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

# Server Engine

Nuxt 3 is powered by a new server engine, [Nitro](https://nitro.unjs.io/).

::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](/docs/guide/directory-structure/server#api-routes) and [Middleware](/docs/guide/directory-structure/server#server-middleware) are added by Nitro that internally uses [h3](https://github.com/unjs/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](https://github.com/unjs/h3) for more information.

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Learn more about the API layer in the [`server/`](/docs/guide/directory-structure/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](https://github.com/unjs/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](https://github.com/unjs/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`](https://www.npmjs.com/package/nuxt-start) or [`nuxt`](https://www.npmjs.com/package/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`](/docs/guide/directory-structure/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.

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Check out the Nitro engine on GitHub: [unjs/nitro](https://github.com/unjs/nitro).
::