
    message: error.value.message
  })
}

Common Anti-Patterns

Using process.env Instead of Runtime Config

// WRONG - Won't work in production!
const apiUrl = process.env.API_URL

// CORRECT
const config = useRuntimeConfig()
const apiUrl = config.public.apiBase

Missing Middleware Guards

// WRONG - No return, middleware continues
export default defineNuxtRouteMiddleware((to) => {
  const { isAuthenticated } = useAuth()
  if (!isAuthenticated.value) {
    navigateTo('/login')  // Missing return!
  }
})

// CORRECT
export default defineNuxtRouteMiddleware((to) => {
  const { isAuthenticated } = useAuth()
  if (!isAuthenticated.value) {
    return navigateTo('/login')  // Return stops middleware chain
  }
})

Non-Reactive Route Params

// WRONG - Not reactive
const userId = route.params.id

// CORRECT - Reactive
const userId = computed(() => route.params.id)

Troubleshooting

Build Errors / Type Errors:

rm -rf .nuxt .output node_modules/.vite && bun install && bun run dev

Route Not Found:

• Check file is in app/pages/ (not root pages/)
• Verify file extension is .vue
• Check for typos in dynamic params [id].vue

Middleware Not Running:

• Ensure file has .global.ts suffix for global middleware
• Check definePageMeta({ middleware: 'name' }) matches filename
• Verify middleware returns navigateTo() or nothing

Meta Tags Not Updating:

• Use reactive values: title: () => post.value?.title
• Ensure useSeoMeta is called in <script setup>

Related Skills

• nuxt-data: Composables, data fetching, state management
• nuxt-server: Server routes, API patterns, database integration
• nuxt-production: Performance, testing, deployment
• nuxt-ui-v4: Nuxt UI component library

Templates Available

See templates/ directory for:

• Production-ready nuxt.config.ts
• app.vue with proper structure
• Middleware examples

---

Version: 4.0.0 | Last Updated: 2025-12-28 | License: MIT