Nuxt/docs/2.guide/1.concepts/4.server-engine.md

Server Engine

Nuxt 3 is powered by a new server engine, Nitro.

::list{type=success}

• Cross-platform support for Node.js, Browsers, service-workers and more.
• Serverless support out-of-the-box.
• API routes support.
• Automatic code-splitting and async-loaded chunks.
• Hybrid mode for static + serverless sites.
• Development server with hot module reloading. ::

API Layer

Server API endpoints and Middleware are added by Nitro that internally uses h3.

Key features include:

• Handlers can directly return objects/arrays for an automatically-handled JSON response
• Handlers can return promises, which will be awaited (res.end() and next() are also supported)
• Helper functions for body parsing, cookie handling, redirects, headers and more

Check out the h3 docs for more information.

::alert{type="info" icon=ℹ️} Learn more about the API layer in the server/ directory. ::

Direct API Calls

Nitro allows 'direct' calling of routes via the globally-available $fetch helper. This will make an API call to the server if run on the browser, but will directly call the relevant function if run on the server, saving an additional API call.

$fetch API is using ofetch, with key features including:

• Automatic parsing of JSON responses (with access to raw response if needed)
• Request body and params are automatically handled, with correct Content-Type headers

For more information on $fetch features, check out ofetch.

Typed API Routes

When using API routes (or middleware), Nitro will generate typings for these routes as long as you are returning a value instead of using res.end() to send a response.

You can access these types when using $fetch() or useFetch().

Standalone Server

Nitro produces a standalone server dist that is independent of node_modules.

The server in Nuxt 2 is not standalone and requires part of Nuxt core to be involved by running nuxt start (with the nuxt-start or nuxt distributions) or custom programmatic usage, which is fragile and prone to breakage and not suitable for serverless and service-worker environments.

Nuxt 3 generates this dist when running nuxt build into a .output directory.

The output contains runtime code to run your Nuxt server in any environment (including experimental browser service workers!) and serve your static files, making it a true hybrid framework for the JAMstack. In addition, Nuxt implements a native storage layer, supporting multi-source drivers and local assets.

::alert{type="info" icon=ℹ️} Check out the Nitro engine on GitHub: unjs/nitro. ::