The middleware directory contains your application middleware. Middleware lets you define custom functions that can be run before rendering either a page or a group of pages (layout).

Shared middleware should be placed in the  middleware/  directory. The filename will be the name of the middleware (middleware/auth.js will be the auth middleware). You can also define page-specific middleware by using a function directly, see anonymous middleware.

A middleware receives the context as the first argument.

export default function (context) {
  // Add the userAgent property to the context
  context.userAgent = process.server
    ? context.req.headers['user-agent']
    : navigator.userAgent
}

In universal mode, middlewares will be called once on server-side (on the first request to the Nuxt app, e.g. when directly accessing the app or refreshing the page) and on the client-side when navigating to further routes. In SPA mode, middlewares will be called on the client-side in both situations.

The middleware will be executed in series in this order:

1. nuxt.config.js (in the order within the file)
2. Matched layouts
3. Matched pages

Router Middleware

A middleware can be asynchronous. To do this return a  Promise or use async/await.

import http from 'http'

export default function ({ route }) {
  return http.post('http://my-stats-api.com', {
    url: route.fullPath
  })
}

Then, in your nuxt.config.js, use the router.middleware key.

export default {
  router: {
    middleware: 'stats'
  }
}

Now the stats middleware will be called for every route change.

You can add your middleware (even multiple) to a specific layout or page as well.

export default {
  middleware: ['auth', 'stats']
}

Named middleware

You can create named middleware by creating a file inside the  middleware/ directory, the file name will be the middleware name.

export default function ({ store, redirect }) {
  // If the user is not authenticated
  if (!store.state.authenticated) {
    return redirect('/login')
  }
}

<template>
  <h1>Secret page</h1>
</template>

<script>
  export default {
    middleware: 'authenticated'
  }
</script>

Anonymous middleware

If you need to use a middleware only for a specific page, you can directly use a function for it (or an array of functions):

<template>
  <h1>Secret page</h1>
</template>

<script>
  export default {
    middleware({ store, redirect }) {
      // If the user is not authenticated
      if (!store.state.authenticated) {
        return redirect('/login')
      }
    }
  }
</script>