Nuxt/docs/content/migration/11.server.md

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Nuxt 2 to Nuxt 3: Server

Server

In a built Nuxt 3 application, there is no runtime Nuxt dependency. That means your site will be highly performant, and ultra-slim. But it also means you can no longer hook into runtime Nuxt server hooks.

Read more about the Nitro server engine.

Steps

1. Remove the render key in your nuxt.config.
2. Any files in ~/server/api and ~/server/middleware will be automatically registered; you can remove them from your serverMiddleware array.
3. Update any other items in your serverMiddleware array to point to files or npm packages directly, rather than using inline functions.
4. If you are adding any server hooks, such as server: or vue-renderer: you will need to remove these and wait for nitropack support for runtime hooks and plugins.