Nuxt/docs/content/1.getting-started/3.bridge.md

Bridge

Experience Nuxt 3 features on existing Nuxt 2 projects.

::alert If you're starting a fresh Nuxt 3 project, please skip this section and go to Nuxt 3 Installation.
Learn more in Introduction. ::

::alert{type=warning} Nuxt Bridge provides identical features to Nuxt 3 (docs) but there are some limitations, notably that useAsyncData and useFetch composables are not available. Please read the rest of this page for details. ::

Bridge is a forward-compatibility layer that allows you to experience many of new Nuxt 3 features by simply installing and enabling a Nuxt module.

Using Nuxt Bridge, you can make sure your project is (almost) ready for Nuxt 3 and have the best developer experience without needing a major rewrite or risk breaking changes.

Upgrade Nuxt 2

Remove any package lock files (package-lock.json and yarn.lock) and use the latest nuxt-edge:

- "nuxt": "^2.15.0"
+ "nuxt-edge": "latest"

Then, reinstall your dependencies:

::code-group

yarn install

npm install

::

::alert Once the installation is complete, make sure both development and production builds are working as expected before proceeding. ::

Install Nuxt Bridge

Install @nuxt/bridge-edge as a development dependency:

::code-group

yarn add --dev @nuxt/bridge@npm:@nuxt/bridge-edge

npm install -D @nuxt/bridge@npm:@nuxt/bridge-edge

::

Update your scripts

You will also need to update your scripts within your package.json to reflect the fact that Nuxt will now produce a Nitro server as build output.

Nuxi

Nuxt 3 introduced the new Nuxt CLI command nuxi. Update your scripts as follows to leverage the better support from Nuxt Bridge:

{
  "scripts": {
-   "dev": "nuxt",
+   "dev": "nuxi dev",
-   "build": "nuxt build",
+   "build": "nuxi build",
-   "start": "nuxt start",
+   "start": "node .output/server/index.mjs"
  }
}

Static target

If you have set target: 'static' in your nuxt.config then you need to ensure that you update your build script to be nuxi generate.

{
  "scripts": {
    "build": "nuxi generate"
  }
}

Server target

For all other situations, you can use the nuxi build command.

{
  "scripts": {
    "build": "nuxi build",
    "start": "node .output/server/index.mjs"
  }
}

Update nuxt.config

Please make sure to avoid any CommonJS syntax such as module.exports, require or require.resolve in your config file. It will soon be deprecated and unsupported.

You can use static import, dynamic import() and export default instead. Using TypeScript by renaming to nuxt.config.ts is also possible and recommended.

import { defineNuxtConfig } from '@nuxt/bridge'

export default defineNuxtConfig({
  // Your existing configuration
})

Update tsconfig.json

If you are using TypeScript, you can edit your tsconfig.json to benefit from auto-generated Nuxt types:

{
+ "extends": "./.nuxt/tsconfig.json",
  "compilerOptions": {
    ...
  }
}

Migrate Composition API

If you were previously using @vue/composition-api or @nuxtjs/composition-api, please read the composition api migration guide.

Avoid CommonJS syntax

Nuxt 3 natively supports TypeScript and ECMAScript Modules.

Update the imports

::code-group

const lib = require('lib')

import lib from 'lib'
// or using code-splitting
const lib = await import('lib').then(e => e.default || e)

::

Update the exports

::code-group

module.exports = ...

export default ...
// or using named export
export const hello = ...

::

Avoid using specific CJS syntax

Avoid the usage of __dirname and __filename as much as possible.

Remove incompatible and obsolete modules

• Remove @nuxt/content (1.x). A rewrite for nuxt 3 is planned (2.x)
• Remove nuxt-vite: Bridge enables same functionality
• Remove @nuxt/typescript-build: Bridge enables same functionality
• Remove @nuxt/typescript-runtime and nuxt-ts: Nuxt 2 has built-in runtime support
• Remove @nuxt/nitro: Bridge injects same functionality
• Remove @vue/composition-api from your dependencies (migration guide).
• Remove @nuxtjs/composition-api from your dependencies (and from your modules in nuxt.config) (migration guide).

Exclude built Nitro folder from git

Add the folder .output to the .gitignore file.

Ensure everything goes well

✔️ Try with nuxt dev and nuxt build (or nuxt generate) to see if everything goes well.

🐛 Is something wrong? Please let us know by creating an issue. Also, you can easily disable the bridge in the meantime:

import { defineNuxtConfig } from '@nuxt/bridge'

export default defineNuxtConfig({
  bridge: false // Temporarily disable bridge integration
})

New plugins format (optional)

You can now migrate to the Nuxt 3 plugins API, which is slightly different in format from Nuxt 2.

Plugins now take only one argument (nuxtApp). You can find out more in the docs.

import { defineNuxtPlugin } from '#app'

export default defineNuxtPlugin(nuxtApp => {
  nuxtApp.provide('injected', () => 'my injected function')
  // now available on `nuxtApp.$injected`
})

New useMeta (optional)

Nuxt Bridge provides a new Nuxt 3 meta API that can be accessed with a new useMeta composable.

<script setup>
import { useMeta } from '#app'
useMeta({
  title: 'My Nuxt App',
})
</script>

You will also need to enable this feature explicitly in your nuxt.config:

import { defineNuxtConfig } from '@nuxt/bridge'

export default defineNuxtConfig({
  bridge: {
    meta: true
  }
})

This useMeta composable uses @vueuse/head under the hood (rather than vue-meta) to manipulate your <head>. Accordingly, it is recommended not to use both the native Nuxt 2 head() properties as well as useMeta, as they may conflict.

For more information on how to use this composable, see the docs.

Feature Flags

You can optionally disable some features from bridge or opt-in to less stable ones. In normal circumstances, it is always best to stick with defaults!

You can check bridge/src/module.ts for latest defaults.

import { defineNuxtConfig } from '@nuxt/bridge'

export default defineNuxtConfig({
  bridge: {

    // -- Opt-in features --

    // Use Vite as the bundler instead of Webpack 4
    // vite: true,

    // Enable Nuxt 3 compatible useMeta
    // meta: true,

    // -- Default features --

    // Use legacy server instead of Nitro
    // nitro: false,

    // Disable nuxt 3 compatible `nuxtApp` interface
    // app: false,

    // Disable composition API support
    // capi: false,

    // Do not transpile modules
    // transpile: false,

    // Disable <script setup> support
    // scriptSetup: false,

    // Disable composables auto importing
    // autoImports: false,

    // Do not warn about module incompatibilities
    // constraints: false
  },

  vite: {
    // Config for Vite
  }
})