Nuxt/docs/6.bridge/4.plugins-and-middleware.md

Plugins and Middleware

New Plugins Format

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.

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

::alert If you want to use the new Nuxt composables (such as useNuxtApp or useRuntimeConfig) within your plugins, you will need to use the defineNuxtPlugin helper for those plugins. ::

::alert{type=warning} Although a compatibility interface is provided via nuxtApp.vueApp you should avoid registering plugins, directives, mixins or components this way without adding your own logic to ensure they are not installed more than once, or this may cause a memory leak. ::

New Middleware Format

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

Middleware now take only two argument (to, from). You can find out more in the docs.

export default defineNuxtRouteMiddleware((to) => {
  if (to.path !== '/') {
    return navigateTo('/')
  }
})

::alert{type=warning} Use of defineNuxtRouteMiddleware is not supported outside of the middleware directory. ::

::alert{type=warning} Nuxt Bridge does not support definePageMeta. ::