# defineNuxtRouteMiddleware > Create named route middleware using defineNuxtRouteMiddleware helper function. Route middleware are stored in the [`app/middleware/`](/docs/4.x/directory-structure/app/middleware) of your Nuxt application (unless [set otherwise](/docs/4.x/api/nuxt-config#middleware)). ## Type ```ts [Signature] export function defineNuxtRouteMiddleware (middleware: RouteMiddleware): RouteMiddleware interface RouteMiddleware { (to: RouteLocationNormalized, from: RouteLocationNormalized): ReturnType } ``` ## Parameters ### `middleware` - **Type**: `RouteMiddleware` A function that takes two Vue Router's route location objects as parameters: the next route `to` as the first, and the current route `from` as the second. Learn more about available properties of `RouteLocationNormalized` in the **Vue Router docs**. ## Examples ### Showing Error Page You can use route middleware to throw errors and show helpful error messages: ```ts [app/middleware/error.ts] export default defineNuxtRouteMiddleware((to) => { if (to.params.id === '1') { throw createError({ status: 404, statusText: 'Page Not Found' }) } }) ``` The above route middleware will redirect a user to the custom error page defined in the `~/error.vue` file, and expose the error message and code passed from the middleware. ### Redirection Use [`useState`](/docs/4.x/api/composables/use-state) in combination with `navigateTo` helper function inside the route middleware to redirect users to different routes based on their authentication status: ```ts [app/middleware/auth.ts] export default defineNuxtRouteMiddleware((to, from) => { const auth = useState('auth') if (!auth.value.isAuthenticated) { return navigateTo('/login') } if (to.path !== '/dashboard') { return navigateTo('/dashboard') } }) ``` Both [navigateTo](/docs/4.x/api/utils/navigate-to) and [abortNavigation](/docs/4.x/api/utils/abort-navigation) are globally available helper functions that you can use inside `defineNuxtRouteMiddleware`. --- - [Source](https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/composables/router.ts)