Nuxt/docs/content/1.getting-started/5.migration.md

Migration

Nuxt 3 migration guide. Work in progress 🚧

Nuxt 2 to Nuxt 3

At the moment, there is no Nuxt 2 to Nuxt 3 migration guide nor is recommanded to do it due to potentially more changes coming. We are working to provide a stable migration guide and tooling to make it as smooth as possible. Please check Bridge for the alternative.

Some features have been dropped from Nuxt 2, some yet need to be implemented for Nuxt 3 and some are new in Nuxt 3 (and Bridge).

Noticable and/or Breaking changes with Nuxt 3 other than the requirements of bridge are:

::list{type=warning}

• Vue app templates are rewritten
• Vue upgraded to 3.x
• Using <Suspense> for async data fetching
• Webpack 5.x (if not using vite)
• Components discovery is rewritten
• Introduced main app.vue component
• Introduced new layouts system
• The pages/ directory conventions changed ::

In table below there is an overall feature comparation table:

Feature / Version	Nuxt 2	Nuxt 3	Changes required
Vue Version	2	3	Yes
app.vue	❌	✅	-
Assets	✅	✅	No
Components	✅	✅	No
Layouts	✅	✅	Yes
Error Pages	✅	🚧	Yes
Pages	✅	✅	Yes
Pages: Dynamic Params	✅	✅	Yes
Pages: _.vue	✅	✅	No
Plugins	✅	✅	Yes (compatible by default)
Store	✅	🚧	Yes
Transitions	✅	🚧	?
Suspense	❌	✅	-
Options API: asyncData	✅	🚧	?
Options API: fetch	✅	🚧	?

Module Compatibility

All Nuxt 2 modules should be forward compatible with Nuxt 3 as long as they migrate to bridge or if they are already following guidelines.

All (upcoming) modules made with @nuxt/kit should be backward compatible with Nuxt 2 projects (even without bridge) as long as they are not depending on a Nuxt 3 / Bridge-only feature.

Plugin Compatibility

Most Nuxt 2 plugins should be forward compatible with Nuxt 3 with a magical compat layer we inject.

Nuxt 3 plugins are not backward compatible with Nuxt 2.

Vue Compatibility

For plugins using composition API or components, it needs exclusive Vue 2 or Vue 3 support.

By using vue-demi they should be compatible with both Nuxt 2 and 3.

Module Migration

When Nuxt 3 users add your module, a compatible module container layer from @nuxt/kit is automatically injected, as long as your code is following below guidelines, it should continue working as is.

Test with @nuxt/bridge

Migrating to @nuxt/bridge is the first and most important step for supporting Nuxt 3.

If you have a fixture or example in your module, add @nuxt/bridge package to its config (see example)

Avoid CommonJS syntax

Nuxt 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.

Ensure plugins default export

If you inject a Nuxt plugin that does not have export default (such as global Vue plugins), ensure you add export default {} to the end of it.

::code-group

// ~/plugins/vuelidate.js
import Vue from 'vue'
import Vuelidate from 'vuelidate'

Vue.use(Vuelidate)

// ~/plugins/vuelidate.js
import Vue from 'vue'
import Vuelidate from 'vuelidate'

Vue.use(Vuelidate)

export default {}

::

Avoid runtime modules

With Nuxt 3, we changed how the build process should work and modules hooking into the Nuxt runtime is now considered an anti-pattern and will not work.

Your module should work fine by adding only to buildModules (instead of modules):

• Avoid updating process.env within a Nuxt module and reading by a nuxt plugin, use runtimeConfig instead.
• (*) Avoid depending on runtime hooks like vue-renderer:* for production
• (*) Avoid adding serverMiddleware by importing them inside module. Add them by referencing to file path so that they are independent of module context

(*) Unless it is for nuxt dev purpose only and guarded with if (nuxt.options.dev) { }.

Add module meta

Ensure your module is exporting meta object.

TODO

Use TypeScript (optional)

While it is not essential, most of Nuxt ecosystem is shifting to use TypeScript, it is highly recommended to consider migration.

::alert{icon=💡} You can start migration by simply renaming .js files, to .ts. TypeScript is designed to be progressive! ::

::alert{icon=💡} You can use TypeScript syntax for Nuxt 2 and 3 modules and plugins without any extra dependencies. ::