Nuxt/docs/content/migration/20.module-authors.md

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Nuxt 2 to Nuxt 3: Modules

Modules

Module Compatibility

Nuxt 3 has a basic backward compatibility layer for Nuxt 2 modules using @nuxt/kit auto wrappers. But there are usually steps to follow to make modules compatible with Nuxt 3 and sometimes, using Nuxt Bridge is required for cross-version compatibility.

We have prepared a Dedicated Guide for authoring Nuxt 3 ready modules using @nuxt/kit. Currently best migration path is to follow it and rewrite your modules. Rest of this guide includes preparation steps if you prefer to avoid a full rewrite yet making modules compatibile with Nuxt 3.

::alert You can check for a list of Nuxt 3 ready modules from Nuxt Modules. ::

Plugin Compatibility

Nuxt 3 plugins are not fully backward compatible with Nuxt 2.

Vue Compatibility

Plugins or components using the Composition API need 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, so as long as your code is following the guidelines below, 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)

Migrate from CommonJS to ESM

Nuxt 3 natively supports TypeScript and ECMAScript Modules. Please check Native ES Modules for more info and upgrading.

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, Nuxt is now a build-time-only dependency, which means that modules shouldn't attempt to hook into the Nuxt runtime.

Your module should work even if it's only added to buildModules (instead of modules). For example:

• 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 the module. Instead, add them by referencing a file path so that they are independent of the module's context

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

::alert{type=info icon=🔎} Continue reading about Nuxt 3 modules in the Modules guide. ::

Use TypeScript (optional)

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

::alert{icon=💡} You can start migration by 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. ::