Nuxt 5 Production Guide

Hydration, performance, testing, deployment, and migration patterns.

What's New in Nuxt 5

v5 Key Changes

Change	Nuxt 4	Nuxt 5
Bundler	Vite 6 (esbuild + Rollup)	Vite 8 (Rolldown)
Server engine	Nitro v2	Nitro v3 (h3 v2)
Server errors	createError({statusCode})	HTTPError({status})
Client-only placeholder	Empty <div>	HTML comment node
callHook	Always returns Promise	May return void
clearNuxtState	Sets to undefined	Resets to initial default
Page names	Auto-generated	Normalized to route names
JSX support	Included by default	Optional (on-demand)
externalVue	Configurable	Removed (always mocked)

Client-Only Comment Placeholders (v5)

Client-only components (.client.vue files and createClientOnly() wrappers) now render an HTML comment on the server instead of an empty <div>. This fixes scoped styles hydration issues.

<!-- If you relied on the placeholder <div> for layout -->
<ClientOnly>
  <MyComponent />
  <template #fallback>
    <div class="placeholder" style="min-height: 200px"></div>
  </template>
</ClientOnly>

To revert to the old <div> behavior:

// nuxt.config.ts
export default defineNuxtConfig({
  experimental: {
    clientNodePlaceholder: false
  }
})

Non-Async callHook (v5)

callHook may now return void instead of always returning Promise. Always use await:

// WRONG
nuxtApp.callHook('my:hook', data).then(() => { ... })

// CORRECT
await nuxtApp.callHook('my:hook', data)

When to Load References

Load references/hydration.md when:

• Debugging "Hydration node mismatch" errors
• Implementing ClientOnly components
• Fixing non-deterministic rendering issues

Load references/performance.md when:

• Optimizing Core Web Vitals scores
• Implementing lazy loading and code splitting
• Reducing bundle size

Load references/testing-vitest.md when:

• Writing component tests with @nuxt/test-utils
• Testing composables with Nuxt context
• Mocking Nuxt APIs

Load references/deployment-cloudflare.md when:

• Deploying to Cloudflare Pages or Workers
• Configuring wrangler.toml
• Setting up NuxtHub integration

Hydration Best Practices

What Causes Hydration Mismatches

Cause	Example	Fix
Non-deterministic values	Math.random()	Use useState
Browser APIs on server	window.innerWidth	Use onMounted
Date/time on server	new Date()	Use useState or ClientOnly
Third-party scripts	Analytics	Use ClientOnly

Fix Patterns

<!-- Non-deterministic values -->
<script setup>
const id = useState('random-id', () => Math.random())
</script>

<!-- Browser APIs -->
<script setup>
const width = ref(0)
onMounted(() => {
  width.value = window.innerWidth
})
</script>

<!-- ClientOnly component -->
<template>
  <ClientOnly>
    <MyMapComponent />
    <template #fallback>
      <div class="skeleton">Loading map...</div>
    </template>
  </ClientOnly>
</template>

Performance Optimization

Lazy Loading Components

<script setup>
const HeavyChart = defineAsyncComponent(() =>
  import('~/components/HeavyChart.vue')
)
</script>

Lazy Hydration

<script setup>
const LazyComponent = defineLazyHydrationComponent(
  'visible',
  () => import('./HeavyComponent.vue')
)

const InteractiveComponent = defineLazyHydrationComponent(
  'interaction',
  () => import('./InteractiveComponent.vue')
)

const IdleComponent = defineLazyHydrationComponent(
  'idle',
  () => import('./IdleComponent.vue')
)
</script>

Route Caching

export default defineNuxtConfig({
  routeRules: {
    '/': { prerender: true },
    '/about': { prerender: true },
    '/blog/**': { swr: 3600 },
    '/products/**': { isr: 3600 },
    '/dashboard/**': { ssr: false },
    '/static/**': {
      headers: { 'Cache-Control': 'public, max-age=31536000' }
    }
  }
})

Image Optimization

<template>
  <NuxtImg
    src="/images/hero.jpg"
    alt="Hero image"
    width="800"
    height="400"
    loading="lazy"
    placeholder
    format="webp"
  />

  <NuxtPicture
    src="/images/product.jpg"
    alt="Product"
    sizes="sm:100vw md:50vw lg:400px"
    :modifiers="{ quality: 80 }"
  />
</template>

Testing with Vitest

Setup

bun add -d @nuxt/test-utils vitest @vue/test-utils happy-dom

// vitest.config.ts
import { defineVitestConfig } from '@nuxt/test-utils/config'

export default defineVitestConfig({
  test: {
    environment: 'nuxt',
    environmentOptions: {
      nuxt: {
        domEnvironment: 'happy-dom'
      }
    }
  }
})

Component Testing

import { describe, it, expect } from 'vitest'
import { mountSuspended } from '@nuxt/test-utils/runtime'
import UserCard from '~/components/UserCard.vue'

describe('UserCard', () => {
  it('renders user name', async () => {
    const wrapper = await mountSuspended(UserCard, {
      props: {
        user: { id: 1, name: 'John Doe', email: 'john@example.com' }
      }
    })

    expect(wrapper.text()).toContain('John Doe')
  })
})

Mocking Composables

import { mockNuxtImport } from '@nuxt/test-utils/runtime'

mockNuxtImport('useFetch', () => {
  return () => ({
    data: ref({ users: [{ id: 1, name: 'John' }] }),
    pending: ref(false),
    error: ref(null)
  })
})

Deployment

Cloudflare Pages (Recommended)

bun run build
bunx wrangler pages deploy .output/public

export default defineNuxtConfig({
  nitro: { preset: 'cloudflare_pages' }
})

Cloudflare Workers

export default defineNuxtConfig({
  nitro: { preset: 'cloudflare_module' }
})

Vercel / Netlify

// Vercel
export default defineNuxtConfig({
  nitro: { preset: 'vercel' }
})

// Netlify
export default defineNuxtConfig({
  nitro: { preset: 'netlify' }
})

NuxtHub (Cloudflare All-in-One)

bun add @nuxthub/core

export default defineNuxtConfig({
  modules: ['@nuxthub/core'],
  hub: {
    database: true,
    kv: true,
    blob: true,
    cache: true
  }
})

Migration from Nuxt 4

Step 1: Update package.json

{
  "devDependencies": {
    "nuxt": "^5.0.0"
  }
}

Step 2: Enable Compatibility Mode

// nuxt.config.ts
export default defineNuxtConfig({
  future: {
    compatibilityVersion: 5
  }
})

Step 3: Update Server Error Handling

// Before (Nuxt 4)
import { createError } from 'h3'
throw createError({ statusCode: 404, statusMessage: 'Not Found' })

// After (Nuxt 5)
import { HTTPError } from 'nitro/h3'
throw new HTTPError({ status: 404, statusText: 'Not Found' })

Step 4: Update Server Event API

// Before (Nuxt 4)
const path = event.path
event.node.res.statusCode = 200
setResponseHeader(event, 'x-custom', 'value')
const config = useRuntimeConfig(event)

// After (Nuxt 5)
const path = event.url.pathname
event.res.status = 200
event.res.headers.set('x-custom', 'value')
const config = useRuntimeConfig()

Step 5: Update Vite Config

// Before (Nuxt 4)
export default defineNuxtConfig({
  vite: {
    build: {
      rollupOptions: { ... }
    }
  }
})

// After (Nuxt 5) - use rolldownOptions
export default defineNuxtConfig({
  vite: {
    build: {
      rolldownOptions: { ... }
    }
  }
})

Step 6: Update Route Rules

// Before
routeRules: {
  '/old': { redirect: { to: '/new', statusCode: 302 } }
}

// After
routeRules: {
  '/old': { redirect: { to: '/new', status: 302 } }
}

Step 7: Update Import Paths

// Before
import { defineEventHandler, getQuery } from 'h3'

// After
import { defineEventHandler, getQuery } from 'nitro/h3'
// Or rely on auto-imports (no import needed)

Step 8: Remove Deprecated Options

// Remove these from nuxt.config.ts
export default defineNuxtConfig({
  experimental: {
    externalVue: false,  // REMOVED - delete this
    viteEnvironmentApi: true,  // REMOVED - always enabled
  }
})

Step 9: Install JSX Plugin (If Needed)

# Only if your project uses .jsx/.tsx files
bun add -D @vitejs/plugin-vue-jsx

Step 10: Update callHook Usage

// Before
nuxtApp.callHook('my:hook', data).then(() => { ... })

// After
await nuxtApp.callHook('my:hook', data)

Common Anti-Patterns

Client-Only Code on Server

// WRONG
const width = window.innerWidth

// CORRECT
if (import.meta.client) {
  const width = window.innerWidth
}

// Or use onMounted
onMounted(() => {
  const width = window.innerWidth
})

Non-Deterministic SSR

// WRONG
const id = Math.random()
const time = Date.now()

// CORRECT
const id = useState('id', () => Math.random())
const time = useState('time', () => Date.now())

Troubleshooting

Hydration Mismatch:

• Check for window, document, localStorage usage
• Wrap in ClientOnly or use onMounted
• Look for Math.random(), Date.now()
• Check if relying on <div> placeholder for client-only components

Build Errors:

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

Vite Plugin Warnings:

• Migrate from extendViteConfig({ server }) to configEnvironment
• Use applyToEnvironment instead of server: false / client: false

Rolldown Build Issues:

• Replace rollupOptions with rolldownOptions
• Replace vite.esbuild with vite.oxc
• Check CJS interop changes in Vite 8

Related Skills

• nuxt-core: Project setup, routing, configuration
• nuxt-data: Composables, data fetching, state
• nuxt-server: Server routes, API patterns (Nitro v3)
• cloudflare-d1: D1 database patterns

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Version: 5.0.0 | Last Updated: 2026-03-30 | License: MIT